ORCID Profile
0000-0002-0677-5195
Current Organisation
Nanyang Technological University
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Publisher: Elsevier BV
Date: 03-2009
DOI: 10.1016/J.WATRES.2008.12.008
Abstract: For decades, glycolysis has been generally accepted to supply the reducing power for the anaerobic conversion of volatile fatty acids (VFAs) to polyhydroxyalkanoates (PHAs) by polyphosphate accumulating organisms (PAOs). However, the importance of the tricarboxylic acid (TCA) cycle has also been raised since 1980s. The aim of this study is to demonstrate the involvement of the TCA cycle in the anaerobic metabolism of PAOs. To achieve this goal, the glycogen pool of an activated sludge highly enriched in Candidatus Accumulibacter Phosphatis (hereafter referred to as Accumulibacter), a putative PAO was reduced substantially through starving the sludge under intermittent anaerobic and aerobic conditions. After the starvation, acetate added was still taken up anaerobically and stored as PHA, with negligible glycogen degradation. The metabolic models proposed by Pereira, Hesselmann and Yagci, which predict the formation of reducing power through glycolysis and the full or partial TCA cycle, were used to estimate the carbon fluxes. The results demonstrate that Accumulibacter can use both glycogen and acetate to generate reducing power anaerobically. The anaerobic production of reducing power from acetate is likely through the full TCA cycle. The proportion of TCA cycle involvement depends on the availability of degradable glycogen.
Publisher: Elsevier BV
Date: 10-2020
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.WATRES.2017.11.066
Abstract: In this study, nitrite was added into sludge during freezing process to evaluate its role in waste activated sludge (WAS) solubilization and effect on sludge dewatering characteristics. The results showed that the introduction of 100 mg L
Publisher: Elsevier BV
Date: 12-2019
Publisher: Elsevier BV
Date: 03-2016
Publisher: Springer Science and Business Media LLC
Date: 30-07-2021
Publisher: Elsevier BV
Date: 04-2021
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.CHEMOSPHERE.2014.10.047
Abstract: A laboratory-scale acidogenic anaerobic sequencing batch reactor was set up to test the effect of pH change on microbial community structure of the reactor biomass and process performance. No immediate performance change on acidogenesis was observed after the pH change. However, as the hydrogenotrophic methanogen population decreased, hydrogen content in biogas increased followed by a sharp decrease in volatile fatty acids (VFAs) with acetic acid (HAc) in particular. Recovery of reactor performance following pH correction was only apparent after recovery of hydrogenotrophic methanogen population. These suggested hydrogenotrophic methanogens played a very important role in performance of the acidogenic process.
Publisher: Elsevier BV
Date: 09-2017
DOI: 10.1016/J.BIORTECH.2017.05.046
Abstract: The major obstacle for thermophilic anaerobic digestion (TAD) is the inhibited microorganism activity and process instability during the start-up period. This study proposed a strategy to accelerate and stabilize the thermophilic reactors start-up via adding conductive materials. The results show that methane production rate in conductive materials supplemented (CMS) reactors was almost two times higher than the control reactors. Caloramator sp., a candidate of electroactive bacteria, was significantly enriched in the carbon nano-tube (CNT) supplemented groups (12.89%) as compared to control groups (1.26% only). Together with the doubled abundance of Methanosaeta and Methanosarcina methanogens in CMS groups, it is highly possible Caloramator sp. and Methanosaeta/Methanosarcina have established syntrophic direct interspecies electron transfer (DIET), via adopting conductive materials as electron conduit. Microbial community analysis indicates DIET was likely to be an unstable condition triggered syntrophic process. This study demonstrated that conductive materials could promote microbial activity and shorten start-up period for thermophilic anaerobic system.
Publisher: Springer Science and Business Media LLC
Date: 11-04-2019
DOI: 10.1007/S00253-019-09799-8
Abstract: Ionic liquids (IL) have emerged as the next-generation "green" solvent that can replace traditional organic solvent due to properties such as high thermal stability and no vapour pressure. However, their increased usage inevitably allows them to find their way into the environment. The objective of this study was to evaluate the role of autotrophic ammonia-oxidising bacteria (AOB) in the potential removal of 1-dodecylpyridinium chloride ([DPy]
Publisher: Elsevier BV
Date: 03-2009
Publisher: Elsevier BV
Date: 10-2016
Publisher: Springer Science and Business Media LLC
Date: 27-05-2015
DOI: 10.1038/NPJBIOFILMS.2015.6
Abstract: Recent reports exploring the role of gradients of quorum sensing (QS) signals in functional activated sludge have raised the question of whether shared systems of signalling synthesis and degradation, or quorum quenching (QQ), across the community inform of the means by which QS biology regulate floccular and granular biofilm assembly. In this study, we aimed to explore the species origin and interactive role of QS and QQ activities in such highly erse microbial biofilm communities. Here, such aims were addressed systematically by a comprehensive multi-pronged RNA-sequencing, microbiological and analytical chemistry experimental approach, using two related but independently evolved floccular and granular sludge communities. Our data revealed a distinct difference between the QS and QQ potentials of the two communities, with different species largely displaying either QS or QQ functions. The floccular sludge community showed a high rate of QQ activity, and this rate was dependent on the acyl chain length demonstrating specificity of degradation. When the floccular biomass was transformed into the granular sludge, the QQ activity of the community was reduced by 30%. N -acyl homoserine lactones with four to eight carbons on the acyl chain accumulated at the granular stage, and their concentrations were at least threefold higher than those of the floccular stage. These findings corroborated meta-community analysis where a major shift in the dominant species from potential signal quenchers to producers was observed during the transition from flocs to granules, indicating the role of species composition and associated signalling activities in coordinating community behaviours. This study suggests that QQ has an important function in regulating community level QS signalling, and provides a mechanistic insight into the role of QS biology in complex community assembly.
Publisher: Elsevier BV
Date: 10-2021
Publisher: Springer Science and Business Media LLC
Date: 21-12-2017
DOI: 10.1038/S41598-017-18198-W
Abstract: The anaerobic digestion process is a multi - step reaction dependent on concerted activities such as exchange of metabolites among physiologically different microbial communities. This study investigated the impact of iron oxide nanoparticles on the anaerobic sludge microbiota. It was shown there were three distinct microbial phases following addition of the nanoparticles: microbial stress and cell death of approximately one log order of magnitude, followed by microbial rewiring, and recovery. Furthermore, it was noted that cellular stress led to the establishment of intercellular nanotubes within the microbial biomass. Intercellular nanotube - mediated communication among genetically engineered microorganisms and ad hoc assembled co - cultures have been previously reported. This study presents evidence of intercellular nanotube formation within an environmental s le – i.e., anaerobic sludge microbiota subjected to stress. Our observations suggested a mode of microbial communication in the anaerobic digestion process not previously explored and which may have implications on bioreactor design and microbial functions.
Publisher: Elsevier BV
Date: 04-2017
DOI: 10.1016/J.BIORTECH.2016.12.113
Abstract: The effects of a biodegradable chelating agent, Ethylenediamine-N,N'-disuccinic acid (EDDS), on the speciation and bioavailability of iron (Fe
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.1016/J.WATRES.2008.04.012
Abstract: A novel 2-sludge 3-stage process using a combination of granular sludge and biofilm was developed to achieve biological removal of nitrogen and phosphorus from nutrient-rich wastewater. The system consists of a granular sequencing batch reactor (SBR) working under alternating anaerobic/anoxic conditions supplemented with a short aerobic phase and an aerobic biofilm SBR. The wastewater is first fed to the granular SBR reactor, where easily biodegradable carbon sources are taken up primarily by polyphosphate accumulating organisms (PAOs). The supernatant resulting from quick settling of the granular sludge is then fed to the biofilm SBR for nitrification, which produces oxidized nitrogen that is returned to the granular reactor for simultaneous denitrification and phosphorus removal. While maximizing the utilization of organic substrates and reducing operational costs, as do other 2-sludge processes previously reported in literature, the proposed system solves the bottleneck problem of traditional 2-sludge systems, namely high effluent ammonia concentration, due to its high-volume exchange ratios. An ammonia oxidation rate of 32 mg N/Lh was achieved in the biofilm SBR, which produced nitrite as the final product. This nitrite stream was found to cause major inhibition on the anoxic P uptake and also to result in the accumulation of N(2)O. These problems were solved by feeding the nitrite-containing stream continuously to the granular reactor in the anoxic phase. With a nitrogen and phosphorus removal efficiency of 81% and 94%, respectively, the system produces an effluent that is suitable for land irrigation from a wastewater stream containing 270 mg N/L of total nitrogen and 40 mg P/L of total phosphorus.
Publisher: Elsevier BV
Date: 2016
Publisher: Elsevier BV
Date: 09-2018
DOI: 10.1016/J.CHEMOSPHERE.2018.04.170
Abstract: This study aims to investigate the effects of solid retention times (SRTs) on hydrogen production via thermophilic alkaline fermentation of waste activated sludge. The reactor was subjected to a SRT from 10 to 6 days during approximately 82 days of operation. The results revealed that SRT had minor influence on hydrolysis and hydrolysis efficiency in different phases were from 48.11% to 50.55%. Nevertheless, the efficiency of acidogenesis process was highly related to SRT and longer SRT could enhance the acidogenesis. On the other hand, acidogenesis efficiency was also related to H
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier BV
Date: 04-2016
DOI: 10.1016/J.JES.2015.06.015
Abstract: This study investigated the degradation and production of volatile fatty acids (VFAs) in the acidogenic phase reactor of a two-phase anaerobic system. 20 mmol/L bromoethanesulfonic acid (BESA) was used to inhibit acidogenic methanogens (which were present in the acidogenic phase reactor) from degrading VFAs. The impact of undissociated volatile fatty acids (unVFAs) on "net" VFAs production in the acidogenic phase reactor was then evaluated, with the exclusion of concurrent VFAs degradation. "Net" VFAs production from glucose degradation was partially inhibited at high unVFAs concentrations, with 59%, 37% and 60% reduction in production rates at 2190 mg chemical oxygen demand (COD)/L undissociated acetic acid (unHAc), 2130 mg COD/L undissociated propionic acid (unHPr) and 2280 mg COD/L undissociated n-butyric acid (unHBu), respectively. The profile of VFAs produced further indicated that while an unVFA can primarily affect its own formation, there were also unVFAs that affected the formation of other VFAs.
Publisher: Elsevier BV
Date: 06-2017
Publisher: Elsevier BV
Date: 12-2017
DOI: 10.1016/J.CHEMOSPHERE.2017.09.049
Abstract: This study developed an innovative A-B process for enhanced nutrients removal in municipal wastewater reclamation, in which a micro-aerated moving bed biofilm reactor served as A-stage and a step-feed sequencing batch reactor (SBR) as B-stage. In the A-stage, 55% of COD and 15% of ammonia nitrogen was removed, while more than 88% of the total nitrogen was removed via nitritation and denitritation, together with 93% of phosphorous removal at the B-stage where ammonia oxidizing bacteria activity was significantly higher than nitrite oxidizing bacteria activity. Meanwhile substantial phenotype of polyphosphate accumulating organisms (PAOs) was also observed in the B-stage SBR. Fluorescence in situ hybridization revealed that Accumulibacter was the dominant PAOs with undetectable Competibacter. Compared to the conventional activated sludge process, the proposed A-B process could offer a more cost-effective alternative for enhanced biological nutrients removal from municipal wastewater with less energy consumption.
Publisher: Elsevier BV
Date: 10-2011
DOI: 10.1016/J.WATRES.2011.06.025
Abstract: Nitrite is known to accumulate in wastewater treatment plants (WWTPs) under certain environmental conditions. The protonated form of nitrite, free nitrous acid (FNA), has been found to cause severe inhibition to numerous bioprocesses at WWTPs. However, this inhibitory effect of FNA may possibly be gainfully exploited, such as repressing nitrite oxidizing bacteria (NOB) growth to achieve N removal via the nitrite shortcut. However, the inhibition threshold of FNA to repress NOB (∼0.02 mg HNO2-N/L) may also inhibit other bioprocesses. This paper reviews the inhibitory effects of FNA on nitrifiers, denitrifiers, anammox bacteria, phosphorus accumulating organisms (PAO), methanogens, and other microorganisms in populations used in WWTPs. The possible inhibition mechanisms of FNA on microorganisms are discussed and compared. It is concluded that a single inhibition mechanism is not sufficient to explain the negative impacts of FNA on microbial metabolisms and that multiple inhibitory effects can be generated from FNA. The review would suggest further research is necessary before the FNA inhibition mechanisms can be more effectively used to optimize WWTP bioprocesses. Perspectives on research directions, how the outcomes may be used to manipulate bioprocesses and the overall implications of FNA on WWTPs are also discussed.
Publisher: Elsevier BV
Date: 03-2017
DOI: 10.1016/J.CHEMOSPHERE.2016.12.053
Abstract: The effect of zinc oxide nanoparticles (ZnO NPs) on the performance of an anoxic-aerobic submerged membrane bioreactor (MBR), and the characterization of the soluble microbial products (SMPs) produced in the presence of ZnO NPs was evaluated. Continuous operation over 144 days showed that ZnO NPs at concentrations of 10 and 50 mg/L exerted a negative impact on chemical oxygen demand (COD) and nitrogen removal, although ZnO NPs were efficiently removed in the MBR (>92%). 10 and 50 mg/L ZnO NPs decreased COD removal substantially from 93.1± 0.6% to 90.1± 0.8% (<0.05) and 86.3± 2.3% (<0.05), respectively. Similarly, with 10 and 50 mg L ZnO NPs, the decreased in NH
Publisher: Elsevier BV
Date: 03-2020
Publisher: Wiley
Date: 15-03-2021
DOI: 10.1111/GEB.13270
Publisher: Elsevier BV
Date: 02-2020
DOI: 10.1016/J.WATRES.2019.115255
Abstract: Biochar derived from enhanced biological phosphorus removal (EBPR) sludge could be a potential phosphorus (P) fertilizer. Soil microorganisms play a regulating role on the turnover of P in soil. When the EBPR sludge biochar is added to soil, it would inevitably interact with soil microorganisms. Thus, for the wise use of the EBPR sludge biochar, it is imperative to understand the interaction between the biochar and soil microorganisms. In this study, Pseudomonas putida (P. putida), a common soil microorganism, was applied to investigate the biotransformation of P in two EBPR sludge biochars. The results reveal that P released from biochar produced at 700 °C (E700) was more easily absorbed by P. putida than that released from biochar produced at 400 °C (E400). This is attributed to the higher polyphosphates (poly-P) content in E700 and poly-P has higher affinity to P. putida surface compared to orthophosphates. Furthermore, E400 has a negative effect on intracellular poly-P formation in P. putida, which is probably caused by the oxidative stress induced by the free radicals from E400. As intracellular poly-P plays a critical role on bacteria survival and their interaction with surrounding environment, high-temperature biochar (E700) in this case would be more suitable for soil remediation.
Publisher: Wiley
Date: 19-10-2022
DOI: 10.1111/WEJ.12754
Abstract: The study investigated the effect of hydrodynamic conditions on the formation of enhanced biological phosphorus removal (EBPR) granular sludge without losing the EBPR capacity, and its structure. The effect of hydrodynamic conditions on the formation of EBPR granular sludge was evaluated by using the minimum settling velocity, ( V s ) min , and superficial air velocity. The application of ( V s ) min strategy was proved to be beneficial in maintaining granular biomass without losing the EBPR capacity. Microscale structure, the chemical composition and chemically stored phosphorus of the matured EBPR granular sludge were determined by using ESEM‐EDX and cold perchloric acid (PCA) analyses. The results of both the ESEM‐EDX and PCA analyses proved that the poly‐P granules were stored extracellular in EPS structure of EBPR granular sludge. Therefore, the EBPR granular sludge has a high potential for both removal and recovery of phosphorus from wastewater, which needs to be investigated in future studies.
Publisher: Elsevier BV
Date: 10-2018
Publisher: IWA Publishing
Date: 03-2013
DOI: 10.2166/WCC.2013.117
Abstract: In recent years, the operating cost of sewage treatment plants (STPs) in some parts of the world has been rising due to increases in the cost of energy. STPs have focused on energy reduction and recovery from treatment processes in order to lower energy consumption. The development involves the improvement of capital set-up for treatment plants in terms of equipment upgrading lant sizing as well as exploration of novel technologies for sewage, excess sludge treatment and biogas recovery. This review compares the current technologies applied in STPs around the world and discusses these technologies and facilities which may enhance energy reduction and recovery in sewage treatment.
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.BIORTECH.2015.10.083
Abstract: This study investigates alkali-solubilized dissolved organic matter (DOM) and its fate in the anaerobic treatment process. DOM was fractionated into high molecular weight (HMW) protein-like substances (PL), HMW saccharide-like substances (SL), low molecular weight (LMW) PL, LMW SL, and humic acid-like substances (HAL). The results indicate alkali-solubilized DOM is primarily composed of LMW PL, HMW SL, and HAL. Alkaline pretreatment improved the overall anaerobic degradability of DOM in sludge (removal efficiency of total DOM increased by 28.4%). However, certain DOM fractions (mainly HMW PL and HAL) exhibited low degradability during anaerobic treatment, primarily caused by the low degradability of aromatic groups (such as aromatic amine groups from tryptophan-like PL). Alkaline pretreatment also resulted in an increase of residual DOM, which is mainly composed of HAL (52.9%) and HMW SL (49.9%).
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.BIORTECH.2019.121621
Abstract: Sludge fermentation liquid (FL) is a promising and sustainable carbon source for biological denitrification. In this study, four types of FLs were prepared using different chemical treatments to enhance denitrification. The profile of effluent organic matter (EfOM) were evaluated. Results indicate that the FL
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 02-2016
DOI: 10.1016/J.CHEMOSPHERE.2015.10.035
Abstract: This study reports on biomass tolerance towards high concentrations of acetic acid (HAc) within the system. Biomass from the second stage of a two-stage anaerobic sludge digestion system was used for this study. Microbial community analysis by 454 pyrosequencing highlighted hydrogenotrophic Methanomicrobiales was the predominant archaeal population in the second stage (>99% of the total archaeal community). Second stage biomass degraded HAc up to 4200 mg HAc L(-1) without observable lag phase. However, at HAc-shock loading of 7400 mg HAc L(-1), it showed a one day lag phase associated with decreased biomass activity. After stepwise HAc-acclimation over 27 d, the biomass degraded HAc of up to 8200 mg HAc L(-1) without observable lag phase. The dominance of Methanomicrobiales had remained unchanged in proportion - while the total archaeal population increased during acclimation. This study showed stepwise acclimation could be an approach to accommodate HAc accumulation and hence higher concentrations resulting from an enhanced first stage.
Publisher: Elsevier BV
Date: 04-2022
Publisher: Springer Science and Business Media LLC
Date: 02-2015
DOI: 10.1007/S00253-015-6423-6
Abstract: The deammonification process combining partial nitritation and anaerobic ammonium oxidation has been considered as a viable option for energy-efficient used water treatment. So far, many full-scale sidestream deammonification plants handling high-ammonia used water have been in successful operation since Anammox bacteria were first discovered in the 1990s. However, large-scale application of this process for treating municipal used water with low ammonia concentration has rarely been reported. Compared to the sidestream deammonification process, the mainstream deammonification process for municipal used water treatment faces three main challenges, i.e., (i) high COD/N ratio leading to denitrifiers outcompeting Anammox bacteria, (ii) numerous difficulties in selective retention of ammonia-oxidizing bacteria (AOB) over nitrite-oxidizing bacteria (NOB), and (iii) sufficient accumulation of Anammox bacteria. Therefore, this paper attempts to provide a detailed analysis of these challenges and possible solutions towards sustainable mainstream deammonification process.
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.CHEMOSPHERE.2017.06.110
Abstract: The formation, composition and characteristics of soluble microbial products (SMPs) were investigated in a novel system which coupled a sequencing batch reactor with a cake filtration system. Both suspended solids (SS) and turbidity were significantly removed, resulting in effluent SS of 0.12 mg L
Publisher: American Society for Microbiology
Date: 26-08-2021
DOI: 10.1128/AEM.01110-21
Abstract: The viable but nonculturable (VBNC) state is known to affect the culturability and activity of microorganisms. However, limited studies have been conducted to investigate the VBNC state of other pollutant degraders, such as fungi.
Publisher: American Chemical Society (ACS)
Date: 08-11-2013
DOI: 10.1021/ES404514G
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.ENVRES.2019.108781
Abstract: Cetyl trimethyl ammonium bromide (CTAB), Tween 20, polyvinyl pyrrolidone (PVP) and polyethylene glycol (PEG) are among the commonly used surfactants and polymers to stabilize silver nanoparticles (AgNPs). However, their interactions with AgNPs are different. The impact of these surfactants and polymers on the colloidal stability of freshly synthesized uncoated AgNPs was evaluated through a series of long-term experiments and analyzed in terms of their physical and chemical behavior. The cationic surfactant, CTAB was able to produce a mono modal particle size distribution in a prolonged period without affecting the dissolution. In the presence of Tween 20, a non-ionic surfactant, dissolution was promoted in the long run and the particles were preserved with minimal aggregation. In the presence of the polymers, PVP and PEG, the particle structure was not affected even though dissolution was observed. This study presents important insights on the interactions of AgNPs with surfactants and polymers, which could significantly affect the transformations and fate of AgNPs in the aquatic environment.
Publisher: Informa UK Limited
Date: 17-06-2021
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.WATRES.2018.10.031
Abstract: The sulfonamide antibiotics sulfamethoxazole (SMX) has been frequently detected in the wastewater. It has been reported that part of SMX can be transformed by the co-metabolism of ammonia oxidizing bacteria (AOB) during nitrifying process. However, previous studies reported inconsistent or even contradictory results in terms of SMX degradation and/or transformation. Literature study revealed that nitrite may play certain role in SMX transformation, which has been neglected previously. In this study, the transformation behavior of SMX was investigated with and without the presence of nitrite in an enriched nitrifying culture. The results clearly show that the elimination of SMX occurred with the presence/accumulation of nitrite, and a linear regression was observed between SMX elimination efficiency and free nitrous acid (FNA) concentration, indicating that FNA was the major factor responsible for the SMX transformation. By reacting with FNA, SMX transformation products, such as 4-nitro-SMX, desamino-SMX and hydroxylated SMX, were detected. However, when FNA concentration decreased, these intermediates may be retransformed back to SMX. These findings improved our understanding on SMX transformation in a biological system and highlighted the role of nitrite/FNA in the sulfonamide antibiotics degradation.
Publisher: Springer Science and Business Media LLC
Date: 16-01-2014
Publisher: Wiley
Date: 16-06-2014
Abstract: In this work, a novel waste-to-resource strategy to convert waste bacteria into a useful class of cathode materials, lithium metal phosphate (LiMPO4 M = Fe, Mn), is presented. Escherichia coli (E. coli) bacteria used for removing phosphorus contamination from wastewater are harvested and used as precursors for the synthesis of LiMPO4. After annealing, LiFePO4 and LiMnPO4 nanoparticles with dimensions around 20 nm are obtained. These particles are found to be enveloped in a carbon layer with a thickness around 3-5 nm, generated through the decomposition of the organic matter from the bacterial cell cytoplasm. The battery performance for the LiFePO4 is evaluated. A high discharge capacity of 140 mAh g(-1) at 0.1 C with a flat plateau located at around 3.5 V is obtained. In addition, the synthesized particles display excellent stability and rate capabilities. Even under a high C rate of 10 C, a stable discharge capacity of 75.4 mAh g(-1) can still be achieved.
Publisher: Elsevier BV
Date: 08-2020
Publisher: Elsevier BV
Date: 2022
DOI: 10.1016/J.BIORTECH.2021.126248
Abstract: Thermal hydrolysis pretreatment (THP), as a step prior to sludge anaerobic digestion (AD), is widely applied due to its effectiveness in enhancing organic solids hydrolysis and subsequent biogas productivity. However, THP also induces a series of problems including formation of refractory compounds in THP cylinder, high residual ammonia and organic in the AD centrate, inhibition on downstream nitrogen removal process and reduction in UV-disinfection effectiveness during post-treatment. More attention should be paid on how to mitigate these negative effects. Despite intensive studies were carried out to reduce refractory compounds formation and enhance biological performance, there is limited effort to discuss the solutions to tackle the THP associated problems in a holistic manner. This paper summarizes the solutions developed to date and analyzes their technology readiness to assess application potential in full-scale settings. The content highlights the limitations of THP and proposes potential solutions to address the technological challenges.
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 08-2015
DOI: 10.1016/J.BIORTECH.2015.04.087
Abstract: Sludge fermentation between pH 4 and 11 was investigated to generate volatile fatty acids (VFA). Despite the highest sludge solubilization of 25.9% at pH 11, VFA accumulation was optimized at pH 8 (12.5% out of 13.1% sludge solubilization). 454 pyrosequencing identified wide ersity of acidogens in bioreactors operated at the various pHs, with Tissierella, Petrimonas, Proteiniphilum, Levilinea, Proteiniborus and Sedimentibacter enriched and contributing to the enhanced fermentation at pH 8. Hydrolytic enzymatic assays determined abiotic effect to be the leading cause for improved solubilization under high alkaline condition but the environmental stress at pH 9 and above might lead to disrupt biological activities and eventually VFA production. Furthermore, molecular weight (MW) characterization of the soluble fractions found large MW aromatic substances at pH 9 and above, that is normally associated with poor biodegradability, making them disadvantageous for subsequent bioprocesses. The findings provided information to better understand and control sludge fermentation.
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.BIORTECH.2022.127574
Abstract: The ecological roles of microbial communities and how they interact with each other in thermal hydrolysis process (THP) assisted thermophilic anaerobic digestion (THP-AD) reactors remain largely unknown, especially under propionate stress. Two thermophilic THP-AD reactors had methane yield of 240-248 mL/g VS
Publisher: Elsevier BV
Date: 08-2017
Publisher: Elsevier BV
Date: 04-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CY00529F
Abstract: Simple construction of WO 3 –g-C 3 N 4 Z-scheme heterojunctions as efficient photocatalysts to degrade sulfamethoxazole, which is one of the most commonly used pharmaceuticals.
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.WATRES.2016.09.030
Abstract: This study investigated the mechanism and effects of ultrasonic pretreatment followed by acidification on sludge dewaterability through looking at the changes of extracellular polymeric substances (EPS) content, composition and stratification. The results suggested sludge filterability was closely correlated with quantity of protein (R = 0.94, p < 0.01) and polysaccharide (R = 0.97, p < 0.01) present in loosely bound EPS rather than in soluble and tightly bound EPS. The fractions of polymers, especially tryptophan-like proteins and microbial by-product like material at molecular weight of 10
Publisher: Elsevier BV
Date: 09-2017
DOI: 10.1016/J.CHEMOSPHERE.2017.04.151
Abstract: A quorum quenching (QQ) consortium comprised of both acyl homoserine lactones (AHLs)- and autoinducer-2 (AI-2)-degrading bacteria, either immobilized in polymer-coated alginate beads or in liquid suspension, was examined for fouling control in lab-scale MBRs under both steady and changing organic loading rates (OLRs). Under steady conditions the QQ consortium retarded biofouling by a factor of 3. However, a continuous increase in OLR vastly reduced the effectiveness of QQ bacteria the biofouling was retarded only by factors of 1.4-1.8. A significant increase in extracellular polymeric substance (EPS), especially loosely-bound EPS in mixed liquor together with an increase in polysaccharide content up to 4 times in EPS resulted from the increase in OLR, was attributed to the impaired QQ efficacy. In control MBRs, cake layer resistance was the major factor (>60%) contributing to the increased trans-membrane pressure, as compared with pore blockage resistance and intrinsic membrane resistance. In contrast, the pore blockage resistance became dominant in QQ MBRs (>40%).
Publisher: American Chemical Society (ACS)
Date: 29-04-2020
Publisher: American Chemical Society (ACS)
Date: 15-04-2021
Publisher: Elsevier BV
Date: 08-2012
Publisher: IWA Publishing
Date: 05-05-2016
DOI: 10.2166/WST.2016.214
Abstract: The combination of simultaneous nitrification-denitrification (SND) with enhanced biological phosphorus removal (EBPR) provides a more efficient and economically viable option for nutrient removal from municipal wastewater compared to conventional two-step nitrification-denitrification. This study analyzed the nutrients (N and P) profiles in a full-scale municipal wastewater reclamation plant (WRP) located in the tropical region, in which more than 90% of nitrogen was removed. Interestingly, average SND efficiency in aerobic zones was found to be up to 50%, whereas phosphorus profile displayed a clear cyclic release and uptake pattern with a phosphorus removal efficiency of up to 76%. The capability of sludge to perform SND and EBPR was further confirmed through a series of batch experiments. Microbial analysis revealed the presence of Accumulibacter and Tetrasphaera phosphate accumulating organisms in the plant, while few glycogen accumulating organisms (GAO) was observed. This study showed the significant occurrence of combined SND and EBPR, known as simultaneous nitrification, denitrification and phosphorus removal (SNDPR), in the studied WRP under warm climate. The possible causes behind the observed SNDPR were also discussed.
Publisher: American Chemical Society (ACS)
Date: 28-07-2020
Abstract: Limited studies have attempted to evaluate pharmaceutical removal during the sidestream partial nitritation (PN) process. In this work, atenolol biodegradation by PN cultures was investigated by maintaining ammonium and pH at different levels. For the first time, free nitrous acid (FNA), other than ammonium, pH, and free ammonia, was demonstrated to inhibit atenolol removal, with biodegradation efficiencies of ∼98, ∼67, and ∼28% within 6 days at average FNA levels of 0, 0.03, and 0.19 mg-N L
Publisher: Elsevier BV
Date: 04-2022
DOI: 10.1016/J.SCITOTENV.2021.151758
Abstract: Nitrogen removal via anammox is a promising and sustainable solution in mainstream wastewater treatment. To maintain stable anammox process, competitors of anammox bacteria should be suppressed while cooperators need to be favoured. This study demonstrated a synchronous aerobic and anaerobic ammonium removal process in a membrane aerated biofilm reactor (MABR) under minimal lumen pressure. By adjusting the lumen pressure, aerobic and anaerobic ammonium oxidation rate can be synchronized to minimize interference of nitrite oxidizing bacteria (NOB) by limiting NOB's access to both oxygen and nitrite. Long-term performance indicated that PN/A in MABR could be achieved at zero positive aeration pressure. Furthermore, by connecting two MABRs in series, high total nitrogen (TN) removal efficiency of 71.1% ± 5.3% was attained with a TN removal rate of 30.1 ± 3.2 mg-N/L/d. The organic carbon present in the wastewater reduced the nitrate concentration in the effluent while not affecting the overall nitrogen removal efficiency and rate. Real-time qPCR analysis suggested that the abundance of amoA gene was relatively stable while K-strategist Nitrospira 16S rRNA gene did not surge in the long-term operation. High throughput sequencing showed that Candidatus Brocadia and uncultured anaerobic ammonium oxidizing bacteria from Chloroflexi were the most abundant anammox taxa. Denitrifiers, such as Denitratisoma may be responsible to reduce the nitrate in the effluent.
Publisher: Springer Science and Business Media LLC
Date: 18-04-2016
DOI: 10.1007/S00253-016-7518-4
Abstract: Enhanced biological phosphorus removal (EBPR) process is one of the most economical and sustainable methods for phosphorus removal from wastewater. However, the performance of EBPR can be affected by available carbon sources types in the wastewater that may induce different functional microbial communities in the process. Glycogen accumulating organisms (GAOs) and polyphosphate accumulating organisms (PAOs) are commonly found by coexisting in the EBPR process. Predominance of GAO population may lead to EBPR failure due to the competition on carbon source with PAO without contributing phosphorus removal. Carbon sources indeed play an important role in alteration of PAOs and GAOs in EBPR processes. Various types of carbon sources have been investigated for EBPR performance. Certain carbon sources tend to enrich specific groups of GAOs and/or PAOs. This review summarizes the types of carbon sources applied in EBPR systems and highlights the roles of these carbon sources in PAO and GAO competition. Both single (e.g., acetate, propionate, glucose, ethanol, and amino acid) and complex carbon sources (e.g., yeast extract, peptone, and mixed carbon sources) are discussed in this review. Meanwhile, the environmental friendly and economical carbon sources that are derived from waste materials, such as crude glycerol and wasted sludge, are also discussed and compared.
Publisher: Elsevier BV
Date: 10-2015
DOI: 10.1016/J.JES.2015.02.017
Abstract: 2-Phase anaerobic digestion (AD), where the acidogenic phase was operated at 2day hydraulic retention time (HRT) and the methanogenic phase at 10days HRT, had been evaluated to determine if it could provide higher organic reduction and methane production than the conventional single-stage AD (also operated at 12days HRT). 454 pyrosequencing was performed to determine and compare the microbial communities. The acidogenic reactor of the 2-phase system yielded a unique bacterial community of the lowest richness and ersity, while bacterial profiles of the methanogenic reactor closely followed the single-stage reactor. All reactors were predominated by hydrogenotrophic methanogens, mainly Methanolinea. Unusually, the acidogenic reactor contributed up to 24% of total methane production in the 2-phase system. This could be explained by the presence of Methanosarcina and Methanobrevibacter, and their activities could also help regulate reactor alkalinity during high loading conditions through carbon dioxide production. The enrichment of hydrolytic and acidogenic Porphyromonadaceae, Prevotellaceae, Ruminococcaceae and unclassified Bacteroidetes in the acidogenic reactor would have contributed to the improved sludge volatile solids degradation, and ultimately the overall 2-phase system's performance. Syntrophic acetogenic microorganisms were absent in the acidogenic reactor but present in the downstream methanogenic reactor, indicating the retention of various metabolic pathways also found in a single-stage system. The determination of key microorganisms further expands our understanding of the complex biological functions in AD process.
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.WATRES.2017.06.024
Abstract: Biomaterials recovery from wasted activated sludge has become an increasing interesting research topic. The purpose of this study was to systemically evaluate different sludge disintegration methods (ultrasonic, alkaline, and thermal treatments) for protein solubilisation from waste activated sludge (WAS). Compared to control without treatment, the soluble protein concentration increased by 11, 23 and 12 times under the optimal treatment conditions (ultrasonic treatment of 1 W mL
Publisher: Elsevier BV
Date: 03-2016
DOI: 10.1016/J.BIOTECHADV.2015.12.006
Abstract: Trace metals are essential for the growth of anaerobic microorganisms, however, in practice they are often added to anaerobic digesters in excessive amounts, which can lead to inhibition. The concept of bioavailability of metals in anaerobic digestion has been poorly understood in the past, and a lack of deep understanding of the relationship between trace metal speciation and bioavailability can result in ineffective metal dosing strategies for anaerobic digesters. Sequential extraction schemes are useful for fractionating trace metals into their different forms, and metal sulfides can serve as a store and source for trace metals during anaerobic digestion, while natural/synthetic chelating agents (soluble microbial products-SMPs, extracellular polysaccharides-EPS, and EDTA/NTA) are capable of controlling trace metal bioavailability. Nevertheless, more work is needed to: investigate the speciation and bioavailability of Ca, Mg, Mn, W, and Se compare the bioavailability of different forms of trace metals e.g. carbonates, sulfides, phosphates to different anaerobic trophic groups determine what factors influence metal sulfide dissolution investigate whether chelating agents can increase trace metal bioavailability develop and adapt specialized analytical techniques, and determine how trace metal dynamics change in an anaerobic membrane bioreactor (AnMBR).
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.CHEMOSPHERE.2016.06.112
Abstract: In this study, a fed-batch acidogenic reactor was operated at a 3 d hydraulic retention time (HRT) and fed with alkaline pre-treated sludge to investigate salinity effects on methanogens' abundance, activities and their consumption of produced acetic acid (HAc) and total volatile fatty acids (VFAs). The salinity concentration was increased step-wise by adding sodium chloride. At 3‰ (parts per thousand) salinity, the average produced volatile fatty acids (VFAs) concentration was 2410.16 ± 637.62 mg COD L(-1) and 2.70 ± 0.36 L methane was produced daily in the acidogenic reactor. Further batch tests indicated methanogens showed a HAc degradation rate of 3.81 mg COD g(-1) VSS h(-1) at initial HAc concentration of 1150 mg COD L(-1), and showed tolerance up to 16‰ salinity (3.76 g Na(+) L(-1)) as indicated by a constant HAc degradation rate. The microbiological study indicated this can be related to the predominance of acetate-utilizing Methanosarcinaceae and Methanomicrobiales in the reactor. However, with salinity increased to 20‰ and 40‰, increases in VFAs and HAc production and decreases in methane production, methanogens population, acidogenic bacteria population and acidification extent were observed. This study demonstrated presence of acetate-utilizing methanogens in an acidogenic reactor and their high tolerance to salinity, as well as their negative impacts on net VFAs production. The results would suggest the presence of methanogens in the acidogenic reactor should not be ignored and the recovery of methane from the acidogenic reactor needs to be considered to avoid carbon loss.
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.WATRES.2022.118332
Abstract: Anaerobic digestion (AD) has been widely employed for wastewater and organic waste treatment, in which methanogenesis is highly driven by close microbial interactions among intricate microbial communities. However, the ecological processes underpinning the community assembly that support methanogenesis in such engineered ecosystems remain largely unknown, especially when exposed to challenging circumstances (e.g., high temperature, ammonium content). Here, eight AD bioreactors were seeded with four different inocula (two from full-scale mesophilic AD systems and the other two from lab-scale mesophilic AD systems), and were operated under thermophilic conditions (55 °C) for treating thermal hydrolysis process (THP) pre-treated waste activated sludge to investigate how mesophilic community responds to thermophilic conditions during the long-term cultivation. Results showed that the inocula collected from the full-scale systems were more resilient than that from the lab-scale systems, which may be primarily attributed to indigenous robust methanogens. As a result, the former efficiently generated methane which was predominantly contributed by Methanothermobacter and Methanosarcina (healthy AD ecosystem), while methanogenic activity was remarkably prohibited in the latter (dysfunctional AD ecosystem). Thermophilic environment was a strong selection force, resulting in the convergence of microbial communities in both the healthy and dysfunctional AD ecosystems. Deterministic processes predominated the community assembly regardless of AD ecosystem function, but stronger influences of stochastic processes were observed in dysfunctional AD ecosystems, which was likely attributable from the stronger effect of immigrants from the feedstock. As indicated by molecular ecological network analysis, the microbial network structures in the healthy AD ecosystems were more stable than those in the dysfunctional AD ecosystems. Although keystone taxa were different among the bioreactors, most of which played vital roles in organic hydrolysis/fermentation. To sum up, this study greatly improved our understanding of the relationships between microbiological traits and AD ecosystem function under thermophilic conditions, which could provide useful information to guide thermophilic AD (e.g., THP-AD) start-up and health diagnosis during operation.
Publisher: Elsevier BV
Date: 07-2022
DOI: 10.1016/J.SCITOTENV.2022.154591
Abstract: Purple non‑sulfur bacteria (PNSB) based bioprocess has been developed to remove carbon, nitrogen and phosphorus from wastewater. However, the interactions of various bioconversion of carbon (C), nitrogen (N) and phosphorus (P) are not completely clear. In this study, a genome-centric metagenomic approach was employed to delineate the shift in microbial community structures and functional genes under light and dark conditions. Seven and 22 metagenomic assembled genomes (MAGs) were recovered from s les in light and dark conditions, accounting for a substantial portion of microbes. Under light, Rhodopseudomonas palustris promoted complex metabolic processes and interactions for C, N and P conversions. Burkholderia contaminans was discovered as new potential organisms for simultaneous C, N and P removal. Metagenomics analysis confirmed genes involved in the synthesis of glycogen, poly-β-hydroxybutyrate, poly-P, amino acids and carotenoids in R. palustris. The substrate transformation mechanisms and potential pathways were proposed according to the detected metabolites. Our findings provided insights into a new biological system with simultaneous C, N and P bioconversions, and improved the understanding of interactions among the key populations.
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 06-2018
Publisher: Springer Science and Business Media LLC
Date: 28-06-2017
DOI: 10.1007/S10529-017-2383-5
Abstract: To improve its phosphate accumulating abilities for phosphate recycling from wastewater, a magnetotactic bacterium, Magnetospirillum gryphiswaldense, was genetically modified to over-express polyphosphate kinase. Polyphosphate kinase was over-expressed in the bacterium. The recombinant strain accumulated ninefold more polyphosphate from synthetic wastewater compared to original wild type. The magnetic property of the recombinant M. gryphiswaldense strain was retained. The recombinant M. gryphiswaldense can be used for phosphate removal and recovery in bioremediation.
Publisher: Elsevier BV
Date: 02-2022
DOI: 10.1016/J.WATRES.2021.117900
Abstract: Thermal hydrolysis process (THP) assisted anaerobic digestion (AD) has been demonstrated to be an efficient approach to improve biogas production and solids reduction. Given the faster reaction kinetics in the THP-AD system, reduction of sludge retention time (SRT) is possible. However, a comprehensive understanding of the effects of sludge retention time (SRT) on microbial dynamics and community assemblages is still lacking in THP-AD systems. Thus, twelve THP-AD reactors were operated at different SRTs (10-30 d) to fulfill the knowledge gap. Results showed that, although all the bioreactors displayed good performance, shorter SRT reactors (SRT 10 d) took a longer time to reach the stable state. The total biogas production at SRT of 10 d was lower than that at other longer SRTs, attributing to the limited hydrolytic/fermentative capacities of AD microbiomes. Different SRTs resulted in distinct succession patterns of AD microbiomes. THP sludge reduced the microbial ersity in all the bioreactors over time, but longer SRTs maintained higher bio ersity. Null model analysis suggested that THP-AD microbial community assembly was predominately driven by deterministic selection at the tested SRT range, but stochasticity increased with elevated SRTs, likely attributing to the immigrants from the feedstock. Phylogenetic molecular ecological networks (pMENs) analysis revealed more stable network structures at longer SRTs, evidenced by the lower modularity, shorter harmonic geodesic distance, and higher connectivity. The potential keystone taxa under varied SRTs were identified, some of which were hydrolytic/fermentative bacteria (e.g., Peptostreptococcus, Lutispora, Synergistaceae), suggesting that these species related to organic hydrolysis/fermentation even with low-abundance could still play pivotal ecological roles in maintaining the THP-AD microbial community structure and functions. Collectively, this study provides comprehensive and in-depth insights into the mechanisms underlying community assembly in THP-AD reactors, which could aid in diagnosing system stability.
Publisher: IWA Publishing
Date: 06-2015
DOI: 10.2166/WPT.2015.032
Abstract: The aerobic granular sludge process is a promising technology for wastewater treatment. The formation and structure of aerobic granules are traditionally thought to depend highly on selection pressures, while the underlying molecular mechanisms are unclear. It is well known that bacteria coordinate their behavior using small signaling molecules, known as quorum sensing (QS). This paper is an attempt to provide updated information on QS mechanisms governing granular sludge processes. It is shown that QS-mediated cellular communication has a significant role throughout aerobic granulation, including granule development, structural stability and integrity maintenance. Such understanding is helpful for developing novel aerobic granular sludge processes.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6RA09964E
Abstract: Silver modified 2D BiOCl showed excellent photocatalytic performance in degrading sulfanilamide and presented good antibacterial efficiency under visible light irradiation.
Publisher: Elsevier BV
Date: 03-2016
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.BIORTECH.2017.05.098
Abstract: This study examined the effects of a deficiency in trace metals (TMs) on the performance of a submerged anaerobic membrane bioreactor (SAMBR). When trace metals were excluded from the feed to the SAMBR, COD removal and methane yield reduced while VFAs in the effluent increased. A reduction of up to 37.48% in the total metal content in the reactor was observed, while the less bioavailable fractions increased up to 13.29%. Pulse addition of trace metals for 7 days at 5-times the daily metal loading was effective in improving the performance of the SAMBR by increasing the amount of trace metals in the bioavailable fractions from 2.12% to 11.92%, with up to 87.7% of added metals retained in the reactor within 24h. However, the second and third pulse at 5 and 10-times daily metal loading did not result in similar changes in metal speciation and might have inhibited the methanogens.
Publisher: Elsevier BV
Date: 10-2018
Publisher: Informa UK Limited
Date: 02-04-2015
DOI: 10.1080/09593330.2015.1025103
Abstract: In this study, low-energy ultrasonic (3 and 6 kJ/g volatile solids of feed biomass (FB) which was lower than the heat value of the FB), alkaline, and ultrasonic-alkaline pretreatments were applied on FB, a biosludge from secondary industrial wastewater treatment. Biochemical methane potential (BMP), particle size distribution, Biomass Stress Index (BSI™), soluble chemical oxygen demand (SCOD), protein, carbohydrate, and size-exclusion chromatography (SEC) fingerprints were used to comparatively study the mechanisms of these pretreatment methods. The results indicated that low-energy ultrasonication and alkali exhibited significantly different impacts on the FB. After ultrasonication with energy input of 6 kJ/g-VS, the average particle size of FB was reduced from 102.6 to 19.4 µm. However, ultrasonication had no obvious effect on microbial cells rupture, solubilization of protein and carbohydrate, and SEC fingerprint. Consequently, low-energy ultrasonication could not enhance methane generation. However, after alkaline pretreatment with dosage of 0.3 g-NaOH/g-VS, SCOD, soluble protein, and soluble carbohydrate concentration of FB increased from 0.66, 0.00, 0.07 to 2.83, 0.83, 0.47 g/L, respectively. At the same time, BSI™ increased from 5.3% to 96.8%, and the SEC fingerprint changed significantly. Consequently, the methane generation in the BMP test increased from 68.9 to 135.0 mL. Ultrasonic-alkaline pretreatment was similar to alkaline pretreatment in terms of methane generation. Based on this study, alkaline pretreatment is recommended over both low-energy ultrasonic and low-energy ultrasonic-alkaline pretreatment to enhance the biodegradability of FB.
Publisher: Elsevier BV
Date: 10-2019
DOI: 10.1016/J.SCITOTENV.2019.06.234
Abstract: Aquatic system is the major source of atmospheric methane. This study explored the influences of ferrihydrite, which is widely existed in natural aquatic system, on methane emission. Results showed that the presence of ferrihydrite led to 26.4% more methane emission. By tracking the transformation of organic compounds, it is revealed that the enhanced methane emission was attributed to greater hydrolysis and degradation of refractory compounds. More specifically, the remaining humic-like substances (HS) in ferrihydrite group (46.4 mg/L-C) were only half of that in control group (80.1 g/L-C) after 30-day incubation. The X-ray photoelectron spectroscopy spectrum confirmed the more active oxidation of organics occurred in ferrihydrite group. It was also found that ferrihydrite aided in sustaining microbial activity at stationary and starvation phases. Further study on microbial communities found that ferrihydrite promoted the enrichment of both functional and electroactive genera. This study provides insights into the greenhouse gas emission in natural environment.
Publisher: Elsevier BV
Date: 11-2018
Publisher: Elsevier BV
Date: 2016
Publisher: Elsevier BV
Date: 05-2017
DOI: 10.1016/J.WATRES.2017.02.051
Abstract: Many studies reported that it is challenging to apply enhanced biological phosphorus removal (EBPR) process at high temperature. Glycogen accumulating organisms (GAOs) could easily gain their dominance over poly-phosphate accumulating organisms (PAOs) when the operating temperature was in the range of 25 °C-30 °C. However, a few successful EBPR processes operated at high temperature have been reported recently. This study aimed to have an in-depth understanding on the impact of feeding strategy and carbon source types on EBPR performance in tropical climate. P-removal performance of two EBPR systems was monitored through tracking effluent quality and cyclic studies. The results confirmed that EBPR was successfully obtained and maintained at high temperature with a multi-cycle strategy. More stable performance was observed with acetate as the sole carbon source compared to propionate. Stoichiometric ratios of phosphorus and carbon transformation during both anaerobic and aerobic phases were higher at high temperature than low temperature (20±1 °C) except anaerobic PHA/C ratios within most of the sub-cycles. Furthermore, the fractions of PHA and glycogen in biomass were lower compared with one-cycle pulse feed operation. The microbial community structure was more stable in acetate-fed sequencing batch reactor (C2-SBR) than that in propionate-fed reactor (C3-SBR). Accumulibacter Clade IIC was found to be highly abundant in both reactors.
Publisher: Wiley
Date: 08-2021
DOI: 10.1111/WEJ.12745
Publisher: Elsevier BV
Date: 11-2019
DOI: 10.1016/J.CHEMOSPHERE.2019.07.001
Abstract: Ionic liquids (ILs) have attracted attention in recent years due to their "greener" properties compared to conventional organic solvents. However, they may still pose a risk to the environment as their toxicity is not fully understood. Bioremediation of such ILs can be an economically and environmentally friendly approach. Therefore, this study aims to examine the interaction of three ILs (1-dodecylpyridnium chloride [DPy]
Publisher: Elsevier BV
Date: 2020
DOI: 10.1016/J.BIORTECH.2019.122366
Abstract: Conventionally, activated carbon is widely applied in water treatment systems due to its capability of adsorbing inhibitors or stimulating methanogenesis rate. This study demonstrates that powder activated carbon (PAC) also stimulate hydrolysis in anaerobic digestion (AD) of thermal hydrolysis pretreated sludge. This is evidenced with 0.95-1.42 times higher methane generation, 12.46-20.06% higher volatile solids removal and greater refractory compounds degradation stimulated by PAC. Functional prediction reveals that genes coding hydrolytic enzymes and xenobiotics metabolism were highly expressed with the presence of PAC. Furthermore, the stimulated hydrolysis activity was effectively maintained at PAC concentration as low as 0.125 g/L, though methanogenesis rate reduced by 80.30% compared to 1 g/L case. This study reports the role of activated carbon on the hydrolysis which has been ignored previously and the impact of PAC on AD performance in long-term operation. The results improve understanding on the true function of PAC in AD system.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CY00110J
Abstract: A novel hybrid multifunctional g-C 3 N 4 –CuS nanocomposite photocatalyst was synthesized for H 2 evolution by integrating a g-C 3 N 4 nanosheet with hexagonal CuS nanoplates.
Publisher: Elsevier BV
Date: 06-2017
Publisher: Elsevier BV
Date: 09-2021
Publisher: Elsevier BV
Date: 2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9EN00861F
Abstract: The colloidal stability of silver nanoparticles (AgNPs) was evaluated using time-resolved dynamic light scattering, electrophoretic mobility and dissolved Ag concentration in the presence of electrolytes and extracellular polymeric substances (EPS).
Publisher: American Chemical Society (ACS)
Date: 12-12-2009
DOI: 10.1021/ES8024726
Abstract: Airborne styrene is a suspected human carcinogen, and traditional ways of mitigation include the use of adsorption technologies (activated carbon or zeolites) or thermal destruction. These methods presenttheir own shortcomings, i.e., adsorbents need to be regenerated or replaced regularly, and relatively large energy inputs are required in thermal treatment. Photocatalysis offers a potentially sustainable and clean means of controlling such fugitive emissions of styrene in air. The present study demonstrates a new type of well-characterized, highly thermostable titania-pillared clay photocatalysts for airborne styrene decomposition in a custom-designed fluidized-bed photoreactor. This photocatalytic system is found to be capable of destroying up to 87% of 300 ppmV airborne styrene in the presence of ultraviolet (UV) irradiation. The effects of relative humidity (RH: 0 or 20%) are also studied, together with the arising physical structures (in terms of porosity and surface characteristics) of the catalysts when subjected to relatively high calcination temperatures of 1000-1200 degrees C. Such a temperature range may be encountered, e.g., in flue gas emissions (1). It is found that relative humidity levels of 20% retard the degradation efficiencies of airborne styrene when using highly porous catalysts.
Publisher: Elsevier BV
Date: 07-2022
DOI: 10.1016/J.BIORTECH.2022.127310
Abstract: Two-stage Partial nitritation/Anammox (PN/A) was firstly performed for recalcitrant organics (RO)-rich thermal hydrolysis pretreated anaerobic digestion (THP-AD) centrate treatment with municipal wastewater (MW) as co-substrate. Results indicated the inhibitory effects of RO was alleviated and high nitrate issue in PN/A effluent was addressed by cotreatment strategy. Stable PN with nitrite accumulation ratio of 95% and N removal efficiency of 97.1% were well maintained at MW of 80%. Nevertheless, nitrate accumulation and anammox activity loss were observed with lowering MW proportion owing to the weakened denitrification activity and aggravated inhibitory effect. Microbial analysis revealed Nitrosomonas was the major ammonium oxidizing bacteria and the ideal PN performance was due to the effective out-selection of nitrite oxidizing bacteria. Candidatus Kuenenia was identified as the primary bacteria for nitrogen removal (82.7%), and the controlled abundance of heterotrophic denitrifiers in anammox system ensured the enhanced nitrogen removal regardless of high COD loading from THP-AD centrate.
Publisher: Elsevier BV
Date: 06-2019
DOI: 10.1016/J.WATRES.2019.03.029
Abstract: Quorum quenching (QQ) is an effective method to control membrane biofouling in aerobic membrane bioreactors (AeMBRs). However, it is not clear if QQ is feasible in an anaerobic membrane bioreactor (AnMBR). In this study, Microbacterium. sp that has QQ capability was embedded in alginate beads, known as QQ beads (QQB), and applied in a lab-scale AnMBR to investigate their potential in fouling control. With the addition of QQB, the operating period of AnMBR-QQB reactor was prolonged by about 8-10 times at constant flux operation before reaching the pre-set maximum transmembrane pressure (TMP). The concentration of Acyl-homoserine lactones (AHLs) in the bulk liquid was significantly higher during the 'TMP jump' period compared to QQB and control phases, while AHLs in the membrane foulants were remarkably lower in QQB phase compared to control phase. Furthermore, a much lower level of soluble microbial production (SMP) was observed in QQB phases. Extracellular polymeric substance (EPS), protein in particular, was reduced by 39.73-80.58% in the cake layer of the membrane from QQB phases. Significant changes of organic functional groups were observed in cake layer from QQB membrane as compared with that from control membrane. At the end of operation, bio-polymer (BP), building blocks (BB) and low molecular weight (LMW) organic matters increased in the foulant from control phases but such increase was not observed in QQB phase. After long-term operation, revival of QQB is required due to the declined activity for AHLs degradation.
Publisher: Elsevier BV
Date: 03-2020
DOI: 10.1016/J.WATRES.2020.115476
Abstract: This study proposed an integrated process for biogas generation and biochar production from thermal hydrolysis pretreated sludge (THP sludge). In this study, the liquid and solids fractions of THP sludge were separately processed for the first time. The liquid fraction of THP sludge (THP-L) reached the biodegradability (262.6 ± 5.1 mL CH
Publisher: American Chemical Society (ACS)
Date: 28-01-2014
DOI: 10.1021/ES500307B
Publisher: IWA Publishing
Date: 05-03-2019
DOI: 10.2166/WPT.2019.020
Abstract: The objective of this study was to establish a demo-scale plant with 1,000 cubic metres per day (CMD) capacity to recycle industrial wastewater from a semiconductor industry. In this study, two wastewater streams from continuous electrodeionization (CEDI) and local scrubber (LS)/controlled decomposition and oxidation (CDO) with flow rate of 1,335 CMD and 1,012 CMD respectively were chosen to be recycled. For the CEDI reject reclaim system, boron selective resin (BSR) and activated carbon filter (ACF) were utilized to remove boron and total organic carbon (TOC) respectively. The water quality was good enough to be used as ultrapure water (UPW) supply. For the CDO reclaim system, the combination of ACF + ultrafiltration (UF) + reverse osmosis (RO) under high pH condition was implemented to recycle the local scrubber wastewater (LSW) for cooling tower top up. Product water from both treatment systems was able to meet the target water specifications. The average cost saving was S$0.91/m3 of reclaimed water produced.
Publisher: American Chemical Society (ACS)
Date: 30-08-2022
Abstract: Fe
Publisher: Springer Science and Business Media LLC
Date: 06-08-2019
DOI: 10.1007/S00253-019-10070-3
Abstract: Anaerobic ammonium oxidation (anammox) is an important scientific discovery in the field of wastewater treatment. This process is a sustainable option in nitrogen removal due to its energy-efficient and cost-effective advantage. Great effort has been made recently to remove ammonium from industrial and municipal wastewater via the anammox process with a preceding partial nitrification (PN) converting part of NH
Publisher: Informa UK Limited
Date: 07-02-2019
DOI: 10.1080/17435390.2018.1548667
Abstract: Silver nanoparticles (AgNP) undergo various transformations into different Ag species in the environment, which determines their toxicity in microorganisms. In aerobic condition, AgNPs release Ag
Publisher: Elsevier BV
Date: 07-2012
DOI: 10.1016/J.BIORTECH.2012.03.111
Abstract: The response of free nitrous acid (FNA)-adapted poly-phosphate accumulating organisms (PAOs) to FNA inhibition under aerobic and anoxic conditions was studied. Anoxic P-uptake was 1-6 times more sensitive to the inhibition compared to aerobic P-uptake. The aerobic nitrite reduction rate increased with FNA concentration, accompanied by an equivalent decrease in the oxygen uptake rate, suggesting under high FNA concentration conditions, electrons were channeled to nitrite reduction from oxygen reduction. In contrast, the nitrite reduction rate decreased with increased FNA concentration under anoxic conditions. Anaerobic metabolism of PAO under both anoxic and aerobic conditions was observed at high FNA concentrations. Growth of PAOs decreased sharply with FNA concentration and stopped completely at FNA concentration of 10 μg HNO(2)-N/L. This study, for the first time, investigated the function of nitrite/FNA in an aerobic denitrifying phosphate removal process by evaluating electron as well as energy balances, and provides explanation for FNA inhibition mechanisms.
Publisher: Elsevier BV
Date: 04-2014
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 11-2020
Publisher: American Chemical Society (ACS)
Date: 15-10-2021
Publisher: Elsevier BV
Date: 05-2022
DOI: 10.1016/J.JHAZMAT.2022.128400
Abstract: Refractory Maillard reaction products (MRPs) produced during thermal hydrolysis pretreatment (THP) of waste activated sludge (WAS) may negatively impact the performance of downstream anaerobic digestion (AD) and nitrogen removal processes. Operating THP at lower temperature can mitigate the production of MRPs and improve biodegradability of WAS, while solubilization of WAS is reduced. This study intends to develop a method to reduce the refractory MRPs of WAS without compromising on the solubilization. Fe
Publisher: Elsevier BV
Date: 06-2019
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.CHEMOSPHERE.2018.10.122
Abstract: Widespread usage of silver nanoparticles (AgNPs) in consumer products has resulted in their presence in the aquatic environment. The evolution of the properties of AgNPs with changes in pH and time in terms of colloidal stability, dissolution and aggregation were investigated in a series of short and long-term experiments using freshly synthesized uncoated AgNPs. The solution pH modifies the surface charge and the oxidative dissolution of AgNPs. As a result, the particle behavior varied in acidic and alkaline conditions. The particle size decreased with the increasing pH at a given time frame resulting in lower aggregation in the higher pH regime and increased particle stability. These results have been further proved with the direct evidence obtained using time resolved in situ imaging acquired through Liquid cell transmission electron microscopy (LCTEM). Furthermore, the magnitude of the impact of the pH on the particle properties is higher than the impact of the dissolved oxygen concentration. The derived empirical formulae reflect that the AgNP oxidation depends on both dissolved oxygen and protons while the AgNP dissolution increasing with the increase of either of these. Overall, our results highlight the impact of the solution pH on the evolution of the properties of AgNPs over the time and provide an insight to confidently extend the results to predict the environmental transformation of AgNPs from ideal systems to the real.
Publisher: Elsevier BV
Date: 11-2017
Publisher: IWA Publishing
Date: 04-2010
DOI: 10.2166/WST.2010.983
Abstract: Glycolysis has been generally accepted to be the source of reducing power used for the synthesis of polyhydroxyalkanoates (PHAs) in the anaerobic metabolism of polyphosphate accumulating organisms (PAOs). However, the tricarboxylic acid cycle (TCA) has also been suggested to contribute to the generation of reducing equivalents, creating some controversy in this research field over the last two decades. Various research approaches have been applied in order to clarify this issue, including the analysis of intracellular compounds, labelled carbon substrates and gene expression. However, the conclusions of these studies seem not to be consolidated. The extent of TCA cycle involvement could be related to the experimental methods employed, the community structure of the cultures used, and also the operational conditions employed. This mini-review analyses the historical findings related to the source of reducing power in PAOs, and highlights the different approaches used in the previous studies. Key factors influencing the generation of reducing power through different metabolic pathways are discussed, and further research directions are also proposed.
Publisher: Springer Publishing Company
Date: 11-2018
DOI: 10.1891/2156-5287.8.2.115
Abstract: This article presents findings from an interpretive phenomenological study that illuminates unique characteristics of the different social representations of antenatal primigravida and multigravida women who book to birth their babies in a birth center, hospital, or at home. Semi-structured interviews were conducted with 19 women and analyzed by interpretive phenomenological analysis. Analysis revealed different social representations independent of each other that illustrate how these social groups, determined by women’s collective voices, are uniquely characterized by group views, beliefs, misinterpretations, and preconceptions that establish what influences women in decision-making about choice of birthplace. Women make decisions about what they want for themselves in this birthing experience. These decisions are made long before this impending experience. Recognizing the different social representations of women in pregnancy reveals deeper insight into the complexities of women’s decision-making about birth choices and highlights why some women might opt for certain choices. Knowing that some women may make decisions based on little or misrepresented information confirms midwives are best placed in their interactions with women to provide positive influences, empowering them to make decisions based upon what they want for themselves. This affirms the woman and her midwife should remain partners in the decision-making process.
Publisher: Elsevier BV
Date: 03-2020
DOI: 10.1016/J.WATRES.2019.115332
Abstract: Attachment to solids is an important process for determining nanomaterial transport and their fate in environments. Here we revealed distinct behaviours in the attachment of silver nanoparticles (AgNPs) to kaolin and bacterial cells. We found preferential attachment of AgNPs to the edges of kaolin. Decreasing pH or adding metal ions promoted AgNP-kaolin attachment due to the increase of positive charge on kaolin's surfaces. Multivalent cations (Mg
Publisher: Wiley
Date: 07-2009
DOI: 10.1002/APJ.321
Publisher: Elsevier BV
Date: 06-2013
Publisher: Elsevier BV
Date: 03-2020
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.CHEMOSPHERE.2014.09.004
Abstract: This paper reports on propionic acid (HPr) degradation in a laboratory scale two-phase anaerobic system, where HPr was accumulated in the acidogenic reactor and degraded in the methanogenic reactor. Batch tests using biomass from the two-phase anaerobic system showed HPr degradation was rarely detectable in the acidogenic reactor when HPr concentration ranged from 639 to 4531mgHPrL(-1) and at pH 4.50 to 6.50. Biomass from the methanogenic reactor could, however, successfully degrade HPr at its initial concentration of up to 4585mgHPrL(-1) at pH 6.40-7.30. ATP results showed that differences in the degradation ability of HPr by the acidogenic and methanogenic biomass may be related with their respective different biomass activities. Results from pyrosequencing showed that the predominant propionic acid oxidizing bacteria (POB) in the methanogenic reactor were Smithella (2.68%) and Syntrophobacter (0.35%) while poor degradation of HPr in the acidogenic reactor may be associated with the low abundance of POB (0.02% Desulfacinum and 0.08% Desulfobulbus). This might have been induced by the long-term unfavorable environment for POB growth in the acidogenic reactor.
Publisher: Elsevier BV
Date: 09-2019
DOI: 10.1016/J.WATRES.2019.06.008
Abstract: The property and release behavior of phosphorus in biochar derived from enhanced biological phosphorus removal sludge (EBPR sludge) were investigated. A low-temperature-steam (LTS) activation method was developed to increase the P availability in the biochar. The results demonstrate that the P content in the biochar is comparable to that in typical P fertilizers. The biochar contained a considerable portion of fast-release P. Polyphosphates (poly-P) were the predominant P species in the biochar. LTS greatly improved P availability in biochar produced at 700 °C by hydrolyzing insoluble poly-P to soluble pyro-P and ortho-P. In addition, the presence of Ca
Publisher: Springer Science and Business Media LLC
Date: 31-03-2021
DOI: 10.1038/S41467-021-22250-9
Abstract: Despite the tremendous progress of coupling organic electrooxidation with hydrogen generation in a hybrid electrolysis, electroreforming of raw biomass coupled to green hydrogen generation has not been reported yet due to the rigid polymeric structures of raw biomass. Herein, we electrooxidize the most abundant natural amino biopolymer chitin to acetate with over 90% yield in hybrid electrolysis. The overall energy consumption of electrolysis can be reduced by 15% due to the thermodynamically and kinetically more favorable chitin oxidation over water oxidation. In obvious contrast to small organics as the anodic reactant, the abundance of chitin endows the new oxidation reaction excellent scalability. A solar-driven electroreforming of chitin and chitin-containing shrimp shell waste is coupled to safe green hydrogen production thanks to the liquid anodic product and suppression of oxygen evolution. Our work thus demonstrates a scalable and safe process for resource upcycling and green hydrogen production for a sustainable energy future.
Publisher: American Chemical Society (ACS)
Date: 15-04-2015
Abstract: Metal vanadium phosphates (MVP), particularly Li3V2(PO4)3 (LVP) and Na3V2(PO4)3 (NVP), are regarded as the next-generation cathode materials in lithium/sodium ion batteries. These materials possess desirable properties such as high stability, theoretical capacity, and operating voltages. Yet, low electrical/ionic conductivities of LVP and NVP have limited their applications in demanding devices such as electric vehicles. In this work, a novel synthesis route for the preparation of LVP/NVP micro/mesoporous 3D foams via assembly of elastin-like polypeptides is demonstrated. The as-synthesized MVP 3D foams consist of microporous networks of mesoporous nanofibers, where the surfaces of in idual fibers are covered with MVP nanocrystallites. TEM images further reveal that LVP/NVP nanoparticles are about 100-200 nm in diameter, with each particle enveloped by a 5 nm thick carbon shell. The MVP 3D foams prepared in this work exhibit ultrafast rate capabilities (79 mA h g(-1) at 100C and 66 mA h g(-1) at 200C for LVP 3D foams 73 mA h g(-1) at 100C and 51 mA h g(-1) at 200C for NVP 3D foams) and excellent cycle performance (almost 100% performance retention after 1000 cycles at 100C) their properties are far superior compared to current state-of-the-art active materials.
Publisher: Elsevier BV
Date: 05-2020
Publisher: Elsevier BV
Date: 05-2008
DOI: 10.1016/J.WATRES.2008.01.003
Abstract: Polyphosphate (poly-P) is known to be a key compound in the metabolism of polyphosphate-accumulating organisms (PAOs). In this study, a sludge highly enriched (80%) in Candidatus Accumulibacter phosphatis (hereafter referred to as Accumulibacter), a widely known PAO, was used to study the ability of these microorganisms to utilize acetate anaerobically under poly-P-limiting conditions. The biomass was subject to several anaerobic and aerobic cycles, during which the poly-P pool of PAOs was gradually emptied by supplying feed deficient in phosphate and washing the biomass at the end of each anaerobic period using media containing no phosphorus. After three cycles, phosphorus was hardly released but PAOs were still able to take up acetate and stored it as polyhydroxyalkanoates (PHA), as demonstrated by post-FISH chemical staining. Glycogen degradation increased substantially, suggesting PAOs were using glycogen as the main energy source. This is a key feature of glycogen-accumulating organisms (GAOs), which are known to compete with PAOs in enhanced biological phosphorus removal (EBPR) systems. The ratios between acetate uptake, polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV) production, and glycogen consumption agree well with the anaerobic models previously proposed for GAOs.
Publisher: Elsevier BV
Date: 04-2021
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.JHAZMAT.2016.06.066
Abstract: Sulfonamides (SAs) are extensively used antibiotics and their residues in the water bodies propose potential threat to the public. In this study, degradation efficiency of sulfanilamide (SAM), which is the precursor of SAs, using WO3 nanoplates and their Ag heterogeneous as photocatalysts was investigated. WO3 nanoplates with uniform size were synthesized by a facile one step hydrothermal method. Different amount of Ag nanoparticles (Ag NPs) were loaded onto WO3 nanoplates using a photo-reduction method to generate WO3/Ag composites. The physio-chemical properties of synthesized nanomaterials were systematically characterized. Photodegradation of SAM by WO3 and WO3/Ag composites was conducted under visible light irradiation. The results show that WO3/Ag composites performed much better than pure WO3 where the highest removal rate was 96.2% in 5h. Ag as excellent antibacterial agent also endows certain antibacterial efficiency to WO3, and 100% removal efficiency against Escherichia Coli and Bacillus subtilis could be achieved in 2h under visible light irradiation for all three WO3/Ag composites synthesized. The improved performance in terms of SAM degradation and antibacterial activity of WO3/Ag can be attributed to the improved electron-hole pair separation rate where Ag NPs act as effective electron trapper during the photocatalytic process.
Publisher: Elsevier BV
Date: 04-2018
Publisher: Elsevier BV
Date: 07-2022
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.SCITOTENV.2022.156559
Abstract: The coming crisis of phosphate rock depletion initiates the development of various solid waste derived P fertilizer. Enhanced biological phosphorus removal (EBPR) sludge is ideal waste biomass to produce biochar-P-fertilizer. Here, the form and transformation pattern of released phosphorus (P) of EBPR sludge biochar pyrolyzed at different temperatures were comprehensively investigated. As pyrolysis temperature increased, the proportion of released polyphosphates (Poly-P) increased. The main Poly-P released from low-temperature biochar was tripolyphosphates (Tri-P), while those released from high-temperature were Tri-P and cyclic Poly-P. The presence of Ca
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.WATRES.2016.11.034
Abstract: The mechanism of Fe (II) - oxone conditioning to improve sludge dewaterability was investigated in this study. Five different types of sludge were tested, including raw sludge (Group 1: mixed primary and secondary sludge, waste activated sludge and anaerobic digested sludge) and pretreated sludge with prior solubilisation (Group 2: ultrasonic or thermal pretreated sludge). After Fe (II) - oxone conditioning, the concentrations of dissolved organic carbon, protein and polysaccharide of soluble extracellular polymeric substances (SB EPS) increased for Group 1, but decreased for Group 2. For all types of sludge investigated, the related organic compounds of loosely bound (LB) and tightly bound (TB) EPS decreased with Fe (II) - oxone conditioning, and increased sludge filterability showed strong and positive correlation with the removal of low molecular weight protein and neutrals in LB EPS. Fe (II) - oxone was very effective in disintegrating cell membrane and caused potential cell lysis, as indicated by increased percentage of damaged microbial cells. From this study, the mechanism of Fe (II) - oxone conditioning was proposed and can be ided into two steps: (1) Oxidation step - sulfate radicals degraded organic compounds in LB and TB EPS in sludge and transformed bound water to free water that was trapped in TB and LB EPS It also damaged cells membrane and may help to release intracellular water content. Sludge flocs were broken into smaller particles (2) Coagulation step - Fe (III), generated from the oxidation step can act as a coagulant to agglomerate smaller particles into larger ones and reduce the repulsive electrostatic interactions. Combined effects from above two steps can greatly improve sludge filterability.
Publisher: Wiley
Date: 02-05-2017
DOI: 10.1002/JCTB.5280
Publisher: Elsevier BV
Date: 07-2021
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.BIORTECH.2018.06.059
Abstract: The detailed dissolved organic matters (DOMs) profile by thermal hydrolysis pretreatment and their transformation during anaerobic digestion (AD) were investigated. Among the temperature tested, 172 °C treatment showed the best sludge solubilization and the maximum methane production. The study revealed that high temperature sludge pretreatment mainly improved the release of low molecular weight (LMW) proteins, LMW neutrals and LMW polysaccharides. Notably, the effluent from thermal treated sludge digesters contained more DOMs residues. The predominant residual DOMs were humic substances, LMW proteins and LMW neutrals. At the molecular level, over 50% of the residual LMW components were slowly biodegradable or nonbiodegradable steroid-like compounds and aromatics. Further profiling of the higher MW compounds detected the recalcitrant or inhibitory compounds, e.g. benzenoids, flavonoids, pyridines and their derivatives. It is recommended that polishing step should be considered to further reduce the refractory residues in AD liquor.
Publisher: Elsevier BV
Date: 08-2019
DOI: 10.1016/J.WATRES.2019.04.063
Abstract: Enhanced biological denitrification for nitrogen removal using sludge alkaline fermentation liquid (SAFL) as an alternative carbon source has been widely reported in previous studies, while limited studies focused on the degradation of the organics presented in SAFL. In this study, an SAFL driven anoxic denitrification sequencing batch reactor (SBR) was established, the mechanism of organics utilization was characterized and the refractory dissolved organic matters (rDOM) was identified. Denitrification could rapidly proceed with the presence of volatile fatty acids (VFAs) initially, while the denitrification rate largely decreased after the VFAs depleted. A great deal of rDOM, which was hard to be utilized by denitrifying microorganism, was found in the effluent. A prolonged hydraulic retention time (HRT) led to the further transformation of particles and colloids to smaller colloids and soluble organics. Extended HRT promoted the degradation of soluble microbial by-product (SMP), but had minor effect on the removal of humic-like, and fulvic acid-like substances. The characterization of the effluent demonstrated the building blocks, were dominated in the rDOM (43.79%-48.78%), followed by high molecular weight protein (HMW-PN) (13.37%-17.39%), HMW polysaccharide (HMW-PS) (12.84%-15.9%), low molecular weight (LMW) neutrals (11.28%-13.65%), and hydrophobic dissolved organic carbon (HO-DOC) (8.0%-12.62%). Moreover, it was found that the building blocks were relatively easy to be degraded with the extension of HRTs, followed by LMW-PS, LMW-PN, LMW neutrals, HMW-PN, and HMW-PS. However, further extended HRT >24 h could not improve the removal of building blocks, LMW-PS and LMW neutrals. This study, for the first time, provided insights into the transformation of organic matters produced by SAFL in a denitrification system and acted as a guide for the subsequent advanced treatment.
Publisher: Elsevier BV
Date: 2021
Publisher: MDPI AG
Date: 18-01-2022
DOI: 10.3390/APP12030956
Abstract: This study evaluated the effects of sodium on anaerobic biomass from the second-stage reactor of a two-stage anaerobic digester. The results indicated that methanogens showed a relatively high sodium tolerance of 2.4 g Na+ L−1. Microbial community analysis showed that viable Methanomicrobiales was the most abundant population by a combined propidium monoazide cross-linking quantitative polymerase chain reaction technique. There was a population shift towards higher abundance of Thermotoga (0.02%), Clostridium (2.50%) and Methanoculleus (13.80%). Biomass activity in relation to increased sodium concentrations was investigated with the adenosine triphosphate test coupled with extracellular polymeric substances measurement. The results showed biomass activity decreased from 33 to 16 µg g−1 volatile suspended solids as sodium concentrations increased from 1.3 to 9.1 g Na+ L−1. Higher EPS production, particularly a greater predominance of carbohydrates, was stimulated by higher sodium concentrations. This study provides insights into the superiority of sodium tolerance of two-stage anaerobic digester in compared with a single-stage anaerobic system.
Publisher: Elsevier BV
Date: 2020
DOI: 10.1016/J.BIORTECH.2019.122300
Abstract: Current high-rate activated sludge (HRAS) process is an aerobic A-stage process that would cause significant organic loss resulted from the mineralization. In this study, the feasibility of operating a high rate A-stage without aeration (HRNS) was carried out in a demo-scale plant (275 m
Publisher: Elsevier BV
Date: 09-2021
Publisher: Elsevier BV
Date: 07-2018
Publisher: Springer Science and Business Media LLC
Date: 29-07-2010
DOI: 10.1007/S00253-010-2780-3
Abstract: Free nitrous acid (FNA) has been identified to be a ubiquitous inhibitor of a wide range of microorganisms, including bacteria involved in wastewater treatment. The FNA-induced inhibition on the anoxic (nitrite as electron acceptor) metabolism of denitrifying poly-phosphate accumulating organisms (DPAOs) was investigated using sludge from a sequencing batch reactor performing carbon, nitrogen, and phosphorus removal from synthetic wastewater. We found that FNA had a much stronger inhibitory effect on phosphorus (P) uptake and glycogen production than on poly-beta-hydroxyalkanoate degradation and nitrite reduction. The intracellular adenosine triphosphate levels decreased sharply during the FNA incubation, and the decreasing rates were positively correlated with increasing FNA concentrations. The electron transport activity of DPAOs when exposed to FNA displayed a similar trend. Further, at FNA concentrations above 0.044 mg HNO(2)-N/L, the anaerobic metabolism of DPAOs was initiated despite of the presence of nitrite, as evidenced by the release of phosphorus and the consumption of glycogen. DPAO metabolism did not recover completely from FNA inhibition in the subsequent FNA-free environment. The recovery rate depended on the concentration of FNA applied in the previous anoxic period. These results suggest that the inhibitory effects are erse and may be attributable to different mechanisms operating simultaneously.
Publisher: Elsevier BV
Date: 10-2020
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.CHEMOSPHERE.2018.10.187
Abstract: The high energy consumption associated with biological treatment of municipal wastewater is posing a serious impact and challenge on the current global wastewater industry and is also inevitably linked to the issue of global climate change. To tackle such an emerging situation, this study aimed to develop strategies to effectively suppress nitrite oxidizing bacteria (NOB) in pilot-scale mainstream nitritation-denitritation system coupled with MBR for municipal wastewater treatment. The results showed that stable nitrite shunt was achieved, while more than 90% of COD and NH
Publisher: Elsevier BV
Date: 02-2021
Publisher: American Chemical Society (ACS)
Date: 13-11-2008
DOI: 10.1021/JP807983A
Publisher: Elsevier BV
Date: 10-2021
Publisher: Elsevier BV
Date: 03-2017
DOI: 10.1016/J.CHEMOSPHERE.2016.12.030
Abstract: An investigation was conducted for 20 different types of sludge in order to identify the key organic compounds in extracellular polymeric substances (EPS) that are important in assessing variations of sludge filterability. The different types of sludge varied in initial total solids (TS) content, organic composition and pre-treatment methods. For instance, some of the sludges were pre-treated by acid, ultrasonic, thermal, alkaline, or advanced oxidation technique. The Pearson's correlation results showed significant correlations between sludge filterability and zeta potential, pH, dissolved organic carbon, protein and polysaccharide in soluble EPS (SB EPS), loosely bound EPS (LB EPS) and tightly bound EPS (TB EPS). The principal component analysis (PCA) method was used to further explore correlations between variables and similarities among EPS fractions of different types of sludge. Two principal components were extracted: principal component 1 accounted for 59.24% of total EPS variations, while principal component 2 accounted for 25.46% of total EPS variations. Dissolved organic carbon, protein and polysaccharide in LB EPS showed higher eigenvector projection values than the corresponding compounds in SB EPS and TB EPS in principal component 1. Further characterization of fractionized key organic compounds in LB EPS was conducted with size-exclusion chromatography-organic carbon detection-organic nitrogen detection (LC-OCD-OND). A numerical multiple linear regression model was established to describe relationship between organic compounds in LB EPS and sludge filterability.
Publisher: Elsevier BV
Date: 02-2021
Publisher: Elsevier BV
Date: 04-2020
Publisher: American Chemical Society (ACS)
Date: 15-10-2008
DOI: 10.1021/ES800650J
Abstract: Nitrite has generally been recognized as an inhibitor of N2O reduction during denitrification. This inhibitory effect is investigated under various pH conditions using a denitrifying-enhanced biological phosphorus removal (EBPR) sludge. The degree of inhibition was observed to correlate much more strongly with the free nitrous acid (FNA) concentration than with the nitrite concentration, suggesting that FNA, rather than nitrite, is likely the true inhibitor on N2O reduction. Fifty percent inhibition was observed at an FNA concentration of 0.0007-0.001 mg HNO2-N/L (equivalent to approximately 3-4 mg NO2(-) -N/L at pH 7), while complete inhibition occurred when the FNA concentration was greater than 0.004 mg HNO2-N/L. The results also suggest that the inhibition on N2O reduction was not due to the electron competition between N2O and NO2- reductases. The inhibition was found to be reversible, with the rate of recovery independent of the duration of the inhibition, but dependent on the concentration of FNAthe biomass was exposed to during the inhibition period. A higher FNA concentration caused slower recovery.
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 12-2020
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.BIORTECH.2017.09.153
Abstract: In this study, a thermophilic (65°C) single-stage wasted activated sludge (WAS) digester was established and the effects of solid retention time (SRT) on the reactor performance were investigated. The result showed that the optimum SRT was 6days with methane yield of 186.16mL/g VS. It was found that SRT had little effect on the hydrolysis and volatile solids (VS) destruction, and the high temperature employed seemed sufficient to achieve maximum hydrolysis and VS destruction performance. Longer SRT, however, promoted the release of recalcitrant compounds and impaired acidification, leading to the low methane yield. The microbial community analysis revealed that the dominant pathway for methane production was through syntrophic activity of acetate oxidizing bacteria and hydrogenotrophic methanogens while acetoclastic methanogens were absent in the system.
Publisher: Elsevier BV
Date: 09-2019
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.SCITOTENV.2019.133914
Abstract: Conventional chemical and physical methods to remove antibiotics from wastewater consume large amount of energy and chemicals, and the efficiency of biological process in converting antibiotics is relatively low. Microbial electrolysis cell (MEC) has been employed to degrade recalcitrant organic compounds recently. Given it is an energy consuming device, it would be more sustainable if driven by renewable energy, e.g. power from microbial fuel cell (MFC). Here, chlor henicol (CAP) was chosen as a representative antibiotic that is abundant in the environment, and Ag ion contained wastewater as electron acceptor in MFC, to demonstrate the feasibility of a self-driven system for recalcitrant removal and resource recovery. It was found that CAP removal in MEC can be successfully driven by Ag(I) reduced MFC without external energy consumption. Method of one-factor-at-a-time (OFAT) and response surface methodology (RSM) with central composite design were used to evaluate the system performance. Under the optimum condition, 99.8% of Ag(I) in MFC and 98.8% of CAP in MEC can be converted. EDX and XPS revealed that pure silver was obtained on the surface of electrode in MFC, reflecting Ag(I) was reduced to valuable product. The concept and methods developed in this study can be also applied to design other types of self-driven BES systems for simultaneous pollutants removal and resources recovery.
Publisher: Elsevier BV
Date: 10-2020
Publisher: American Chemical Society (ACS)
Date: 10-01-2017
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.WATRES.2022.118499
Abstract: The increasing amount of sewage sludge produced in wastewater treatment plants (WWTPs) poses a great challenge to both environment and economy globally. As a requisite process during sludge treatment, sludge dewatering can significantly minimize the sludge volume and lower the operational cost for downstream transportation and disposal. Iron-based advanced oxidation process (AOP), a robust and cost-effective technique with relatively low technical barriers for high-level sludge dewatering, has been widely explored in the past 20 years. The development was mainly driven by the demands of efficient and sustainable sludge conditioning technology and the flexible sludge management approaches. The application of iron-based AOPs in sludge dewatering process attracts more and more attention. In this work, we discussed the current application of iron-based AOPs technology in the sludge dewatering processes in a holistic manner, summarized the factors affecting the sludge dewaterability in the treatment processes, and analyzed the mechanisms of iron-based AOPs to improve dewatering processes. Furthermore, we elaborated potential advantages, limitations, and challenges associated with implementing iron-based AOPs in the full-scale plants and shared the opportunities for sludge reutilization. This review aims to contribute to the development of highly efficient iron-based AOPs for sludge dewatering and offer perspectives and directions towards the new-generation of WWTPs with the sustainable and eco-friendly benefits.
Publisher: Elsevier BV
Date: 11-2017
DOI: 10.1016/J.BIORTECH.2017.07.040
Abstract: This study investigated the effect of changes in pH (7, 6.5 and 6), hydraulic retention time (HRT) (6h, 4h, and 2h), solids retention time (SRT) (100d and 25d) on the speciation of trace metals (TMs) in submerged anaerobic membrane bioreactors (SAMBRs). The results showed that the metal retention capacity of SAMBRs reduced when the pH, HRT and SRT were reduced i.e. up to 21.9%, 39.1%, and 17.1%, respectively, but it was also found that the speciation of these TMs generally shifted towards highly bioavailable fractions i.e. Soluble and Exchangeable. The degree of shifting in speciation depended on the affinity of the TMs for anaerobic sludge and their sensitivity to the changes. TMs with the most and the least significant changes in speciation were Fe and Mn, respectively.
Publisher: Elsevier BV
Date: 09-2012
DOI: 10.1016/S1001-0742(11)60996-0
Abstract: Nitrous oxide (N2O) emission has been reported to be enhanced during denitrification when internally-stored compounds are used as carbon sources. However, negligible N2O emissions have been detected in the few studies where polyhydroxyalkanoates (PHA) were specifically used. This study investigated and compared the potential enhancement of N2O production, based on utilization of an internally-stored polymer and external carbon (acetate) by a denitrifying phosphorus removal culture. Results indicated that at relatively low chemical oxygen demand-to-nitrogen (COD/N) ratios, more nitrite was reduced to N2O in the presence of an external carbon source as compared to an internal carbon source (PHA). At relatively higher COD/N ratios, similar N2O reduction rates were obtained in all cases regardless of the type of carbon source available. N2O reduction rates were, however, generally higher in the presence of an internal carbon source. Results from the study imply that when the presence of an external carbon source is not sufficient to support denitrification, it is likely competitively utilized by different metabolic pathways of denitrifying polyphosphate accumulating organisms (DPAOs) and other ordinary denitrifiers. This study also reveals that the consumption of PHA is potentially the rate-limiting step for N2O reduction during denitrification.
Publisher: Elsevier BV
Date: 04-2017
DOI: 10.1016/J.WATRES.2017.01.067
Abstract: In this study, a mixture of primary and wasted activated sludge was fermented in a semi-continuous reactor aiming for enhanced volatile fatty acids (VFAs) production. The reactor was subjected to a stepwise pH increase from 7 to 10 during approximately 130 days of operation. The result revealed that the maximum acidification was obtained at pH 8.9 (21%) resulting in the maximum production of VFAs (423.22 ± 25.49 mg COD/g VSS), while the maximum hydrolysis efficiency was observed at pH 9.9 (42%). The high pH was effective in releasing dissolved organic matter (DOM) including protein, carbohydrate, building blocks and low molecular weight (LMW) neutrals. More LMW DOMs were released than high molecular weight (HMW) DOMs fractions at higher pH. pH 9.9 favored hydrolysis of HMW DOMs while it did not enhance the acidogenesis of LMW DOMs. The microbial community analysis showed that the relative abundance of phyla Actinobacteria and Proteobacteria increased with the increased pH, which may lead to the maximum hydrolysis at pH 9.9. At pH 8.9, class Clostridia (59.16%) was the most dominant population where the maximum acidification (21%) was obtained. This suggested that the dominance of Clostridia was highly related to acidification extent. The relative abundance of Euryarchaeota decreased significantly from 58% to 2% with increased pH.
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.JHAZMAT.2022.128599
Abstract: Anaerobic digestion centrate produced from thermal hydrolysis pretreated sludge (THP-AD centrate) has serious inhibitory effect on ammonium oxidizing bacteria (AOB) and anammox bacteria. This imposes huge challenge to employ partial nitritation/anammox (PN/A) process to treat THP-AD centrate. This study, for the first time, presented an effective strategy, ozone pretreatment, to alleviate such inhibitory effect. The activities of AOB and anammox bacteria increased with increasing ozone dosage, which were likely related to the transformation of organic compounds including humic acid-like and fulvic acid-like substances as well as high molecular weight (HMW) protein. Long-term operation of PN/A system further demonstrated the improved performance in term of nitrogen removal, organics degradation as well as sludge settleability and effluent solids. Nitrogen removal rate (NRR) of 0.64 Kg N/m
Publisher: Springer Science and Business Media LLC
Date: 02-07-2015
DOI: 10.1007/S00253-015-6742-7
Abstract: The effects of temperature on nitrous oxide (N2O) accumulation during denitrification and denitritation were investigated. Batch experiments were performed to measure N2O accumulation at 25 and 35 °C. More N2O accumulation was observed during denitritation at the higher temperature as compared with full denitrification and low temperature tests. The highest nitrite concentration tested in this study (25 mg/L NO2 (-)N and pH 8.0) did not show inhibitory effect on N2O reduction. It was found that the major cause of more N2O accumulation during denitrification at higher temperature was due to higher N2O production rate and lower N2O solubility. Specific nitrate, nitrite, and N2O reduction rates increased 62, 61, and 41 %, respectively, when temperature rose from 25 to 35 °C. The decrease of N2O solubility in mixed liquor at 35 °C (when compared to 25 °C) resulted in faster diffusing rate of N2O from liquid to gas phase. It was also more difficult for gas phase N2O to be re-dissolved. The diffused N2O was then accumulated in the headspace, which was not available for denitrification by denitrifiers. The results of this study suggest higher temperature may worsen N2O emission from wastewater treatment plants (WWTPs).
Publisher: Elsevier BV
Date: 03-2022
DOI: 10.1016/J.CHEMOSPHERE.2021.133386
Abstract: Integrating the aeration-efficient membrane aerated biofilm reactor (MABR) with anaerobic ammonium oxidation (anammox) could yield further reduction in energy in wastewater treatment facilities. However, nitrite oxidizing bacteria (NOB) suppression remained challenging due to the absence of intrinsic inhibition factors in mainstream conditions. This study investigated selective NOB suppression strategies in MABR under <5 kPa lumen pressure. Three MABRs were seeded from different seeding sludge, and operated under various ammonium loading rates, aeration pressure, and temporary inhibitory shock conditions. The three reactors were operated for 170-456 days depending on studied parameters. The results showed that higher ammonium loading could create a substrate-oxygen imbalance and quickly contain emergent NOB activity when aeration pressure was not excessive. In addition, lowering of aeration pressure reversed nitrite oxidizing activities without affecting ammonium oxidizing bacteria (AOB). Cultivating partial nitritation biofilm under zero positive aeration pressure slowed down the growth of NOB yet resulted in self-induced anammox activities. With the aid of temporary free ammonia (FA)/free nitrous acid (FNA) treatment, full-nitrifying biofilm could be transformed to stable partial nitritation biofilm. More than 84% nitrite accumulation ratio (NAR) was sustained during stable operation in each reactor together with an ammonium removal rate of more than 100 mg-N/L/d. Microbial analysis revealed that Nitrosomonas was the main AOB taxon in the three reactors while K-strategist Nitrospira showed presence despite low nitrite oxidizing activities. Under zero positive pressure, proliferation of Nitrospira was much slower while Candidatus Brocadia was self-induced. Furthermore, Nitrospira showed downturn after temporary inhibition treatment.
Publisher: Informa UK Limited
Date: 22-12-2018
DOI: 10.1080/08927014.2017.1409892
Abstract: A fluid dynamic gauging (FDG) technique was used for on-line and in situ measurements of Pseudomonas aeruginosa PAO1 biofilm thickness and strength on flat sheet polyethersulphone membranes. The measurements are the first to be successfully conducted in a membrane cross-flow filtration system under constant permeation. In addition, FDG was used to demonstrate the removal behaviour of biofilms through local biofilm strength and removal energy estimation, which other conventional measurements such as flux and TMP cannot provide. The findings suggest that FDG can provide valuable additional information related to biofilm properties that have not been measured by other monitoring methods.
Publisher: Mark Allen Group
Date: 05-2010
DOI: 10.12968/BJOM.2010.18.5.47872
Abstract: This article critically examines the existing midwifery literature associated with reflexivity. Reflexivity is a widely accepted concept central to qualitative research methodology. The importance of this process is highlighted demonstrating how it remains an integral part of ensuring the transparency and quality of research inquiry. This article sets out to review the literature expand the concept of reflexivity from a midwifery perspective and reinforces the need for practitioner researchers to gain understanding and acknowledge reflexivity. This will ensure strong and trustworthy inquiry and allow the researcher to explore and make sense of the relationship between themselves, the research and the object of research.
Publisher: Elsevier BV
Date: 02-2020
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.CHEMOSPHERE.2014.11.027
Abstract: In this paper, a linear state space model for the two-phase anaerobic reactor system was developed based on historical data. Subsequently, the model was used to predict its future behavior. The state space model developed involved correlation analysis and model development. The model would be updated at every time point when a new data set became available, giving it an "adaptive" feature. The model was then applied to monitor two-phase anaerobic co-digestion of a feed comprising 2 industrial secondary sludges and 2 industrial wastewaters. The case study showed the proposed model was able to provide good predictions of various process parameters. In addition, it also predicted impending process failure and this would have allowed the operator to take necessary measures to prevent or reduce impact of such failure during plant operation.
Publisher: American Chemical Society (ACS)
Date: 20-09-2019
Publisher: Wiley
Date: 07-05-2007
DOI: 10.1002/BIT.21458
Abstract: Nitrite has been found in previous research an inhibitor on anoxic phosphorus uptake in enhanced biological phosphorus removal systems (EBPR). However, the inhibiting nitrite concentration reported varied in a large range. This study investigates the nitrite inhibition on anoxic phosphorus uptake by using four different mixed cultures performing EBPR with pH considered an important factor. The results showed that the protonated species of nitrite, HNO(2) (or free nitrous acid, FNA), rather than nitrite, is likely the actual inhibitor on the anoxic phosphorus uptake, as revealed by the much stronger correlation of the phosphorus uptake rate with the FNA than with the nitrite concentration. All the four EBPR sludges showed decreased anoxic phosphorus uptake rates with increased FNA concentrations in the studied range of 0.002-0.02 mg HNO(2)-N/L. The phosphorus uptake by all four cultures was completely inhibited at 0.02 mg HNO(2)-N/L. Granular sludge appeared to be more tolerant to HNO(2) than flocular sludge likely due to its stronger resistance to the transfer of nitrite into the bacterial aggregates. Furthermore, denitrification by the phosphorus-accumulating organisms (PAOs) was also found to be inhibited by HNO(2). The denitrification rate decreased by approximately 40% when the FNA concentration was increased from 0.002 to 0.02 mg HNO(2)-N/L.
Publisher: Elsevier BV
Date: 12-2017
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.CHEMOSPHERE.2014.07.028
Abstract: This study compared reactor performance and the respective microbial community dynamics in the conventional single-stage and 2-phase anaerobic digestion (AD) systems, treating municipal sludge to generate methane. The 2-phase system's COD and VS reduction, and methane production could be maintained throughout the three HRTs tested (p=0.05), which was associated with an increase in organic loading (30d=1.5gCODL(-1)d(-1), 20d=2.2gCODL(-1)d(-1) and 10d=3.5gCODL(-1)d(-1)) but this was not so in the single-stage system where it deteriorated at HRT of 10d (p=0.05) due to impairment of particulate COD reduction. qPCR, DGGE and the subsequent phylogenetic analysis revealed that microbial adaptation occurred as the seed sludge formed a different community in each reactor at 30d HRT however, no further significant microbial shift occurred at lower HRTs. The presence of specific hydrolytic and acidogenic Flavobacteriales and Clostriales in the acidogenic reactor may have allowed for enhanced hydrolysis and acidogenesis, leading to higher organic loading tolerance at 10d HRT. Methanogenic activity in the acidogenic reactor may have been performed by Methanobacteriales and Methanosarcinaceae. Operation of the acidogenic reactor at neutral pH may have to be considered to ensure the cultivation of propionate oxidising bacteria, which could in turn, prevent reactor "souring" during high load conditions.
Publisher: Elsevier BV
Date: 08-2017
DOI: 10.1016/J.BIORTECH.2017.04.020
Abstract: This study aimed to develop an in-situ sludge pretreatment method by increasing the temperature from thermophilic to extreme thermophilic condition in a single-stage anaerobic digester. The results revealed that a stable performance was obtained within the temperature range of 55-65°C, and the maximum methane yield of 208.51±13.66mL/g VS was obtained at 65°C. Moreover, the maximum extent of hydrolysis (33%) and acidification (27.1%) was also observed at 65°C. However, further increase of temperature to 70°C did not improve the organic conversion efficiency. Microbial community analysis revealed that Coprothermobacter, highly related to acetate oxidisers, appeared to be the abundant bacterial group at higher temperature. A progressive shift in methanogenic members from Methanosarcina to Methanothermobacter was observed upon increasing the temperature. This work demonstrated single-stage sludge digestion system can be successfully established at high temperature (65°C) with stable performance, which can eliminate the need of conventional thermophilic pretreatment step.
No related grants have been discovered for Yan Zhou.