Oily wastewater generated by various industries creates a major ecological problem throughout the world. The tra- ditional methods for the oily wastewater treatment are inefficient and costly. Surfactants can promote ...Oily wastewater generated by various industries creates a major ecological problem throughout the world. The tra- ditional methods for the oily wastewater treatment are inefficient and costly. Surfactants can promote the biodegradation of pe- troleum hydrocarbons by dispersing oil into aqueous environment. In the present study, we applied rhamnolipid-containing cell-free culture broth to enhance the biodegradation of crude oil and lubricating oil in a conventional aerobically-activated sludge system. At 20 ℃, rhamnolipids （11.2 mg/L） increased the removal efficiency of crude oil from 17.7% （in the absence of rham- nolipids） to 63%. At 25 ~C, the removal efficiency of crude oil was over 80% with the presence of rhamnolipids compared with 22.3% in the absence of rhamnolipids. Similarly, rhamnolipid treatment （22.5 mg/L） for 24 h at 20℃ significantly increased the removal rate of lubricating oil to 92% compared with 24% in the absence of rhamnolipids. The enhanced removal of hydrocarbons was mainly attributed to the improved solubility and the reduced interfacial tension by rhamnolipids. We conclude that a direct application of the crude rhamnolipid solution from cell culture is effective and economic in removing oily contaminants from wastewater.展开更多
Anaerobic ammonia oxidation(Anammox)is an economical and sustainablewastewater nitrogen removal technology,and its application in the mainstream process is the inevitable trend of the development of Anammox.However,ho...Anaerobic ammonia oxidation(Anammox)is an economical and sustainablewastewater nitrogen removal technology,and its application in the mainstream process is the inevitable trend of the development of Anammox.However,how to effectively enriching Anammox bacteria from the activated sludge remains challenging and restricts its extensive applications.In this study,the rapid and efficient enrichment of Anammox bacteriawas achieved by raising the reflux ratio and nitrogen loading rate(NLR)using conventional activated sludge as the inoculant.In the screening phase(days 1–90),the reflux ratio was increased to discharge partial floc sludge,resulting in the relative abundance of Candidatus Brocadiaceae increased from0.04%to 22.54%,which effectively reduced thematrix and spatial competition between other microorganisms and Anammox bacteria.On day 90,the stoichiometric ratio of the Anammox process closely approached the theoretical value of 1:1.32:0.26,indicating that the Anammox reaction was the primary nitrogen removal process in the system.In the enrichment phase(days 91–238),the NLR increased from 0.43 to 1.20 kgN/(m^(3)·d)and removal efficiency was 71.89%,resulting in the relative abundance of Candidatus Brocadiaceae increased to 61.27%on day 180.The reactor operated steadily from days 444 to 498,maintaining the nitrogen removal rate(NRR)of 3.00 kgN/(m^(3)·d)and achieving successful sludge granulation with the particle size of 392.4μm.In short,this study provided a simple and efficient approach for enriching Anammox bacteria from the activated sludge,supporting to start an Anammox process efficiently.展开更多
As a key step in waste activated sludge(WAS)treatment and disposal,WAS dewatering can minimize the amount of WAS and decrease the costs of transportation,storage management,treatment,and disposal.Advanced oxidation pr...As a key step in waste activated sludge(WAS)treatment and disposal,WAS dewatering can minimize the amount of WAS and decrease the costs of transportation,storage management,treatment,and disposal.Advanced oxidation processes(AOPs)have been widely explored in WAS dewatering due to the excellent oxidizing properties and efficient decomposition capacity since the 21^(st)century.This review outlined the mechanisms of AOPs to improve WAS dewatering and pointed out the shortcomings of the existing mechanisms.Then,the applications of AOPs-based WAS dewatering processes for enhanced WAS dewatering were reviewed,and the intrinsic limitations of AOPs-based WAS dewatering processes in engineering applications were proposed.In addition,an overall review of AOPs-based WAS dewatering researches was also conducted through bibliometric analysis,and future research hotspots in the field of AOPs-based WAS dewatering were proposed.Finally,the positive effects of the AOPs-based WAS dewatering processes on pollutant removal and resource recovery were investigated,and an integrated plan for the harmless disposal of WAS was constructed to achieve a positive reform of the traditional WAS management plan.This review provided theoretical basis and technical reference for the development of efficient,economical,and environmental AOPs for enhanced WAS dewatering to facilitate the application of AOPs in actual WAS dewatering engineering.展开更多
Cresyl diphenyl phosphate(CDP),an emerging aryl organophosphate ester(OPE),exhibits potential toxic effects and is frequently found in diverse environmental media,thereby raising concerns about environmental pollution...Cresyl diphenyl phosphate(CDP),an emerging aryl organophosphate ester(OPE),exhibits potential toxic effects and is frequently found in diverse environmental media,thereby raising concerns about environmental pollution.Biodegradation demonstrates substantial potential for CDP removal from the environment.This study investigated the biodegradation mechanisms of CDP using anaerobic activated sludge(AnAS).The biodegradation of 1-mg/L CDP followed a first-order kinetic model with a degradation kinetic constant of 0.943 d^(-1),and the addition of different electron acceptors affected the degradation rate.High-resolution mass spectrometry identified seven transformation products(TPs)of CDP.The pathways of CDP degradation in anaerobic conditions were proposed,with carboxylation products being the most dominant intermediate products.The structure of the anaerobic microbial community at different degradation time points in CDP-amended microcosms was examined.The linear discriminant analysis(LDA)of effect size(LEfSe)potentially underscored the pivotal role of Methyloversatilis in CDP biodegradation.Zebrafish embryotoxicity experiments revealed both lethal and morphogenetic impacts of CDP on zebrafish embryos.The survival rate,hatching rate,and body length indicators of zebrafish embryos underscored the detoxification of CDP and its resultant intermediates by AnAS.This study offers new insights into the fate and biodegradation mechanisms of CDP in wastewater treatment plants.展开更多
This study embarks on an explorative investigation into the effects of typical concentrations and varying particle sizes of fine grits(FG,the involatile portion of suspended solids)and fine debris(FD,the volatile yet ...This study embarks on an explorative investigation into the effects of typical concentrations and varying particle sizes of fine grits(FG,the involatile portion of suspended solids)and fine debris(FD,the volatile yet unbiodegradable fraction of suspended solids)within the influent on themixed liquor volatile suspended solids(MLVSS)/mixed liquor suspended solids(MLSS)ratio of an activated sludge system.Through meticulous experimentation,it was discerned that the addition of FG or FD,the particle size of FG,and the concentration of FD bore no substantial impact on the pollutant removal efficiency(denoted by the removal rate of COD and ammonia nitrogen)under constant operational conditions.However,a notable decrease in the MLVSS/MLSS ratio was observed with a typical FG concentration of 20 mg/L,with smaller FG particle sizes exacerbating this reduction.Additionally,variations in FD concentrations influenced both MLSS andMLVSS/MLSS ratios;a higher FD concentration led to an increased MLSS and a reduced MLVSS/MLSS ratio,indicating FD accumulation in the system.A predictive model for MLVSS/MLSS was constructed based on quality balance calculations,offering a tool for foreseeing the MLVSS/MLSS ratio under stable long-term influent conditions of FG and FD.This model,validated using data from the BXH wastewater treatment plant(WWTP),showcased remarkable accuracy.展开更多
Biochar is a massively produced by-product of biomass pyrolysis to obtain renewable energy and has not been fully used. Incomplete separation of sludge and effluent and insufficient denitrification of sewage are two o...Biochar is a massively produced by-product of biomass pyrolysis to obtain renewable energy and has not been fully used. Incomplete separation of sludge and effluent and insufficient denitrification of sewage are two of main factors that influence the efficiency of activated sludge process. In this work, we proposed a new utilization of biochar and investigated the effect of biochar addition on the performance of settleability and denitrification of activated sludge. Results show that the addition of biochar can improve the settleability of activated sludge by changing the physicochemical characteristics of sludge （e.g., flocculating ability, zeta-potential, hydrophobicity, and extracellular polymeric substances constituents）. Moreover, the dissolved organic carbon released from biochar obtained at lower pyrolysis temperature can improve the nitrate removal efficiency to a certain extent.展开更多
This paper researched a promising biological treatment of methyl violet waste water by methods of activated sludge.Effects of temperature and pH were studied on this process.Kinetic equation ...This paper researched a promising biological treatment of methyl violet waste water by methods of activated sludge.Effects of temperature and pH were studied on this process.Kinetic equation of the substrate biodegradation was investigated in the experimental range.It was studied and simulated that flow within the bubble region of this bioreactor according to the κ ε two fluid equation.Simulation results agree well with experimental data.展开更多
[Objective] To explore the optimal extraction conditions of extracellular polymeric substances （EPS） from activated sludge. [Method] The efficiency of five methods （H2SO4, formaldehyde-NaOH, mixing, heating and NaO...[Objective] To explore the optimal extraction conditions of extracellular polymeric substances （EPS） from activated sludge. [Method] The efficiency of five methods （H2SO4, formaldehyde-NaOH, mixing, heating and NaOH） on the extraction of EPS was investigated comparatively. The optimal extraction conditions of the most suitable method were determined. [Result] NaOH method is most effective in extracting EPS with less DNA contamination and shortened extraction period. The optimal extraction condition was pH of 11, extraction time of 10 min and agitation speed of 80-120 r/min. [Conclusion] The determined optimal extraction condition provided theoretical basis for EPS study.展开更多
The bacterial community structures in two sewage treatment plants with different processes and performance were investigated by denaturing gradient gel electrophoresis （DGGE） of nested polymerase chain reaction （ne...The bacterial community structures in two sewage treatment plants with different processes and performance were investigated by denaturing gradient gel electrophoresis （DGGE） of nested polymerase chain reaction （nested PCR） amplified 16S rRNA gene fragments with group-specific primers. Samples of raw sewage and treated effluents were amplified using the whole-cell PCR method, and the activated sludge samples were amplified using the extracted genomic DNA before the PCR products were loaded on the same DGGE gel for bacterial community analysis. Ammonia-oxidizing bacterial and actinomycetic community analysis were also carried out to investigate the relationship between specific population structures and system or sludge performance. The two plants demonstrated a similarity in bacterial community structures of raw sewage and activated sludge, but they had different effluent populations. Many dominant bacterial populations of raw sewage did not appear in the activated sludge samples, suggesting that the dominant bacterial populations in raw sewage might not play an important role during wastewater treatment. Although the two plants had different sludge properties in terms of settleability and foam forming ability, they demonstrated similar actinomycetic community structures. For activated sludge with bad settling performance, the treated water presented a similar DGGE pattern with that of activated sludge, indicating the nonselective washout of bacteria from the system. The plant with better ammonium removal efficiency showed higher ammonia-oxidizing bacteria species richness. Analysis of sequencing results showed that the major populations in raw sewage were uncultured bacterium, while in activated sludge the predominant populations were beta proteobacteria.展开更多
Alkaline and ultrasonic sludge disintegration can be used as the pretreatment of waste activated sludge （WAS） to promote the subsequent anaerobic or aerobic digestion. In this study, different combinations of these ...Alkaline and ultrasonic sludge disintegration can be used as the pretreatment of waste activated sludge （WAS） to promote the subsequent anaerobic or aerobic digestion. In this study, different combinations of these two methods were investigated. The evaluation was based on the quantity of soluble chemical oxygen demand （SCOD） in the pretreated sludge as well as the degradation of organic matter in the subsequent aerobic digestion. For WAS samples with combined pretreatment, the released COD levels were higher than those with ultrasonic or alkaline pretreatment alone. When combined with the ultrasonic treatment, NaOH treatment was more efficient than Ca（OH）2 for WAS solubilization. The COD levels released in various sequential options of combined NaOH and ultrasonic treatments were in the the following descending order： simultaneous treatment 〉 NaOH treatment followed by ultrasonic treatment 〉 ultrasonic treatment followed by NaOH treatment. For simultaneous treatment, low NaOH dosage （100 g/kg dry solid）, short duration （30 min） of NaOH treatment, and low ultrasonic specific energy （7500 kJ/kg dry solid） were suitable for sludge disintegration. Using combined NaOH and ultrasonic pretreatment with optimal parameters, the degradation efficiency of organic matter was increased from 38.0% to 50.7%, which is much higher than that with ultrasonic （42.5%） or with NaOH pretreatment （43.5%） in the subsequent aerobic digestion at the same retention time.展开更多
Extracellular polymeric substances （EPS） are the predominant constituents of activated sludge and represent up to 80% of the mass of activated sludge. They play a crucial role in the flocculation, settling and dewat...Extracellular polymeric substances （EPS） are the predominant constituents of activated sludge and represent up to 80% of the mass of activated sludge. They play a crucial role in the flocculation, settling and dewatering of activated sludge. Furthermore, EPS also show great efficiency in binding heavy metals. So EPS are key factors influencing reduction in sludge volume and mass, as well as activity and utilization of sludge. EPS are of considerable environmental interest and hundreds of articles on EPS have been published abroad, while information on EPS in China is limited. In this paper, results of over 60 publications related to constituents and characteristics of EPS and their influences on flocculation, settling and dewatering of sludge are compiled and analyzed. Metal-binding ability of EPS is also discussed, together with a brief consideration of possible research interests in the future.展开更多
The removal of heavy-metal ions from aqueous solutions by using dried activated sludge has been investigated in batch systems. Effect of solution pH, initial metal ion concentration, and temperature were determined. T...The removal of heavy-metal ions from aqueous solutions by using dried activated sludge has been investigated in batch systems. Effect of solution pH, initial metal ion concentration, and temperature were determined. The results of the kinetic studies showed that the uptake processes of the two metal ions（Cd（Ⅱ） and Pb（Ⅱ）） followed the pseudo-second-order rate expression. The equilibrium data fitted very well to both the Langmuir and Freundlich adsorption models. The FT-IR analysis showed that the main mechanism of Cd（Ⅱ） and Pb（Ⅱ） biosorption onto dried activated sludge was their binding with amide I group.展开更多
We investigated the communities of ammonia-oxidizing bacteria （AOB） in activated sludge collected from eight wastewater treatment systems using polymerase chain reaction （PCR） followed by terminal restriction frag...We investigated the communities of ammonia-oxidizing bacteria （AOB） in activated sludge collected from eight wastewater treatment systems using polymerase chain reaction （PCR） followed by terminal restriction fragment length polymorphism （T-RFLP）, cloning, and sequencing of the α-subunit of the ammonia monooxygenase gene （amoA）. The T-RFLP fingerprint analyses showed that different wastewater treatment systems harbored distinct AOB communities. However, there was no remarkable difference among the AOB T- RFLP profiles from different parts of the same system. The T-RFLP fingerprints showed that a full-scale wastewater treatment plant （WWTP） contained a larger number of dominant AOB species than a pilot-scale reactor. The source of influent affected the AOB community, and the WWTPs treating domestic wastewater contained a higher AOB diversity than those receiving mixed domestic and industrial wastewater. However, the AOB community structure was little affected by the treatment process in this study. Phylogenetic analysis of the cloned amoA genes clearly indicated that all the dominant AOB in the systems was closely related to Nitrosomonas spp. not to Nitrosospira spp. Members of the Nitrosomonas oligotropha and Nitrosomonas communis clusters were found in all samples, while members of Nitrosomonas europaea cluster occurred in some systems.展开更多
Activated sludge was immobilized into Ca-alginate beads via entrapment, and biosorption of three heavy metal ions, copper(Ⅱ), zinc(Ⅱ), and chromimum(Ⅱ), from aqueous solution in the concentration range of 10\_100 m...Activated sludge was immobilized into Ca-alginate beads via entrapment, and biosorption of three heavy metal ions, copper(Ⅱ), zinc(Ⅱ), and chromimum(Ⅱ), from aqueous solution in the concentration range of 10\_100 mg/L was studied by using both entrapped activated sludge and inactivated free biomass at pH≤5. A biphasic metal adsorption pattern was observed in all immobilized biomass experiments. The biosorption of metal ions by the biosorbents increased with the initial concentration increased in the medium. The adsorption rate of immobilized pre-treated activated sludge(PAS) was much lower than that of free PAS due to the increase in mass transfer resistance resulting from the polymeric matrix. Biosorption equilibrium of beads was established in about 20 h and the adsorbed heavy metal ions did not change further with time. No significant effect of temperature was observed in the test for free biomass while immobilized PAS appeared to be strong temperature dependent in the test range of 10 and 40℃. Besides, the content of activated sludge in the calcium alginate bead has an influence on the uptake of heavy metals. The sorption equilibrium was well modeled by Langmuir isotherm, implying monomolecular adsorption mechanism. Carboxyl group in cell wall played an important role in surface adsorption of heavy metal ions on PAS.展开更多
The anaerobic ammonia oxidation(Anammox) bioreactor was successfully started up with the nitrifying activated sludge. After anaerobically operated for 105 d, the bioreactor reached a good performance with removal perc...The anaerobic ammonia oxidation(Anammox) bioreactor was successfully started up with the nitrifying activated sludge. After anaerobically operated for 105 d, the bioreactor reached a good performance with removal percentage of both ammonia and nitrite higher than 95% and volumetric total nitrogen removal as high as 149.55 mmol/(L·d). The soft padding made an important contribution to the high efficiency and stability because it held a large amount of biomass in the bioreactor.展开更多
Activated sludge process has been widely used to remove phosphorus and nitrogen from wastewater. However,the nitrogen and phosphorus removal is sometimes unsatisfactory due to the low influent COD.Another problem with...Activated sludge process has been widely used to remove phosphorus and nitrogen from wastewater. However,the nitrogen and phosphorus removal is sometimes unsatisfactory due to the low influent COD.Another problem with the activated sludge process is that large amount of waste activated sludge is produced,which needs further treatment.In this study,the waste activated sludge alkaline fermentation liquid was used as the main carbon source for phosphorus and nitrogen removal under anaerobic followed by alternating aerobic-anoxic conditions,and the results were compared with those using acetic acid as the carbon source.The use of alkaline fermentation liquid not only affected the transformations of phosphorus,nitrogen,intracellular polyhydroxyalkanoates and glycogen, but also led to higher removal efficiencies for phosphorus and nitrogen compared with acetic acid.It was observed that ammonium was completely removed with either alkaline fermentation liquid or acetic acid as the carbon source. However,the former resulted in higher removal efficiencies for phosphorus(95%)and nitrogen(82%),while the latter showed lower ones(87%and 74%,respectively).The presence of a large amount of propionic acid in the alkaline fermentation liquid was one possible reason for its higher phosphorus removal efficiency.Exogenous instead of endogenous denitrification was the main pathway for nitrogen removal with the alkaline fermentation liquid as the carbon source,which was responsible for its higher nitrogen removal efficiency.It seems that the alkaline fermentation liquid can replace acetic acid as the carbon source for phosphorus and nitrogen removal in anaerobic fol- lowed by alternating aerobic-anoxic sequencing batch reactor.展开更多
The accumulation of short-chain fatty acids （SCFAs）, a preferred carbon source for enhanced biological phosphorus removal microbes, was significantly improved when waste activated sludge （WAS） was fermented at pH ...The accumulation of short-chain fatty acids （SCFAs）, a preferred carbon source for enhanced biological phosphorus removal microbes, was significantly improved when waste activated sludge （WAS） was fermented at pH 10. The kinetics of WAS hydrolysis and SCFAs production at pH 10 was investigated. It was observed that during WAS anaerobic fermentation the accumulation of SCFAs was limited by the hydrolysis process, and both the hydrolysis of WAS particulate COD and the accumulation of SCFAs followed first-order kinetics. The hydrolysis and SCFAs accumulation rate constants increased with increasing temperature from 10 to 35℃, which could be described by the Arrhenius equation. The kinetic data further indicated that SCFAs production at pH 10 was a biological process. Compared with the experiment of pH uncontrolled （blank test）, both the rate constants of WAS hydrolysis and SCFAs accumulation at 20℃ were improved significantly when WAS was fermented at pH 10.展开更多
Two bacterial stains were isolated from the activated sludge and identified as Leucobacter sp. and Alcaligenesfaecalis by 16S rDNA sequencing. Pure cultures of these two strains, representing well or poorly settled ba...Two bacterial stains were isolated from the activated sludge and identified as Leucobacter sp. and Alcaligenesfaecalis by 16S rDNA sequencing. Pure cultures of these two strains, representing well or poorly settled bacteria, were used to investigate the mechanism of bioflocculation in activated sludge. Based on the analyses of the characteristics of cells hydrophobicity, ζ-potential, flocculation ability and extracellular polymeric substance （EPS） composition under different growth stages, it was found that the ratio of cell EPS protein had the highly influence on ζ-potential and hydrophobicity, which were important factors to bioflocculation. Cellulase and Proteinase K could destroy the extracellular biopolymer and resulted in a decrease in the hydrophobicity and ζ-potential. However, in our study, the flocculation characteristics exhibited differently in relation to cellulase and Proteinase K. Flocculation of cells treated with cellulase and Proteinase K decreased sharply, and then recovered quickly in cellulase treatment, while cells treated with Proteinase K showed no sign of recovery. This reveals that the presence of protein in extracellular biopolymer plays an important role to the bioflocculation of cells.展开更多
Diatomite is a kind of natural low-cost mineral material. It has a number of unique physical properties and has been widely used as an adsorbent in wastewater treatment. This study was conducted to investigate the aer...Diatomite is a kind of natural low-cost mineral material. It has a number of unique physical properties and has been widely used as an adsorbent in wastewater treatment. This study was conducted to investigate the aerobic biodegradation of coal gasification wastewater with and without diatomite addition. Experimental results indicated that diatomite added in the activated sludge system could promote the biomass and also enhance the performance of the sludge settling. The average mixed-liquor volatile suspended solids （MLVSS） is increased from 4055 mg.L^-1 to 4518 mg.L^-1 and the average settling volume （SV） are changed only from 45.9% to 47.1%. Diatomite additive could enhance the efficiency of chemical oxygen demand （COD） and total phenols removal from the wastewater. The COD removal increased from 73.3% to near 80% and the total phenols removal increased from 81.4% to 85.8%. The mechanisms of the increase of biomass and pollutants removal may correlates to the improvement of bioavailability and sludge settlement characteristics by diatomite added. Micrograph of the sludge in the diatomite-activated sludge system indicated that the diatomite added could be the carrier of the microbe and also affect the biomass and pollutant removal.展开更多
To investigate the influences of alkaline pretreatment on anaerobic digestion （AD） and sludge dewaterability after AD, waste activated sludge was adjusted to different pH values （8, 9, 10, 1 1, 12） and placed at a...To investigate the influences of alkaline pretreatment on anaerobic digestion （AD） and sludge dewaterability after AD, waste activated sludge was adjusted to different pH values （8, 9, 10, 1 1, 12） and placed at ambient temperature for 24 hr. The samples were then adjusted to the initial pH and subjected to 25 days of AD. The results showed that, when compared with the control （pH 6.8）, total suspended solids （TSS） and volatile suspended solids （VSS） reduction following pretreatment at pH 9-11 increased by 10.7%-13.1% and 6.5%- 12.8%, respectively, while biogas production improved by 7.2%-15.4%. Additionally, significant enhancement of sludge dewaterability after AD occurred when pretreatment at pH 8-9 was conducted. The proteins and carbohydrates transferred from the pellet and tightly bound extracellular polymeric substances （TB-EPS） fractions to the slime and loosely bound EPS （LB-EPS） fractions after pretreatment and during the AD process, and the concentrations of proteins and carbohydrates in the slime fraction had a good linear relationship with the normalized capillary suction time （CST）. During the AD process, the normalized CST was positively correlated with the organic materials in the loosely bound fraction of the sludge matrix （R2/〉 0.700, p 〈 0.01）, while it was negatively correlated with the organic materials in the tightly bound fraction （R2≥ 0.702, p 〈 0.01）. These results suggest that alkaline pretreatment could break the EPS matrix and release inner organic materials, thus influencing the efficiency of the AD process and dewaterability after AD.展开更多
基金Project (No. 56310503014) supported by the Department of Education of Zhejiang Province, China
文摘Oily wastewater generated by various industries creates a major ecological problem throughout the world. The tra- ditional methods for the oily wastewater treatment are inefficient and costly. Surfactants can promote the biodegradation of pe- troleum hydrocarbons by dispersing oil into aqueous environment. In the present study, we applied rhamnolipid-containing cell-free culture broth to enhance the biodegradation of crude oil and lubricating oil in a conventional aerobically-activated sludge system. At 20 ℃, rhamnolipids （11.2 mg/L） increased the removal efficiency of crude oil from 17.7% （in the absence of rham- nolipids） to 63%. At 25 ~C, the removal efficiency of crude oil was over 80% with the presence of rhamnolipids compared with 22.3% in the absence of rhamnolipids. Similarly, rhamnolipid treatment （22.5 mg/L） for 24 h at 20℃ significantly increased the removal rate of lubricating oil to 92% compared with 24% in the absence of rhamnolipids. The enhanced removal of hydrocarbons was mainly attributed to the improved solubility and the reduced interfacial tension by rhamnolipids. We conclude that a direct application of the crude rhamnolipid solution from cell culture is effective and economic in removing oily contaminants from wastewater.
基金supported by the National Natural Science Foundation of China(No.52070149)Shaanxi Innovative Research Team for Key Science and Technology(No.2023-CXTD-36)+1 种基金Shaanxi Province Key Program for International S&T Cooperation Projects(No.2024GH-ZDXM-04)the Bureau of Science and Technology of Xi’an City of China(No.23SFSF0011).
文摘Anaerobic ammonia oxidation(Anammox)is an economical and sustainablewastewater nitrogen removal technology,and its application in the mainstream process is the inevitable trend of the development of Anammox.However,how to effectively enriching Anammox bacteria from the activated sludge remains challenging and restricts its extensive applications.In this study,the rapid and efficient enrichment of Anammox bacteriawas achieved by raising the reflux ratio and nitrogen loading rate(NLR)using conventional activated sludge as the inoculant.In the screening phase(days 1–90),the reflux ratio was increased to discharge partial floc sludge,resulting in the relative abundance of Candidatus Brocadiaceae increased from0.04%to 22.54%,which effectively reduced thematrix and spatial competition between other microorganisms and Anammox bacteria.On day 90,the stoichiometric ratio of the Anammox process closely approached the theoretical value of 1:1.32:0.26,indicating that the Anammox reaction was the primary nitrogen removal process in the system.In the enrichment phase(days 91–238),the NLR increased from 0.43 to 1.20 kgN/(m^(3)·d)and removal efficiency was 71.89%,resulting in the relative abundance of Candidatus Brocadiaceae increased to 61.27%on day 180.The reactor operated steadily from days 444 to 498,maintaining the nitrogen removal rate(NRR)of 3.00 kgN/(m^(3)·d)and achieving successful sludge granulation with the particle size of 392.4μm.In short,this study provided a simple and efficient approach for enriching Anammox bacteria from the activated sludge,supporting to start an Anammox process efficiently.
基金funded under the auspices of the National Key Research and Development Program of China(No.2023YFC3207404-01)the Postdoctoral Fellowship Program of CPSF(No.GZC20233450)the Heilongjiang Province Postdoctoral Science Foundation(No.LBHZ23154)。
文摘As a key step in waste activated sludge(WAS)treatment and disposal,WAS dewatering can minimize the amount of WAS and decrease the costs of transportation,storage management,treatment,and disposal.Advanced oxidation processes(AOPs)have been widely explored in WAS dewatering due to the excellent oxidizing properties and efficient decomposition capacity since the 21^(st)century.This review outlined the mechanisms of AOPs to improve WAS dewatering and pointed out the shortcomings of the existing mechanisms.Then,the applications of AOPs-based WAS dewatering processes for enhanced WAS dewatering were reviewed,and the intrinsic limitations of AOPs-based WAS dewatering processes in engineering applications were proposed.In addition,an overall review of AOPs-based WAS dewatering researches was also conducted through bibliometric analysis,and future research hotspots in the field of AOPs-based WAS dewatering were proposed.Finally,the positive effects of the AOPs-based WAS dewatering processes on pollutant removal and resource recovery were investigated,and an integrated plan for the harmless disposal of WAS was constructed to achieve a positive reform of the traditional WAS management plan.This review provided theoretical basis and technical reference for the development of efficient,economical,and environmental AOPs for enhanced WAS dewatering to facilitate the application of AOPs in actual WAS dewatering engineering.
基金supported by the National Natural Science Foundation of China(Grants No.52270155 and 92047201).
文摘Cresyl diphenyl phosphate(CDP),an emerging aryl organophosphate ester(OPE),exhibits potential toxic effects and is frequently found in diverse environmental media,thereby raising concerns about environmental pollution.Biodegradation demonstrates substantial potential for CDP removal from the environment.This study investigated the biodegradation mechanisms of CDP using anaerobic activated sludge(AnAS).The biodegradation of 1-mg/L CDP followed a first-order kinetic model with a degradation kinetic constant of 0.943 d^(-1),and the addition of different electron acceptors affected the degradation rate.High-resolution mass spectrometry identified seven transformation products(TPs)of CDP.The pathways of CDP degradation in anaerobic conditions were proposed,with carboxylation products being the most dominant intermediate products.The structure of the anaerobic microbial community at different degradation time points in CDP-amended microcosms was examined.The linear discriminant analysis(LDA)of effect size(LEfSe)potentially underscored the pivotal role of Methyloversatilis in CDP biodegradation.Zebrafish embryotoxicity experiments revealed both lethal and morphogenetic impacts of CDP on zebrafish embryos.The survival rate,hatching rate,and body length indicators of zebrafish embryos underscored the detoxification of CDP and its resultant intermediates by AnAS.This study offers new insights into the fate and biodegradation mechanisms of CDP in wastewater treatment plants.
基金supported by the National Special Project for Science and Technology on Water Pollution Control and Management(No.2017ZX07102-003)the Fundamental Research Funds for the Central Universities,and the Research Funds of Renmin University of China(No.2020030257).
文摘This study embarks on an explorative investigation into the effects of typical concentrations and varying particle sizes of fine grits(FG,the involatile portion of suspended solids)and fine debris(FD,the volatile yet unbiodegradable fraction of suspended solids)within the influent on themixed liquor volatile suspended solids(MLVSS)/mixed liquor suspended solids(MLSS)ratio of an activated sludge system.Through meticulous experimentation,it was discerned that the addition of FG or FD,the particle size of FG,and the concentration of FD bore no substantial impact on the pollutant removal efficiency(denoted by the removal rate of COD and ammonia nitrogen)under constant operational conditions.However,a notable decrease in the MLVSS/MLSS ratio was observed with a typical FG concentration of 20 mg/L,with smaller FG particle sizes exacerbating this reduction.Additionally,variations in FD concentrations influenced both MLSS andMLVSS/MLSS ratios;a higher FD concentration led to an increased MLSS and a reduced MLVSS/MLSS ratio,indicating FD accumulation in the system.A predictive model for MLVSS/MLSS was constructed based on quality balance calculations,offering a tool for foreseeing the MLVSS/MLSS ratio under stable long-term influent conditions of FG and FD.This model,validated using data from the BXH wastewater treatment plant(WWTP),showcased remarkable accuracy.
文摘Biochar is a massively produced by-product of biomass pyrolysis to obtain renewable energy and has not been fully used. Incomplete separation of sludge and effluent and insufficient denitrification of sewage are two of main factors that influence the efficiency of activated sludge process. In this work, we proposed a new utilization of biochar and investigated the effect of biochar addition on the performance of settleability and denitrification of activated sludge. Results show that the addition of biochar can improve the settleability of activated sludge by changing the physicochemical characteristics of sludge （e.g., flocculating ability, zeta-potential, hydrophobicity, and extracellular polymeric substances constituents）. Moreover, the dissolved organic carbon released from biochar obtained at lower pyrolysis temperature can improve the nitrate removal efficiency to a certain extent.
文摘This paper researched a promising biological treatment of methyl violet waste water by methods of activated sludge.Effects of temperature and pH were studied on this process.Kinetic equation of the substrate biodegradation was investigated in the experimental range.It was studied and simulated that flow within the bubble region of this bioreactor according to the κ ε two fluid equation.Simulation results agree well with experimental data.
基金Supported by the National High-tech Research and Develop Program of China("863"Program)(2009AA064704)the National Natural Science Foundation of China(51038003)the Program for New Century Excellent Talents in University by the State Education Ministry(NCET-08-161)~~
文摘[Objective] To explore the optimal extraction conditions of extracellular polymeric substances （EPS） from activated sludge. [Method] The efficiency of five methods （H2SO4, formaldehyde-NaOH, mixing, heating and NaOH） on the extraction of EPS was investigated comparatively. The optimal extraction conditions of the most suitable method were determined. [Result] NaOH method is most effective in extracting EPS with less DNA contamination and shortened extraction period. The optimal extraction condition was pH of 11, extraction time of 10 min and agitation speed of 80-120 r/min. [Conclusion] The determined optimal extraction condition provided theoretical basis for EPS study.
基金Project supported by the National Natural Science Foundation of China (No. 20510076, 50238050).
文摘The bacterial community structures in two sewage treatment plants with different processes and performance were investigated by denaturing gradient gel electrophoresis （DGGE） of nested polymerase chain reaction （nested PCR） amplified 16S rRNA gene fragments with group-specific primers. Samples of raw sewage and treated effluents were amplified using the whole-cell PCR method, and the activated sludge samples were amplified using the extracted genomic DNA before the PCR products were loaded on the same DGGE gel for bacterial community analysis. Ammonia-oxidizing bacterial and actinomycetic community analysis were also carried out to investigate the relationship between specific population structures and system or sludge performance. The two plants demonstrated a similarity in bacterial community structures of raw sewage and activated sludge, but they had different effluent populations. Many dominant bacterial populations of raw sewage did not appear in the activated sludge samples, suggesting that the dominant bacterial populations in raw sewage might not play an important role during wastewater treatment. Although the two plants had different sludge properties in terms of settleability and foam forming ability, they demonstrated similar actinomycetic community structures. For activated sludge with bad settling performance, the treated water presented a similar DGGE pattern with that of activated sludge, indicating the nonselective washout of bacteria from the system. The plant with better ammonium removal efficiency showed higher ammonia-oxidizing bacteria species richness. Analysis of sequencing results showed that the major populations in raw sewage were uncultured bacterium, while in activated sludge the predominant populations were beta proteobacteria.
基金supported by the China NationalEleventh Five-Year Scientific and Technical Support Plan(No. 2006BAC02A18)
文摘Alkaline and ultrasonic sludge disintegration can be used as the pretreatment of waste activated sludge （WAS） to promote the subsequent anaerobic or aerobic digestion. In this study, different combinations of these two methods were investigated. The evaluation was based on the quantity of soluble chemical oxygen demand （SCOD） in the pretreated sludge as well as the degradation of organic matter in the subsequent aerobic digestion. For WAS samples with combined pretreatment, the released COD levels were higher than those with ultrasonic or alkaline pretreatment alone. When combined with the ultrasonic treatment, NaOH treatment was more efficient than Ca（OH）2 for WAS solubilization. The COD levels released in various sequential options of combined NaOH and ultrasonic treatments were in the the following descending order： simultaneous treatment 〉 NaOH treatment followed by ultrasonic treatment 〉 ultrasonic treatment followed by NaOH treatment. For simultaneous treatment, low NaOH dosage （100 g/kg dry solid）, short duration （30 min） of NaOH treatment, and low ultrasonic specific energy （7500 kJ/kg dry solid） were suitable for sludge disintegration. Using combined NaOH and ultrasonic pretreatment with optimal parameters, the degradation efficiency of organic matter was increased from 38.0% to 50.7%, which is much higher than that with ultrasonic （42.5%） or with NaOH pretreatment （43.5%） in the subsequent aerobic digestion at the same retention time.
基金The National Natural Science Foundation of China (No. 50578053) and the Harbin Young Scientist Fund (No. 2003AFXXJ025)
文摘Extracellular polymeric substances （EPS） are the predominant constituents of activated sludge and represent up to 80% of the mass of activated sludge. They play a crucial role in the flocculation, settling and dewatering of activated sludge. Furthermore, EPS also show great efficiency in binding heavy metals. So EPS are key factors influencing reduction in sludge volume and mass, as well as activity and utilization of sludge. EPS are of considerable environmental interest and hundreds of articles on EPS have been published abroad, while information on EPS in China is limited. In this paper, results of over 60 publications related to constituents and characteristics of EPS and their influences on flocculation, settling and dewatering of sludge are compiled and analyzed. Metal-binding ability of EPS is also discussed, together with a brief consideration of possible research interests in the future.
基金The National New Century Scholarship (No. NCET-05-0387) the France-China P2R Programs and the Specialized Research Fundfor the Doctoral Program of Higher Education (No. 20050247016)
文摘The removal of heavy-metal ions from aqueous solutions by using dried activated sludge has been investigated in batch systems. Effect of solution pH, initial metal ion concentration, and temperature were determined. The results of the kinetic studies showed that the uptake processes of the two metal ions（Cd（Ⅱ） and Pb（Ⅱ）） followed the pseudo-second-order rate expression. The equilibrium data fitted very well to both the Langmuir and Freundlich adsorption models. The FT-IR analysis showed that the main mechanism of Cd（Ⅱ） and Pb（Ⅱ） biosorption onto dried activated sludge was their binding with amide I group.
基金supported by the Key Projects in National Science & Technology Pillar Program during the Eleventh Five-Year Plan Period (No.2006BAC19B01-02)the Mega-projects of Science Research for Water (No.2008ZX07313-3)the Program of Introducing Talents of Discipline to Universities
文摘We investigated the communities of ammonia-oxidizing bacteria （AOB） in activated sludge collected from eight wastewater treatment systems using polymerase chain reaction （PCR） followed by terminal restriction fragment length polymorphism （T-RFLP）, cloning, and sequencing of the α-subunit of the ammonia monooxygenase gene （amoA）. The T-RFLP fingerprint analyses showed that different wastewater treatment systems harbored distinct AOB communities. However, there was no remarkable difference among the AOB T- RFLP profiles from different parts of the same system. The T-RFLP fingerprints showed that a full-scale wastewater treatment plant （WWTP） contained a larger number of dominant AOB species than a pilot-scale reactor. The source of influent affected the AOB community, and the WWTPs treating domestic wastewater contained a higher AOB diversity than those receiving mixed domestic and industrial wastewater. However, the AOB community structure was little affected by the treatment process in this study. Phylogenetic analysis of the cloned amoA genes clearly indicated that all the dominant AOB in the systems was closely related to Nitrosomonas spp. not to Nitrosospira spp. Members of the Nitrosomonas oligotropha and Nitrosomonas communis clusters were found in all samples, while members of Nitrosomonas europaea cluster occurred in some systems.
文摘Activated sludge was immobilized into Ca-alginate beads via entrapment, and biosorption of three heavy metal ions, copper(Ⅱ), zinc(Ⅱ), and chromimum(Ⅱ), from aqueous solution in the concentration range of 10\_100 mg/L was studied by using both entrapped activated sludge and inactivated free biomass at pH≤5. A biphasic metal adsorption pattern was observed in all immobilized biomass experiments. The biosorption of metal ions by the biosorbents increased with the initial concentration increased in the medium. The adsorption rate of immobilized pre-treated activated sludge(PAS) was much lower than that of free PAS due to the increase in mass transfer resistance resulting from the polymeric matrix. Biosorption equilibrium of beads was established in about 20 h and the adsorbed heavy metal ions did not change further with time. No significant effect of temperature was observed in the test for free biomass while immobilized PAS appeared to be strong temperature dependent in the test range of 10 and 40℃. Besides, the content of activated sludge in the calcium alginate bead has an influence on the uptake of heavy metals. The sorption equilibrium was well modeled by Langmuir isotherm, implying monomolecular adsorption mechanism. Carboxyl group in cell wall played an important role in surface adsorption of heavy metal ions on PAS.
文摘The anaerobic ammonia oxidation(Anammox) bioreactor was successfully started up with the nitrifying activated sludge. After anaerobically operated for 105 d, the bioreactor reached a good performance with removal percentage of both ammonia and nitrite higher than 95% and volumetric total nitrogen removal as high as 149.55 mmol/(L·d). The soft padding made an important contribution to the high efficiency and stability because it held a large amount of biomass in the bioreactor.
基金Supported by the National High Technology Research and Development Program of China(2007AA06Z326)the Programfor New Century Excellent Talents(06-0373)in University
文摘Activated sludge process has been widely used to remove phosphorus and nitrogen from wastewater. However,the nitrogen and phosphorus removal is sometimes unsatisfactory due to the low influent COD.Another problem with the activated sludge process is that large amount of waste activated sludge is produced,which needs further treatment.In this study,the waste activated sludge alkaline fermentation liquid was used as the main carbon source for phosphorus and nitrogen removal under anaerobic followed by alternating aerobic-anoxic conditions,and the results were compared with those using acetic acid as the carbon source.The use of alkaline fermentation liquid not only affected the transformations of phosphorus,nitrogen,intracellular polyhydroxyalkanoates and glycogen, but also led to higher removal efficiencies for phosphorus and nitrogen compared with acetic acid.It was observed that ammonium was completely removed with either alkaline fermentation liquid or acetic acid as the carbon source. However,the former resulted in higher removal efficiencies for phosphorus(95%)and nitrogen(82%),while the latter showed lower ones(87%and 74%,respectively).The presence of a large amount of propionic acid in the alkaline fermentation liquid was one possible reason for its higher phosphorus removal efficiency.Exogenous instead of endogenous denitrification was the main pathway for nitrogen removal with the alkaline fermentation liquid as the carbon source,which was responsible for its higher nitrogen removal efficiency.It seems that the alkaline fermentation liquid can replace acetic acid as the carbon source for phosphorus and nitrogen removal in anaerobic fol- lowed by alternating aerobic-anoxic sequencing batch reactor.
基金supported by the Hi-TechResearch and Development Program (863) of China(No. 2007AA06Z326)the Key Projects of National Wa-ter Pollution Control and Management of China (No.2008ZX07315-003, 2008ZX07316-002)the Key Lab-oratory of Environmental Science and Engineering ofJiangsu Province (No. ZD071201).
文摘The accumulation of short-chain fatty acids （SCFAs）, a preferred carbon source for enhanced biological phosphorus removal microbes, was significantly improved when waste activated sludge （WAS） was fermented at pH 10. The kinetics of WAS hydrolysis and SCFAs production at pH 10 was investigated. It was observed that during WAS anaerobic fermentation the accumulation of SCFAs was limited by the hydrolysis process, and both the hydrolysis of WAS particulate COD and the accumulation of SCFAs followed first-order kinetics. The hydrolysis and SCFAs accumulation rate constants increased with increasing temperature from 10 to 35℃, which could be described by the Arrhenius equation. The kinetic data further indicated that SCFAs production at pH 10 was a biological process. Compared with the experiment of pH uncontrolled （blank test）, both the rate constants of WAS hydrolysis and SCFAs accumulation at 20℃ were improved significantly when WAS was fermented at pH 10.
基金supported by the National Natural Science Foundation of China(No. 20977031)the Natural Science Foundation of Shanghai(No. 09zr1409000)+2 种基金the Research Initiatives of the University of Hong Kong(2006)the Royal Society of New Zealand(ISAT B09-33)Faculty of Health & Environmental Sciences,Auckland University of Technology
文摘Two bacterial stains were isolated from the activated sludge and identified as Leucobacter sp. and Alcaligenesfaecalis by 16S rDNA sequencing. Pure cultures of these two strains, representing well or poorly settled bacteria, were used to investigate the mechanism of bioflocculation in activated sludge. Based on the analyses of the characteristics of cells hydrophobicity, ζ-potential, flocculation ability and extracellular polymeric substance （EPS） composition under different growth stages, it was found that the ratio of cell EPS protein had the highly influence on ζ-potential and hydrophobicity, which were important factors to bioflocculation. Cellulase and Proteinase K could destroy the extracellular biopolymer and resulted in a decrease in the hydrophobicity and ζ-potential. However, in our study, the flocculation characteristics exhibited differently in relation to cellulase and Proteinase K. Flocculation of cells treated with cellulase and Proteinase K decreased sharply, and then recovered quickly in cellulase treatment, while cells treated with Proteinase K showed no sign of recovery. This reveals that the presence of protein in extracellular biopolymer plays an important role to the bioflocculation of cells.
基金Supported by the Shanghai Committee of Education (07ZZ158)
文摘Diatomite is a kind of natural low-cost mineral material. It has a number of unique physical properties and has been widely used as an adsorbent in wastewater treatment. This study was conducted to investigate the aerobic biodegradation of coal gasification wastewater with and without diatomite addition. Experimental results indicated that diatomite added in the activated sludge system could promote the biomass and also enhance the performance of the sludge settling. The average mixed-liquor volatile suspended solids （MLVSS） is increased from 4055 mg.L^-1 to 4518 mg.L^-1 and the average settling volume （SV） are changed only from 45.9% to 47.1%. Diatomite additive could enhance the efficiency of chemical oxygen demand （COD） and total phenols removal from the wastewater. The COD removal increased from 73.3% to near 80% and the total phenols removal increased from 81.4% to 85.8%. The mechanisms of the increase of biomass and pollutants removal may correlates to the improvement of bioavailability and sludge settlement characteristics by diatomite added. Micrograph of the sludge in the diatomite-activated sludge system indicated that the diatomite added could be the carrier of the microbe and also affect the biomass and pollutant removal.
基金supported by the National Natural Science Foundation of China (No. 20977066)the Program of Shanghai Subject Chief Scientist (No. 10XD1404200)
文摘To investigate the influences of alkaline pretreatment on anaerobic digestion （AD） and sludge dewaterability after AD, waste activated sludge was adjusted to different pH values （8, 9, 10, 1 1, 12） and placed at ambient temperature for 24 hr. The samples were then adjusted to the initial pH and subjected to 25 days of AD. The results showed that, when compared with the control （pH 6.8）, total suspended solids （TSS） and volatile suspended solids （VSS） reduction following pretreatment at pH 9-11 increased by 10.7%-13.1% and 6.5%- 12.8%, respectively, while biogas production improved by 7.2%-15.4%. Additionally, significant enhancement of sludge dewaterability after AD occurred when pretreatment at pH 8-9 was conducted. The proteins and carbohydrates transferred from the pellet and tightly bound extracellular polymeric substances （TB-EPS） fractions to the slime and loosely bound EPS （LB-EPS） fractions after pretreatment and during the AD process, and the concentrations of proteins and carbohydrates in the slime fraction had a good linear relationship with the normalized capillary suction time （CST）. During the AD process, the normalized CST was positively correlated with the organic materials in the loosely bound fraction of the sludge matrix （R2/〉 0.700, p 〈 0.01）, while it was negatively correlated with the organic materials in the tightly bound fraction （R2≥ 0.702, p 〈 0.01）. These results suggest that alkaline pretreatment could break the EPS matrix and release inner organic materials, thus influencing the efficiency of the AD process and dewaterability after AD.
