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Effect of sludge retention time on sludge characteristics and membrane fouling of membrane bioreactor

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Journal of Environmental Sciences 2009年第10期21卷 1329-1335页

作者： OUYANG Ke liu junxin Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China.

Three identical membrane bioreactors （MBRs） were operated over 2 years at different sludge retention time （SRT） of 10 d, 40 d and no sludge withdrawal （NS）, to elucidate and quantify the effect of SRT on the sludge characteristics and membrane fouling. The hydraulic retention times of these MBRs were controlled at 12 h. With increasing SRT, the sludge concentrations in the MBRs increased, whereas the ratio of volatile suspended solid to the total solid decreased, and the size of sludge granule diminished in the meantime. A higher sludge concentration at long SRT could maintain a better organic removal efficiency, and a longer SRT was propitious to the growth of nitrifiers. The performance of these MBRs for the removal of COD and NH4^＋-N did not change much with different SRTs. However, the bioactivity decreased as SRT increase. The measurement of specific oxygen uptake rates （SOUR） and fluorescence in situ hybridization （FISH） with rRNA-targeted oligonucleotide probes testified that SOUR and the proportion of the bacteria-specific probe EUB338 in all DAPI-stainable bacteria decreased with increasing SRT. The concentrations of total organic carbon, protein, polysaccharides and soluble extracellular polymeric substance （EPS） in the mixed liquor supernatant also decreased with increasing SRT. The membrane fouling rate was higher at shorter SRT, and the highest fouling rate appeared at a SRT of 10 d. Both the sludge cake layer and gel layer had contribution to the fouling resistance, but the relative contribution of the gel layer decreased as SRT increase.

关键词： membrane bioreactor sludge retention time extracellular polymeric substances wastewater treatment

Performance of two biofilters with neutral and low pH treating off-gases

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Journal of Environmental Sciences 2008年第12期20卷 1409-1414页

作者： liu Jianwei liu junxin LI Lin Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China

Two different functional biofilters were carried out and compared for the treatment of off-gas containing multicomponent odors and volatile organic compounds (VOCs) in this study. The effects of pH values and the empty bed retention time (EBRT) on the performance of the bioreactors were studied; and the characteristics of microbial populations in the two biofilters were also determined. The experimental results indicated that the removal effciencies of hydrophilic compounds such as butyric acid and ammonia ...

关键词： waste gas treatment biofiltration VOCs and odors bacteria fungi

Simultaneous removal of hydrogen sulfide and toluene in a bioreactor:Performance and characteristics of microbial community

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Journal of Environmental Sciences 2011年第3期23卷 353-359页

作者： Min Gao LinLi junxin liu Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China

We investigated the correlation between performance and the bacteria community composition by H2S and toluene co-treatment. Operation of the bioreactor was divided into four stages, in which the inlet concentration of toluene and H2S were gradually increased. In Stage I, toluene was the sole target compound with an average removal efficiency of 86.49%. After adding HeS in Stage II, removal efficiency of toluene decreased immediately and recovered gradually to 85.96%. When the inlet concentration of toluene and HzS was increased in Stage III and Stage IV, respectively, the average removal efficiency for toluene increased continuously from 86.31% to 87.24%. The elimination capacities of toluene increased with increasing inlet loading rates of toluene and H2S. Results of the PCR-DGGE analysis showed a turnover growth and decline of the microbial populations in the bioreactor. In Stage I, the dominant toluene-degrading bacteria mainly contained Pseudomonas sp. strain PS ＋ and Hydrogenophaga sp. In Stage IV, however, the dominant toluene-degrading bacteria was aciduric bacteria （Clostridium populeti）. The dominant microbial community in the bioreactor enhanced the elimination capacity of toluene, and adding H2S changed the environment of microbial growth, thus resulted in an evolution of dominant microorganisms. Analyses of microbial community and their activities provides valuable information to efficiently enhance simultaneous removal of toluene and H2S in the bioreactor.

关键词： off-gas treatment bacterial community hydrogen sulfate toluene

Characterization of the airborne bacteria community at different distances from the rotating brushes in a wastewater treatment plant by 16S rRNA gene clone libraries

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Journal of Environmental Sciences 2013年第1期25卷 5-15页

作者： Yunping Han Lin Li junxin liu Department of Water Pollution Control Technology Research Center for Eco-Environmental SciencesChinese Academy of Sciences

Biological risks of bioaerosols emitted from wastewater treatment processes have attracted wide attention in the recent years. However, the culture-based analysis method has been mostly adopted for detecting the bacterial community in bioaerosols, which may result in the underestimation of total microorganism concentration as not all microorganisms are cultivable. In this study, oligonucleotide fingerprinting of 16S rRNA genes was applied to reveal the composition and structure of the bacterial community in bioaerosols from an Orbal oxidation ditch in a Beijing wastewater treatment plant （WWTP）. Bioaerosols were collected at different distances from the aerosol source, rotating brushes, and the sampling height was 1.5 m which is the common respiratory height of a human being. The bacterial communities of bioaerosols were diverse, and the lowest bacterial diversity was found at the sampling site just after the rotating brush rotating brush. A large proportion of bacteria in bioaerosols were affiliated with Proteobacteria and Bacteroidetes. Numerous bacteria present in the bioaerosols also emerged in water, indicating that the bacterial community in the bioaerosols was related to that of the aerosols＇ sources. The forced aeration of rotating brushes brought about observably distinct bacterial communities between sampling sites situated before and after the rotating brush. Isolation sources of closest relatives in bioaerosols clone libraries were associated with the aqueous environment in the WWTP. Common potential pathogens in bioaerosols as well as those not reported in previous research were also analyzed in this study. Measures should be adopted to reduce the emission of bioaerosols and prevent their exposure to workers.

关键词： airborne bacteria genetic structure clone library wastewater treatment plant rotating brushes

Characteristics of greenhouse gas emission in three full-scale wastewater treatment processes

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Journal of Environmental Sciences 2014年第2期26卷 256-263页

作者： Xu Yan Lin Li junxin liu Department of Water Pollution Control Technology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences

Three full-scale wastewater treatment processes, Orbal oxidation ditch, anoxic/anaerobic/aerobic （reversed A^2O） and anaerobic/anoxic/aerobic （A^2O）, were selected to investigate the emission characteristics of greenhouse gases （GHG）, including carbon dioxide （CO2）, methane （CH4） and nitrous oxide （N2O）. Results showed that although the processes were different, the units presenting high GHG emission fluxes were remarkably similar, namely the highest CO2 and N2O emission fluxes occurred in the aerobic areas, and the highest CH4 emission fluxes occurred in the grit tanks. The GHG emission amount of each unit can be calculated from its area and GHG emission flux. The calculation results revealed that the maximum emission amounts of CO2, CH4 and N2O in the three wastewater treatment processes appeared in the aerobic areas in all cases. Theoretically, CH4 should be produced in anaerobic conditions, rather than aerobic conditions. However, results in this study showed that the CH4 emission fluxes in the forepart of the aerobic area were distinctly higher than in the anaerobic area. The situation for N2O was similar to that of CH4： the N2O emission flux in the aerobic area was also higher than that in the anoxic area. Through analysis of the GHG mass balance, it was found that the flow of dissolved GHG in the wastewater treatment processes and aerators may be the main reason for this phenomenon. Based on the monitoring and calculation results, GHG emission factors for the three wastewater treatment processes were determined. The A^2O process had the highest CO2 emission factor of 319.3 g CO2/kg CODremoved, and the highest CH4 and N2O emission factors of 3.3 g CH4/kg CODremoved and 3.6 g N2O/kg TNremoved were observed in the Orbal oxidation ditch process.

关键词： wastewater treatment greenhouse gas carbon dioxide methane nitrous oxide emission factor

Investigation on mechanism of phosphate removal on carbonized sludge adsorbent

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Journal of Environmental Sciences 2018年第2期30卷 335-344页

作者： Lei Zhang junxin liu Xuesong Guo Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China University of Chinese Academy of Sciences Beijing 100049 China

For the removal of phosphate（PO43-） from water, an adsorbent was prepared via carbonization of sewage sludge from a wastewater treatment plant： carbonized sludge adsorbent（CSA）. The mechanism of phosphate removal was determined after studying the structure and chemical properties of the CSA and its influence on phosphate removal. The results demonstrate that phosphate adsorption by the CSA can be fitted with the pseudo second-order kinetics and Langmuir isotherm models, indicating that the adsorption is single molecular layer adsorption dominated by chemical reaction. The active sites binding phosphate on the surface are composed of mineral particles containing Si/Ca/Al/Fe. The mineral containing Ca, calcite, is the main factor responsible for phosphate removal. The phosphate removal mechanism is a complex process including crystallization via the interaction between Ca2＋ and PO43-; formation of precipitates of Ca2＋, Al3＋, and PO43-; and adsorption of PO43-on some recalcitrant oxides composed of Si/Al/Fe.

关键词： Sewage sludge Carbonization Phosphate removal Mechanism

Temporal variation of microbial population in a thermophilic biofilter for SO_2 removal

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Journal of Environmental Sciences 2016年第1期28卷 4-12页

作者： Jingying Zhang Lin Li junxin liu Research Center for Eco-Environmental Sciences Chinese Academy of Sciences

The performance of a biofilter relies on the activity of microorganisms during the gas contaminant treatment process. In this study, SO2 was treated using a laboratory-scale biofilter packed with polyurethane foam cubes（PUFC）, on which thermophilic desulfurization bacteria were attached. The thermophilic biofilter effectively reduced SO2 within 10 months of operation time, with a maximum elimination capacity of 48.29 g/m^3/*** shifts in the microbial population in the thermophilic biofilter were determined through polymerase chain reaction-denaturing gradient gel electrophoresis and deoxyribonucleic acid（DNA） sequence analysis. The substrate species and environmental conditions in the biofilter influenced the microbial population. Oxygen distribution in the PUFC was analyzed using a microelectrode. When the water-containing rate in PUFC was over 98%, the oxygen distribution presented aerobic–anoxic–aerobic states along the test route on the PUFC. The appearance of sulfate-reducing bacteria was caused by the anaerobic conditions and sulfate formation after 4 months of operation.

关键词： Thermophilic biofilter Sulfur dioxide Microbial population DGGE analysis O2 distribution

Flocculating characteristic of activated sludge flocs:Interaction between Al^(3+) and extracellular polymeric substances

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Journal of Environmental Sciences 2013年第5期25卷 916-924页

作者： Xiaodong Ruan Lin Li junxin liu Research Center for Eco-Environmental Science Chinese Academy of Sciences

Aluminum flocculant can enhance the flocculating performance of activated ***,the binding mechanism of aluminum ion（Al 3＋） and extracellular polymeric substances（EPS） in activated sludge is unclear due to the complexity of *** this work,threedimensional excitation emission matrix fluorescence spectroscopy（3DEEM）,fluorescence quenching titration and Fourier transform infrared spectroscopy（FT-IR） were used to explore the binding behavior and mechanism between Al 3＋ and *** results showed that two fluorescence peaks of tyrosineand tryptophan-like substances were identified in the loosely bound-extracellular polymeric substances（LB-EPS）,and three peaks of tyrosine-,tryptophanand humic-like substances were identified in the tightly boundextracellular polymeric substances（TB-EPS）.It was found that these fluorescence peaks could be quenched with Al 3＋ at the dosage of 3.0 mg/L,which demonstrated that strong interactions took place between the EPS and Al 3＋.The conditional stability constants for Al 3＋ and EPS were determined by the Stern-Volmer *** to the binding mechanism,the-OH,N-H,C=O,C-N groups and the sulfurand phosphorus-containing groups showed complexation action,although the groups in the LB-EPS and TB-EPS showed different *** TB-EPS have stronger binding ability to Al 3＋ than the LB-EPS,and TB-EPS play an important role in the interaction with Al 3＋.

关键词： extracellular polymeric substances activated sludge aluminum ion three-dimensional excitation emission matrix fluorescence quenching Fourier transform infrared spectroscopy

Effects of various pretreatments on biohydrogen production from sewage sludge

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Chinese Science Bulletin 2009年第12期54卷 2038-2044页

作者： XIAO BenYi liu junxin Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China

The sewage sludge of wastewater treatment plant is a kind of biomass which contains many organics, mainly carbohydrates and proteins. Four pretreatments, acid pretreatment, alkaline pretreatment, thermal pretreatment and ultrasonic pretreatment, were used to enhance biohydrogen production from sewage sludge. The experimental results showed that the four pretreatments could all increase the soluble chemical oxygen demand (SCOD) of sludge and decrease the dry solid (DS) and volatile solid (VS) because the pretreatments could disrupt the floc structure and even the microbial cells of sludge. The results of batch anaerobic fermentation experiments demonstrated that all of the four pretreatments could select hydrogen-producing microorganisms from the microflora of sludge and enhance the hydrogen production. The hydrogen yield of the alkaline pretreated sludge at initial pH of 11.5 was the maximal (11.68 mL H2/g VS) and that of the thermal pretreated sludge was the next (8.62 mL H2/g VS). The result showed that the hydrogen yield of pretreated sludge was correlative with its SCOD. The hydrogen yields of acid pretreated sludge and alkaline pretreated sludge were also influenced by their initial pH. No methane could be detected in the anaerobic fermentation of alkaline pretreated sludge and thermal pretreated sludge, which suggested that these pretreatments could fully inhibit the activity of methanogens. The volatile fatty acids (VFA) production in anaerobic fermentation of alkaline pre- treated sludge was the maximum and the next is that of thermal pretreated sludge.

关键词：污泥预处理碱预处理生物制氢挥发性脂肪酸碱性预处理污水处理厂挥发性固体初始pH值