Biodegradation of triclosan and formation of methyl-triclosan in activated sludge under aerobic conditions

Triclosan is an antimicrobial agent which is widely used in household and personal care products. Widespread use of this compound has led to the elevated concentrations of triclosan in wastewater, wastewater treatment plants (WWTPs) and receiving waters. Removal of triclosan and formation of triclosan-methyl was investigated in activated sludge from a standard activated sludge WWTP equipped with enhanced biological phosphorus removal. The removal was found to occur mainly under aerobic conditions while under anoxic (nitrate reducing) and anaerobic conditions rather low removal rates were determined. In a laboratory-scale activated sludge reactor 75% of the triclosan was removed under aerobic conditions within 150 h, while no removal was observed under anaerobic or anoxic conditions. One percent of the triclosan was converted to triclosan-methyl under aerobic conditions, less under anoxic (nitrate reducing) and none under anaerobic conditions.     

Two-stage biodegradation coupled with ultrafiltration for treatment of municipal landfill leachate

The municipal landfill leachate was treated in a hydrolysis–acidification reactor (HAR)/aerobic bio-contact oxidation reactor (ABOR) following a pretreatment with ultrafiltration (UF) membrane. Experiments were conducted continuously for 44 days at a constant flow rate of 20 l d⁻¹ and organic loading rates (OLRs) from 0.75 to 1.5 kgCOD m⁻³ per day. The results showed that COD of the leachate steadily decreased from 20,015 mg l⁻¹ to less than 3000 mg l⁻¹, and NH₄-N decreased from 368.6 mg l⁻¹ to 259.3 mg l⁻¹ in the UF process. The COD and NH₄-N removal efficiency of HAR was 56.7% and 27.7%, and that of ABOR was 94.6% and 86.7%, respectively. The total COD and NH₄-N removal efficiency reached 99.6% and 93.2%, respectively. UF and HAR played a critical role in raising the biodegradability of the landfill leachate, while ABOR had an important function on removing the dissolved NH₄-N in leachate.     

Aerobic biotransformation of decabromodiphenyl ether (PBDE-209) by Pseudomonas aeruginosa

Aerobic biodegradation of decabromodiphenyl ether (PBDE-209) by Pseudomonas aeruginosa under the influence of co-metabolic substrates and heavy metal cadmium ion was studied, The results showed that certain amount of co-metabolic substrates, such as glucose, sucrose, lactose, starch, and beef extract, would promote the biodegradation of PBDE-209, among which glucose most favorably accelerated PBDE-209 degradation by about 36% within 5 d. The highest degradation efficiency was reached at the ratio of PBDE-209 and glucose 1:5 while excessive carbon source would actually hamper the degradation efficiency. Exploration of influences of cadmium ion on PBDE-209 biodegradation indicated that degradation efficiency was stimulated at low concentrations of Cd²⁺ (0.5–2 mg L⁻¹) while inhibited at higher levels (5–10 mg L⁻¹), inferring that the heavy metals of different concentrations possessed mixed reactions on PBDE-209 bioremoval. Bromine ion was produced during the biotransformation process and its concentration had a good negative correlation with the residues of PBDE-209. Two nonabromodiphenyl ethers (PBDE-208, PBDE-207), four octabromodiphenyl ethers (PBDE-203, PBDE-202, PBDE-197, PBDE-196) and one heptabromodiphenyl ethers (PBDE-183) were formed with the decomposition of PBDE-209, demonstrating that the main aerobic transformation mechanism of PBDE-209 was debromination.     

Persistence of perfluoroalkylated substances in closed bottle tests with municipal sewage sludge

BACKGROUND, AIM, AND SCOPE: Perfluoroalkylated substances (PFAS) are chemicals with completely fluorinated alkyl chains. The specific properties of the F-C bond give PFAS a high stability and make them very useful in a wide range of applications. PFAS also pose a potential risk to the environment and humans because they have been recently characterized as persistent, bioaccumulative, and toxic. The objective of this work is to study the bacterial degradation of PFAS under aerobic and anaerobic conditions in municipal sewage sludge as a contribution toward understanding their environmental fate and behavior. MATERIALS AND METHODS: Bacterial communities from sewage sludge were exposed to a mixture of PFAS under aerobic or anaerobic conditions. Individual PFAS concentrations were determined in the experiment media at different exposure times using liquid chromatography-mass spectrometry analysis after extraction with solid-phase extraction. RESULTS: The PFAS analyses of samples of sludge showed repeatable replicate results, allowing a reliable quantification of the different groups of PFAS analyzed. No conclusive evidence for PFAS degradation was observed under the experimental conditions tested in this work. Reduction in concentrations, however, was observed for some PFAS in sludge under aerobic conditions. DISCUSSION: The largest concentration decrease occurred for the fluorotelomer alcohols (FTOHs), especially for the 8:2 FTOH, which have been described as biodegradable in the literature. However, this concentration decrease could be due to different causes: sorption to glass, septa, or matrix components, as well as bacterial activity. Therefore, it is not certain that biodegradation occurred. CONCLUSIONS: PFAS are very recalcitrant chemicals, especially when fully fluorinated. Although some decreases in concentration have been observed for some PFAS, such as the FTOHs, there is no conclusive evidence for biodegradation. It can be concluded that the PFAS tested in these experiments are non-biodegradable under these experimental conditions. RECOMMENDATIONS AND PERSPECTIVES: Since the presence of PFAS is ubiquitous in the environment and they can be toxic, more research is needed in this field to elucidate which PFAS are susceptible to biodegradation, the conditions required for biodegradation, and the possible routes followed. A possible inhibitory effect of PFAS on bacteria, the threshold concentrations, and conditions of inhibition should also be investigated.     

常温下向ABR反应器中加入惰性载体促进颗粒污泥形成

常温条件下(21～25℃),用实验室规模的2个厌氧折流板反应器进行颗粒污泥培养实验,向其中一个反应器(称为B反应器)接种厌氧污泥的同时加入惰性载体,另一个反应器(称为A反应器)作为对照只接种厌氧污泥,考察了惰性载体对ABR反应器中颗粒污泥的形成和反应器运行效果的影响.结果表明,惰性载体的加入促进了反应器中颗粒污泥的形成,提高了反应器的处理效果.运行162 d后,B反应器每个隔室均出现大量颗粒污泥,4个隔室中粒径>0.5 mm的颗粒达到57.6%～72.7%;A反应器仅第1隔室中形成了大量颗粒污泥,其他3个隔室中粒径>0.5 mm的颗粒仅占11.3%～34.7%.COD去除率稳定保持在85%以上所需时间,B反应器比A反应器少用了51 d.     

厌氧-水解反应器稳定运行的试验研究

采用造纸废水对厌氧水－水解反应器的启动、运行进行试验研究。结果表明，当ＭＬＶＳＳ在１５ｇ／Ｌ左右，ＣＯＤ容积负荷为１．４５ｋｇ／（ｍ＾３·ｄ），水力负荷为２．０ｍ＾３／（ｍ＾２·ｈ），水国停留时间为４ｈ，污泥颗粒化程度较高，反应器运行效果稳定可靠。     

生物转鼓过滤器中一株好氧反硝化菌的分离鉴定与降解特性研究

从稳定运行处理NO废气的生物转鼓过滤器中筛选分离到1株好氧反硝化细菌DN3,发现该菌在好氧条件下能有效去除培养液中的硝酸根,培养28h后的反硝化率大于80%.扫描电镜结果显示,菌株DN3为短杆菌,带有鞭毛,大小为(0.4～0.8)μm ×(2.0～2.5)μm,菌落表面呈现乳白色.通过生理生化特性及16S rRNA基因...     

活性污泥颗粒化过程中理化性状及脱氮性能的研究

在SBR反应器中对活性污泥进行颗粒化培养,研究了活性污泥在颗粒化过程中的理化性状及脱氮性能.结果表明,活性污泥颗粒化过程可以分为颗粒形成、颗粒生长和颗粒成熟3个阶段.第1阶段SVI值迅速降低,在30 d内由接种时的110mL/g降低到23 mL/g;第2阶段颗粒粒径迅速增加,在15 d内由0.25 mm增加到0.82 ...     

Analysis of aerobic granular sludge formation based on grey system theory

Based on grey entropy analysis,the relational grade of operational parameters with aerobic granular sludge’s granulation indicators was studied.The former consisted of settling time(ST),aeration time(AT),superficial gas velocity(SGV),height/diameter(H/D) ratio and organic loading rates(OLR),the latter included sludge volume index(SVI) and set-up time.The calculated result showed that for SVI and set-up time,the influence orders and the corresponding grey entropy relational grades(GERG) were:SGV(0.9935) > AT(0.9921) > OLR(0.9894) > ST(0.9876) > H/D(0.9857) and SGV(0.9928) > H/D(0.9914) > AT(0.9909) > OLR(0.9897) > ST(0.9878).The chosen parameters were all key impact factors as each GERG was larger than 0.98.SGV played an important role in improving SVI transformation and facilitating the set-up process.The influence of ST on SVI and set-up time was relatively low due to its dual functions.SVI transformation and rapid set-up demanded different optimal H/D ratio scopes(10-20 and 16-20).Meanwhile,different functions could be obtained through adjusting certain factors’ scope.     

选择压法培育好氧颗粒污泥的试验

以普通絮状活性污泥为接种污泥,葡萄糖为碳源,在序批式反应器中培育出好氧颗粒污泥增加COD负荷的同时,减少沉降时间以造成选择压,强化好氧颗粒污泥的形成根据污泥的形态变化,颗粒污泥的形成可分为3个阶段.反应器启动67d出现颗粒污泥COD负荷4.8kg/(m³·d)、表面气体流速0.0175m/s时,反应器中活性污泥完全颗粒化颗粒污泥粒径大多6～9mm,MLSS 7800mg/L,最小沉降速率32.7m/h.好氧颗粒污泥具有在高负荷下良好的COD去除率.对好氧颗粒污泥的基本性质及其形成的影响因素进行了初步分析.