Potential and Limitations of Microbial Reductive Dechlorination for Bioremediation Applications

Current knowledge and recent advances in the area of microbial reductive dechlorination of polychlorinated organic compounds are summarized. Factors which may limit the efficacy of the dechlorination process for the in situ bioremediation of contaminated soil and sediment systems are identified. Results of recent studies on the anaerobic biotransformation of soil-sorbed chlorinated ethenes and sediment-sorbed chlorinated benzenes are provided to illustrate how low contaminant bioavailability may control the rate and extent of dechlorination in subsurface systems, especially those with long-term contamination. Use of nonionic, polysorbate surfactants as the sole electron donors of a mixed, methanogenic culture supported the microbial sequential reductive dechlorination of either free or sediment-bound hexachlorobenzene (HCB) to primarily 1,3-dichlorobenzene, but did not enhance the bioavailability of sediment-bound HCB as compared to microcosms, which used glucose. Because current knowledge on the interactions of dechlorinating populations with other microbial populations in the presence of alternative terminal electron acceptors (e.g., nitrate, Fe³⁺ , Mn⁴⁺) is limited, such interactions and their effect on the dechlorination process in subsurface systems need to be further explored to improve our understanding of the reductive dechlorination process in complex environmental systems and lead to the development of more efficient in situ bioremediation technologies and strategies.     

Fate and effects of amphoteric surfactants in the aquatic environment

Amphoteric surfactants form part of specialty surfactants available for formulators to improve or design new formulations in response to environmental, toxicity, safety and performance demands. Nevertheless, limited information on the ecological properties of amphoterics is available. In the present work, the aerobic and anaerobic biodegradability and the aquatic toxicity of different types of amphoteric surfactants (three alkyl betaines, one alkylamido betaine and three alkyl imidazoline derivatives) were studied. The amphoteric surfactants tested were readily biodegradable under aerobic conditions (CO(2) headspace test) and alkylamido betaines and alkyl imidazoline derivatives were also easily biodegradable under anaerobic conditions (test based on the ECETOC method). Toxicity to Photobacterium phosphoreum and Daphnia magna increased with the fatty chain length of the surfactant. The EC(50) toxicity values of the amphoterics tested were higher than 5 mg/L, and alkyl imidazoline derivatives, with EC(50) values from 20 to >200 mg/L, showed the lowest aquatic toxicity.     

工业废水处理中应用磁性载体技术的研究

本文介绍了采用磁性载体与A／O联合工艺处理南京金陵石化研究院中试车间产生的含表面活性剂废水技术。采用磁性载体取代一般填料对MBBR工艺进行改良,磁性载体完成挂膜后,微生物的活性明显提高污水处理厂处理能力大幅提升。对比不同工艺处理相同污水时,改良MBBR工艺能保证污水能够平稳达标排放,同时提高了污水处理效率,降低了污水处理厂运行成本,提高了污水处理能力。     

表面活性剂对土壤中重金属清洗及有效态的影响

采用两种常用的表面活性剂-十二烷基苯磺酸钠(阴离子型)、Tween-80(非离子型),对锦州铁合金厂周边Zn、Cd及Pb重金属污染土壤进行化学修复试验,研究两种表面活性剂对重金属Zn、Cd及Pb的去除率及化学形态影响.结果表明,随着表面活性剂浓度的提高,两种表面活性剂对Pb、Cd及Zn的去除作用增强,Tween-80溶液的浓度越高,对重金属的萃取效果越好,对重金属的去除能力大小顺序为Cd>Zn>Pb,最大去除率分别为83.07%、56.78%及42.57%;十二烷基苯磺酸钠在低浓度时对Cd和Pb的去除效果不明显,而对金属Zn的去除效果较好,在0.09 mol.L-1时达到最大值83.86%;与淋溶前土壤中重金属有效态含量相比较,经不同浓度十二烷基苯磺酸钠淋洗后土壤中Cd有效态含量随LAS浓度的升高而先增加后下降,而Pb的有效态含量随十二烷基苯磺酸钠升高而增加;经不同浓度Tween-80淋洗后土壤中Zn及Cd有效态含量都是随Tween-80浓度的升高而先增加后下降,Pb有效态含量随Tween-80升高而下降.     

Controlling microbiological interfacial behaviors of hydrophobic organic compounds by surfactants in biodegradation process

Bioremediation of hydrophobic organic compounds （HOCs） contanlinated soils involves several physicochemical and microbiological interracial processes among the soil-water-microorganism interfaces. The participation of surfactants facilitates the mass transport of HOCs in both the physicochemical and microbiological interfaces by reducing the interfacial tension. The effects and underlying mechanisms of surfactants on the physi-cochemical desorption of soil-sorbed HOCs have been widely studied. This paper reviewed the progress made in understanding the effects of surfactant on microbiological interlhcial transport of HOCs and the underlying mechanisms, which is vital for a better understanding and control of the mass transfer of HOCs in the biodegradation process. In summary, surfactants affect the microbiological interfacial behaviors of HOCs during three consecutive processes： the soil solution-microorganism sorption, the transmembrane process, and the intracellular metabolism. Surfactant could promote cell sorption of HOCs depending on the compatibility of surfactant hydrophile hydrophilic balance （HLB） with cell surface properties; while the dose ratio between surfactant and biologic mass （membrane lipids） determined the transmembrane processes. Although surfactants cannot easily directly affect the intracellular enzymatic metabolism of HOCs due to the steric hindrace, the presence of surfactants can indirectly enhanced the metabolism by increasing the substrate concentrations.     

溢油分散剂中吐温80对石油中多环芳烃在海水中光降解的影响

溢油事故发生后喷洒溢油分散剂是常用的应急措施之一,这使得溢油分散剂中的表面活性剂与石油中的重要污染物多环芳烃(PAHs)在海水中共存。光化学转化是水中PAHs的重要转化途径,这些共存表面活性剂如何影响PAHs在海水中的光化学消减还有待阐明。本研究选取溢油分散剂的重要活性成分吐温80和石油中2种不同类型的PAHs(菲和二苯并噻吩),通过光化学实验考察不同浓度吐温80对菲(PHE)和二苯并噻吩(DBT)在海水中的光降解速率常数和光解量子产率的影响,并通过量子化学计算的手段研究其影响机制。研究发现:吐温80可以使PHE和DBT的阳离子自由基回到稳定的基态,降低PHE和DBT的光解量子产率,从而抑制PHE和DBT的光降解。该结果表明,在评价溢油分散剂的风险性时不可忽视其对PAHs环境转化行为的影响。     

粉煤灰处理阴离子表面活性剂废水及机理研究

采用粉煤灰作为吸附混凝剂,研究了粉煤灰对阴离子表面活性剂十二烷基磺酸钠(SDS)模拟废水的去除效果及机理.结果表明,粉煤灰投加量和pH值对去除效果有较大影响;在200 mL 50 mg/L的SDS溶液中,调节pH值为13,加入70 g粉煤灰,搅拌20min时,SDS的去除率为83.3％.粉煤灰对SDS的吸附符合Freundlich吸附等温式.     

不同类型表面活性剂对1，2，4-三氯苯的增溶作用

研究了阴离子表面活性剂十二烷基硫酸钠、阳离子表面活性剂十六烷基三甲基溴化铵和非离子表面活性剂脂肪醇聚氧乙烯醚LAE对1,2,4-三氯苯（TCB）的增溶作用。讨论了表面活性剂类型对增溶作用的影响。比较发现,非离子型表面活性剂的增溶能力高于离子型表面活性剂。其原因主要是疏水有机物在非离子表面活性剂胶束中的增溶方式不同造成的。3种表面活性剂对TCB的增溶数据还表明,增港作用不仅在临界胶束浓度（MC）以上发生,而且在表面活性剂浓度低于CMC时亦有明显的增溶作用。     

鼠李糖脂对铜绿假单胞菌降解颗粒有机质的影响

通过好氧降解实验研究了生物表面活性剂鼠李糖脂对1株铜绿假单胞菌(Pseudomonas Aeruginosa)降解颗粒有机质的影响,着重探讨了其作用方式,并与TritonX-100和SDS等2种化学表面活性剂作了对比.结果表明,浓度高于临界胶束浓度的鼠李糖脂在基质表面的等温吸附呈线性规律.鼠李糖脂在基质和微生物表面的吸附使菌体在基质表面的吸附性能减弱.鼠李糖脂和2种化学表面活性剂的物化作用使基质水分得以较长时间地保持,并加强了有机质在基质液相中的分散.在鼠李糖脂的作用下,有机质的降解从颗粒表面转移到液相,降解方式发生了改变.通过以上作用,鼠李糖脂促进了微生物的生长和有机质的降解.SDS和TritonX-100对有机质颗粒的降解也产生了一定的促进作用.     

复合表面活性剂对燃煤陶瓷窑炉黑烟润湿作用的研究

为了有效控制燃煤陶瓷窑炉黑烟的污染,根据理论和实验研究的结果,选择合适的润湿剂和助剂,研究了阴离子表面活性剂Y1、非离子表面活性剂F1与无机盐Z1复配后溶液表面张力的变化,筛选出了表面张力较小的配比。利用所选配比对燃煤陶瓷窑炉黑烟的润湿作用进行了W alker实验研究和理论分析。实验结果表明,0.5 mmol/L Y1+50mmol/L Z1+0.03 mmol/L F1的配比对黑烟的润湿作用较好。并对其润湿机理进行了探讨。