Characterization of a phenanthrene-degrading methanogenic community

Polycyclic aromatic hydrocarbons (PAHs) often occur in oil-contaminated soil, coke wastewater and domestic sludge; however, associated PAH degraders in these environments are not clear. Here we evaluated phenanthrene degradation potential in the mixed samples of above environments, and obtained a methanogenic community with different microbial profile compared to those from sediments. Phenanthrene was efficiently degraded (1.26 mg/L/d) and nonstoichiometric amount of methane was produced simultaneously. 16S rRNA gene sequencing demonstrated that bacterial populations were mainly associated with Comamonadaceae Nocardiaceae and Thermodesulfobiaceae, and that methanogenic archaea groups were dominated by Methanobacterium and Methanothermobacter. Substances such as hexane, hexadecane, benzene and glucose showed the most positive effects on phenanthrene degradation. Substrate utilization tests indicated that this culture could not utilize other PAHs. These analyses could offer us some suggestions on the putative phenanthrene-degrading microbes in such environments, and might help us develop strategies for the removal of PAHs from contaminated soil and sludge.

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Hydroxyquinol Pathway for Microbial Degradation of Halogenated Aromatic Compounds

Several peripheral metabolic pathways can be used by microorganisms to degrade toxic aromatic compounds that are known to pollute the environment. Hydroxyquinol (1,2,4-trihydroxybenzene) is one of the central intermediates in the degradative pathway of a large variety of aromatic compounds. The present review describes the microorganisms involved in the degradative pathway, the key enzymes involved in the formation and splitting of the aromatic ring of (chloro)hydroxyquinol as well as the central intermediates formed. An attempt was also made to provide some estimation for genetic basis of the hydroxyquinol pathway.     

Biodegradation of mixed pesticides by mixed pesticide enriched cultures

This paper discusses the degradation kinetics of mixed (lindane, methyl parathion and carbofuran) pesticides by mixed pesticide enriched cultures (MEC) under various environmental conditions. The bacterial strains isolated from the mixed microbial consortium were identified as Pseudomonas aeruginosa (MTCC 9236), Bacillus sp. (MTCC 9235) and Chryseobacterium joostei (MTCC 9237). Batch studies were conducted to estimate the biokinetic parameters like the maximum specific growth rate (μ_max), Yield Coefficient (Y_T), half saturation concentration (K_s) and inhibition concentration (Ki) for individual and mixed pesticide enriched cultures. The cultures enriched in a particular pollutant always showed high growth rate and low inhibition in that particular pollutant compared to MEC. After seven weeks of incubation, mixed pesticide enriched cultures were able to degrade 72% lindane, 95% carbofuran and 100% of methyl parathion in facultative co-metabolic conditions. In aerobic systems, degradation efficiencies of lindane methyl parathion and carbofuran were increased by the addition of 2g L^{? 1} of dextrose. Though many metabolic compounds of mixed pesticides were observed at different time intervals, none of the metabolites were persistent. Based on the observed metabolites, a degradation pathway was postulated for different pesticides under various environmental conditions.     

餐厨垃圾厌氧消化工艺的影响与优化

从厌氧消化工艺选择、产甲烷性能优化和联合消化等3个方面,概述了近年来国内外餐厨垃圾厌氧消化产甲烷工艺的研究进展,比较了国内外的研究差异,提出我国餐厨垃圾厌氧消化处理产甲烷性能优化及工业化应用的研究方向。     

两相厌氧工艺的研究现状及其应用

两相厌氧工艺因产酸相和产甲烷相的分离而具有一系列的特点和优势。在此对两相厌氧系统进行了分析,阐述了它的理论依据和运行机理．着重剖析了两相厌氧工艺的影响因素、工艺特点和适用范围,并对其发展和实际应用现状进行了论述。表明此工艺的先进性和适用性。     

芦苇人工湿地对农村生活污水磷素的去除及途径

构建了芦苇(Phragmites australis)水平潜流人工湿地处理农村生活污水中的磷素,考察了湿地除磷效果以及地上植物吸磷量。结果表明,人工湿地对磷素的去除随水力停留时间的延长而增加,停留时间大于5.3 d时,芦苇湿地除磷效率可以高于88%。湿地进水TP负荷与磷去除速率之间有较好的线性关系(R2>0.91)。湿地植物在11月份收割时,地上生物量为1.65 kg.m-2,芦苇地上部分吸收磷量为3.68 g.m-2.a-1。分析了湿地除磷途径,在试验条件下,湿地填料的吸附和沉淀等作用是水平潜流人工湿地除磷的主要途径,植物吸收仅占湿地总磷去除量的9.1%,但是湿地水生植物是人工湿地重要组成部分,可以通过影响湿地的其他条件间接影响湿地除磷效果。试验证明,人工湿地是适用于农村地区的优良的污水处理技术。     

电子束辐照降解水体中磺胺间甲氧嘧啶

应用电子束辐照初步探索了去除水体中磺胺间甲氧嘧啶（SMM）10mg/L的过程.研究了吸收剂量、自由基清除剂、无机盐等对辐照降解的影响.通过实验数据和模拟计算,推测了降解机理和降解路径,并对降解产物进行了毒性评估.结果表明,当吸收剂量为3.0kGy时,去除率高于99%,辐照降解效率高.在辐照降解过程中,还原消除占主导作用.降解反应遵循一级动力学方程.碳酸根、硫酸根和硝酸根等无机阴离子在一定的程度上会抑制SMM的降解.根据超高效液相色谱-质谱（UHPLC-MS）对降解产物的分析,结合高斯理论模拟,推断出9种可能的降解产物和相应的降解途径.费氏弧菌的毒性测试显示,辐照降解中间体毒性先升高后降低,在吸收剂量为2.0kGy达到最高值.     

城市污泥生物沥滤过程中重金属滤出途径的研究

以硫酸亚铁为底物,嗜酸氧化亚铁硫杆菌为沥滤微生物对城市污泥进行生物沥滤实验,并以硫酸化学沥滤污泥处理和硫酸亚铁化学氧化沥滤污泥处理为对照来分析生物沥滤过程中6种重金属(Cu、Pb、Zn、Cd、Cr、Ni)的滤出途径。根据各处理中重金属去除率和化学形态的变化,通过估算生物沥滤过程中酸溶作用和Fe~(3+)氧化作用对重金属滤出的贡献率来推测各重金属的主要滤出途径。结果表明:Zn、Cu及Cd主要滤出途径为Fe~(~(3+))氧化作用,Pb和Cr主要通过酸溶作用滤出,而Ni的滤出则由Fe~(3+)氧化作用和酸溶作用共同控制。     

Comparison of UV and UV-LED activated sodium percarbonate for the degradation of O-desmethylvenlafaxine

As an active metabolite of venlafaxine and emerging antidepressant, O-desmethylvenlafaxine (ODVEN) was widely detected in different water bodies, which caused potential harm to human health and environmental safety. In this study, the comparative work on the ODVEN degradation by UV (254 nm) and UV-LED (275 nm) activated sodium percarbonate (SPC) systems was systematically performed. The higher removal rate of ODVEN can be achieved under UV-LED direct photolysis (14.99%) than UV direct photolysis (4.57%) due to the higher values of photolysis coefficient at the wavelength 275 nm. Significant synergistic effects were observed in the UV/SPC (80.38%) and UV-LED/SPC (53.57%) systems and the former exhibited better performance for the elimination of ODVEN. The degradation of ODVEN all followed the pseudo-first-order kinetics well in these processes, and the pseudo-first-order rate constant (k_obs) increased with increasing SPC concentration. Radicals quenching experiments demonstrated that both ·OH and CO₃·⁻ were involved in the degradation of ODVEN and the second-order rate constant of ODVEN with CO₃·⁻ (1.58 × 10⁸ (mol/L)⁻¹ sec⁻¹) was reported for the first time based on competitive kinetic method. The introduction of HA, Cl⁻, NO₃⁻ and HCO₃⁻ inhibited the ODVEN degradation to varying degrees in the both processes. According to quantum chemical calculation, radical addition at the ortho-position of the phenolic hydroxyl group was confirmed to be the main reaction pathways for the oxidation of ODVEN by ·OH. In addition, the oxidation of ODVEN may involve the demethylation, H-abstraction, OH-addition and C-N bond cleavage. Eventually, the UV-LED/SPC process was considered to be more cost-effective compared to the UV/SPC process, although the UV/SPC process possessed a higher removal rate of ODVEN.     

The impact of climate change mitigation on water demand for energy and food: An integrated analysis based on the Shared Socioeconomic Pathways

Climate change mitigation, in the context of growing population and ever increasing economic activity, will require a transformation of energy and agricultural systems, posing significant challenges to global water resources. We use an integrated modelling framework of the water-energy-land-climate systems to assess how changes in electricity and land use, induced by climate change mitigation, impact on water demand under alternative socioeconomic (Shared Socioeconomic Pathways) and water policy assumptions (irrigation of bioenergy crops, cooling technologies for electricity generation). The impacts of climate change mitigation on cumulated global water demand across the century are highly uncertain, and depending on socioeconomic and water policy conditions, they range from a reduction of 15,000 km³ to an increase of more than 160,000 km³. The impact of irrigation of bioenergy crops is the most prominent factor, leading to significantly higher water requirements under climate change mitigation if bioenergy crops are irrigated. Differences in socioeconomic drivers and fossil fuel availability result in significant differences in electricity and bioenergy demands, in the associated electricity and primary energy mixes, and consequently in water demand. Economic affluence and abundance of fossil fuels aggravate pressures on water resources due to higher energy demand and greater deployment of water intensive technologies such as bioenergy and nuclear power. The evolution of future cooling systems is also identified as an important determinant of electricity water demand. Climate policy can result in a reduction of water demand if combined with policies on irrigation of bioenergy, and the deployment of non-water-intensive electricity sources and cooling types.