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321.
322.
强化生物除磷(EBPR)工艺在污水脱氮除磷中扮演着重要角色,其机理研究与工程应用也较为成熟.长期以来,Accumulibacter菌属(A菌)作为EBPR工艺最主要的聚磷菌(PAOs)已被广泛接受.同时,具有聚磷能力的Tetrasphaera菌属(T菌)亦被发现,且在某些特定环境下其丰度甚至远高于A菌,进而引发业内一定的关注.本文通过对T菌发现、研究过程的梳理,总结了关于T菌丰度、代谢途径及影响其活性的因素等方面的研究成果.与A菌不同,T菌代谢途径具有多样性,可依赖发酵代谢进行细胞维持和增殖,其发酵产物甚至可以供给A菌利用.T菌可利用大分子有机物(如葡萄糖、氨基酸等)和VFAs(亲和性较低)进行厌氧释磷,继而完成好氧、甚至缺氧吸磷过程.T菌主要菌株(T.elongata)因缺少合成PHA相关酶基因而不能以PHA作为内聚产物在厌氧环境下储能;糖原和游离氨基酸被检测到可作为T菌的能源/碳源内聚物,但亦有结果相左的研究.借助于拉曼光谱技术,一些污水处理厂中T菌与A菌被证实对磷去除的贡献大小相当.总之,目前对T菌的研究还十分有限,现有研究仍不足以证明它们在EBPR中可稳定发挥除磷贡献.今后应在T菌不同代谢途径控制因素及所需环境条件方面进行深入研究,以确认T菌可否持续、稳定地实现除磷作用. 相似文献
323.
芦苇人工湿地对农村生活污水磷素的去除及途径 总被引:9,自引:0,他引:9
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。 相似文献
324.
The aim of this study was to examine the effects of chemical nonylphenols (NPs) on the antioxidant system of Microcystis aeruginosa strains. The degradation and sorption of NPs by M. aeruginosa were also evaluated. High concentrations of NPs (1 and 2 mg/l) were found to cause increases in superoxidase dismutase (SOD)
and glutathione-S-transferase (GST) activities and in glutathione (GSH) levels. These results suggest that toxic stress manifested by elevated
SOD and GST levels and GSH contents may be responsible for the toxicity of NPs to M. aeruginosa and that the algal cells could improve their antioxidant and detoxification ability through the enhancement of enzymatic
and nonenzymatic prevention substances. The observed elevations in GSH levels and GST activities were relatively higher than
those in SOD activities, indicating that GSH and GST contributed more in eliminating toxic effects than SOD. Low concentrations
of NPs (0.05–0.2 mg/l) enhanced cell growth and decreased GST activity in algal cells of M. aeruginosa, suggesting that NPs may have acted as a protecting factor, such as an antioxidant. The larger portion of the NPs (>60%)
disappeared after 12 days of incubation, indicating the strong ability of M. aeruginosa to degrade the moderate persistent NP compounds. The sorption ratio of M. aeruginosa after a 12-day exposure to low nominal concentrations of NPs (0.02–0.5 mg/l) was relatively high (>30%). The fact that M. aeruginosa effectively resisted the toxic effects of NPs and strongly degraded these pollutants indicate that M. aeruginosa cells have a strong ability to adapt to variations in environmental conditions and that low and moderate concentrations of
organic compounds may favor its survival. Further studies are needed to provide detailed information on the fate of persistent
organic pollutants and the survival of algae and to determine the possible role of organic pollutants in the occurrence of
water blooms in eutrophic lakes. 相似文献
325.
Xuejun Long Jun Luo Zhenxing Zhong Yanxu Zhu Chunjie Zhang Jun Wan Haiyan Zhou Beiping Zhang Dongsheng Xia 《Frontiers of Environmental Science & Engineering》2023,17(9):113
326.
Natural attenuation of xenobiotic organic compounds in a landfill leachate plume (Vejen,Denmark) 总被引:1,自引:0,他引:1
Baun A Reitzel LA Ledin A Christensen TH Bjerg PL 《Journal of contaminant hydrology》2003,65(3-4):269-291
Demonstration of natural attenuation of xenobiotic organic compounds (XOCs) in landfill leachate plumes is a difficult task and still an emerging discipline within groundwater remediation. One of the early studies was made at the Vejen Landfill in Denmark in the late 1980s, which suggested that natural attenuation of XOCs took place under strongly anaerobic conditions within the first 150 m of the leachate plume. This paper reports on a revisit to the same plume 10 years later. Within the strongly anaerobic part of the plume, 49 groundwater samples were characterized with respect to redox-sensitive species and XOCs. The analytical procedures have been developed further and more compounds and lower detection limits were observed this time. In addition, the samples were screened for degradation intermediates and for toxicity. The plume showed fairly stationary features over the 10-year period except that the XOC level as well as the level of chloride and nonvolatile organic carbon (NVOC) in the plume had decreased somewhat. Most of the compounds studied were subject to degradation in addition to dilution. Exceptions were benzene, the herbicide Mecoprop (MCPP), and NVOC. In the early study, NVOC seemed to degrade in the first part of the plume, but this was no longer the case. Benzyl succinic acid (BSA) was for the first time identified in a leachate plume as a direct indicator, and as the only intermediate of toluene degradation. Toxicity measurements on solid phase-extracted (SPE) samples revealed that toxic compounds not analytically identified were still present in the plume, suggesting that toxicity measurements could be helpful in assessing natural attenuation in leachate plumes. 相似文献
327.
Effectiveness of pulsed power plasma for the degradation of two toxic volatile organic compounds (VOCs), toluene and methyl isobutyl ketone (MIBK), in aqueous solution was evaluated. The plasma degradation of MIBK has been studied for the first time. The influence of initial concentration of target compound, solution pH and scavengers on percentage degradation was evaluated. 100% removal of 200 mg/L of toluene and MIBK was achieved both in liquid and gaseous phases after 12 and 16 min of plasma treatment, respectively. The first order rate constant of toluene and MIBK degradation (for 200 mg/L each) was 0.421 and 0.319 min?1 respectively when they were treated individually, and these values decreased slightly during degradation of their mixture. MIBK degradation was slower than toluene and it might be due to semi volatile and hydrophilic nature of MIBK. The effect of initial concentration of toluene and MIBK showed different degradation patterns. Highest degradation of both the compounds was obtained in neutral pH and in absence of scavengers. ?OH radical was the major reactive species involved in their degradation. Their degradation in real environmental matrices showed that removal reduced significantly in secondary effluent due to scavenging of reactive species by various ions and organic matter. The total number of degradation intermediates identified in case of toluene and MIBK was 11 and 14 respectively and formate was the one recalcitrant byproduct generated. The degradation pathway of toluene and MIBK involving reactions of reactive oxygen and nitrogen species and reductive species is proposed. 相似文献
328.
挥发性有机物(VOCs)的不同化学去除途径:城市与区域站点的对比 总被引:1,自引:0,他引:1
VOCs在大气中主要是与OH自由基、NO3自由基和O3等反应氧化去除,部分OVOCs的自身光解也是重要的化学去除途径.本研究基于2018年和2019年秋季在珠三角地区的城市和区域站点的外场观测实验,使用VOCs、常规痕量气体及气象参数的观测数据,对烷烃、烯烃、芳香烃和OVOCs等VOCs组分不同化学去除途径的去除速率进行分析.结果表明,烷烃和芳香烃主要通过与OH自由基反应去除,最高占比超过99%.与NO3自由基和O3的反应可贡献烯烃去除速率的80%以上,特别是一些天然源的烯烃(如单萜烯)与NO3自由基的氧化去除是贡献最大的氧化途径.光解是甲醛最重要的去除途径,在两个站点均达到了50%以上,酮类的光解贡献会高于其他OVOCs类物质.OH自由基的氧化去除途径在城市和区域站点的人为源及天然源VOCs去除中占主导地位.区域站点,烯烃尤其是天然源的烯烃物种,与NO3自由基和O3反应的贡献要高于城市站点.本研究对促进不同VOCs物种在大气中的去除... 相似文献
329.
文章在查阅相关文献的基础上,开展实地考察、咨询专家学者和有关管理部门,对西藏高原草地研究进行梳理归纳形成了4个时段;同时评析了不同调查结果的西藏草地面积,认为第二次西藏草原普查的8 820.15×104hm2比较符合现状;对西藏高原草地生态系统目前面临的最大问题—草地退化进行了探究,截至2012年,西藏天然草地退化面积... 相似文献
330.
建立了高效液相色谱测定氯苯及其电催化降解中间产物对氯苯酚、对苯二酚、邻苯二酚、苯酚、反丁烯二酸的方法,优化了色谱条件.采用外标法定量,方法线性关系良好,RSD在0.3%~1.7%之间,加标回收率在90.5%~104%之间,适用于氯苯电催化降解过程的追踪测定. 相似文献