感潮河段污水处理厂尾水对受纳水体的水质影响研究

感潮河段污水处理厂尾水排放对受纳水体产生一定影响,利用二维水动力水质耦合模型,以COD、NH3-N、TP为污染因子,分别以正常排放和事故排放两种条件,模拟江苏南部某污水处理厂尾水排放,分析江段大小潮时污染物浓度增量情况。实验结果表明:正常排放,尾水对排放口附近江段保护区水质影响小;事故排放,尾水对保护区水质无影响,但长江水体影响范围增大,沿岸污染物浓度增高,且小潮周期影响作用强于大潮周期,污水处理厂应加强管理,尤其在小潮时应避免污水事故排放。     

城市污水处理厂尾水排放对水环境质量影响定量评估

定量评估污水处理厂尾水排放对水环境的影响是科学规划污水处理厂入河排污口的基础和前提。采用环境流体动力学模型EFDC对宣城市某污水处理厂排污口进行模拟预测。结果表明:在达标排放时,排污口不会对下游取水口水质产生影响。在事故排放时,90%保证率最枯月流量时污染团到达和离开下游水厂取水口的时间分别为1.7 d和3.1 d,取水口附近COD最大浓度超Ⅲ类水标准1.96倍,对下游水厂的正常运行造成严重威胁。因此排污口的设计应考虑事故排放时对下游取水口的影响。     

城镇污水处理厂尾水对受纳水体影响的研究进展

城镇污水处理厂尾水作为城市受纳水体的潜在污染源,对城市水环境的影响不容忽视。在当前面临水环境治理挑战的前提下,对污水处理厂尾水排入城市水体后造成的影响进行系统性研究,对改善尾水排放对受纳水体的作用具有重要意义。文章介绍了我国污水处理厂尾水和城市水环境的现状,综述了国内外污水处理厂尾水排放对城市水环境影响的研究,主要介绍了尾水排放对下游水体营养盐负荷和底栖微生物群落及功能菌的影响,以及水质水动力模型在该研究方向的应用,并根据国内外该领域的研究现状提出了后续需要进行深入研究的方向。     

沿江污水处理厂环境影响评价案例分析

对于地处长江边的污水处理厂而言,其建设与运行将直接影响排污口所在江段取水口的水环境安全。结合具体案例(上海通用汽车武汉项目配套基础设施金口污水处理厂的环境影响评价)的分析,认为以长江为尾水排放通道的污水处理厂,其环境影响评价应重点关注厂址选择、尾水排放、污水处理方案优化、风险评价、恶臭评价及污泥的处置等问题,并提出相应的措施和建议,最大程度减少污水处理厂的环境负面影响。     

污水处理厂尾水中不同形态氮、磷在景观河道和入湖口的衰减特征

水源补给不足是高原富营养化湖泊治理的难点,污水处理厂尾水补给可有效增加入湖水量。基于氮、磷形态的变化分析,对污水处理厂尾水进入景观河道和入湖口汇水区的变化特征开展实验。结果发现:污水处理厂尾水中氮、磷含量可达到GB 18918—2002《城镇污水处理厂污染物排放标准》一级A标准,NO_3~--N含量占比超过93%。河道中氮、磷含量随河道延伸有波动但总体呈下降趋势。在汇水区,草海水倒灌对河道水体中的氮、磷起到稀释作用,ρ(TN)和ρ(TP)分别达到5. 74,0. 258 mg/L。河道中底泥的氮、磷含量均高于水体中的,说明经过长期累积底泥已吸附了大量的N、P,但汇水区因受到草海水体中悬浮颗粒物沉降的影响,底泥中的氮含量低于水体中。因此,建议在利用尾水补给草海水源时,应在河道中栽种一些沉水植物来吸收NO_3~--N。     

污水处理厂尾水排放对受纳水体影响研究

随着城镇污水处理厂建设规模的不断扩大,尾水排放对周边受纳水体的影响问题不容忽视。本文以某拟建污水处理厂为例,探讨了污水处理厂尾水排放对受纳水域环境影响评价分析,并提出污水防治对策,最大限度地降低项目对水环境的影响,发挥项目的经济、社会和环境效益。     

城镇污水处理厂尾水排放水环境影响及对策

城镇污水处理厂虽将污水处理实现达标排放,但进入其他水体后,出水中残留的氮、磷对地表水来说依然浓度较高,影响水体自净能力。本文以某污水处理厂为例,通过地表水监测,分析城镇污水处理厂尾水排放对水环境影响及对策,对水环境保护具有积极的现实意义。     

污水处理厂尾水排放对受纳河流细菌和真菌微生物群落的影响

污水处理厂尾水的持续排放会重塑受纳河流的理化和生物条件,对河流水质和水生态产生潜在影响.选取惠州市东江沿线2座污水处理厂的受纳河流进行水样采集及分析,利用高通量测序进行样品DNA分析,系统研究细菌和真菌群落的组成结构及其分布,结合水体的理化指标更全面地反映尾水排放对受纳河流的影响.结果表明,污水处理厂尾水排放口处TP和NH₄⁺-N等营养盐指标均高于受纳河流上游,尾水排放对受纳河流微生物的影响显著,细菌群落的丰富度明显降低.对受纳河流微生物群落组成和水体理化指标进行统计分析,发现DOM、TP和NH₄⁺-N的变化对浮游微生物群落结构可能起关键作用.通过对浮游细菌和真菌群落结构及水体的理化性质综合分析研究,能够更加全面地揭示污水处理厂尾水排放对受纳河流引起的复合生态效应,对污水处理厂提标改造和城市河流的保护具有重大意义.     

生化生态组合人工湿地系统对城镇污水处理厂尾水的净化效果研究

以江阴市新桥镇人工湿地系统为研究对象,采用生态生化组合湿地工艺处理污水处理厂尾水,研究生物-生态组合湿地的运行状况和小城镇污水处理厂尾水的进一步净化效果。研究结果表明:生物生态组合人工湿地系统对尾水中污染物具有较好的去除效果,对COD、氨氮、TN和TP的平均去除率分别为29%、31%、18%和8%,平均出水浓度分别为35.54,0.97,10.77,0.11 mg/L,完全符合GB 18918—2002《城镇污水处理厂污染物排放标准》一级A标准。研究结果能够为城镇污水处理厂尾水生态处理技术和管理的改进提供数据支撑和理论基础,为以后湿地生态系统的推广和示范研究提供直接的理论依据和实践经验。     

河源城南污水处理厂尾水深度处理效果的研究

河源市城南污水处理厂利用垂直流人工湿地对该厂A2-O工艺处理的尾水进行深度处理,研究了人工湿地对尾水中TN、NH4+-N、TP、COD、BOD5的去除效果。结果表明:人工湿地对污水处理厂尾水具有较好的深度处理效果,垂直流人工湿地处理系统对尾水中TN、NH4+-N、TP、COD和BOD5平均去除率分别达到97.4%、97.8%、95.06%、91.87%和95.87%以上,其出水水质基本达GB 18918—2002《城镇污水处理厂污染物排放标准》一级A标准,地表水Ⅲ类标准。     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.     

Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Alterations of organ histopathology and metallolhionein mRNA expression in silver barb, Puntius gonionotus during subchronic cadmium exposure

Common silver barb,Puntius gonionotus,exposed to the nominal concentration of 0.06 mg/L Cd for 60 d,were assessed for histopathological alterations(gills,liver and kidney),metal accumulation,and metallothionein(MT)mRNA expression.Fish exhibited pathological symptoms such as hypertrophy and hyperplasia of primary and secondary gill lamellae,vacuolization in hepatocytes,and prominent tubular and glomerular damage in the kidney.In addition,kidney accumulated the highest content of cadmium,more than gills and liver.Expression of MT mRNA was increased in both liver and kidney of treated fish.Hepatic MT levels remained high after fish were removed to Cd-free water.In contrast,MT expression in kidney was peaked after 28 d of treatment and drastically dropped when fish were removed to Cd-free water.The high concentrations of Cd in hepatic tissues indicated an accumulation site or permanent damage on this tissue.     

Sorption of 1-naphthol by plant cuticular fractions

The contribution of aliphatic-rich plant biopolymer to sorption of hydrophobic organic compounds is significantly important because of their preservation and accumulation in the soil environment,but sorption mechanism is still not fully understood.In this study, sorption of 1-naphthol by plant cuticular fractions was examined to better understand the contributions of respective fraction.Toward this end,cuticular materials were isolated from the fruits of tomato by chemical method.The tomato cuticle sheet consisted of waxes (6.5 wt%),cuticular monomer (69.5 wt%),and polysaccharide (24.0 wt%).Isotherms of l-naphthol to the cuticular fractions were nonlinear (N value (0.82-0.90)) at the whole tested concentration ranges.The KodKow ratios for bulk cuticle (TC1),dewaxed cuticle (TC2),cutin (TC4),and desugared cuticle (TC5) were larger than unity,suggested that tomato bulk cuticle and cutin are much powerful solption medium.Sorption capability of cutin (TC4) was 2.4 times higher than the nonsaponifiable fraction (TC3).The 1-naphthol interactions with tomato cuticular materials were governed by both hydrophobic-type interactions and polar (H-bonding) interactions. Removal of the wax and polysaccharide materials from the bulk tomato cuticle caused a significant increase in the sorption ability of the cuticular material.There was a linear negative trend between K_(oc) values and the amount of polysaccharides or fraction's polarities ((N O)/C);while a linear positive relationship between K_(oc) values and the content of cutin monomer (linear R~2=0.993) was observed for present in the cuticular fractions.Predominant sorbent of the hydrophobic organic compounds (HOCs) in the plant cuticular fraction was the cutin monomer,contributing to 91.7% of the total sorption of tomato bulk cuticle.     

Seed selections for crystallization of calcium phosphate for phosphorus recovery

Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite （AP）, Juraperle （JP） and phosphate-modified Juraperle （M-JP） were tested and compared. Batch and fixed-bed column experiments of seeded crystallization of calcium phosphate were undertaken by using synthetic wastewater with 10 mg/L P phosphate. It shows that AP has bad enduring property in the crystallization process, while JP has better performance for multiple uses, and M-JP is a hopeful seed for P recovery by crystallization of calcium phosphate.