【作者】 张晶；

【导师】 全燮；

【作者基本信息】 大连理工大学 ， 环境工程， 2014， 博士

【摘要】 目前,污水水质评价多以生化需氧量(BOD)、化学需氧量(COD)等传统指标作为评价标准。这些指标能够有效地评估水中难以生化分解的有机化合物含量。然而传统的水质评价指标无法对污水的生态风险进行全面的评估。生物毒性测试技术恰好能弥补传统评价指标的不足,为环境质量退化提供早期预警。此外,随着工业生产技术的不断发展和生产规模的扩大,越来越多的新型有毒物质被排放到水体中,传统的水处理技术对这些污染物的处理能力有限,尤其是对污水生物毒性的削减能力不足。因此,评估污水生态风险以及研发高效的毒性减排技术,对保护水环境安全具有重要意义。本研究旨在利用基于斑马鱼的生物毒性测试技术评价了A/O和A2/O工艺对污水急性毒性和遗传毒性的削减效果,同时研究了高级氧化技术对印染污水毒性的减排能力,为完善水质生物监测指标以及开发污水毒性减排工艺提供理论依据。本论文的主要研究内容如下：(1)采用斑马鱼评价了A/O工艺对市政污水的急性毒性和遗传毒性的削减效果。选取三个应用A/O工艺并且运行条件相似的市政污水厂(A,B,C)进行考察,其缺氧段与好氧段的水力停留时间分别约为2.5h和5h。原水COD为104-147mg/L,经过A/O工艺处理后,出水COD下降至23.0-49.8mg/L,均达到我国《城镇污水处理厂污染物排放标准》一级A的排放标准。污水急性毒性评价结果显示,A,B,C三厂原水对斑马鱼的96h致死率分别为50%,0和25%,经过A/O工艺处理后,出水对斑马鱼的96h致死率均为0,表明A/O工艺能去除市政污水的急性毒性。采用微核试验和彗星试验对所有水样在25%稀释浓度下的遗传毒性进行评价,结果显示A厂污水处理前后微核率分别为2.7‰和5.3‰,彗星尾距分别为13.6和13.5；B厂污水处理前后微核率分别为1.5‰和3.0‰,彗星尾距分别为7.8和7.2；C厂污水处理前后微核率分别为2.0‰和3.0‰,彗星尾距分别为6.9和6.1。结果表明A/O工艺处理后的出水对斑马鱼的遗传毒性没有降低,可见A/O工艺处理后的市政污水虽然符合排放标准,但对水生生物具有潜在的遗传毒性风险。(2)采用斑马鱼评价了某市政污水处理厂应用A2/O工艺对污水急性毒性和遗传毒性的削减效果。该厂厌氧段,缺氧段和好氧段的水力停留时间分别约为1h,1h和5h。原水COD为177mg/L,经过A2/O工艺处理后,出水COD下降至18.8mg/L,达到我国《城镇污水处理厂污染物排放标准》一级A的排放标准。生物毒性分析结果显示,入水对斑马鱼的96h致死率为55%,经过A2/O工艺的处理后,斑马鱼的96h致死率下降到0,急性毒性被完全去除。采用微核试验和彗星试验对所有水样在25%稀释浓度下的遗传毒性进行分析,结果显示污水的微核率和彗星尾距分别由6.0‰和14.4变为5.3‰和13.3,出水与原水相比无显著性差异。说明A2/O工艺能完全去除市政污水对斑马鱼的急性毒性,但无法降低其遗传毒性。(3)考察了Fenton-絮凝工艺对实际印染废水COD以及对斑马鱼的急性毒性和遗传毒性的削减效果。实际印染废水二级出水初始COD为96.1mg/L,当pH=3,Fe2+浓度为0.36mM, Fenton试剂比率为12：1时,反应4h后出水的COD下降至33.6mg/L。生物毒性测试结果显示,印染废水对斑马鱼的96h致死率由17%下降至0,急性毒性去除率为100%。微核试验和彗星试验对水样在75%的稀释浓度下的遗传毒性进行分析结果显示处理后微核率和彗星尾距分别由4.5‰和7.4下降至1.8‰和2.0,出水与空白对照组相比,无显著性差异,说明Fenton-絮凝工艺能降低实际印染废水二级出水的急性毒性和遗传毒性。(4)采用浸渍法制备了催化剂MCM-Mn,其中MCM-41(Mobil Composition of MatterNo.41)为载体,Mn为活性组分,并考察了MCM-Mn催化臭氧氧化技术对实际印染出水的矿化能力及急性毒性和遗传毒性的削减效果。催化剂MCM-Mn能明显提高臭氧对印染废水的处理效果。当臭氧剂量为300mg/h-L,催化剂剂量为1g/L,反应2h后,出水COD和TOC分别由82.4mg/L和37.3mg/L降至23.4mg/L和17.3mg/L。生物毒性测试结果显示,原水对斑马鱼的96h致死率为77%,对发光菌的发光抑制率为21.9%。经过MCM-Mn催化臭氧氧化技术处理后印染废水对斑马鱼的96h致死率下降至0,对发光菌的发光抑制率下降至12.6%。微核试验和彗星试验对水样在75%的稀释浓度下遗传毒性的分析结果显示印染废水的微核率和彗星尾距分别由6.3‰和14.4下降至3.3%o和7.3,遗传毒性分别下降了47.6%和49.3%,可见MCM-Mn催化臭氧氧化技术对印染废水的急性毒性和遗传毒性具有较好的控制效果。更多还原

【Abstract】 At present, the wastewater quality are often evaluated by conventional indexes, such as biochemical oxygen demand (BOD), chemical oxygen demand (COD) and so on. These conventional indexes can be used to quantify the refractory componds in wastewater. which cannot monitor the ecotoxicity of wastewater. This limitation of convertional evaluation standards can be compensated by biological toxicity determination, which can completely assess the ecological risk of wastewater and provide precausions for degradation of environmental quality. In addition, more refractory organic pollutants have been discharged into the water, which are difficult to be mineralized by traditional treatment processes. Therefore, it is meaningful to evaluate the toxicity of the wastewater before its discharge into the environment and develop new detoxification technologies for environmental safety.This research focuses on evaluating the ability of A/O and A2/O processes to reduce the acute toxicity and genotxocity of municipal wastewater using zebrafish (Danio rerio). Furthermore, typical advanced oxidation processes were employed to reduce the acute toxicity and genotxocity of dye wastewater. The objectives of this research are to provide theoretical bases for perfecting the indexes of biological toxicity in water quality assessment and designing wastewater treatment processes to reduce biological toxicity. Correspondingly, the main works and results are as follows:(1) The acute toxicity and genotoxicity of municipal wastewater from three different municipal wastewater treatment plants (A, B, C) employed anoxic-oxic (A/O) process were evaluated. The hydraulic retention time of anoxic and aerobic periods in the three plants were all about2.5h and5h, respectively. The COD of raw wastewater were104-147mg/L. After the treatement of A/O process, the COD were reduced to23.0-49.8mg/L, which met the first grade of discharge standard of pollutants for municipal wastewater treatment plant in China. Then for acute toxicity assessment, the mortality rate of zebrafish exposed to raw wastewater from plant A, B and C for96h were50%,0and25%, respectively. After the treatment of A/O process, they were all reduced to0, indicating the A/O process can effectively remove the acute toxicity from municipal wastewater. The genotoxicity results showed before and after the treatment by A/O process from plant A, the MN frequency of municipal wastewater at25%dilution were2.7%and5.3%, the tail moment were13.6and13.5, respectively. For plant B, the MN frequency of municipal wastewater at25%dilution were1.5‰and3‰, the tail moment were7.8and7.2, respectively. For plant C, the MN frequency of municipal wastewater at25%dilution were2.0%o and3.0‰, the tail moment were6.9and6.1, respectively. These results demonstrated the A/O process cannot reduce the genotoxicity. The eliminated effluent may pose genotoxic threaten although its COD level has met the sewage discharge standard.(2) One wastewater treatment plant employed anaerobic-anoxic-oxic (A2/O) process was evaluated its ability to remove96h acute toxicity and genotoxicity of municipal wastewater on zebrafish, in which hydraulic retention time of anaerobic, anoxic and aerobic periods were1h,1h and5h, respectively. The COD of wastewater was reduced from177mg/L to18.8mg/L after the treatement of A2/O process, which met the first grade of discharge standard of pollutants for municipal wastewater treatment plant in China. The toxicity assessment results indicated, the mortality rate of zebrafish exposed to wastewater for96h was reduced from55%to0after A2/O process, and the MN frequency and tail moment were changed from6.0‰and14.4to5.3‰and13.3, respectively. There is no significant differences between raw wastewater and effluent. The results indicated the A2/O process cannot reduce the genotoxicity effectively.(3) Fenton-coagulation process was carried out for COD removal, acute toxicity and genotoxicity reduction of dye wastewater. The dye wastewater was collected from an industrial wastewater treatment plant of a textile factory, which exhibited COD of96.1mg/L and zebrafish mortality rate of17%. The results indicated that at Fe2+concentration of0.36mM, Fenton reagent ratio of12:1and pH3, the COD of effluent was reduced to33.6mg/L after4h of treatment by Fenton-coagulation process. Meanwhile, the mortality rate of zebrafish exposed to wastewater for96h was reduced to0, the acute toxicity removal was100%. The MN frequency and tail moment of dye wastewater at75%dilution were reduced from4.5‰and7.4to1.8‰and2.0, and the effluent exhibited no significant genotoxicity to zebrafish. The results illustrated the Fenton-coagulation process can effectively reduced the acute toxicity and genotoxicity of dye wastewater.(4) The catalyst MCM-Mn was synthesized using MCM-41(Mobil Composition of Matter No.41) as support and Mn as active component by dip-coating method, and applied in catalytic ozonation of dye wastewater to investigate the ability of mineralization as well as detoxification efficiency. The catalyst MCM-Mn can improve the treatment efficiency of dye wastewater by ozonation. The results indicated the COD and TOC were respectively reduced from82.4mg/L and37.3mg/L to23.4mg/L and17.3mg/L treated by catalytic ozonation for2h at ozone dose of300mg/h·L and catalyst dose of1g/L. Furthermore, the bioassays revealed the mortality rate of zebrafish exposed to it for96h was77%and the inhibition of luminous bacteria was21.9%. After the treatment of catalytic ozonation, the inhibition of luminous bacteria was reduced to12.6%, and the mortality rate of zebrafish was reduced to0. The MN frequency and tail moment of dye wastewater at75%dilution were reduced from6.3‰and14.4to3.3%o and7.3, respectively. And the genotoxicity reduction was47.6%and 49.3%detected by MN and comet assays, respectively. The results illuminated the catalytic ozonation can effectively reduce acute toxicity as well as genotoxicity.更多还原