榴莲壳提取液抗亚硝化反应的研究

在模拟人胃液条件下,研究榴莲壳提取液对N.N-二甲基亚硝胺体外合成的阻断作用,通过正交实验法得到最佳提取条件:以蒸馏水为溶剂,100℃水浴回流1h,此榴莲壳提取液对亚硝胺合成的阻断率可达82.15%,对亚硝酸根清除率可达82.62%。     

Applicability of Ozone and Biological Activated Carbon for Potable Reuse

The Upper San Gabriel Valley Municipal Water District in California is considering groundwater replenishment as a potential strategy to augment its potable water supply. This case study demonstrates the broad applicability of ozone and biological activated carbon (BAC) for such potable reuse systems based on recently developed criteria and models for bulk organics, trace organic contaminants, disinfection byproducts, and cost. Using an advanced treatment train composed of ozone (ozone to total organic carbon ratio of 1.0) and BAC (empty bed contact time of 20 min), a 10 million gallon per day potable reuse facility can achieve savings of $25–$51 million in capital costs, $2–$4 million per year in operations and maintenance costs, and 4–8 GWh per year in energy consumption in comparison to alternative treatment trains with reverse osmosis. This ozone-based treatment train is also capable of achieving public health criteria recently developed by the California Department of Public Health and the National Water Research Institute for potable reuse applications.     

砂滤前置或后置对消毒副产物生成潜能的影响

采用常规一深度处理工艺处理东太湖原水,对比砂滤前置与后置对各工艺流程出水消毒副产物生成潜能去除效果的影响。研究发现,无论砂滤前置还是后置,生物活性炭工艺对有机物都有着良好的去除效果,整套工艺出水COD和uV。的去除率分别稳定在74．2％～87．1％和75．0％～80．2％。两套工艺对二甲基亚硝胺生成潜能（NDMAFP）的去除效果没有明显差别,出水NDMAFP降低35％～41％。砂滤前置工艺对三卤甲烷生成潜能（THMFP）和卤乙酸生成潜能（HAAFP）的控制效果优于砂滤后置工艺,砂滤前置工艺活性炭单元出水和砂滤后置工艺砂滤单元出水的THMFP分别降低31．0％～37．4％和28．2％～35．3％,HAAFP分别降低20．0％～24．6％和16．3％～23．2％。     

偏二甲肼大气氧化生成亚硝基二甲胺(NDMA)的机理

为确定大气中偏二甲肼(UDMH)转化为亚硝基二甲胺(NDMA)的反应路径,采用量子化学方法对UDMH在大气中氧化生成NDMA的反应机理进行了研究,在B3LYP/6-311+G(d,p)和M06-2X/6-311+G(d,p)水平上对反应体系的反应物、中间体、过渡态及产物进行了几何构型优化和频率计算,在CCSD(T)/aug-cc-pVTZ水平下进行单点能校正,构筑了反应的势能剖面。结果表明,UDMH氧化反应引发的过程是一个脱氢或加氧过程;考虑到大气中氧化剂(HO·/O_3/O_2)的浓度,不同氧化剂引发UDMH反应速率的比例关系为v(O_3)≈10~4×v(HO·)≈10~8×v(O_2)。因此UDMH在大气氧化的引发过程中最主要是被O_3氧化,UDMH摘除氢原子后生成中间体(CH_3)_2NN(H)·(IM1)。IM1在大气环境中HO·、HO_2·及O_3作用下都可以转化为NDMA,臭氧参与过程将降低反应活化能,促进NDMA在大气中生成。     

活性炭吸附水中新型含氮消毒副产物二甲基亚硝胺

二甲基亚硝胺（N-nitrosodimethylamine, NDMA）是水处理领域中颇为关注的强致癌性新兴含氮消毒副产物。该文系统研究了常见水处理材料及各类型改性颗粒炭活性炭（GAC）对NDMA的静态吸附特征。研究发现煤质颗粒活性炭和木质粉末活性炭对NDMA具有较好的吸附效果,活性炭纤维和煤质粉末活性炭次之,而石英砂、粉末沸石和硅藻土等基本不能吸附NDMA;煤质颗粒活性炭和木质粉末活性炭吸附NDMA的等温线可采用Freundlich模型描述,其k值仅分别为1．295和1．462（mg／g）（L／mg）^n,其1／n值分别为0．95和0．68,该结果说明活性炭难于有效吸附水中NDMA;起始溶液pH和不同离子背景条件下,颗粒活性炭的NDMA系统未见明显变化;对吸附效果较好的颗粒活性炭进行酸改性、碱改性和氮气热改性,结果表明三种改性方法均无法有效提高颗粒活性炭吸附NDMA的效果,酸性改性活性炭Freundlich吸附等温线的k值下降为0．5（mg／g）（L／mg）^n,其它两种改性方法较原碳的吸附容量略有降低。总体研究表明,部分类型活性炭对NDMA具有一定的吸附效果,但吸附容量均较低,不同改性方法均难于有效提高GAC吸附NDMA吸附效果,水处理用常规吸附法难于应对水中NDMA污染。     

Aerobic treatment of N-nitrosodimethylamine in a propane-fed membrane bioreactor

N-Nitrosodimethylamine (NDMA) is a suspected human carcinogen that has recently been detected in wastewater, groundwater and drinking water. Treatment of this compound to low part-per-trillion (ng/L) concentrations is required to mitigate cancer risk. Current treatment generally entails UV irradiation, which while effective, is also expensive. The objective of this research was to explore potential bioremediation strategies as alternatives for treating NDMA to ng/L concentrations. Batch studies revealed that the propanotroph Rhodococcus ruber ENV425 was capable of metabolizing NDMA from 8 μg/L to <2 ng/L after growth on propane, and that the strain produced metabolites that do not pose a significant risk at the concentrations generated (Fournier et al., 2009). A laboratory-scale membrane bioreactor (MBR) was subsequently constructed to evaluate the potential for long-term ex situ treatment of NDMA. The MBR was seeded with ENV425 and received propane as the primary growth substrate and oxygen as an electron acceptor. At an average influent NDMA concentration of 7.4 μg/L and a 28.5 h hydraulic residence time, the reactor effluent concentration was 3.0 ± 2.3 ng/L (>99.95% removal) over more than 70 days of operation. The addition of trichloroethene (TCE) to the reactor resulted in a significant increase in effluent NDMA concentrations, most likely due to cell toxicity from TCE-epoxide produced during its cometabolic oxidation by ENV425. The data suggest that an MBR system can be a viable treatment option for NDMA in groundwater provided that high concentrations of TCE are not present.     

零价锌还原水中痕量亚硝基二甲胺的效能

为去除水中亚硝基二甲胺(NDMA)污染,研究采用零价锌还原降解水中痕量亚硝基二甲胺(NDMA)的效能,考察反应体系中锌粉投量、NDMA初始质量浓度、溶解氧、pH值、反应温度等对处理效果的影响.结果表明:零价锌可以有效还原降解NDMA,锌粉初始投量为10 g.L-1时,反应14 h后去除率可达99%以上;水中溶解氧和NDMA初始质量浓度对去除率的影响不大;pH值和温度对零价锌还原降解NDMA的影响显著,pH值越小,温度越高,反应进行得越快.     

贻贝蒸煮液体外抗氧化及阻断N-亚硝胺合成的研究

为了研究贻贝蒸煮液的抗氧化活性和阻断亚硝胺合成能力,采用DPPH.法测定了试样的抗氧化活性,并模拟胃液在体外进行亚硝胺合成阻断实验,测定了试样对亚硝酸根离子的清除率和N-亚硝胺合成的阻断率。结果表明,在DPPH.清除实验中,贻贝蒸煮液(以可溶性固形物计)的IC50为3.80μg/mL,对照品TBHQ的IC50为7.55μg/mL。另外,贻贝蒸煮液清除亚硝酸根离子与阻断N-亚硝胺合成的最佳剂量水平(以可溶性固形物计)为64μg/mL,此时,清除率和阻断率分别达到84.08%和71.04%,相同浓度下,对照品VC的清除率和阻断率分别为30.90%和29.27%。     

在钴/氧化铝(Co/Al_2O_3)上臭氧催化降解水体中痕量N-亚硝基二甲胺(NDMA)

在实验室的间歇反应器中研究了在Al_2O_2和Co/Al_2O_3催化剂上臭氧催化降解水体中N-亚硝基二甲胺(NDMA)的效果,结果表明两种催化剂的添加显著地提高了NDMA的降解效率。主要试验参数的研究表明:Co/Al_2O_3的投加量、臭氧的投加量、温度等试验参数对于降解率有很大影响;当单位体积溶液中催化剂Co/Al_2O_3的投加量为167 mg/L、臭氧的投加量为3 mg/L时可以获得最佳的降解效果。随着温度的升高,NDMA降解去除率逐渐升高,当反应温度由283 K升高到323 K时,在Al_2O_3和Co/Al_2O_3上NDMA的降解效率分别由17.4%、55.4%提高到69.4%、82.5%。另外,在催化剂上添加K元素可明显提高Co/Al_2O_3臭氧催化降解NDMA的效率。     

Solid-phase microextraction of N-nitrosodimethylamine in beer

N-nitrosodimethylamine (NDMA) is a highly active carcinogen that has been detected in trace levels in beers. Solid-phase microextraction (SPME) was used to develop a method for the extraction of NDMA from beer using headspace sampling and gas chromatography with mass spectrometry detection. Polydimethylsiloxane/divinylbenzene (PDMS–DVB) fibres were used to evaluate the influence of equilibrium time, ionic strength, extraction time and temperature by means of a factorial design. The method was validated calculating the linearity, reproducibility, limit of detection and limit of quantification. The method was applied to the quantitative analysis of NDMA combining the standard addition method with an internal standard method.