UV/H_2O_2/O_3联用降解饮用水中的三氯硝基甲烷

分别采用O3、H2O2、UV及其联用技术降解饮用水中的含氮消毒副产物三氯硝基甲烷(TCNM),考察了不同反应条件下对TCNM的降解效果及其影响因素,并探讨了其降解机理。结果表明,单独O3、H2O2和UV工艺对TCNM的去除效果不理想,而UV/H2O2和UV/H2O2/O3组合工艺能够有效去除TCNM。当TCNM初始浓度为20μg/L、紫外光强为31μW/cm2、H2O2投加量为15 mg/L、臭氧投加量为10 mg/L时,反应150 min后,UV/H2O2、UV/H2O2/O3组合工艺对TCNM的去除率分别为82.26%和97.28%,两种工艺对TCNM的降解均符合一级反应动力学。     

无锡地区出厂水消毒副产物变化趋势及致癌风险研究

目的了解2008—2012年无锡地区出厂水中消毒副产物(DBPs)变化趋势,评估其对成人的致癌风险。方法选取无锡市四家市政供水水厂,于2008—2012年间丰枯水期(8月和2月)采集水样进行监测,监测指标包括4种三卤甲烷类消毒副产物(THMs,三氯甲烷、二氯一溴甲烷、一氯二溴甲烷和三溴甲烷)和两种卤乙酸类消毒副产物(HAAs,二氯乙酸和三氯乙酸),采用美国环保局推荐的低剂量致癌风险评价方法对其进行评价。结果所有消毒副产物检出值都低于《生活饮用水卫生标准》(GB 5749-2006)[1]的限值。THMs在丰水期的含量高于枯水期的含量,有明显的季节特征。而HAAs则无明显变化规律。无锡地区6种DBPs对成人的致癌风险均超过了USEPA认为可以忽略的水平(<10-6),处于具有潜在致癌风险的区间(10-6~10-4),其中各DBPs总致癌风险从高到低分别为三氯乙酸>二氯乙酸>一氯二溴甲烷>三溴甲烷>二氯一溴甲烷>三氯甲烷。结论无锡地区出厂水中THMs有明显的季节性特征,DBPs对成人具有潜在的致癌风险。     

Fenton氧化法降解水中致嗅物质2,3,6-三氯苯甲醚

采用 Fenton高级氧化法降解致嗅物质 2,3,6-三氯苯甲醚(2,3,6-TCA),考察其降解效果及动力学,探讨了溶液pH、Fe²⁺与H₂O₂物质的量之比、Fe²⁺浓度和反应时间对Fenton氧化法降解2,3,6-TCA的影响,并确定了最佳反应条件。结果表明,在溶液pH为3.0、Fe²⁺与H₂O₂物质的量之比为1∶136、Fe²⁺浓度为16 mg/L、反应时间为10 min条件下,Fenton氧化法可有效降解水中2,3,6-TCA,降解率可以达到91.6%。Fenton氧化法降解水中2,3,6-TCA的过程符合准一级动力学,且其反应速率常数随2,3,6-TCA初始浓度的升高而降低。水中2,3,6-TCA在Fenton氧化作用下主要发生脱氯反应,生成二氯苯酚。可见,Fenton高级氧化法可以有效应对水中致嗅物质2,3,6-三氯苯甲醚污染问题。     

硫自养反硝化深度处理污水厂生化出水中的NO3--N

针对呼和浩特市某污水处理厂A²O工艺出水中残余的NO3^--N,利用生物滤池进行单质硫自养反硝化中试研究。结果表明,单质硫自养反硝化工艺启动周期短(15 d)、去除NO3^--N能力强,NO3^--N去除负荷(以N计)基本可保持在200 g/(m³·d)以上。在启动过程中,Thiobacillus逐渐成为优势菌属,硫自养反硝化反应成为了生物滤池的主要代谢路径。此外,水温对该工艺性能有一定影响,当水温<15℃时生物滤池内的微生物群落结构会受到一定影响,平均NO3^--N去除负荷迅速降至122.7 g/(m³·d),即使延长水力停留时间,系统亦无法恢复至最佳状态。     

不同氮源对一株溶藻弧菌好氧反硝化效率的影响

为研究溶藻弧菌Vibrio alginolyticus HA2同步硝化反硝化过程中氮的代谢产物,分别用以铵态氮(NH_4⁺-N)、硝态氮(NO_3+-N)、硝态氮(NO_3^--N)、亚硝态氮(NO_2--N)、亚硝态氮(NO_2^--N)为氮源的培养基培养溶藻弧菌HA2 120 h,测定不同时间段菌液浓度,以及NH_4--N)为氮源的培养基培养溶藻弧菌HA2 120 h,测定不同时间段菌液浓度,以及NH_4⁺-N、NO_3+-N、NO_3^--N、NO_2--N、NO_2^--N、pH和发酵罐中气体(N_2、NO、N_2O)的含量,并且拟合菌株生长曲线。结果表明:溶藻弧菌对NH_4--N、pH和发酵罐中气体(N_2、NO、N_2O)的含量,并且拟合菌株生长曲线。结果表明:溶藻弧菌对NH_4⁺-N、NO_3+-N、NO_3^--N、NO_2--N、NO_2^--N降解率最高分别为99.97%、99.95%、36.87%;生长极限k值分别为4.769、5.477、5.567;培养基中的NH_4--N降解率最高分别为99.97%、99.95%、36.87%;生长极限k值分别为4.769、5.477、5.567;培养基中的NH_4⁺-N直接被氧化为NO_3+-N直接被氧化为NO_3^--N;试验中均未检测出NO、N_2O气体,各培养基中N_2量均有上升趋势;各培养基中pH均有增加趋势。研究表明,溶藻弧菌HA2具有开发为高效、环保、安全的硝化反硝化细菌的研究价值。     

不同饮用水处理工艺中消毒副产物的生成潜能

对取自饮用水处理过程中的水样分别进行氯消毒和氯胺消毒,分析不同饮用水处理工艺对7类18种消毒副产物(DBPs)生成潜能的影响,测定的DBPs包括含碳DBPs[三卤甲烷(THMs)、卤乙酸(HAAs)、卤代酮(HKs)、三氯乙醛(CH)]和含氮DBPs[卤乙腈(HANs)、三氯硝基甲烷(TCNM)、总亚硝胺(TONO)]。结果表明,混凝、沉淀和过滤工艺均能有效降低卤代DBPs的生成潜能,活性炭吸附反而会增大TONO的生成潜能。混凝和砂滤工艺对去除含碳DBPs前体物更有效,氧化处理工艺则更有利于含氮DBPs前体物的去除。细胞毒性主要来源于HANs和HAAs,且其变化趋势大致与HANs和HAAs生成潜能一致。水中Br~-浓度的增加会显著增大溴代DBPs的生成潜能,并使细胞毒性大幅升高。     

净水工艺对黄浦江水TCNM生成潜能的去除特性

卤代硝基甲烷( HNMs)具有较强的细胞遗传毒性和致突变特性,是水处理领域颇受关注的新兴含氮消毒副产物之一.以HNMs中最为常见的三氯硝基甲烷(TCNM)为研究对象,开展了微污染原水中TCNM前体物组成及常规和深度处理工艺中TCNM氯(胺)化生成潜能的调查和分析.研究发现:原水中TCNM的前体物主要由分子质量＜1 ku的亲水性有机物构成;在原水和水厂净水工艺出水中未检出TCNM,但各单元出水经过氯化和氯胺化均可产生TCNM,且氯胺化的TCNM生成浓度均高于氯化的;常规净水工艺对TCNM氯化和氯胺化生成潜能的去除率分别为12.3％和17.9％;深度处理工艺中的臭氧氧化可大幅提高TCNM的前体物含量,后续生物活性炭则可有效降低TCNM生成潜能,整个工艺对TCNM的削减率可达到33.3％(氯化)和23.2％(氯胺化).     

臭氧/氯消毒中藻类有机物生成消毒副产物的特征

饮用水源地藻华会释放大量藻类有机物(AOM),AOM与氯消毒剂反应生成的消毒副产物(DBPs)会给饮用水用户带来不容忽视的健康风险。为此,探究了臭氧/氯消毒对AOM结构和DBPs生成的影响。结果表明,臭氧氧化能有效去除AOM中芳香蛋白和酚类、叶绿素a、藻蓝蛋白结构物质,但是对腐殖酸类结构的去除效果相对较差。DBPs生成总量随臭氧投加浓度的升高而增加,其中主要是三氯甲烷(TCM);卤代乙腈和卤代酮的生成总量随臭氧投加浓度的变化趋势不明显。延长臭氧接触时间会明显增加1 h氯化中TCM的生成量,氯化24 h时DBPs生成总量与臭氧接触时间无关。在臭氧/氯消毒过程中,AOM的DBPs生成潜能低于天然有机物(NOM)。AOM有利于一溴一氯乙腈的生成,而NOM会生成更多的二氯乙腈。     

磺胺甲口恶唑氯化消毒副产物生成势及影响因素研究

研究了东太湖水源水中典型抗生素磺胺甲口恶唑(SMX)氯化消毒副产物(DBPs)生成势及影响因素。结果表明:SMX经氯化反应后可生成三卤甲烷、卤乙腈、卤乙酸、卤乙醛、卤代丙酮等多种DBPs,且加氯量、反应时间、反应温度、pH值等因素均会影响其DBPs生成势。当溶液中存在溴离子时,SMX氯化生成的三卤甲烷、卤乙酸的组分及生成量有较大变化,且随着溴离子浓度的增大,一些氯代消毒副产物(Cl-DBPs)会转化为具有更高毒性的溴代消毒副产物(Br-DBPs)。     

顶空气相色谱法测定水中氯化消毒副产物的不确定度评定

根据《测量不确定度评定与表示》(JJF 1059.1-2012)和实验室的技术管理要求,评定了顶空气相色谱法测定水中5种氯化消毒副产物(包括三氯甲烷、四氯化碳、二氯一溴甲烷、一氯二溴甲烷和三溴甲烷)的不确定度,并对标准溶液、样品测定的重复性和校准曲线拟合等影响测定结果的不确定度进行了分析和量化。     

Formation of carbonaceous and nitrogenous disinfection by-products from the chlorination of Microcystis aeruginosa

Formation of carbonaceous disinfection by-products (C-DBPs), including trihalomethanes (THMs), haloacetic acids (HAAs), haloketones (HKs), chloral hydrate (CH), and nitrogenous disinfection by-products (N-DBPs), including haloacetonitriles (HANs) and trichloronitromethane (TCNM) from chlorination of Microcystis aeruginosa, a blue-green algae, under different conditions was investigated. Factors evaluated include contact time, chlorine dosages, pH, temperature, ammonia concentrations and algae growth stages. Increased reaction time, chlorine dosage and temperature improved the formation of the relatively stable C-DBPs (e.g., THM, HAA, and CH) and TCNM. Formation of dichloroacetonitrile (DCAN) followed an increasing and then decreasing pattern with prolonged reaction time and increased chlorine dosages. pH affected DBP formation differently, with THM increasing, HKs decreasing, and other DBPs having maximum concentrations at certain pH values. The addition of ammonia significantly reduced the formation of most DBPs, but TCNM formation was not affected and 1,1-dichloropropanone (1,1-DCP) formation was higher with the addition of ammonia. Most DBPs increased as the growth period of algal cells increased. Chlorination of algal cells of higher organic nitrogen content generated higher concentrations of N-DBPs (e.g., HANs and TCNM) and CH, comparable DCAA concentration but much lower concentrations of other C-DBPs (e.g., THM, TCAA and HKs) than did natural organic matter (NOM).     

Formation of disinfection by-products after pre-oxidation with chlorine dioxide or ferrate

The effect of pre-oxidation with chlorine dioxide (ClO₂) or ferrate (Fe(VI)) on the formation of disinfection by-products (DBPs) during chlorination or chloramination was tested with natural waters from 12 sources (9 surface waters, 1 groundwater, and 2 wastewater effluents). DBPs investigated included trihalomethanes (THM), chloral hydrate (CH), haloketones (HK), haloacetonitriles (HAN) and trichloronitromethane (TCNM), chlorite and chlorate. Chlorite and chlorate were found in the ClO₂-treated waters. Application of 1 mg/L ClO₂ ahead of chlorination reduced the formation potential for THM by up to 45% and the formation of HK, HAN and TCNM in most of the samples. The CH formation results were mixed. The formation of CH and HK was enhanced with low doses of Fe(VI) (1 mg/L as Fe), but was greatly reduced at higher doses (20 mg/L Fe). Fe(VI) reduced the formation of THM, HAN and TCNM in most of the samples. Reduced potential for the formation of NDMA was observed in most of the samples after both ClO₂ and Fe(VI) pre-oxidation.     

Human health risk assessment of chlorinated disinfection by-products in drinking water using a probabilistic approach

The presence of chlorinated disinfection by-products (DBPs) in drinking water is a public health issue, due to their possible adverse health effects on humans. To gauge the risk of chlorinated DBPs on human health, a risk assessment of chloroform (trichloromethane (TCM)), bromodichloromethane (BDCM), dibromochloromethane (DBCM), bromoform (tribromomethane (TBM)), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) in drinking water was carried out using probabilistic techniques. Literature data on exposure concentrations from more than 15 different countries and adverse health effects on test animals as well as human epidemiological studies were used. The risk assessment showed no overlap between the highest human exposure dose (EXP(D)) and the lowest human equivalent dose (HED) from animal test data, for TCM, BDCM, DBCM, TBM, DCAA and TCAA. All the HED values were approximately 10(4)-10(5) times higher than the 95th percentiles of EXP(D). However, from the human epidemiology data, there was a positive overlap between the highest EXP(D) and the lifetime average daily doses (LADD(H)) for TCM, BDCM, DCAA and TCAA. This suggests that there are possible adverse health risks such as a small increased incidence of cancers in males and developmental effects on infants. However, the epidemiological data comprised several risk factors and exposure classification levels which may affect the overall results.     

Modeling of trihalomethane cometabolism in nitrifying biofilters

The computer program AQUASIM was used to model biofilter experiments seeded with Lake Austin, Texas mixed-culture nitrifiers. These biofilters degraded four trihalomethanes (THMs) (trichloromethane (TCM) or chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), tribromomethane (TBM) or bromoform) commonly found in treated drinking water. Apparent steady-state data from the biofilter experiments and supporting batch experiments were used to estimate kinetic parameters for TCM, DBCM and ammonia degradation. Subsequently, the model was verified against other experimental biofilter data. To allow for full-scale simulations, BDCM and TBM rate constants were estimated using data from batch kinetic studies. Finally, the model was used to simulate full-scale filter performance under different filter surface loading rates and THM speciation seen in practice. Overall, total THM removals ranged from 16% to 54% in these simulations with influent total THM concentrations of 75-82microg/L, which illustrates the potential of THM cometabolism to have a significant impact on treated water quality.     

新恢复湿地对近岸水域水质的净化效果研究

为了探究新恢复湿地对近岸水体的深度净化与水生态功能提升效果,于2017年8月—2019年4月对鹦鹉洲生态湿地各生态单元进出水水质进行监测,并分析了湿地内各个组块对污染物去除的贡献。结果显示,鹦鹉洲生态湿地对来水中NH4⁺-N、NO2^--N和NO3^--N的平均去除率分别为49.2%、46.3%和52.9%,对溶解性无机磷(DIP)和TP的平均去除率分别为53%和55%,对SS的平均去除率为59.6%;湿地不同区块的协同作用可以实现对多种污染物的有效去除,有效提升了水体透明度,深度净化了水质。     

Comparison of the disinfection by-product formation potential of treated waters exposed to chlorine and monochloramine

The formation of disinfection by-products (DBPs) from chlorination and monochloramination of treated drinking waters was determined. Samples were collected after treatment at 11 water treatment works but before exposure to chlorine or monochloramine. Formation potential tests were carried out to determine the DBPs formed by chlorination and monochloramination. DBPs measured were trihalomethanes (THMs), haloacetic acids (HAAs), halonitromethanes (HNMs), haloacetonitriles (HANs), haloaldehydes (HAs), haloketones (HKs) and iodo-THMs (i-THMs). All waters had the potential to form significant levels of all the DBPs measured. Compared to chlorine, monochloramination generally resulted in lower concentrations of DBPs with the exception of 1,1-dichloropropanone. The concentrations of THMs correlated well with the HAAs formed. The impact of bromine on the speciation of the DBPs was determined. The literature findings that higher bromide levels lead to higher concentrations of brominated DBPS were confirmed.     

Evaluation of bromine substitution factors of DBPs during chlorination and chloramination

Bromine substitution factor (BSF) was used to quantify the effects of disinfectant dose, reaction time, pH, and temperature on the bromine substitution of disinfection byproducts (DBPs) during chlorination and chloramination. The BSF is defined as the ratio of the bromine incorporated into a given class of DBPs to the total concentration of chlorine and bromine in that class. Four classes of DBPs were evaluated: trihalomethanes (THMs), dihaloacetonitriles (DHANs), dihaloacetic acids (DHAAs) and trihaloacetic acids (THAAs). The results showed that the BSFs of the four classes of DBPs generally decreased with increasing reaction time and temperature during chlorination at neutral pH. The BSFs peaked at a low chlorine dose (1 mg/L) and decreased when the chlorine dose further increased. The BSFs of chlorination DBPs at neutral pH are in the order of DHAN > THM & DHAA > THAA. DHAAs formed by chloramines exhibited distinctly different bromine substitution patterns compared to chlorination DHAAs. Brominated DBP formation was generally less affected by the pH change compared to chlorinated DBP formation.     

Degradation of trichloronitromethane by iron water main corrosion products

Halogenated disinfection byproducts (DBPs) may undergo reduction reactions at the corroded pipe wall in drinking water distribution systems consisting of cast or ductile iron pipe. Iron pipe corrosion products were obtained from several locations within two drinking water distribution systems. Crystalline-phase composition of freeze-dried corrosion solids was analyzed using X-ray diffraction, and ferrous and ferric iron contents were determined via multiple extraction methods. Batch experiments demonstrated that trichloronitromethane (TCNM), a non-regulated DBP, is rapidly reduced in the presence of pipe corrosion solids and that dissolved oxygen (DO) slows the reaction. The water-soluble iron content of the pipe solids is the best predictor of TCNM reaction rate constant. These results indicate that highly reactive DBPs that are able to compete with oxygen and residual disinfectant for ferrous iron may be attenuated via abiotic reduction in drinking water distribution systems.     

The formation of halogen-specific TOX from chlorination and chloramination of natural organic matter isolates

The formation of disinfection by-products (DBPs) is a public health concern. An important way to evaluate the presence of DBPs is in terms of the total organic halogen (TOX), which can be further specified into total organic chlorine (TOCl), bromine (TOBr), and iodine (TOI). The formation and distribution of halogen-specific TOX during chlorination and chloramination of natural organic matter (NOM) isolates in the presence of bromide and iodide ions were studied. As expected, chloramination produced significantly less TOX than chlorination. TOCl was the dominant species formed in both chlorination and chloramination. TOI was always produced in chloramination, but not in chlorination when high chlorine dose was used, due to the limited presence of HOI in chlorination as a result of the oxidation of iodide to iodate in the presence of excess chlorine. The formation of TOI during chloramination increased as the initial iodide ion concentration increased, with a maximum of ∼60% of the initial iodide ion becoming incorporated into NOM. Iodine incorporation in NOM was consistently higher than bromine incorporation, demonstrating that the competitive reactions between bromine and iodine species in chloramination favoured the formation of HOI and thus TOI, rather than TOBr. Correlations between the aromatic character of the NOM isolates (SUVA₂₅₄ and % aromatic C) and the concentrations of overall TOX and halogen-specific TOX in chloramination were observed. This indicates that the aromatic moieties in NOM, as indicated by SUVA₂₅₄ and % aromatic C, play an important role in the formation of overall TOX and halogen-specific TOX in chloramination. THMs comprised only a fraction of TOX, up to 7% in chloramination and up to 47% in chlorination. Although chloramine produces less TOX than chlorine, it formed proportionally more non-THM DBPs than chlorine. These non-THM DBPs are mostly unknown, corresponding to unknown health risks. Considering the higher potential for formation of iodinated DBPs and unknown DBPs associated with the use of chloramine, water utilities need to carefully balance the risks and benefits of using chloramine as an alternative disinfectant to chlorine in order to satisfy guideline values for THMs.     

Cometabolism of trihalomethanes by mixed culture nitrifiers

Three mixed-culture nitrifier sources degraded low concentrations (25-450 microg/L) of four trihalomethanes (THMs) (trichloromethane (TCM) or chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), tribromomethane (TBM) or bromoform) commonly found in treated drinking water. Individual THM rate constants (k1THM) increased with increasing THM bromine-substitution with TBM>DBCM>BDCM>TCM and were comparable to previous studies with the pure culture nitrifier, Nitrosomonas europaea. A decrease in temperature resulted in a decrease in both ammonia and THM degradation rates with ammonia rates affected to a greater extent than THM degradation rates. The significant effect of temperature indicates that seasonal variations in water temperature should be a consideration for technology implementation. Product toxicity, measured by transformation capacity (T(c)), was similar to that observed with N. europaea. Because both rate constants and product toxicities increase with increasing THM bromine-substitution, a water's THM speciation is an important consideration for process implementation during drinking water treatment. Even though a given water is kinetically favored, the resulting THM product toxicity may not allow stable treatment process performance.