The control of red water occurrence and opportunistic pathogens risks in drinking water distribution systems: A review

Many problems in drinking water distribution systems (DWDSs) are caused by microbe, such as biofilm formation, biocorrosion and opportunistic pathogens growth. More iron release from corrosion scales may induce red water. Biofilm played great roles on the corrosion. The iron-oxidizing bacteria (IOB) promoted corrosion. However, when iron-reducing bacteria (IRB) and nitrate-reducing bacteria (NRB) became the main bacteria in biofilm, they could induce iron redox cycling in corrosion process. This process enhanced the precipitation of iron oxides and formation of more Fe₃O₄ in corrosion scales, which inhibited corrosion effectively. Therefore, the IRB and NRB in the biofilm can reduce iron release and red water occurrence. Moreover, there are many opportunistic pathogens in biofilm of DWDSs. The opportunistic pathogens growth in DWDSs related to the bacterial community changes due to the effects of micropollutants. Micropollutants increased the number of bacteria with antibiotic resistance genes (ARGs). Furthermore, extracellular polymeric substances (EPS) production was increased by the antibiotic resistant bacteria, leading to greater bacterial aggregation and adsorption, increasing the chlorine-resistance capability, which was responsible for the enhancement of the particle-associated opportunistic pathogens in DWDSs. Moreover, O₃-biological activated carbon filtration-UV-Cl₂ treatment could be used to control the iron release, red water occurrence and opportunistic pathogens growth in DWDSs.     

O3-BAC-Cl2: A multi-barrier process controlling the regrowth of opportunistic waterborne pathogens in drinking water distribution systems

Simulated drinking water distribution system (DWDS) treated with O₃-BAC-Cl₂ (ozone-biological activated carbon-chlorine) was constructed to study its effects on the regrowth of five typical opportunistic pathogens (OPs). It was found that O₃-BAC-Cl₂ could significantly reduce the regrowth of target OPs in the effluents of DWDS compared with Cl₂ and O₃-Cl₂ with the same residual chlorine levels. However, the effect of O₃-BAC-Cl₂ on the average numbers of target OPs gene markers in the biofilms of DWDS was not apparent, suggesting that OPs in the biofilms of DWDS were tolerant to the upstream disinfection process. The quantification of target OPs in the BAC-filter column demonstrated that OPs decreased with the increase of depth, which was likely due to the organic nutrient gradient and microbial competition inside the BAC-filter. Increase in the ozone dose could further reduce the OPs at the bottom of the BAC-filter. Spearman correlation analysis demonstrated that some significant correlations existed between target microorganisms, suggesting potential microbial ecological relationships. Overall, our results demonstrated that the BAC-filter may act as a “battlefield” suppressing the OPs through microbial competition. O₃-BAC-Cl₂ could be an effective multi-barrier process to suppress the proliferation of OPs in the bulk water of DWDS. However, OPs protected by the biofilms of DWDS should receive further attention because OPs may be detached and released from the biofilms.     

臭氧生物活性炭工艺运行中产生溴酸盐的可能性分析

为合理评估应用臭氧生物活性炭工艺中溴酸盐的生成情况,提出既能保证出水水质又能降低溴酸盐超标风险的方案.进行了小试与中试试验,系统地从原水水质和工艺参数两个方面入手,研究水质因素、初始溴离子浓度和臭氧氧化条件等对溴酸盐生成的影响,同时分析生物活性炭对溴酸盐的去除能力.结果表明:高初始溴离子浓度水平和臭氧接触程度(Ct值)促使更多BrOx-生成.在相同Ct值条件下,升高臭氧投加浓度可使溴酸盐生成量增高200%左右.以长江南京段江心洲夹江下游原水进行臭氧生物活性炭深度处理不会产生溴酸盐超标风险.生物活性炭(BAC)对于溴酸盐去除效果并不明显.运用臭氧生物活性炭工艺进行深度处理时,工艺中应着重注意控制溴酸盐在臭氧化过程中的生成而非依靠后续生物活性炭将其去除.     

umu试验研究饮用水氯和氯胺消毒过程中遗传毒性的变化以及消毒条件的影响

采用umu遗传毒性测试方法考察了消毒剂投加量、反应时间和消毒剂氯氮比对某饮用水厂臭氧-生物活性炭出水加氯或氯胺消毒前后遗传毒性的影响.结果表明,炭后水具有一定的遗传毒性(20～70 ng/L),加氯或氯胺消毒后遗传毒性增加.反应时间为24 h,在相同投加量下氯消毒遗传毒性(40～95 ng/L)高于氯胺消毒遗传毒性(20～40 ng/L);当氯初始投加量从0 mg/L增加到10 mg/L时,炭后水的遗传毒性先迅速增加,在0.5～1 mg左右达到极大值,然后再降低,在3～5 mg左右达到极小值后缓慢上升,但是氯胺消毒后水样遗传毒性变化规律不如氯消毒的明显.当投加量为3 mg/L时,随着反应时间从0 h延长至72 h,无论是氯消毒还是氯胺消毒,炭后水遗传毒性均是先迅速增加,在2 h时达到极大值后再下降,在18 h左右达到极小值然后缓慢上升,而且任意反应时间内,氯胺消毒的遗传毒性(20～62 ng/L)均小于氯消毒(83～120 ng/L).本试验还研究了消毒剂氯氮比对炭后水氯消毒后遗传毒性的影响.在本试验条件下,从遗传毒性的角度看,对于饮用水消毒氯胺比氯更安全,而且2种消毒方式的遗传毒性的变化规律均不同于总HAAs的变化规律.     

Effects of disinfection efficiency on microbial communities and corrosion processes in drinking water distribution systems simulated with actual running conditions

The effects of disinfection efficiency on microbial communities and the corrosion of cast iron pipes in drinking water distribution systems (DWDSs) were studied. Two annular reactors (ARs) that simulated actual running conditions with UV/Cl₂ disinfection and chlorination alone were used. High chlorine consumption and corrosion rate were found in the AR with UV/Cl₂. According to functional genes and pyrosequencing tests, a high percentage of iron recycling bacteria was detected within the biofilm of the AR with Cl₂ at early running stage, whereas siderophore-producing bacteria were dominant in the biofilm of the AR with UV/Cl_2. At the early running stage, the sequential use of UV light and an initial high chlorine dosage suppressed the biomass and iron-recycling bacteria in both bulk water and biofilms, thereby forming less protective scales against further corrosion, which enhanced chlorine consumption. Non-metric multidimensional scaling analysis showed that the bacterial communities in the ARs shaped from within rather than being imported by influents. These results indicate that the initial high disinfection efficiency within the distribution system had not contributed to the accumulation of iron-recycling bacteria at the early running stages. This study offer certain implications for controlling corrosion and water quality in DWDSs.     

Review on corrosion and corrosion scale formation upon unlined cast iron pipes in drinking water distribution systems

The qualified finished water from water treatment plants (WTPs) may become discolored and deteriorated during transportation in drinking water distribution systems (DWDSs), which affected tap water quality seriously. This water stability problem often occurs due to pipe corrosion and the destabilization of corrosion scales. This paper provides a comprehensive review of pipe corrosion in DWDSs, including corrosion process, corrosion scale formation, influencing factors and monitoring technologies utilized in DWDSs. In terms of corrosion process, corrosion occurrence, development mechanisms, currently applied assays, and indices used to determine the corrosion possibility are summarized, as well as the chemical and bacterial influences. In terms of scale formation, explanations for the nature of corrosion and scale formation mechanisms are discussed and its typical multilayered structure is illustrated. Furthermore, the influences of water quality and microbial activity on scale transformation are comprehensively discussed. Corrosion-related bacteria at the genus level and their associated corrosion mechanism are also summarized. This review helps deepen the current understanding of pipe corrosion and scale formation in DWDSs, providing guidance for water supply utilities to ensure effective measures to maintain water quality stability and guarantee drinking water safety.     

臭氧-生物活性炭对南方河网典型污染物的去除特性

以我国南方河网原水中有机物和季节性溴化物(Br^-)为对象,研究臭氧-生物活性炭(BAC)工艺净化过程中有机物相对分子质量(M_r)分布变化及溴酸盐(BrO^-₃)和消毒副产物(THMs)的形成规律.结果表明,原水中M_r在10³以下的有机物(DOC)约占总量的80%,常规工艺主要表现为对M_r >100×10³有机物的去除,出水DOC去除率为8%、 SUVA(UV₂₅₄/DOC)值下降14%;臭氧-活性炭工艺主要去除10³<M_r<5×10³的有机物,但亲水性小分子有机物抑制生物降解作用,出水DOC去除率仅提高至30%、SUVA值下降31%.当臭氧投加量高于2 mg/Ｌ时,臭氧氧化出水中BrO^-₃增加明显,氧化过程原水中Br^-浓度升高BrO^-₃生成量增大;生物活性炭对BrO^-₃的去除率平均仅为13%,且波动较大.与常规处理相比,臭氧-生物活性炭处理后各类THMs均有减少,总量减少40%;但氯量和Br^-对溴代副产物影响大,主要为CHBr₃生成量增加.     

膜生物反应器工艺与常规和深度处理工艺处理长江原水比较

研究比较膜生物反应器(MBR)工艺与常规工艺和臭氧生物活性炭(O3-BAC)工艺处理长江原水的污染物去除效果。MBR工艺对浊度、UV254和CODMn的去除率分别达到96%、36%和32%,与常规工艺基本相当,弱于O3-BAC工艺。MBR工艺对氨氮去除率稍低于O3-BAC工艺,对挥发性有机毒物的去除效果却好于后者,常规工艺去除这2种污染物不理想。O3-BAC工艺出水加氯后消毒副产物生成量最少,仅有MBR工艺和常规工艺的70%,这表明O3-BAC工艺在减少加氯后消毒副产物的生成方面优势明显,同时也说明依靠MBR工艺的生物降解能力大幅减少消毒副产物生成的可行性不高。     

臭氧-生物活性炭对微污染原水中典型持久性有机物的去除效果

以长三角地区J市典型有机微污染水源P水厂为研究对象,考察了臭氧-生物活性炭深度处理工艺对微污染水源水中有机物的去除效果.结果表明,臭氧-生物活性炭深度处理使高锰酸盐指数、总有机碳(TOC)和UV254的平均去除率分别提升19. 2%、10. 4%和23. 0%.水厂原水中检出8种多环芳烃(polycyclic aromatic hydrocarbon,PAHs)、16种有机氯农药(organochlorine pesticides,OCPs)、5种卤乙酸(haloacetic acids,HAAs),其总浓度分别为53. 9~100. 0、6. 5~41. 8、2. 5×103~1. 1×104ng·L~(-1),臭氧-生物活性炭深度处理对多环芳烃和有机氯农药的平均去除率分别为32. 5%和25. 9%,比常规处理工艺出水的水质有显著提升.卤乙酸的去除率为33. 8%~87. 0%,主要通过常规处理工艺去除;臭氧-生物活性炭深度处理对氯代乙酸略有去除,溴代乙酸有少量生成.     

低温磁性铁基SCR烟气脱硝的实验研究

在流化床反应器中,以磁性铁氧化物(Fe3O4、γ-Fe2O3)颗粒为床料,氨为还原剂,进行了中低温SCR烟气脱硝实验研究,然后对反应辅加磁场,初步研究磁场对磁性γ-Fe2O3催化剂SCR脱硝的影响,并对床料进行了XRD分析.结果表明,Fe3O4的SCR活性较差,γ-Fe2O3的SCR活性较佳,在250℃其催化脱硝效率能达到90%,但在250℃以上Fe2O3会对氨的氧化起作用,因而在250℃及以下的邻近温度区间是最佳催化温度区间.此外,在150~290℃,外加磁场能促进γ-Fe2O3对NO的吸附,提高脱硝效率,使250℃时的脱硝效率达到95%左右,但在290℃以上,则会降低脱硝效率.为了抑制氨的氧化,发挥磁场对γ-Fe2O3脱硝的作用,适合在200~250℃低温区间内采用γ-Fe2O3催化剂进行SCR脱硝.     

预臭氧与后臭氧-生物活性炭联用工艺研究

利用静态批量和动态连续试验初步研究了预臭氧及预臭氧与后臭氧-BAC组合工艺对南方某含溴离子水库水的处理效果和相应的处理条件.静态实验结果表明,预臭氧反应量在0.5～1.0mg/L范围内,在有效去除消毒副产物(DBPFP,主要包括THMFP和HAAFP)的同时,臭氧副产物溴酸可以控制在10μg/L以下,而继续增加臭氧反应量则会导致DBPFP的增加.当水中溴离子浓度达到96μg/L时,使用臭氧必须采取溴酸控制措施.连续动态实验结果表明,预臭氧与臭氧-生物活性炭组合工艺对于2μm以上颗粒物、COD_Mn、TOC等的去除均有明显的效果,可以进一步抑制DBPs的形成.     

含铁、锰水源水深度处理工艺的运行实验研究

对铁、锰含量较高又存在有机微污染的原水进行深度处理的生产规模的净水厂（规模10m^3/h），进行了运行效能的试验研究。该水厂由射流曝气→砂滤罐→臭氧接触氧化罐→生物活性炭滤罐→木鱼石滤罐→紫外线照射清水箱等处理单元组成。通过曝气充氧－砂滤预处理，去除溶解性的二价铁60％以上,关剩余臭氧的量为0.4mg/L（相应的臭氧投量为：4mg/L)的条件下，经臭氧接触氧化和生物活性炭过滤，在HRT20min时，可去除铁锰高达100％，CODMn的去除率达90%左右。     

紫外光在臭氧降解不同有机物过程中的协同作用

利用O3／UV分别对与臭氧有不同反应活性的对氯苯酚、硝基苯、乙酸和草酸进行了降解试验,结果表明,UV与臭氧化降解的协同作用与目标有机物本身的性质有很大关系,在本实验条件下,UV与臭氧的联用反而降低了对氯苯酚的臭氧化降解效率,30min后体系的TOC去除率仅有59％,而单独臭氧化TOC的去除率达到了66％;对硝基苯和草酸而言,UV均明显地提高了臭氧的降解效率,40min时两者TOC的去除率分别为44％和90％,比单独臭氧化处理分别高出了6％和33％;但是,O3／UV对乙酸几乎无降解活性．在这4种有机物的单独臭氧化降解过程中,除对氯苯酚外,水中均可检测到溶解臭氧．以上的实验结果表明,目标有机物对紫外光的吸收及单独臭氧化过程水中溶解臭氧的存在是O3／UV降解效率提高的必要条件．除UV对目标有机物的活化作用外,降解过程的中间产物H2O2也是O3／UV降解效率提高的一个重要因素,UV分解溶解臭氧在此过程可能仅起了辅助作用。     

腐蚀电池-Fenton工艺用于垃圾渗滤液的预处理研究

采用铁屑和颗粒活性炭通过原电池反应产生的Fe2 离子取代FeSO4组成腐蚀电池-Fenton工艺,采用该工艺对垃圾渗滤液进行预处理.结果表明,最佳运行条件为pH值为2、H2O2投加量为理论投加量的50%、铁屑投量为30 g(500 mL渗滤液中)、Fe/C质量比为2.5、反应时间为1 h、絮凝pH值为7,其COD去除率可达到60%(其中活性炭吸附占19%),TOC去除率可达47%(其中活性碳吸附占13%),BOD5/COD值从原水的0 35提高到出水的0.69;而传统Fenton工艺在H2O2/Fe2 比值等于5、其它条件与腐蚀电池-Fenton工艺相同的条件下,COD去除率为26%,TOC去除率为19%,BOD5/COD比值从原水的0.43提高到0.69.将腐蚀电池-Fenton工艺用于垃圾渗滤液的预处理,在有机物去除率和提高可生化性方面效果均明显优于传统Fenton工艺.     

Advanced oxidation of bromide-containing drinking water：A balance between bromate and trihalomethane formation control

Addition of H2O2 has been employed to repress bromate formation during ozonation of bromide-containing source water. However, the addition of H2O2 will change the oxidation pathways of organic compounds due to the generation of abundant hydroxyl radicals, which could affect the removal efficacy of trihalomethane precursors via the combination of ozone and biological activated carbon （O3-BAC）. In this study, we evaluated the effects of H2O2 addition on bromate formation and trihalomethane formation potential （THMFP） reduction during treatment of bromide-containing （97.6-129.1 μg/L） source water by the O3-BAC process. At an ozone dose of 4.2 mg/L, an H2O2/O3 （g/g） ratio of over 1.0 was required to maintain the bromate concentration below 10.0 μg/L, while a much lower H2O2/O3 ratio was sufficient for a lower ozone dose. An H2O2/O3 （g/g） ratio below 0.3 should be avoided since the bromate concentration will increase with increasing H2O2 dose below this ratio. However, the addition of H2O2 at an ozone dose of 3.2 mg/L and an H2O2/O3 ratio of 1.0 resulted in a 43% decrease in THMFP removal when compared with the O3-BAC process. The optimum H2O2/O3 （g/g） ratio for balancing bromate and trihalomethane control was about 0.7-1.0. Fractionation of organic materials showed that the addition of H2O2 decreased the removal efficacy of the hydrophilic matter fraction of DOC by ozonation and increased the reactivity of the hydrophobic fractions during formation of trihalomethane, which may be the two main reasons responsible for the decrease in THMFP reduction efficacy. Overall, this study clearly demonstrated that it is necessary to balance bromate reduction and THMFP control when adopting an H2O2 addition strategy.     

复合纳米Fe_3O_4的制备及其控磷效能的研究

采用氧化沉淀法在羧甲基纤维素(CMC)体系中制备了以纳米Fe3O4为核心,外包覆羧甲基纤维素的复合纳米Fe3O4.对比研究了复合纳米Fe3O4和微米Fe3O4对水中磷的吸附以及对土壤中磷的固化,并考察了添加纤维素酶在此过程中所起的作用.结果表明,在水中微米Fe3O4的平衡吸附量为3.2 mg/g,而复合纳米Fe3O4为2.1 mg/g.当将纤维素酶(用以降解包覆在氧化铁表面的羧甲基纤维素)添加到复合纳米Fe3O4吸附磷的溶液中,复合纳米Fe3O4的除磷效率(86%)接近于微米Fe3O4(90%),说明羧甲基纤维素的存在减弱了复合纳米Fe3O4的吸附能力.在土柱实验中,将2种Fe3O4悬浊液注入到10 cm高的土壤柱中,72%的复合纳米Fe3O4穿过土壤柱溢出,而微米Fe3O4完全滞留在土壤柱中没有溢出.原始土壤的固磷率为30%,注入复合纳米Fe3O4的土壤固磷率达到45%,而将纤维素酶和复合纳米Fe3O4一起注入土壤中固磷效率提高到74%.     

臭氧对中温循环冷却水系统的缓蚀性能研究

循环冷却水系统中普遍存在结垢腐蚀现象,目前常用的解决方法是在系统中加入缓蚀阻垢药剂,臭氧(O3)对循环水冷却系统同时具备阻垢、缓蚀、杀菌等多重功能。采用臭氧处理中温循环冷却水,研究在不同臭氧投加量时系统的腐蚀情况,确定最佳投加量。结果表明:当臭氧投加量为4.5 mg/L时,20碳钢和铸铁的缓蚀能力最佳。20碳钢腐蚀率最低为0.228 mm/a,比空白对照组降低了75%;铸铁的最低腐蚀率为0.282 mm/a,比空白对照组降低了61.5%。当臭氧投加量为9.0 mg/L时,镀锌试片的腐蚀率在0.206~0.275 mm/a,比空白对照组降低了38.2%左右,缓蚀效果较为明显。     

氯、氯胺消毒下钱江源水源水消毒副产物形成特征研究

以钱江源水源水为研究对象,以氯、氯胺为消毒方式,研究了不同消毒条件下,三卤甲烷(THMs)、卤乙腈(HANs)、氯代酮(CKs)、二卤乙酸(DHAAs)、三卤乙酸(THAAs)等消毒副产物(DBPs)的形成情况,以便为水务工作者监测钱江源建库前后水质、DBPs形成的变化提供基础数据.结果显示,氯消毒下DBPs的产量比氯胺消毒高出3~7倍甚至1个数量级,但不管是氯消毒还是氯胺消毒,THMs、HAAs形成量均在我国饮用水标准范围内.氯消毒下,大部分DBPs产量为中、碱性条件酸性条件(除了CKs),氯胺消毒则呈现不同的情况(所有DBPs的产量均为p H=6、p H=7p H=8).消毒剂量对所有DBPs形成具有明显的促进作用;溴离子对THMs、DHANs、DHAAs的形成有明显的促进作用.进一步研究表明,钱江源水源水的水质比钱塘江下游九溪水源水好,DBPs形成也较低,某些指标(如有机碳、有机氮、HANs形成量等)甚至比同省水质较好的金兰水库还要好;而且由于其较高的比紫外吸收值(SUVA),DBPs的溴嵌入能力均比九溪水源水、金兰水库低.此外,就目前的钱江源水源水来说,控制消毒剂量(氯、或氯胺)是控制DBPs形成的有效策略.     

臭氧对生物活性炭中微生物及出水消毒副产物的影响

为探究饮用水处理过程中臭氧(O_3)对生物活性炭(BAC)中微生物及出水消毒副产物(DBPs)的影响,以饮用水小试装置的O_3-BAC工段开展研究,系统分析在不同O_3浓度下的水质变化,溶解性有机物(DOM)特征,微生物活性和DBPs产生情况.结果表明,O_3对BAC过滤的影响主要表现为提升微生物对DOM的利用效率,但O_3浓度过高会导致出水中蛋白质和微生物代谢产物(SMPs)等有机物增加.当O_3浓度从0 mg·L~(-1)提升到2. 0 mg·L~(-1)时,BAC中微生物存活率从95. 10%降至62. 60%,但O_3将出水中难降解有机物转变为易生物降解物质,使得微生物活性提高了62. 52%,BAC的生物过滤得到强化;当O_3浓度增加到4. 0 mg·L~(-1)时,微生物存活率降至49. 90%,同时微生物产生的蛋白质和SMPs增加,导致含碳消毒副产物(CDBPs)和含氮消毒副产物(N-DBPs)的生成浓度与不通O_3相比分别上升41. 93%和7. 18%,大大增加水体潜在危险.综上,合适O_3浓度有利于O_3-BAC对DOM的去除,O_3浓度过高会导致BAC过滤效果变差并产生新的DBPs前体物.     

O3/H2O2法灭活水中剑水蚤类浮游动物

为解决水源水中孳生的水蚤类浮游动物难以被常规的水处理工艺有效地去除,困扰水厂正常生产运行的问题,进行了O2氧化、H2O2氧化和O3／H2O2高级氧化对水体中剑水蚤类浮游动物灭活效果的试验研究．发现3种方法中,O3／H2O2联合时除蚤效果最佳,在蒸馏水中投量为031．0mg／L、H2O24mg／L时,接触30min达到100％的灭蚤率;单独O3氧化效果也较好,投加1．0mg／L的灭蚤率为80％;H2O2氧化效果不理想,投加4mg／L几乎无灭蚤效果。进而考察确定了03／H2O2灭活剑水蚤的最佳工艺条件为：先加O3后加H2O2,投加间隔时间30～60s为宜;并探讨了H2O2投量、水体pH值以及有机物含量对O3／H2O2系统灭活剑水蚤效果的影响。试验中发现H2O2投量在4～10mg／L之间效果无较大变化,有机物含量对灭蚤影响较大,pH值的影响则较小。最后对O3／H2O2预氧化与水处理混凝沉淀工艺的协同除蚤效能进行了考察。结果表明,O3／H2O2预氧化与水处理混凝沉淀工艺的协同作用将会进一步提高除蚤的效果。