Biostability in distribution systems in one city in southern China：Characteristics, modeling and control strategy

This study investigated the bacterial regrowth in drinking water distribution systems receiving finished water from an advanced drinking water treatment plant in one city in southem China. Thirteen nodes in two water supply zones with different aged pipelines were selected to monitor water temperature, dissolved oxygen （DO）, chloramine residual, assimilable organic carbon （AOC）, and heterotrophic plate counts （HPC）. Regression and principal component analyses indicated that HPC had a strong correlation with chloramine residual. Based on Chick-Watson＇s Law and the Monod equation, biostability curves under different conditions were developed to achieve the goal of HPC 100 CFU/mL. The biostability curves could interpret the scenario under various AOC concentrations and predict the required chloramine residual concentration under the condition of high AOC level. The simulation was also carded out to predict the scenario with a stricter HPC goal （≤50 CFU/mL） and determine the required chloramine residual. The biological regrowth control strategy was assessed using biostability curve analysis. The results indicated that maintaining high chloramine residual concentration was the most practical way to achieve the goal of HPC ≤ 100 CFU/mL. Biostability curves could be a very useful tool for biostability control in distribution systems. This work could provide some new insights towards biostability control in real distribution systems.     

臭氧-生物活性炭组合工艺中最佳臭氧投加剂量的确定

在水处理过程中投加臭氧,可提高饮用水的可生物降解性.臭氧氧化后继的生物过滤,可以减少水中可生物降解有机物数量,提高饮用水的生物稳定性.试验表明,臭氧投加量2～8mg/L可使AOC-P17,AOC-NOX和BDOC分别增加20.9%～85.5%,42.1%～158.2%和21.4%～84.4%.臭氧投加量为3mg/L时,AOC和BDOC增加得最多,即3mg/L的臭氧投量为最佳投加剂量.生物活性炭滤柱(BAC)出水AOC浓度(乙酸碳)均低于50μg/L,在35.9～46.6μg/L之间,属于生物稳定性水质.     

饮用水生物稳定性评价指标研究进展

保障管网中生物稳定性是饮用水安全保障的重点,本文概述了饮用水中生物稳定性评价指标的研究进展,对比分析了国内外不同生物稳定性评价指标及其各优缺点,并提出了今后研究的重点和方向。     

Experimental study using the dilution incubation method to assess water biostability

Water biostability is of particular concern to water supply as a major limiting factor for heterotrophic bacterial growth in water distribution systems. This study focused on bacterial growth dynamics in the series dilution of water samples with TOC（total organic carbon） values determined beforehand. The results showed that the specific growth rate of Pseudomonas fluorescens P17 varied dramatically and irregularly with TOC value when TOC concentrations were low enough during the initial periods of incubation under given conditions. According to this relationship between bacterial growth rate and TOC, a dilution incubation method was designed for the study of water biostability. With the method under a given condition, a turning-point TOC value was found at a relatively fixed point in the curve between bacterial growth rate and TOC of water sample, and the variation of growth rate had different characteristics below the turning-point TOC value relative to that over this value. A turning-point TOC value similarly existed in all experiments not only with tap water, but also with acetate and mixed solutions. And in the dilution incubation method study, the affections were analyzed by condition factors such as inoculum amount,incubation time and nature of the organic carbon source. In very low organic carbon water environments, the variation characteristics of bacterial growth rate will be useful to further understand the meaning of water biostability.     

模拟再生水配水管网生物稳定性的研究

以T市J再生水厂出厂水为研究对象,利用生物膜反应器模拟再生水配水管网系统.通过微生物的培养和加氯消毒发现,培养40 d后出水和生物膜异养菌达到平衡,出水达5.63 log(CFU/mL),膜片达5.13 log(CFU/cm2).加氯消毒后出水和膜片上异养菌随着出水自由氯和总氯的增加而降低,通过比较可知控制出水自由氯0...     

饮用水中的磷及其在常规处理工艺中的去除

对某市某水厂水源水和出厂水中磷的存在形式、常规处理工艺对总磷 (TP)和微生物可利用磷 (MAP)的去除进行了研究 .结果表明 :①水源水中的磷主要以非溶解性形式存在 ,溶解性总磷酸盐约占总磷 30 % ;溶解性正磷酸盐只在个别月份检出 ,且浓度很低 ;②水源水中微生物可利用磷浓度一般高于溶解性总磷酸盐浓度 ,说明微生物也可以利用非溶解性磷 ;③出厂水中溶解性总磷酸盐占总磷的比例较水源水中溶解性总磷酸盐占总磷的比例升高 ,说明其去除较非溶解性的磷困难 ;④常规处理工艺对总磷和微生物可利用磷去除效果较好 ,平均去除率分别为 6 6 %和 6 9% ,混凝沉淀单元和过滤单元对总磷去除效果均较好 .强化混凝工艺 ,降低出厂水中的MAP ,有可能保证饮用水生物稳定性     

供水管壁的磷释放对管网水质生物稳定性的影响

为了研究供水系统金属管壁磷释放及其对管网水质生物稳定性的影响,采用新旧有水泥涂衬球墨铸铁管,考察了管壁和水泥涂衬中磷的含量,管网水中可同化有机碳(AOC)、异养菌平板计数(HPC)及生物可利用磷(MAP)的变化规律.结果表明,在铸铁管金属管壁和水泥涂衬中均有磷元素及其他微生物生长所需微量元素存在.旧管和新管均可向悬浮水中释放磷元素并可被微生物吸收利用,旧管释放水平高于新管;同时旧管释放产生的AOC和旧管水中的HPC也明显高于新管;新管对水中pH值有明显影响,但随时间推移逐渐减弱.     

Pilot plant study on ozonation and biological activated carbon process for drinking water treatment

A study on advanced drinking water treatment was conducted in a pilot scale plant taking water from conventional treatment process. Ozonation-biological activated carbon process （O3-BAC） and granular activated carbon process （GAC） were evaluated based on the following parameters： CODMn, UV254, total organic carbon （TOC）, assimilable organic carbon （AOC） and biodegradable dissolved organic carbon （BDOC）. In this test, the average removal rates of CODMn, UV254 and TOC in O3-BAC were 18.2%, 9.0% and 10.2% higher on （AOC） than in GAC, respectively. Ozonation increased 19.3-57.6 μg Acetate-C/L in AOC-P17, 45.6-130.6 μg Acetate-C/L in AOC-NOX and 0.1-0.5 mg/L in BDOC with ozone doses of 2 8 mg/L. The optimum ozone dose for maximum AOC formation was 3 mgO3/L. BAC filtration was effective process to improve biostability.