氯氨消毒条件下供水系统水质生物-化学特性研究

由于城市供水系统存在细菌滋生且难以控制等问题,水质生物安全及其稳定性问题的研究愈显其必要性。在我国南方某地区的原水-净水厂-供水管网全流程选取18个采样点进行常规水质及生物稳定性指标检测与分析,结果表明原水预氯化导致水中AOC含量由210μg乙酸碳/L上升至348μg乙酸碳/L,这可能是由于预加氯氧化过程将大分子质量有机物分解为易于细菌利用的小分子质量有机物所致;澄清与砂滤工艺对AOC具有一定的去除效果;氯胺消毒可有效降低水中的异养菌菌落总数,对异养菌平均去除效率达95%以上。对供水管网水质检测数据统计分析结果表明,管网水中余氯浓度低于0.43mg/L时,异养菌菌落总数与AOC含量呈显著性正相关(R=0.27,P<0.05,n=97),这表明氯氨含量与AOC和异养菌菌落总数存在相关性特征;在余氯浓度高于0.43mg/L时,细菌总数与AOC含量相关性不显著(R=0.18,P>0.05,n=91),说明此时氯氨为细菌生长的限制条件。因此,适当的氯氨投加量条件可有效限制城市供水系统中细菌的生长。

Bio-chemical correlation study on water quality of water supply system under chloramine disinfection

Due to unpleasant bacterial growth in urban water supply systems,studies on biological security and stability of water quality are becoming more and more necessary.In the present study,we compared water quality and biological stability from water samples from raw water(RW)– drinking water treatment plant(DWTP)-drinking water distribution system(DWDS)of 18 sampling stations in southern China.The results show that the average content of AOC in raw water increases from 210μg-acete/L to 348μg-acete/L after pre-chlorination and the possible reason may be the decomposition of organic matters with large molecular weight into those with small molecular weight which can be used by bacteria easily.Moreover,the clarification and sand filtration process have certain effects on the removal of AOC and the disinfection of chloramine can reduce the quantity of heterotrophic bacteria in water(average removal efficiency reaches over 95%).The results of water distribution system show that the quantity of heterotrophic bacteria is positively correlated with the AOC content(R =0.27,P <0.05,n=97)when the residual chlorine concentration in distribution system is less than 0.43 mg/L,This indicates that there is a correlation between the content of chlorinated ammonia and the total number of AOC and heterotrophic bacteria.When the residual chlorine concentration is higher than 0.43 mg/L,the correlation between the total number of bacteria and AOC content is not significant(R=0.18,P>0.05,n=91),indicating that chloramine is an important limiting factor for bacterial growth.Therefore,appropriate dosage of chloramine can probably be a good solution in limiting the growth of bacteria in urban water supply systems.