给水管网中污染物在管垢上的累积和释放

给水管网中,管垢是各种污染物的源和汇,但目前污染物在管垢中的累积释放特征尚缺乏系统研究.本文以实际的城市供水管网的球墨铸铁管和灰口铸铁管为对象,一方面采用扫描电镜(SEM)、能谱分析(EDS)、晶体衍射结构分析(XRD)等手段对其管垢进行表征,另一方面运用管段滞流反应器研究了三氯甲烷、铅、锰和锌等污染物滞流状态下在管垢上累积和释放特征.结果表明:同为铸铁管,使用一定年限后,管垢成分有所差异,灰口管管垢量较大,具有明显的锈蚀和管瘤出现,成分以二氧化硅、金属复合氧化物为主,而球墨管管垢量较小,以二氧化硅为主;随着初始浓度的提高,管垢对污染物的累积量逐步提高,对于三氯甲烷,其吸附量和释放量都非常低,而对于Pb、Mn和Zn 3种金属,管垢的吸附量远大于释放量,说明在实验条件下它们易累积不易释放,但水质条件的改变有可能引起大规模释放.研究结果对饮用水管网生物化学安全提出了更高的要求,为管网的饮用水安全保障提供了理论依据.

Accumulation and release of contaminants in pipe scales of drinking water distribution system

In drinking water distribution system, pipe scales was not only a breeding ground for microorganism, but also a source and a sink of contaminants. However, there were few systematic studies reporting the regulation of the accumulation and release of contaminants in pipe scales. In this paper, on one hand, the surface character of pipe scales in ductile cast iron pipe and grey cast iron pipe was investigated by using SEM, EDS and XRD; On the other hand, the accumulation and release of chloroform, Pb, Mn and Zn was examined in the stagnant reactor. Results showed that, the gray cast iron pipe serving for years has a great amount of pipe scales and high degrees of corrosion. The crystalline of pipe scales in ductile cast iron pipe was mainly consisted of quartz, while quartz and metal composite oxide were in grey cast iron pipe. In accumulation and release experiment, with the increasing of initial concentration of pollutants, the accumulation of pollutants in pipe scales was increasing. For chloroform, the adsorption capacity and release amount was very low. But the accumulation amount of heavy metals (Fe, Mn and Zn) was much higher than the release amount, indicating it was easier to accumulate than to release, but the change of water quality maybe cause massive release of the pollutants. This study puts forward higher biochemical safety requirements for drinking water distribution system, and provides a theoretical basis for drinking water safety.