饮用水分配系统(DWDS)的腐蚀产物中的金属污染物可以在特定条件下释放到饮用水中,从而污染饮用水并构成健康风险。在停滞状态下,释放特性,发生的形式,和十种金属的环境风险是在具有长期使用历史的无衬里铸铁管的松散和结节规模固体中确定的,浸泡前后。大多数Al,As,Cr,Fe,和V在腐蚀规模中存在的残余部分,释放浓度和污染风险较低。由于管垢中超过59%的Ca存在于可交换部分中,Ca释放量高。虽然腐蚀固体中的Pb和Cd含量较低,在具有高迁移率的非残留馏分中存在高比例的Pb和Cd。DWDS中突发的重度Pb或Cd污染事件可能导致高污染和环境风险水平。腐蚀垢中Mn和Zn的总含量和释放量均较高。因此,虽然应该特别注意锰和锌,Pb和Cd在管道尺度中也存在高风险,尽管浓度低。在停滞浸泡期间,通过质量释放过程发生粉末管垢中的金属释放,重新吸附到水垢中,并缓慢释放直至达到平衡。金属再吸附到水垢中的水平远高于溶解到本体水中的浓度。然而,金属再吸附到结节鳞块中的量较少。重要的是,这些发现突出表明,在DWDS操作期间,应避免管道水垢破裂引起的金属污染物突然释放。
Metal contaminants in corrosion products of drinking water distribution systems (DWDS) can be released into potable water under specific conditions, thereby polluting drinking water and posing a health risk. Under stagnation conditions, the release characteristics, occurring forms, and environmental risks of ten metals were determined in loose and tubercle scale solids of an unlined cast iron pipe with a long service history, before and after immersion. Most Al, As, Cr, Fe, and V in corrosion scales existed in the residual fraction, with the released concentration and pollution risk being low. Since more than 59% of Ca in pipe scales existed in the exchangeable fraction, Ca release was high. Although the Pb and Cd content of corrosion solids was low, a high proportion of Pb and Cd was present in non-residual fractions with high mobility. Sudden severe Pb or Cd pollution events in DWDS could result in high pollution and environmental risk levels. The total content and released amount of Mn and Zn in corrosion scales were both high. Therefore, while special attention should be paid to Mn and Zn, Pb and Cd also present a high risk in pipe scales, despite their low concentrations. During stagnation immersion, metal release from powdered pipe scales occurred via the processes of mass release, re-adsorption into scales, and slow release until equilibrium was reached. The levels of metal re-adsorption into scales were much higher than the concentrations dissolved into bulk water. However, the amount of metal re-adsorption into tubercle scale blocks was less. Importantly, these findings highlight that during DWDS operation, the sudden release of metal pollutants caused by pipe scale breakage should be avoided.