水质变化对循环水系统排污水回用的影响及对策

Effects and countermeasures in reuse of blow down water in water circulating system with water quality change

针对循环水系统调整运行工艺后水质变化对排污水回用的影响进行了研究,认为水中Ca2+浓度的增加和总碱的降低是导致排污水回用装置出水硬度超标的主要原因,并提出了通过加入直接成垢因子的方法来去除水中的硬度。对三种软化方法的考察结果表明,对于永硬较高的循环水系统排污水,纯碱烧碱法的软化效果优于纯碱法和纯碱石灰法。在排污水中分别加入与其Ca2+和Mg2+浓度相同当量的纯碱和烧碱,可以使处理出水的Ca2+浓度和总硬度达到回用水的标准。反应时间对絮体的形成和沉降效果有一定影响,加药后的反应时间宜控制在30min以内。对于稳定运行的循环水系统,以固定的适当加药量进行投加,可获得良好的软化效果。

Effects on the water quality in case when the blow down water was reused in water circulating system were discussed, and believed that the increase of calcium hardness and the decrease of total alkalinity could be considered as the main reason to make total hardness of the system effluent exceeds the allowable limit of the standard after the system operation process had been adjusted. The method of adding direct scale-forming factors to remove hardness had been suggested. Three softening methods had been tested, and the result showed that the efficiency of calcined soda - caustic soda softening method was better than calcined soda softening method and calcined soda - lime softening method to treat the system effluent with higher permanent hardness. It would meet the standard of circulating water system effluent reuse by adding calcined soda and caustic soda into the system as the same quantity as its calcium hardness and magnesium hardness respectively. The reaction time would affect floc formation and sedimentation efficiency, and the reaction time should be limited in 30 minutes. It would get good softening efficiency by adding agents at the same proper quantity when the system operated steadily.