污水回用中的循环浓缩水质模型与污水回用率

污水回用中因循环浓缩，存在着水质变差问题．探索其变化规律，定量确定运行参数，做到既节水又保证回用水质合格、稳定，具有重要理论和实用意义．通过数学归纳法推导出一个循环浓缩水质数学模型和计算杂用水质和污水回用率的公式．应用该模型，以厕所污水回用为例，就污水水质、污染物去除率、处理水质和杂用水质标准对杂用水质、污水回用率的影响进行讨论．结果表明，在符合城市杂用水水质标准的前提条件下，分别按生化需氧量、浊度、氨氮及色度等水质指标计算得出的污水回用率是65．3％，82．9％，57．5％和37％．在厕所污水回用中，色度为水回用率的限制指标．由于色度指标的限制，经计算水循环厕所的污水回用率一般不宜超过40％。

A water quality model for water reuse and the reusing rate of the treated wastewater

A water quality model for water reuse was derived with mathematical induction. Based on the model, two formulas were derived to calculate Cs and r, the concentration of pollutants in the reused water and the reusing rate of the treated wastewater. The relationships among Cs, E (the removal efficiency of pollutants of wastewater)and C_0(the concentration of pollutants in influent), and also relationship between r and the standards of reused water were discussed. The reusing rates of the treated wastewater were different for the different water quality parameters. The r for the "black water" reuse were 65.3%, 82.9%, 57.5%, and 37%, of BOD_5, turbidity, ammonia and color, respectively. According to the study, the reusing rate of the reused waterfrom a toilet will be less than 40%, where every parameter can be up to the reused water standards.