石灰乳-聚合氯化铝处理高含氟废水的研究

Study on the treatment of highly concentrated fluoride-containing wastewater with lime milk-polyaluminum chloride

为解决某大型氟化盐厂高含氟废水达标排放的问题,采用石灰乳-聚合氯化铝两段法除氟工艺进行处理,确定了一段和二段的最佳工艺条件,同时对比了聚合氯化铝和硫酸铝两种絮凝剂的除氟效果。结果表明：一段工艺在将废水pH调节至12左右,即控制石灰乳投加量达到m（Ca2＋实际）/m（Ca2＋理论）为2.0-2.5,以及搅拌时间为30-50 min,搅拌速度为150 r/min,沉淀时间为90-120 min条件下,二段工艺参数在聚合氯化铝投加质量浓度为500 mg/L,絮凝沉降pH为6-8时,能将废水中残留氟的质量浓度控制在10 mg/L以下,达到了《污水综合排放标准》（GB 8978—1996）的一级标准。聚合氯化铝的处理效果优于硫酸铝。

In order to make the discharge of highly concentrated fluoride-containing wastewater meet the discharge standard at a large-scale fluoride salt plant,the lime milk-PAC two stage fluoride removing process has been conducted.The optimum process parameters of the first stage and second stage are determined.At the same time,the effectiveness of fluoride removal from the flocculants aluminum sulfate and aluminum sulfate are compared.The results show that the residual mass concentration of fluoride ion in wastewater can be controlled under 10 mg/L,when the process parameters of the first stage are designed as follows：the pH is adjusted to around 12,i.e.the dosage of lime milk is controlled at of m（Ca ^2＋ real）/m（Ca^ 2＋ theo）=2.0-2.5,stirring time 30-50 min,stirring speed 150 r/min,and precipitation time 90-120 min;and the process parameters of the second stage is designed as follows：the mass concentration of PAC is 500 mg/L,and the pH of flocculating precipitation is 6-8.Thus,it reaches the first class of Integrated Wastewater Discharge Standard（GB 8978—1996）.The treatment efficiency of PAC is superior to aluminum sulfate.