化学沉淀法处理高盐含磷废水

高盐含磷废水具有盐含量高、污染物成分复杂和生物处理难等特点。生产鸟粪石后的浓海水因添加过量的Na₂HPO₄及NH₄HCO₃等诱导剂和稀释剂,其上清液中会有PO3-₄-P残留。针对其上清液磷含量超标的问题,使用化学沉淀法进行除磷实验。选用聚合氯化铝(PAC)、FeCl₃、Ca (OH)₂、聚丙烯酰胺(PAM)作为实验药剂,研究了反应时间、单一药剂添加量和药剂复配等因素对除磷效果的影响,筛选出2种满足出水磷含量要求(0.5 mg/L)的工艺条件。方案1:添加n (Ca)/n (P)=4.5的Ca (OH)₂,处理后溶液PO3-₄-P含量为0.2 mg/L;方案2:添加n (Al)∶n (P)=0.5的PAC+n (Ca)/n (P)=4.0的Ca (OH)₂+0.5 g/L PAM,处理后溶液PO3-₄-P含量为0.4 mg/L。综合分析,方案1操作方便,方案2有助于固液分离,二者均可以用作废水处理方案,研究结果为高盐含磷废水处理提供了一个切实可行的思路。

TREATMENT OF HIGH-SALINITY PHOSPHATE-CONTAINING WASTEWATER BY CHEMICAL PRECIPITATION METHOD

High-salinity phosphate-containing wastewater has the characteristics of high salt content, complex pollutant composition and is difficult to be treated by the biological method. The supernatant will contain some PO3-₄-P after struvite production by adding excessive inducers and diluents such as Na₂HPO₄ and NH₄HCO₃ to seawater. A chemical precipitation method was applied for excessive phosphate removal. In our experiment, poly-aluminium chloride(PAC), FeCl₃, Ca(OH)₂ and polyacrylamide(PAM) were selected as experimental chemical reagents. The effect of reaction time, the additive amount of a single chemical reagent and a combination of chemical reagents on the phosphate removal effect were studied. Finally, two strategies were selected, which could make the phosphate content in the effluent meet the emission standard. Strategy 1:adding Ca(OH)₂ with a molar ratio of Ca:P of 4.5 made the PO3-₄-P content decrease to 0.2 mg/L. Strategy 2:adding Ca(OH)₂ with a molar ratio of Ca:P of 4.0, PAC with a molar ratio of Al:P of 0.5, and PAM with a concentration of 0.5 g/L made PO3-₄-P content decrease to 0.4 mg/L. Strategy 1 was easy to operate while strategy 2 was helpful for solid-liquid separation. Both of them can be used for the treatment of high-salinity phosphate-containing wastewater. The results provide a practical idea for the treatment of high-salinity phosphate-containing wastewater in the future.