城市污水处理厂二级处理出水中磷的组成及去除特性研究

Composition and Removal of Phosphorous in Effluent from Urban Sewage Treatment Plant

以某市第4污水处理厂A^2/O处理工艺的二级处理出水中的P为对象,对其组成及去除特性进行实验。结果表明,通过理论计算,水中的磷酸盐主要以H_2PO_4^-、HPO_4^(2-)存在,而非常规认识的PO_4^(3-);二级出水中悬浮态P(粒径>0.45μm)、胶体态P(粒径0.45μm^1 nm)和溶解态P(粒径<1 nm)分别为TP的5%~15%、15%~25%、60%~70%;以溶解态P为主的二级处理出水,随着混凝剂的加入,溶解态P首先与Al^(3+)反应形成Al PO4沉淀,然后形成絮体,被沉淀去除;当水中TP的质量浓度为0.94 mg/L时,PAC和Al2_(SO_4)_3以Al计的投加量分别为4、6 mg/L时,处理后TP的质量浓度小于0.5 mg/L,可以达到GB 18918-2002的一级A标准。

Experimental study of the composition and removal characteristics of P in the secondary effluent treated by a A^2/O process in the fourth sewage treatment plant of Xi＇an was carried out. The results showed that： Through the theoretical calculation, the phosphate in the water mainly exist in the forms of H_2PO_4^- and HPO_4^（2-）, not the conventionally known from of PO_4^（3-）; Field measurements showed that the suspended P（diameter 0.45 μm）, colloidal P（diameter 0.45 μm^1 nm） and dissolved P（particle diameter 1 nm） respectively accounted for 5%～15%, 15%～25%, and 60%～70% of the total P; In the secondary treatment effluent with dissolved P, with the addition of coagulant, dissolved P first react with Al^（3＋） to form AlPO_4 precipitation, which then form flocs, and finally be removed by precipitation. When the mass concentration of TP was 0.94 mg/L, and the dosage mass concentrations of PAC and Al_2（SO_4）_3 were respectively 4 mg/L and 6 mg/L（Al）. After treatment the mass concentration of TP became less than 0.5 mg/L, which can meet the A level of GB 18918-2002.