PAC和PAFC对内循环连续砂滤器处理石化二级出水的影响

采用PAC（聚合氯化铝）和PAFC（聚合氯化铝铁）作为絮凝剂，探讨不同絮凝剂及其投量对于内循环连续砂滤器处理效果和滤料板结潜在趋势的影响.结果表明，PAC和PAFC投量由5mg/L升至30mg/L时，COD和SS的去除率随着投加量的增大均呈现出先升高后降低的趋势.10mg/L为试验水质下的最佳投量，在该投量下，PAC对SS和COD去除率为分别为49.7%和12.9%；PAFC对SS和COD去除率分别为50.6%和13.8%.内循环连续砂滤器主要去除的是相对分子量在3k以上的溶解性有机物，但对相对分子量1k以下的溶解性有机物去除效果不好，总DOC去除率低于5%，需进一步深度处理以满足最新的排放标准.PAFC混合液比PAC混合液黏度低，有利于缓解滤料板结.总体来看，更适合于石化二级出水的混凝剂为PAFC，最佳投量为10-15mg/L，可保障对SS高效去除同时并使内循环连续砂滤器运行更加稳定.

Effect of PAC and PAFC on the performance and operation of inner loop continuous sand filter treating petrochemical secondary effluent

The inner loop continuous sand filter (ILCSF) is often used as the pretreatment process for the removal of SS and COD during the advanced treatment of biological secondary effluent. ILCSF can guarantee the operation stability of the following connected advanced treatment unit. In this study, poly aluminum chloride (PAC) and poly aluminum ferric chloride (PAFC) were used as the coagulant and the performance and operation of ILCSF were investigated. The results showed that when the dosages of PAC and PAFC ranged from 5to 30mg/L, the removal of SS and COD increased at the beginning and then decreased when the dosage was over 10mg/L. The optimized coagulant dosage was 10mg/L for PAC and PAFC. The removal rates of SS and COD were 49.7% and 12.9% for PAC and 50.6% and 13.8% for PAFC on the optimized dosage. The ILCSF could preferentially remove the macromolecular organic matters with the relative molecular weight higher than 3k. However, the ILCSF has the poor ability to remove the dissolved organic matters (DOM). The dissolved organic carbon (DOC) removal rate was lower than 5% even on the optimized conditions. The dose of PAFC was more suitable for the stable operation of ILCSF than dose of PAC. The viscosity of the mixture dosing PAFC was lower than that of dosing PAC. In this study, the optimized dosage of PAFC was determined with the value of 10to 15mg/L. It could guarantee the high removal rate of SS and the stable operation of the ILCSF.