光合细菌法处理后之糖蜜酒精废水的化学混凝处理研究

Study on Coagulation of Secondary Effluent from PSB Process

糖蜜酒精废水经过光合细菌处理后，ＢＯＤ５和氨氮均能达到 ＧＢ８９７８－１９９６二级排放标准，但ＣＯＤｃｒ仍然上千。本文进行了化学混凝法处理光合细菌法出水的试验，研究了几种混凝剂在不同投药量、ｐＨ及投加阳离子聚丙烯酰胺情况下的混凝效果。结果表明，投加 ＦｅＣｌ３和聚合硫酸铁使ＣＯＤｃｒ的去除率达到７０％以上，可以达标。投加阳离子聚丙烯酰胺试验结果表明其对絮体的形成、絮体大小及分离速度有帮助，但对ＣＯＤｃｒ的削减作用不大。该废水含有较高的碱度，投加混凝剂后引起ｐＨ下降导致ＣＯ２气体析出与絮体结合后带动絮体上浮。

After treated by PSB(Photosynthetic Bacteria)process, the sugar-syrup alcohol wastewater can meet the national discharge requirements(GB8978-1996)in terms of BOD5 and ammonia, but its CODcr concentration is still mere than 1000 mg· L- 1. Because of the low biodegradability of the effluent, coagulation was chosen as the polishing treatment before discharge. In this study four coagulants were investigated on their optimal dosage and CODcr removal performance. The results showed that CODcr concentration could be reduced below 300 mg· L- 1 with FeCl3 and PFS as the coagulants. The influence of PAM was also studied. The result showed that there were no significant promotions of the COD removal efficiency in presence of PAM, but the settling velocity of the flocs did increased drastically. Due to the high alkalinity of the effluent, a lot of fine CO2 bubbles were formed and released after the effluent was mixed with acidic coagulants, which made the floc rise to the surface instead of settling to the bottom.