Pretreatment experiments for photographic waste water

A series of pretreatment experiments to photographic waste water have been done to get the highest COD removal rate by different methods of coagulation and ozone oxidization on the condition of different factors. The optimum coagulation conditions were listed as follows: 10 minutes coagulation time, 10 pH value, 2.5% ratio of volume for coagulant dosage. Through pretreatment process of coagulation, the COD of photographic waste water could reduce 25% approximately to 20000~50000mg/L. the optimum ozone oxidization reacting time was 4 hours and packing media, high temperature, alkaline condition can improve the COD removal efficiency. In the optimum condition the COD removal ratio can achieve 56%.