Study On Advanced Treatment Of Refinery Wastewater As Circulating Water

Reusing the refinery wastewater for industrial cooling water was one of the effective ways to eliminate the water resource shortage. The organics in the water had been already disposed into low concentrations after the secondary biological treatment.But the remains of COD, suspended solids and NH4+-N could not reach water quality standards of recirculating cooling water. Directly reusing the refinery wastewater for circulating cooling water was likely to produce microorganism slime, corrosion and scaling for the bacterial reproduction. In this study, the experiment used the combination of ozone oxidation, activated carbon absorption and lime softening to treat the secondary effluent from oil refineries in order to meet the quality requirements of the circulating cooling water system and improve the cooling water system operation stability.The test of the combination of ozone oxidation, activated carbon absorption and lime softening to treat the secondary effluent when the concentration of COD and NH4+-N was respectively60-105mg/L and10-20mg/L indicates, the concentration of COD, NH4+-NH3, SO42-, Cl-, total hardness and alkalinity was less than10mg/L,13mg/L,90mg/L,60mg/L,100mg/L and100mg/L respectively,which could meet the water quality standards for recirculating cooling water. When the contact time of ozone oxidation was40min, the removal rate of COD and NH4+-N could reach44.44%and11.45%. The unit of activated carbon absorption had strong adsorption of organic,but low absorption of NH4+-N, SO42-, Cl-, total hardness, and alkalinity.When the adding concentration of lime was0.32g/L, the concentration of Na2CO3was0.06～0.10g/L, and the mixing time for softening the lime was15～20min, the removal rate of total hardness could reach a maximum.After the advanced treatment of refinery wastewater, COD, NH4+-N, total hardness and alkalinity of the effluent had a large reduce. Static simulation experiment was carried out when the effluent was all used as make-up water, corrosion rate was still less than0.075mm/a which was accord with GB50050-2007in the "Design Code for the Treatment of Industrial Recirculating Cooling Water". Throgh a sterilization test towards the effluent, germicide of NaClO,1227and1427played an important role in control the growth and reproduction of the heterotrophic bacteria in water,the bactericidal rate was all more than90%and the total number of bacteria in the circulating water was far less than the proposed control standards(5×105/ml) of reusing the refinery wastewater for industrial cooling water.