Study On Flocculation Kinetics Applied In Advanced Treatment Process Of Petrochemical Wastewater

ABSTRACT:Flocculation-sedimentation-filtration technology is a typical technology of the water treatment and sewage water advanced treatment technology. Compared with other physical and chemical methods, not only does it have good water quality, but also it is stable, economical, practical and easy to operate.Coagulation which is the basis and key of this technology determines the effectiveness and efficiency of the sedimentation and filtration process. Coagulation technology in recent years mainly focus on the research of the coagulant. The innovation of article is the Spiral flocculation reactor used in the wastewater treatment process of the Liaoyang Petrochemical and the theory of the spiral flocculation reactor is the self-preserving coagulation theory, so that the performance of process can be improved and meet new discharge standard (DB21/1627-2008).The wastewater using in the pilot test is the effluent of a secondary treatment of Liaoyang Petrochemical 450# plant. The secondary effluent has the characteristics of low COD and low turbidity and the coagulation treatment is very difficult to success. The spiral flocculation reactor has enough softness to make the velocity gradient close enough to reach the velocity gradient requirements of the self-preserving dynamics, so that the high efficient coagulation could occur in order to successfully achieve the coagulation effect.Pilot studies have shown that:Using PSAF coagulant, through the treatment the turbidity of raw water can be reduced from 6.73 NTU to 0.06 NTU, with the removal rate of 91.79%; COD can be reduced from 54.85mg/L down to 28.19 mg/L, with the removal rate of 48.40%; TP can be reduced from 2.52 mg/L down to 0.11 mg/L, with the removal rate of 95.57%; SS can be reduced from 16 mg/L down to 3 mg/L, with the removal rate of 78.44%.The feasibility of coagulation-sedimentation-filtration technology used in the advanced treatment of petrochemical wastewater was proved, and also the results were proved that the effectiveness and efficiency of the spiral flocculation reactor treating low turbidity water. After process optimization in pilot experiments, take the experimental results and the running stability and cost into consideration, this paper has gotten the coagulation time was 15min and the PSAF dosage was 40mg/L are the best operating parameters.