Flocculation Kinetics And Its Application In The Advanced Treatment Of Petrochemical Wastewater

It has been several hundred years since coagulation process was applied in water treatment.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. In this article, coagulation and sedimentation processes is applied in the depth treatment of Liaoyang Petrochemical effluent to reach new discharge standard (DB21/1627-2008).Under the guidance of enhanced coagulation theory, series of jar tests were done. Results show that:the optimal coagulant is PSAF, its optimal dosage is 30mg/l and the optimum pH range is 6 to 9. Under this condition, COD and TP removal rates are of up to 53% and 89%. By monitoring and analyzing COD removing efficiency under different flocculation time with different speed, G values variation trend is derived. Aiming to solving the problem of high energy consumption and uneven distribution in the flocculation reactor, a new spiral flocculation reactor was designed and consistent with flocculation kinetic theory.At the same time, good result was obtained with the appliance of this spiral flocculation reactor in the pilot test. The effluent COD and TP removal rates are of up to 50.28% and 93.79%.The spiral flocculation reactor and the conventional rotation reactor were simulated with CFD software for better understanding of interior flow field.Results show that:with spiral structure, the curvature changes evenly and the vortex fill the entire area, which avoids the dead areas and even energy distribution in space is available; as the reactor is designed based on flocculation kinetic energy distribution formula, the energy consumption decreases with flocculation time. Thus a better condition for the formation of dense flocs is provided and in this way the efficiency of flocculation can be improved.