Macro-Kinetic Study On High-salt Petroleum Wastewater In Oxidation Pond

The treatment of high-salt petroleum wastewater is always one of important questions for discussion, and worth studying and exploring. Many scientific research institutions and wastewater companies had carried out some experiments and research work all over the world. Ultimately, they did not reach perfect effect, because of complicate character. In this paper, integrated the different water quality with some successful experience at Xianhe oil plant in Shengli oil-field, a series of macro-kinetic parameters for COD degradation on high-salt petroleum wastewater were derived as the base of the macro-kinetic model using oxidation pond.Firstly, the quality of high-salt petroleum wastewater was analyzed. The main characteristics were high temperature, high-salt, and instability.Secondly, COD degradation law and main factors that influenced COD degradation velocity were investigated, by simulating Xianhe oxidation pond on the scale of 353L. The processes of COD degradation accorded with zero level kinetic law. Temperature, pH , solvent oxygen and other factors had some certain impact on COD degradation from 18 centigrade to 35 centigrade. The kinetic parameters were that reaction level n equaled to zero, and pH was eight point five, temperature coefficient 6 was 1.051, reaction velocity constant equaled to 0.221mg.L"'.h"' at 20 centigrade, and pH was nine point zero, temperature coefficient was 1.049, reaction velocity constant equaled to 0.196 mg.L/'.h'1 at 20 centigrade, and the equation were C=C0-Kt, K=7.058pH"4 345.Tl%3 at joint effect. This equation provedthat influence of pH was more important than temperature to COD degradation.Finally, COD degradation was restricted because of the lake of solvent oxygen by contrasting free surface oxygen transfer to aeration oxygen transfer. Gross transfer coefficient maintained l0-6m/s through free surface transfer, and gross transfer coefficient maintained l0-6m/s through aeration oxygen transfer. Therefore Xianhe oxidation pond was considered as facultative pond. The oxygen demand for COD degradation was more than free surface oxygen transfer. In addition, COD diffusion coefficient was bigger than oxygen diffusion coefficient. As a result, efficiency would be evidently elevated, if some aeration equipment was added or oxidation pond configuration was ameliorated.This study discovered that COD degradation complied with zero level kinetic law, and oxygen insufficiency was main factor restricting COD degradation. The effect of pH was very remarkable. These conclusions provide a reference for building macro-kinetic model and a guide for prediction of pond system. It is one important supplement for macro-kinetic study on high-salt petroleum wastewater in oxidation pond.