Study On Coupled Photocatalytical-biological System For The Treatment Of Non-biodegradable Organophosphorus Pesticides Wastewater

Organophosphorus pesticides wastewater was characterized as highconcentration of organic matter, high toxicity for biotic systems, biorecalcitrant, so itis always a difficult mission for wastewater disposal. Photocatalysis as an advancedoxidation processes is a very promising methods for its high oxidant power, nosecondary pollution, and no selectivity when completely mineralizing variespollutants to inorganic ions. But the operational costs are relatively high compared tothose of biological treatments, which are, at present, the cheapest and the mostcompatible with the environment. So there are more potential advantages of thecombined process than of the single process in the non-biodegradable wastewatertreatment field. The experiment of photocatalytic degradation of organophosphorus pesticideswas conducted. The chemical and biological characteristics of photocatalytic solutionswere analyzed, and the efficiency of several AOP was compared. Subsequently, theeffect of catalyst, pH, the concentration of catalyst, illumination intensity, H2O2 on thedegradation process was studied and the optimal conditions were found. The result indicates that the biodegradability of photocatalytically treatedorganophosphorus pesticides wastewater was enhanced by measuring the BOD5 andCOD of samples. The sequent experiment was implemented in gas-liquid-solid threephase fludized bed bioreactor to investigate the influence of photocatalytic time on thebiological treatment, and the optimum photocatalytic time were acquired. Theexperimental results also demonstrate that it is possible to combine photocatalysiswith conventional biological treatment for the remedy of wastewater containinggenerally non-biodegradable organophosphorus pesticides. Meanwhile, the effect ofCODCr removal efficiency, and H2O2 added in the photocatalytic on biologicaltreatment was studied in the batch experiment. The kinetic equation, expressed by the COD degradation, is given. Thephotocatalytic degradation kinetics followed pseudo-first order reaction and the CODdegradation Monod equation is employed to achieve kinetics analysis in the biologicaltreatment. The experimental data were much well fitted with the model.