Photoelectrocatalytic Combined With Constructed Wetland Treatment With Organic Pesticides Wastewater

As a nano semiconductor oxide, TiO₂ is a photocatalyst that shows high photoefficiency and oxidation activity. TiO₂ has become a hot research area because it can decompose organic pollutants in gases and liquids into CO₂ and H₂O. In recent years, the technique of TiO₂ photocatalysis oxidation is recognized as a new kind of water treatment process with great potential application especially in the organic substances degradation for its remarkable effect. If other elements are mixed in TiO₂, the photocatalytic activity can be improved. The method of electrically assisted photocatalysis makes use of the bias potential to take away the photoelectrons and decrease the combination of electron-holes. In this way ,the photocatalytic activity can also be improved.Constructed wetlands(CWs) were new wastewater treatment technology which based on natural system for wastewater treatment. CWs were widely applied around the world for its particular advantages. Removal of pollutants in a constructed wetland is believed to be accomplished in the ways of filtration, plant uptake and degradation and so on. It showed that CWs are expected to have bright prospects in future.In this paper, Photoelectrocatalytic combined with constructed wetland treatment with pesticides wastewater was studied. Firstly, photoelectrocatalytic degradation of pesticides wastewater by using immobilized RuO₂-TiO₂ as catalyst was investigated. The effects of time of baking, quantity of catalyst, light intensity, density of electric current, initial pH, and reaction time applied on reduction of COD_cr and decolorization were studied. The results showed that the highest photocatalytic activity of RuO₂-TiO₂ was 1.38 times of Degussa P-25 TiO₂, 1.81 times of Ru_0.3Ti_0.7O₂ under the same condition. In addition, the photocatalyst responded to visible light. The decolorization rate of visible-light electrocatalysis is 34.8% higher than that of electrocatalysis without light.After treated by photoelectrocatalytic, the pesticides wastewater was further treated by constructed wetland, by 5 days treatment. The water quality was obviously improved. The COD, Colorization, TN, TP, DTP, Sulfide and SS were reduced 97.2%, 99.2%, 96.7%, 99.4%, 69.7%, 100%, 73.5% respectively.The pesticides wastewater quality were obviously improved by Photoelectrocatalytic Combined with Constructed Wetland technics. The treated effluent quality attained the first criteria specified in the integrated wastewater diacharge standard(GB8978-1996). It showed that the new technology has potential promising prospect in the future.