An Innovative Double-Layer Microsphere Used as Slow-Release Carbon Source for Biological Denitrification

Abstract

The key problem of in situ biological nitrogen removal in domestic sewage is the lack of carbon source. A new type of double-layer sustained-release carbon source microspheres was prepared using cheap agricultural waste as carbon source. The carbon release performance and denitrification performance of three kinds of agricultural wastes, peanut shell, corn cob, and walnut shell, under different particle sizes were studied, and the optimal inner carbon source was chosen. And the carbon release performance and application in biological denitrification of sodium alginate microspheres were studied by immobilization technology. The results showed that corn cob with particle size < 0.125 mm had better carbon and nitrogen release properties. After embedding and fixing, the total nitrogen (TN) concentration of double-layer carbon source microspheres can be treated to 13.92 mg/L at a temperature of 30 °C, pH 7.2~7.5, and TN concentration of 42.95 mg/L, and the treatment effect was satisfactory with the national standard (GB 18918-2002) for municipal wastewater, which is better than the treatment effect of single-layer carbon source microspheres. It can be seen that double-layer slow-release carbon source microspheres have greater potential than single-layer microspheres for denitrification of domestic sewage.