Pilot-Study Of Orbal Oxidition Ditch To Enhance Biological Nitrogen Removal

Eutrophication, which is caused by excessive discharges of nitrogen and phosphorurs, is still the main water pollution problem worldwidely. With the development of ecomomic and society, the projects of wastewater treatment have been greatly developed, and the ratio of wastewater disposal keeps increasing in the recent years. However, the problem of eutrophication still remains seriously. In general, the operation technique of wastewater treatment plants relatively lags behind in our country, with high cost and worse effluent water quality. At the same time, many efforts should be made to develop novel processes and improve the understanding of the new technique. It becomes urgent to keep popularization and development of biological nutrient remval, and realizing the operation and update of the existed wastewater treatment plants (WWTPs) to get nutrient removal with low costs.In this study, a pilot-scale Orbal oxidation ditch with 330 liters working volume was used to investigate nitrogen removal and cost-efficient operation, and to give supports to the update of the existed WWTPs. Both typical municipal wastewater and low C/N domestic wastewater were used to carry out the experiment. Meanwhile, because the low C/N of the domestic wastewater, which would make the denitrification processs lack of carbon source, a new technique to realize partial nitrification only by low dissolved oxygen control was put forward, treating domestic wastewater at ambient temperature.During the study of Orbal oxidation ditch treating domestic wastewater, operation parameters, such as different dissolved oxygen, C/N ratio and sludge recycle flow rate, which would influence nitrogen removal were analyzed, in order to provide valuable data to the real WWTPs. Practical methods, such as to limit oxygen supply and lower the DO concentration in outer channel, were proposed to enhance nitrogen removal performance and save the energy. Under hydraulic retention time of 16.5 hours, mixed liquor suspended solids (MLSS) concentration of 3000mg/L, sluge recycle flow rate of 100%, the DO of outer, middle and inner channel of 0.4, 1.5 and 2.5mg/L, respectively, average total nitrogen removal efficiency could reach 75.2%, with effluent total nitrogen concentration of less...