Study On Advanced Treatment Of The CAST Effluent By Stabilization Ponds

With the rapid development of urbanization, water pollution has become more and more serious. Enhancing the treatment of wastewater and improving the quality of effluent are important approaches to prevent water from further contamination. The improvement of our Environmental awareness and quality of wastewater treatment plant effluent, make the advanced treatment of wastewater becoming more important. Stabilization ponds are biological treatment system that purfying water by natural self-purification capability.Stabilization ponds has many advantages, such as low cost of investment and energy, convenience of management, and can remove the substance effectively. They have been widely applied both at home and abroad recend years, and have a broad market prospect.Zhenjiang, located in the Yangtze river delta, is an integrated industrial, ports and travel for the integration of the city. Enhancing the protection of water environment become particularly important.Recently years the country payed more attention to environmental protection, and Zhenjiang also strengthened the protection measures of water environment. In accordance with the "Eleventh Five-Year" plan of pollutant discharge reduction of Zhenjiang City, effluent of all the wastewater treatment plant should reach grade-one standard A of the urban WWTP pollutant discharge standards (GB18918-2002).Zheng Runzhou wastewater treatment plant, which uses CAST process, is mainly responsible for the urban district. The effluent can reach grade-one standard B of the urban WWTP pollutant discharge standards (GB18918-2002). Through the analysis of effluent water quality, we find that Zheng Runzhou wastewater treatment plan has good effect on COD, BOD₅ and TP, while the TN, NH₃-N, SS removal effect are poor, which often exceeding standards. Nitrogen removal effect is poorer, especially in case of low temperature of winter.The paper describes the design of stabilization ponds and experimental equipment. The system consists of regulating pond, aerobic ponds, facultative ponds and biological pond system components in series. And the experimental equipment is simulation of the stabilization ponds by the same HRT. The stabilization ponds system is used for advanced treatment of secondary effluent. The depth of aerobic pond is deeper than normal, and DO in pond is supplemented by aerator. We plant C.alternifolius L, cress cripus and water caltrop, and farm carp, crucian, silver carp and so on, which can make up an artifical ecosystem.The experiment studies the impact of temperature, DO, HRT that haved on the treatment effect and the relationship, which can provide a basis for process control. The experiment studies efficiency and contribution of each unit, which can provide a basis for selection of operation mode.The experiment mainly divided into two stages: winter and summer. We will study the removal condition of nitrogen, phosphorus and organic matter, etc, at each stage. When HRT is 6.4d in winter, parameters including COD, TN, NH₃-N, TP and SS removal efficiency is 50%, 40%, 70% and 55%. When HRT is 10.6d in summer, parameters including COD, TN, NH3-N, TP and SS removal efficiency is 60%, 90%, 98% and 92%. When HRT is 7.9d, parameters including COD, TN, NH3-N, TP and SS removal efficiency is 58%, 74%, 98% and 95%.When HRT is 5.4d, parameters including COD, TN, NH₃-N, TP and SS removal efficiency is 55%, 56%, 97% and 76%. Based on the comparion of results that whether water plants are in the ponds or not, we find that water plants can promote the parameters including COD, TN, NH3-N and TP removal efficiency by 6¹2%, 15²5%, 20³0% and 13²2%.The results show that water plants can promote the removal efficiency of pollutant. The system can remove the pollutant effectively, and the effluent can reach grade-one standard A of the urban WWTP pollutant discharge standards (GB18918-2002).