Enhanced Primary Municipal Wastewater Treatment And Applicability Study At Guanzhong Area

The most popular enhanced primary treatment processes include chemical coagulation, bio-flocuulation-adsorption, bio-chemical ftocuulation, etc. In this study, chemical coagulation process using new type MJ combined coagulant and traditional inorganic coagulant PAC has been developed to treat the municipal wastewater from Xi'an Dnegjiacun sewage plant, and compared with normal primary and secondary treatment. In the mean time, for both enhanced primary treatment and normal secondary treatment, investment and operation cost assessment and economic analysis have been done for Shaanxi Sanyuan 20000m3/d sewage plant as a typical sewage plant for small cities. After technology and economic analysis and comparison, the concept of firstly enhanced primary treatment while later secondary treatment when feasible has been proposed for Sanyuan sewage plant, and the applicability of enhanced primary treatment for municipal wastewater at Guanzhong Area has been studied.The result shows that: using MJ multiple coagulant with dosage of 25 mg/L for municipal wastewater, removal efficiency of CODcr, BOD5, SS, TP and TN could be 75%, 70%, 85%, 80% and 30% respectively. For same quantity of municipal wastewater, construction cost and operation cost using enhanced primary treatment will be only 25% and 30% respectively of that using secondary treatment, and result in BOD5 and SS removal rate of 20-40% and 50-60%. With same construction cost, wastewater flow treated by enhanced primary treatment will be 3-4 times of that by secondary treatment, SS removal amount will be 2-3 times, and BOD5 removal amount will be 1.5 times, that means quite considerable economic benefit The optimization of plan for municipal wastewater plants at Guanzhong Area indicates that: capital investment will reduce 75% (RMB 23514 x 104), and operation cost will reduce 70% (RMB 2794.12 x 104), that means quite considerable environmental benefit.For process design of Sanyuan sewage plant, the concept of firstly enhanced primary treatment while later secondary treatment when feasible has been proposed. This is a new typeof process that adapt to current wastewater treatment situation in our country especially at the undeveloped area. It requires simple equipment, less cost, and short running time, while results in easier operation, good removal efficiency and peak loading resistant. It is helpful to water pollution control and continuable economic development.