Research On Fixed Aeration Technology For Stream Water Purification

Aeration technology is effective in the pollution control of stream.Which have been proved by lots of investigations.The technology has many virtues such as little space requirement,low costs,high treatment capacity,low secondary pollution,and so on.There were pollutants discharged into the streams in spite of the pollution interception. However,how to use the fixed aeration system in the existing stream space to further cut down the pollutants for aquatic eco-systems restoration and reclamation? What about the adaptation and performance of the fixed aeration system to different pollution status in streams for its wide promotion? Until now,the above technical problems still cry for solution for lacking systematic research.In the dissertation,the pollutants discharged into Daqing Stream were first surveyed quantitatively and hence the change of hydrology and water quality was characterized.Based on the above investigation,the large scale application of fixed aeration technology on the stream was studied systmaticaUy.The main results were as follows:There were four types of typical operation conditions in the experimental part of the Daqing Stream:the regulating gate closing completely,the overflow or leakage of water from the regulating gate,the regulating gate opening partly and the regulating gate opening completely.The condition that the regulating gate closing completely was the most status, accounted for more than three-fourth in 2006.The stream water was always low DO,the high BOD₅,NH₄⁺-N concentration and easily biodegradable.Hence,it was suitable to be treated by biological way.On the condition of the overflow or leakage of water from the regulating gate with the mean flow velocity of 0.014m/s,the removal efficiencies of COD,NH₄⁺-N,TN and TP were respectively 20.2%,21.9%,9.3%and 13.1%,the increment of DO was more than 0.5mg/L. When on the regulating gate partly opening with the mean flow velocity of 0.20m/s,the DO showed transitory increase in the area of aeration,the COD was also reduced slightly(＜10%). However,the NH₄⁺-N,TN and TP was hardly removed.While for the regulating gate complete closing,the mean removal efficiencies of COD_Cr,NH₄⁺-N,TN and TP were respectively 30.1%,35.0%,17.3%and 21.4%,the increment of DO was also more than 0.5mg/L.The effects of aeration on the release of the pollutants from the sediment were also investigated.The results showed that aeration made the pH of overlying water to sediment followed increase-decreasing trend,exactly opposing to the control.The rise of the pH value could accelerate the release of phosphorus from the sediment.Therefore,aeration could reduce the release of N,P and SCOD from sediment into overlying water.During the period of aeration,the average release rate of TN,TDP and SCOD from the sediments were-55.79mg/(m²Â·d),-3.43 mg/(m²Â·d)and -75.53mg/(m²Â·d),while for the control were 294.92mg/(m²Â·d),0.029mg/(m²Â·d)and -9.52mg/(m²Â·d),respectively.With the static economic evaluation method,the investment and operational cost were estimated.The investment of the fixed aeration system wasï¿¥52/t,which was 1/15～1/22 or so of the traditional municipal wastewater treatment.The operational cost wasï¿¥0.0085/t, which was about 1/100～1/200 of the traditional municipal wastewater treatment The cost wasï¿¥0.42 kg^-1COD for removal the pollutants from the serious polluted stream,which was approximately 11.76%of the traditional municipal wastewater treatment.