Study On Remediation Of Contaminatied River By Sedimentstabilization And Biofiltration

With the implementation of water pollution control action plan in China,the trend of deterioration of urban water environment has been reversed in recent years,and the water quality of rivers has been gradually improved.Based on the understanding that suspended solids in river water will inevitably deposit into river sediment and that sediment will interact with overlying water,this paper analyzed contamination releasing law in sediment,studied the effectiveness of controlling contamination release in sediment by biological stimulation method,treating overlying water body by biological filtration and channel circulation method,and discussed the effect of water quality improvement and sediment pollutant reduction by relevant technological parameters.The validity was verified in Xier River project in Jiangchuan Road Street Area of Minhang District.The main conclusions include:In the study of releasing law in sediment,with the increase of pH in the overlying water,the release of COD,NH₄⁺-N decreased,but TN increased gradually;Partial acid or alkali promoted the release of TP.The higher the content of organic matter in overlying water,the lower the release of NH₄⁺-N and TN in the early stage of the experiment,which was contrary to the release of TP.The increase of dissolved oxygen in overlying water promoted the release of COD,NH₄⁺-N and TN.The COD and NH₄⁺-N decreased rapidly with the increase of dissolved oxygen at the later stage of the experiment,and the release of TP in sediment was significantly inhibited when dissolved oxygen was controlled at 4⁶ mg/L.The increase of suspended solids inhibited the release of COD and TN,but promoted the release of TP.According to the improvement of water quality and the reduction of sediment pollutants,3.2 g/kg was chosen as the best dosage of biological activator in the remediation experiment.The most obvious improvement of water quality was at 20 mL/?min.L?of the aeration,20?of temperature and 1:3 of sediment-water ratio.Combining with the biological filtration system,the arrangement of biological fillers improved the degradation efficiency of pollutants,with 60%as the best filler density.Under this condition,the removal rates of COD,NH₄⁺-N,TN and TP in the overlying water were 49.38%,99.37%,37.81%and 71.43%,respectively.The ORP was significantly increased and the organic matter was reduced by 41.52%in the sediment.In the application of demonstration project,after 10 months of restoration project implementation,the removal rates of COD,NH₄⁺-N and TP were 73.47%,96.94%and 84.38%respectively,which met the surface water quality standards of III;the removal rate of TN was 91.88%,which was close to the surface water quality standards of IV;and the water transparency was improved to a certain extent.