Mechanism And Strengthening Measures Of Humic Acid Reducing Bacteria To Reduce Nutrients In River Sediment

The eutrophication of water caused by human activities can impair the ecosystem,cause economic losses,and harm the surrounding human activities.The migration of nitrogen and phosphorus between the sediment and the overlying water remarkablely affects the process of eutrophication,so the remediation of contaminated sediments is very important.Since there is a certain defect in the use of a certain remediation method alone,the strengthening remediation can combine the advantages of different remediation technologies and maintain the balance of the ecosystem.Therefore,this study investigated the remediation process of rivers using chemical-biogical remediation measures.The feasibility of humic-reducing bacteria or activated sludge to reduce nutrients in river sediments was investigated.The results showed that both of them could significantly improve the reduction of humus analogue.The humic-reducing bacteria increased the nitrogen removal efficiency and removal rate in the sediment.At the same time,the denitrification rate in the overlying water and the removal efiiciency of NH₄⁺-N in the interstitial water were all improved.The humic-reducing bacteria contributed the highest nitrogen removal rate of 47.7%.Bioremediation promoted the succession of microbial communities in the direction of pollutants’degradation,and didn’t impair the indigenous microorganisms.To provide more favorable conditions for microbial degradation to remove pollutants,chemical agents was introduced,and the effect of their dosage on nutrients removal in river was investigated.The results showed that in the gradient range of calcium nitrate dosage of 0.35,0.70,1.05 and 1.40 g/kg NO₃^--N（calculated by wet sediments）,the dosage of 0.70 g/kg NO₃^--N had a better effect on improving the water quanlity,completely removing acid volatile sulfide,reducing the concentration of NO₃^--N in interstitial water by 78.1%,and had little effect on nitrogen release.The ammonia nitrogen removal rate can reach more than 99.0%by the dosage of 0.70 g/kg NO₃^--N in the simulated river systems.The release of phosphorus from sediments was restrained,and the solidification efficiency of phosphorus in overlying water was also improved.Chemicals improved the physical and chemical conditions in the sediment,increased the proportion of functional bacteria involved in nitrogen circulation and phosphorus removal,and improved the micro-ecological environment in the sediment.The effects of chemicals on enhancing the functionality of humic-reducing bacteria to reduce nutrients in the simulated river systems were investigate.The results showed that the strengthening remediation can improve the eco-environment of the water and sediment.The removal rate of TN in the overlying water and the denitrification rate in the interstitial water were higher,compared with the single remediation technology.The total nitrogen removal efficiency in sediments was up to28.4%.The maximum phosphorus retention was 1.42 mg/g.In the remediation process,chemicals improved the micro-ecological environment of sediments,improved the nitrogen removal and phosphorus solidification,and enhanced the reduction of nutrients by the humic-reducing bacteria;humic-reducing bacteria reduced the release of nitrogen induced by the addition of the chemicals.Also,the bacteria had a good synergy with the indigenous microorganisms in the sediment.Strengthening remediation took the advantages of the biotechnology for nitrogen reduction and removal and combined chemical remediation technology with biotechnology to enhance the solidification of phosphorus,leading to the improvement of micro-ecological environment and achieving the goal of river remediation.