In Situ Bioremediation Of River Sediment And Engineering Application

The treat of black and odorous river has become a hot spot in recent years.As an important contributor to the pollution of black and odorous river,the treatment of sediment is of great significance.Without sediment treatment,even if the water pollution is controlled,it will soon return to the the initial state under the release of endogenous pollution.There are many methods for sediment treatment,including dredging,sediment soverlay and chemical treatment,etc.Bioremediation technology become a research hotspot because of its low cost and more thoroughly pollution degradation.But the research on bioremediation of sediment pollutant reduction and sediment decrement is far away from enough.Sediment properties and microbial diversity in part of BaMi River were analyzed,the results show that the organic pollution and nutrient pollution was serious together with high sediment pollution release rate.The anaerobic microorganism population dominated the sediment,and the sediment was in the anaerobic condition for a long time.Different strains were isolated from different samples in this article,including four strains which have good degradation ability for general pollutants,those strains A1,A2,A5 and A7 were identified as Klebsiella sp.,Pseudomonas sp.,Comamonas sp.And Chryseobacterium sp.,and all four strains showed the COD degradation rate of more than70%,A1 and A7 have a better COD degradation rate,which were 82.4%and 79.6%,while strain A2 has a better degradation rate of COD and TP.One heterotrophic nitrification and aerobic denitrification strain HF2 was isolated and identified as Bacillus sp.,the degradation rate of NH₃-N was 89.7%,the denitrification effect is obvious.One strain NS3 which showed a simultaneous sulfide and nitrate removal was isolated and identified as Roseateles sp.,with the denitrification rate of 48.2%and desulfurization rate of 35.3%.The physiological characteristics of the strains were studied and their growth curves and oxygen taxis were measured.The optimum inoculation ratio of strains A1,A2,A5 and A7 were determined by orthogonal test,the result showed that the optimum inoculation ratio is A1?2%?,A2?2%?,A5?1%?and A7?0.5%?,the COD,NH₃-N and TP degradation were 83.3%,43.5%and48.2%under this inoculation ratio and compound microbial agent J1 was made with the same inoculation ratio.Dosing ratio experiment was carried to determine the optimal dosing ratio of J1 and NS3.The results showed that when the ratio of J1 and NS3 is 1:1,it has a good degradation rate for both the general pollutants and S^2-.The growth characteristics of compound microbial agent J1,agent HF2 and NS3 were studied,and the influence of environmental factors on the growth of bacteria was investigated and the optimum growth conditions were determined.To explore the impact of different aeration modes,and bacteria agent on water and sediment pollutant reduction,laboratory tests were conducted.The results show that the COD,NH₃-N and TP removal rate in overlying watr in experimental group with sediment aeration and bioaugmentation reached 76.72%,91.45%and 91.63%respectively.While organic matter,total nitrogen and Fe²⁺reduction rate in sediment reached 55.96%,61.63%and 60.14%respectively.Significant increase in total phosphorus and SO₄^2-in sediment was observed after the experiment,and sediment anaerobic condition was improved.The removal rate of sediment contribution to the overlying water pollution load was 80.37%,82.39%and 86.75%,respectively.The sediment release rate was significantly decreased,and the sediment thickness was reduced by 15.15%,which changed from black to normal yellowish brown.The in situ sediment bioremediation technology was applied for River restoration project.After 90 days of treatment,the COD,NH₃-N and TP concentration in water correspond to the V standards for surface water environmental quality and the DO concentration maintained at 4⁶ mg/L.The reduction of river sediment is 996.9 m³,while the organic matter reduction rate in sediment is 37.6%,the total nitrogen reduction rate is53.1%and the Fe²⁺reduction rate is 43.9%.The total reduction of organic matter is about133.4t,the total nitrogen reduction is about 10.8t,the sediment release rate is greatly reduced,and the sediment condition is improved obviously.The analysis of sediment biodiversity showed that after treatment,the relative abundance and quantity of anaerobic microbes decreased,and the relative abundance and quantity of aerobic and facultative microbes increased.In situ bioremediation of sediment has good economic performance together with the effect of water quality improvement,sediment reduction and sediment pollutants reduction at the same time.