Effect And Mechanism Of Chemical And Biological Collaborative Remediation To River Sediment

In recent years,urban river is polluted seriously,which causes serious pollution of sediment directly.After the effective control of external pollution,the sediment has become the pollution source of river,so the treatment to sediment is very necessary.The in situ remediation technology has become a research focus in the field of sediment remediation,with advantages of low cost and little damage to river’s ecological environment.However,there are some limitations in the single species repair technology.Combined repair technology can play out the advantages of various technologies by complementary advantages and technology integration,which can be an important means for the sediment’s treatment.Therefore,the chemical and biological remediation technology is used to repair river sediment in this project.Firstly,under the maximum dosage of the promoting agent,this experiment explored the effects on the river sediment restoration with different types of promoting agent,through the water and sediment’s nitrogen and organic indicators.The results show that the solid promoting agent(biological promoting agent,nitration agent and denitrification agent)had smaller effects on total nitrogen in water than liquid promoting agent(biological promoting agent,biological nutrition agent and nutrient synergistic agent).Among them,the experimental group with denitrification agent was better.The total nitrogen in water was lower,and the sediment’s nitrogen had small reduction.Then,the dosing concentration of calcium nitrate,denitrification agent and the dosing sequence of calcium nitrate and denitrification agent was explored initially in this experiment.The results show that,in the experimental group of 0.75 g/L calcium nitrate dosing concentration,the nitrogen in water and sediment was increased less and decreased rapidly.The total nitrogen in water and sediment was decreased by 20% and 34% respectively compared with the experimental initial values.In the experimental group of 0.1 g/L denitrification agent dosing concentration,the total nitrogen degradation rate had obvious advantages compared with other concentrations.The total nitrogen in water and sediment was decreased by 81% and 40% respectively compared with the experimental initial values.In the experimental group of dosing calcium nitrate first and then dosing denitrifying agent,the nitrogen in water and sediment was decreased by about 87% and 40%,which showed a clear advantage.Finally,in order to explore the effect of the dosing concentration of calcium nitrate and denitrification agent on river restoration,the simulated river pilot device was designed and built in this experiment.The results show that,in the experiment period,due to the addition of calcium nitrate,total nitrogen concentration in the water had increased,but there was a trend of decrease.Total nitrogen in the sediment was about 3% of the reduction and the change of TOC was slightly,which was consistent with the small lightly elevation of the urease activity and little change in the activity of polyphenol oxidase in the sediment.The nitrogen in the sediment was obviously changed,the SAEF-N and WAEF-N were transformed into IEF-N in the form of organic nitrogen,and nitrogen binding capacity became weak,which was conducive to the absorption and degradation of microorganisms.The total nitrogen in the water of dosing denitrification agent showed a downward trend in fluctuation,the effect of dosing concentration of 0.1 g/L was better.There were fluctuation of total nitrogen and TOC in sediment,but they changed little,which were consistent with slight change in the activity of the urease and polyphenol oxidase in the sediment.There were some changes of the morphology of the available nitrogen in the sediment.The total amount of WAEF-N and SAEF-N decreased and the total amount of IEF-N increased.This shows that the transformation of nitrogen form was from strong binding state to weakly bound state,nitrogen in the sediment was easy to release,and it can be absorbed and degraded by microorganisms.