Study On Remediation Of Polluted River Water By Immobilized Microorganisms

Biological remediation is an effective method for water pollution control.Compared to microbial agent,immobilized microorganisms have the advantages of simple operation,long-term operation,easy reaction control and strong tolerance to the environment.This study investigated the optimal method of microorganisms immobilization.Using the immobilized granules prepared by the optimal method,nitrogen and COD_Crremoval efficiencies of surface water were studied.Also,the possibility of reutilization of the immobilized granules was investigated.Experiment results showed that the immobilized microbial granules prepared by PVA-PAC embedding and PVA-PEG embedding methods had poor strength and stability.Besides,their long-term use would bring secondary pollution into the river.In this study,new immobilized granules were developed using carrier binding method.Five cycles of river water purification experiments were carried out using the new immobilized granules.The removal efficiencies of COD_Cr,ammonia nitrogen,nitrate and total nitrogen were 75%-95%,45%-95%,95%-100%and 55%-80%,respectively,without nitrite accumulation.Results showed that the new-developed immobilized granules had good stability,and could be reused for many times.Purification of actual river water by immobilized microorganisms coupling micro-aeration technology was studied in a pilot-scale reactor.The concentrations of ammonia nitrogen,total nitrogen and COD_Crdecreased from 3.00 mg/L,3.15 mg/L and 46 mg/L to 0.49 mg/L,0.74 mg/L and 28 mg/L,respectively within 10 days.The river water could be purified from inferior class V to class IV considering these three indicators.After adding exogenous pollution,the immobilized microorganisms still had the continuous purification property.After 60 days of experiment,the removal efficiencies of ammonia nitrogen,nitrate nitrogen,total nitrogen and COD_Crwere86.56%,87.20%,85.21%and 59.38%,respectively.The immobilized microorganisms could accelerate the denitrification in river water,and had better anti-impact ability and better water quality retention ability.Under the static condition,the removal efficiency of ammonia nitrogen was highest,with a value of 87.59%.The COD_Crremoval efficiency was relatively higher with a value of 60.87%when the flow rate was 2 cm/s.The immobilized microorganism coupling micro-aeration technology had a potential of application on river water purification.