Study On Identification And Removal Of Geosmin And MIB In Water

At present,along with more and more pollutants being discharged into drinking water source,eutrophication was one of popular environmental problems happened in waters. Blooming aglae consume dissolved oxygen in water,release some components smelling disgusting.Geosmin and MIB(G&M)are the most common unpleasant compounds in water, and they can not be removed by conventional water treatment processes.Paired Comparison Test,Triangle Test and Sensitivity/Discrimination Test Ranking were used to train the panel of Flavor Profile Analysis(FPA)and the PFA method was established.Results showed that the olfactory threshold of Geosmin was 5ng/L,and the olfactory threshold of MIB was 8ng/L.At the same time,SPME-GC/MS was used to determine G&M in water,and the optimized operating condition was that the samples were extracted on a stirrer/hot plate schott for 30min at 65℃.The desorb time is 3min.The recovery rate of G&M can reach 93.9%～99.2%and 93.8%～96.2%repetively.FPA was introduced to the system of the analysis and identification on earthy and musty odors.The water samples from four water treatment plants along Changjiang River,Tai Lake and four lakes in Nanjing Sun Yat-sen in a year,were detected by PFA panel and SPME-GC/MS.The research showed that the G&M concentration in the water samples above were 5ng/L～25ng/L,and it was higher in spring and summer than that in autumn and winter.The impacts of residual chlorine on detecting G&M were studied.When the concentration of residual chlorine is more than 0.8mg/L,the earthy and musty odors can hardly been apperceived,and 11%～79%of reduction for G&M concentrations was observed in the presence of residual chlorine.The addition of sodium thiosulfate can effectively counteract the influence of chlorine.Ozone,UV,and activated carbon were used to remove G&M in water.It was found that ozone and UV have a little effect on removing G&M,but they could not decrease G&M to the concentration below olfactory threshold.Powder activated carbon(PAC)could effectively get rid of G&M,but PAC could hardly been regenerated,and it was not suggested to be used on a large scale.The removal effect of G&M in water with hyphenated techniques of granular activated carbon(GAC)and ozone was researched.The results showed that GAC of 30mg/L and ozone of 3g/h could remove these compounds to the concentration below olfactory threshold.