Investigation And Analysis On Taste And Odor Compounds:MIB And GSM In Reservoirs

In recent years,aquatic environmental pollution caused by taste and odor has aroused more and more attention.MIB?2-methylisoborneol?and GSM?geosmin?are two typical taste and odor compounds related to poor organoleptics in drinking water.During ice-covered period,the water quality and the distributions of MIB and GSM in Huanren Reservoir,Dahuofang Reservoir,Biliuhe Reservoir,Dongfeng Reservoir and Wazidian Reservoir were investigated.Meanwhile,the kind and the concentration of the compound which caused off-flavor event of Dalian City in summer was identified and analyzed.In order to master the source of the taste and odor,further research on its distribution and influencing factors was developed in the Biliuhe Reservoir.The main results are as follows:?1?MIB and GSM concentrations in Huanren Reservoir,Dahuofang Reservoir and Biliuhe Reservoir during ice-covered period were less than 10ng/L,limits of MIB and GSM concentrations in treated drinking water based on the Chinese Drinking Water Standard.There was no taste and odor pollution in these three reservoirs during investigation.However,MIB concentrations in Dongfeng Reservoir and Wazidian Reservoir were close to the standard.It's necessary to develop long-term monitoring on these compounds and to explore their sources in future study.?2?MIB was the target compound causing off-flavor event of Dalian City in summer.The highest concentration reached 27.8ng/L and the lowest was 9ng/L.The temporal distributions of MIB and GSM in Biliuhe Reservoir were investigated,the results showed that the concentrations of these two compounds in winter,spring and summer were less than 10ng/L.MIB concentration in these three seasons generally remained the same,however,GSM concentration increased from winter to summer.As for spatial distribution,relevance ration of MIB in the zone close to dam was showed lower values than other zones in reservoir during winter and spring.MIB was ubiquitous in reservoir during summer.Besides,there was no remarkable characteristic of the spatial distribution of GSM.?3?Most water quality indexes of Biliuhe Reservoir reached?^?water quality standard according to Environmental quality standards for surface water.Total nitrogen?TN?always exceeded the standard and Total phosphorus?TP?might exceed the standard seasonally.Surface phytoplankton community structure of Biliuhe Reservoir was significantly diverse in different seasons and sites.The density of surface phytoplankton decreased in order of summer>spring>winter.The study on the temporal and spatial of water quality and phytoplankton was beneficial to water quality monitoring,water environment simulation and prevention of water quality problems such as off-flavor event.?4?Correlation analysis between MIB/GSM and the density of phytoplankton and aquatic factors showed that there was no remarkable relationship between MIB and the density of phytoplankton.This suggested that phytoplankton was not the only source of MIB.GSM was correlated with the density of cyanobacteria,which meant cyanobacteria might be a source of GSM.In addition,there was no remarkable relationship between MIB and aquatic factors.GSM was significantly related to water temperature,NO₂-N,COD and TP,indicating that water temperature and COD were of great importance to the production of GSM.Phosphorous,the limiting nutrient,was an important factor that influenced the growth of algae and their release of the taste and odor compounds.