Study On Microbial Diversity Of Drinking Water Treatment System

Seasonal ammonia nitrogen and organic micro-pollution was widespread in drinking water sources in South China.At present,the most economical and effective method for removing ammonia nitrogen and organic micro-pollution in source water is biological treatment.Drinking water treatment plants?DWTPs?in South China using biological treatment may contain higher microbial biomass even excessive microbiological indicators.The water quality especially biological safety can't be guaranteed.Based on this,the microbial community diversity in a full-scale DWTP?raw water–flocculation-sedimentation-carbon-sand filter-disinfection?in Guangzhou,South China,was investigated by Illumina Hiseq sequencing analyses combined with cultivation-based techniques during different seasons.In addition,we analyzed the relationship among microbial biomass,microbial activity and environmental factors.Meanwhile,the functional diversity of microbial communities in caron-sand filters was preliminarily explored by Biolog technology.The main results are as follow:?1?The microbial biomass and activity of drinking water treatment system?DWTS?and biofilters were analyzed by measuring total heterotrophic bacterial counts?HPCs?,and adenosine tri-phosphate?ATP?respectively.The results showed that seasonal variation had no significant effect on biomass and microbial activity of effluent from each treatment step.In spatial,the microbial biomass and activity showed a trend of gradual decline,however,the biomass increased slightly after filtration.The microbial biomass and activity of filtered water and biofilters continued to increase,which has potential risk for biological leakage.Correlation analysis showed that pH,turbidity and chemical oxygen demand(COD_Mn)were the key factors affecting the microbial biomass and activity.There was not significant correlation between microbial biomass and activity.The biomass in the active carbon layer decreased along the bed depth,but microbial activity was increased along the depth.The microbial activity in sand particles was significantly higher than that of activated carbon.?2?The bacterial community in DWTP and biofilters during different seasons was investigated by cultivation-based techniques.In total,210 isolates were successfully identified and belonged to 72 genera.The isolates were found to belong mainly to five phyla:Proteobacteria,Actinobacteria,Bacterioidetes,Firmicutes and Deinococcus-Thermus.The dominant phylum was Proteobacteria,which comprised 74.29%of all isolates.In the bulk water,there were great differences in the bacterial community structure during different seasons.Most of the isolates during the wet season were Sphingomonas,Bosea,and Pseudomonas.While the proportions of species in the genera Acidovorax and Pelomonas were high.It is noteworthy that a series of conditional pathogenic bacteria in DWTP has a potential threat to the biological safety of drinking water.In particular,two isolates belonging to Actinobacteria,identified as Blastococcus aggregatus and Mycobacterium obuense,were obtained from finished water.?3?High-throughput sequencing technology was used to investigate the microbial diversity in DWTS.The results showed that the highest bacterial community diversity was observed in the raw-water samples.The bacterial community diversity in raw water and finished water during the summer and winter was higher than that during the spring and autumn,whereas the bacterial community diversity in filtered water varied little among seasons.Multivariate data analysis showed that the bacterial community diversity was significantly positively correlated with COD_Mn,turbidity and pH.Actinobacteria,Proteobacteria,and Firmicutes predominated in water samples.The relative abundance of bacterial communities was relatively stable in finished water and did not change with the season.The finished water mainly comprised Citrobacter,Acinetobacter,and Pseudomonas.In the biofilm samples,sand samples were mainly composed of Nitrospira,Gemmata and Planctomyces.Citrobacter,Nitrospira,Pseudomonas,and Acinetobacter were the major genus groups in all granule active carbon?GAC?samples,which was consistent with the dominant bacterial groups observed in finished water.There were a lot of opportunistic pathogens in treated water,such as Acinetobacter,Mycobacterium,Salmonella,Streptococcus,Legionella and so on,which was threatening to the water quality and biological safety.In addition,there were significant differences in the eukaryotic community of DWTS in different seasons.The eukaryotic community diversity during the wet season was obviously higher than that during the dry season.?4?The microbial community functional diversity in biofilters was studied by Biolog technology.The results showed that average well-color development?AWCD?values in biofilters during different seasons in the order from the large to the small were:spring>summer>winter>autumn.Meanwhile,the comprehensive utilization ratio of carbon source in the autumn was much lower than that of other three seasons.Along the filter depth,the metabolic activity of surface activated carbon biofilms was higher than that of the bottom activated carbon biofilms.And the metabolic activity of sand biofilms was significantly higher than that of activated carbon biofilms.Different filter materials in biofilters had a preference for different types of carbon sources.The utilization of esters in the layer of activated carbon was highest,and the utilization of sugars,amino acids and esters by the microorganisms of sand layer was significantly higher than the other three types of carbon sources.The richness and diversity of microbial communities in sand samples were higher than those in activated carbon.This study revealed the characteristics of spatiotemporal changes in microbial community in a full-scale drinking water treatment plant,and explored the functional diversity of microbial communities in carbon-sand filter.In addition to providing insight into the spatiotemporal microbial dynamics in DWTPs,the results of this study provide a theoretical basis for practical applications and process optimization.