Characterization of raw water biofilm pretreatment processes in response to organic carbon sources:An example of nitrogen removal performance and bacterial community structure
The operation performance of the raw water pretreatment biofilm system is limited by the water quality of raw water.A laboratory-scale raw water pretreatment biofilm system was constructed with synthetic polluted raw water as the treatment object and comet type fiber filler and activated carbon filler as biofilm carriers.Batch tests were conducted to explore the response characteristics of operation performance and bacterial community structure to different organic carbon sources including sodium acetate and humic acid.Experimental results showed that the raw water pretreatment biofilmsystem operated stably for a long time with the average ammonia nitrogen removal efficiency(ARE)of 90.1%.Sodium acetate had little effect on the ammonia nitrogen removal performance of biofilm attached on two kinds of carriers.Stronger nitrification ability with the highest ARE of 90.5%±5.6%was obtained using humic acid as the organic carbon source.Using comet type fiber filler as biofilm carrier,sodium acetate promoted the formation of extracellular polymer(EPS)in biofilm,and humic acid reduced the PN content in EPS.The usage of activated carbon as the biofilm carrier significantly increased the PN/PS value of EPS,and had higher bacteriall diversity,which was more conducive to the formation of biofilm.In the biofilm samples,the top three phyla are Proteobacteria,Planctomycetes,and Acidobacteria.When comet type fiber filler was used as biofilm carrier,sodium acetate and humic acid enhanced the accumulation of Proteobacteria(53.9%)and Nitrospira(10.7%),respectively.The dominant genera of biofilm samples of comet type fiber filler and activated carbon were Nitrospira and Aridibacter,respectively.Humic acid was more conducive to the enrichment of Nitrospira and Bdellovibrio,and sodium acetate was more conducive to the enrichment of Aridibacter.
raw waterbiofilmorganic carbon sourceoperation performancebacterial structureextracellular polymers
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