Fluorescence in Situ Hybridization Analysis of Nitrifying Biofilms in Landfill Leachate Aerated Treating System

Abstract:

The cultivation and rapid detection of ammonia-oxidizers have been nodus in debugging and monitoring of high ammonia concentration wastewater treatment engineering.In this research，landfill leachate biofilms and suspended active sludge in different operation periods were sampled in Guangzhou Datianshan landfill leachate treating system.The in situ spacial organization of ammonia-oxidizing β-proteobacteria of samples was investigated by using fluorescence in situ hybridization (FISH) and with scan electron microscope (SEM).FISH and SEM observation revealed that in the start up period，micro-organisms initially attached on the lacunose part of carrier matrix.The bacteria total quantity kept growing in the biofilms of 7，20，50，106，155 day.The proportion of ammonia-oxidizing β-roteobacteria is approximately 60％ among all biomass in the early 7th day and 40％ in the 20th day samples，which means that ammonia-oxidizers firstly inhabit on the surface of the carrier matrix as the dominant component of the community in the process of biofilm forming.The biofilm was mature in the 50 day samples detected by FISH and SEM.The proportion of ammonia-oxidizer attached on the surface of carrier kept a relatively steady value of approximately 35% among all biomass in the 50th day，106th day and 155th day biofilms samples.The proportion of ammonia-oxidizers in the suspended active sludge sampling at the same time with biofilm samples is unstable and far below the proportion in biofilm grown on the carrier surface.The proportion of ammonia-oxidizers in suspended active sludge declined obviously when the concentration of NH4-N in the effluents increased to 70mg/L，but the proportion of ammonia-oxidizers in biofilms was not affected and kept a relatively steady value of approximately 30%，meanwhile，the ammonia-oxidizers still work well in the treating system.These results indicate that the application of FISH provide a rapid method for detection of nitrifying bacteria and an academic reference for debugging of environmental engineering.