The Characteristics Of The Microorganisms Involved In Carbon And Nitrogen Simultaneous Removal From The Water Column Of Dongjiang River

The traditional view holds，ammonia oxidation process is the initially andlimiting step in the nitrogen cycle，and its mainly performed by autotrophic ammoniaoxidizing microorganisms. But more and more researches found that someheterotrophic microorganisms were directly involved in the ammonia oxidationprocess, even removal of carbon source and nitrogen source simultaneously, and playan important role of microbial remediation in eutrophic water. However，we have lesswell understood about the characteristics of heterotrophic ammonia oxidation, andeven the characteristics of removal of carbon and nitrogen source simultaneously. Itrestricted our apply this kind of microbial in eutrophic water.Dongjiang River is one of the three major rivers in the Pearl River Basin, and it’svery important drinking water in Guangdong Province. The severe economic andenvironmental pressure on the river likely received tremendous COD andammonia-nitrogen. But the monitoring results of water quality showed that DongjiangRiver has strong self-puriifcation ability. The COD and ammonia-nitrogen in the rivercan be effectively removed, and the overall water quality is still in good condition.We hypothesized that the microorganisms involved in carbon and nitrogensimultaneous removal played an important role in Dongjiang River self-puriifcation.In order to understand the characteristics of Dongjiang River self-puriifcation, weinvestigated the microorganisms involved in carbon and nitrogen simultaneousremoval from the upper reaches (Xinfeng and Heyuan) of Dongjiang River and foundthe following main research results and scientiifc understandings:(1)Twenty-eight strains, which could remove carbon and nitrogen simultaneously,were isolated from Dongjiang River. Based on the16S rRNA gene sequences, theisolates were mainly associated with: Bacillus, Pseudomonas, Acinetobacter,Comamonas, Stenotrophomonas, Alcaligenes, Microbacterium, Rhodococcus. Thepreliminary results showed that, the diversities of the microorganisms were positivelyrelated with the degree of water pollution.(2)Stenotrophomonas maltophilia DJ1，which could utilize glucose as carbonsource and oxidize ammonium-nitrogen simultaneously, was isolated. When the initialconcentrations of total organic carbon (TOC) and NH4+-N were500mg/L and25-100mg/L, strain DJ1could reach100%removal rate under aerobic conditions, andmore than75%removal rate under anaerobic conditions after48hours, respectively.(3)Alcaligenes faecalis Y5had eiffciently simultaneous carbon and nitrogenremoval ability when taking sodium acetate as the sole carbon source. The carbon and nitrogen removal dynamics of strain Y5，as well as the inlfuencing factors such ascarbon source, ratio of carbon to nitrogen (C/N), dissolved oxygen concentration(DO)，temperature, and pH were investigated. Its optimal conditions for simultaneouscarbon and nitrogen removal using sodium acetate as the sole carbon source wereC/N=10〉, pH=7-8, D06.20mg/L,30°C. When the initial concentrations of TOC andNH+4-N were1000mg/L and110mg/L，the NH+4-N，TOC and TN removal rates were99.54%，92.95%and86.55%after48hours aerobic incubation, respectively.Our research provides useful information about the microorganisms involved incarbon and nitrogen simultaneous removal, especially the two species{Stenotrophomonas maltophilia and Alcaligenes faecalis) existing widely in thenatural water column, to improve the signiifcant water pollution phenomena thatcarbon and nitrogen pollutants copresented.