Study On Separation And Piggery Wastewater Treatment Of Heterotrophic Nitrobacteria

With its features of high COD, SS and organic nitrogen, piggery wastewater is becoming a non-negligible pollution source. Autotrophic nitrobacteria are always applied in a traditional process of biological nitrogen removal which can be finished in their nitrification. However, this nitrification of autotrophic nitrobacteria is inclined to be inhibited by a high organic nitrogen concentration, resulting in a low nitrogen removal rate. Four strains of heterotrophic nitrobacteria with a high capability of nitrogen and carbon removal were selected from sewage sludge of a piggery treatment pool and their functions in treating piggery wastewater were also demonstrated in this paper. The results were as follows:Firstly, four strains of heterotrophic nitrobacteria were enriched, separated and selected from sewage sludge of a piggery treatment pool, which were followed by observing the colony morphology, identifying the strains as Alcalignes faecalis through 16SrDNA sequence analysis and the United States automatic microbial analyzer- Biolog and then labeling as 79,84, L116 and L117.Secondly, nitrogen removal abilities of these four strains were tested in an experimental pure culture condition. Experiments showed that different levels of nitrification and denitrification existed in four strains. To be specific, the concentrations of NH4+-N and TN decreased sharply in the first 48h and remained stable in later hours. The NH4+-N removal rates of 79,84, L116 and L117 reached 44.42%,47.87%,61.29% and 56.38% respectively within 48h. Meanwhile, TN removal rates amounted to 39.92%,38.52%,43.37% and 40.74% respectively.Thirdly, compound bacteria were obtained through combining 3 other strains of bacillus with these 4 strains of Alcalignes faecali. In the following experiments, nitrogen removal efficiency of these compound bacteria all witnessed a decrease of NH4+-N, TN and COD in early domestication stage and continuous stabilization in later stages even under different HRT, influent concentrations and inoculation amounts.Finally, diversity and disparity of microorganism colony in the reactors were studied by the means of Biolog-ECO micro-plate and PCR-DGGE. The research found that marginal differences existed in diversity and homogeneity of species by virtue of analyzing indexes of Shannon, Simpson and McIntosh. What's more, there were specialized microorganism colonies as well as some common ones in different reactors. The most diverse species appeared in No.9 reactor contrary to the least ones in No.6 and the high similarity of species appeared between No 4 and 5 reactors.