Studies On Denitrification And Desulphurization By Microorganism

Biodenitrification and biodesulphurization are important techniques in the slight-polluted water treatment and water ecological control. Commonly, they are accomplished by denitrification bacteria and sulfur bacteria separately. In this paper, adopting selective inorganic culture media, 45 strains were enriched and isolated from soil. 5 strains were selected after initial screening. Then they were further rescreened by doing denitrification and desulphurization tests. A strain T39 (coded T39, the same to the following) which could remove nitrate and sulfide simultaneously was picked up for its higher ratio of denitrification and its higher ratio of desulphurization. The biology characteristics of strain T39 were researched. The results showed that T39 could grow in inorganic culture media using sulfide as energy substrate, carbon dioxide as carbon source and nitrate as nitrogen source. The addition of yeast extract could make benefit to the growth of T39.The colony was round, dotlike and pale yellow. The cell was of short bar shape, no spore, gramnegative , and mobile by single polar flagella lium.T39 was facultative anaerobic, low salt tolerance. For growth, the optimal initiative pH was 6.5-7.5 and the optimal temperature was 25³0℃. Meanwhile, the 16SrDNA of T39 was sequenced .Sequence comparison showedthat the similarities between the 16SrDNA sequence of T39 and several strains of Pseudomonas stutzeri are more than 99%. Forthmore, orthogonal experiments were carried out for selecting denitrification and desulphurization conditions. Under these selected conditions: anareod, inoculating 0.5%(W/V) cells in reaction fluid having initial NO₃^-'-N 10.35mg/L, S²- 41.91mg/L, initiative pH8.0,temperature 35℃, C/N(HCO₃^-/NO₃^--N)4/1, S/N(S²- /NO₃^--N)4/1, T39 was tested. 18h the ratio of denitrification and desulphurization were 98.5% and 99.6% respectively. After adjusted to the results of blank test, the amounts were 95.6% and 55.8%. T39 was also used to deal with slight-polluted water. The results were as follows. Under anareob condition, inoculating 0.5g cells in per 100mL water,24h NO₃^--N removal ratio reached 98.6% and S²- removal ratio reached 62.6% when the water contained initial NO₃^--N 7.74mg/L, S²-28.15mg/L.