Study On Denitrification Of Aerobic Effective Microorganisms Flora

Nitrogen is one of the most important pollutants in the water.It is hazardous to people's health and environment.Two forms of nitrogen element in the water are organic nitrogen and inorganic nitrogen. Traditional biological denitrogenation involves two procedures—nitrification and denitrification. First of all, ammonia nitrogen is transformed, by autotrophic nitrobacteria in the presence of oxygen, into nitrate nitrogen which will then be reduced to nitrogen by heterotrophic denitrifyimg bacteria in the absence of oxygen, with nitrogen eliminated from the water. Therefore, biological denitrogenation procedures invovle many steps, making the processing cost very high. In addtion, there are other disadvantages, like the complication in the process, which to a great extent restrict the application of biological denitrogenation techniques. And the discovery of aerobic denitrifyimg bacteria offers a new perspective to biological denitrogenation. This reseach screened and isolated from soil possessing highly aerobic denitrification effective microorganisms flora(EMF), which then provides biological denitrogenation with a good source of bacteria and related technologies. All the results are descripted as follows:(1) A newly OAI-EMF directed-screened by denitrification culture medium and isolated from soil possessing highly effective denitrification under aerobic condition. The denitrification rate of OAI-EMF is 143.71 mg/L·d. This research reveals that with the starch as its organic carbon source, the denitrification rate of OAI-EMF can reach as high as 144 mg/L·d. Though strongly inhibited by ions like Cu²⁺,Ni²⁺ and Hg²⁺ , the process of denitrification is activated by ions of Fe³⁺,Zn²⁺ and Mn²⁺ . Nitrate with rich content also inhibits the denitrification of OAI-EMF, the increasing C/N, however, improves its denitrification rate as well as the removal rate of nitrate, which will reach 184 mg/L·d and 100% respectively when the C/N is 25:1.(2) Two aerobic denitrifying bacterial strains named NCDX—1 and NCDX—2 were isolated from OAI-EMF . After physiological and biochemical experiments, the strain NCDX—1 was preliminary classified within the Planococcus sp. and the strain NCDX—2 was preliminary classified within the Marinococcus albus. It can be concluded that these effective microorganisms flora are composed of more than two kinds of bacteria, through traditional isolating and purifying technologies.(3) Polyvinyl alcohol (PVA) was selected as the immobilized carrier of EMF and sodium alginate as the shaping assistant. The immobilized EMF bacteria were produced through PVA—boric acid crosslinking method. The immobolized EMF particles have good biological denitrogenation activity, mechanical stability and resistant to pH of sovlent, which then makes possible the application of immobilized EMF to waste water treatment.(4) The thesis discussed the optical process of immobized EMF denitrogenation. And it's been found that in the triangular flasks of 250 mL with pH 6.2～11.2, the temperature 28℃～32℃, and the loading coefficient about 20～40 %, after 48 hours of culture, immobilzed EMF could realize the highest the removal rate of nitrate—100 %. Compared with free bacteria, immobolized EMF has better temperature consistency and PH stability, which shows it has stronger resistance against the outside unpleasant environment and it's more suitable for industrial application.(5) Under the conditions of the initial pH 8.2, the air flow rate 0.025 m³/h, the temperature 30℃, the activated PVA immobolized bacteria particles 40 g(natural weight), the fluidized bed bioreactor (φ40×430mm) of 300 mL of dinitrogenation experiment medium, and the initial concentration of nitrate 0.64 g/L, the rule ofdenitrification kinetics is:...