Screening Of Microorganism And Their Performance By Biological Removal Of Ammonia Nitrogen And Hydrogen Sulfied Derived From Livestock Farm

With the rapid development of economy, and the improvement of people’s living conditions, under the government’s support, livestock and poultry breeding industry has developed rapidly. And the odor gases from livestock farm could lead serious pollution to human beings, animals and the surrounding environment. The main composition of odor from livestock farm are ammonia nitrogen and hydrogen sulfide, and they should be removed immediately. Biological deodorization has the advantages of low cost, high removal efficiency and no secondary pollution, so it has been widely used all over the world. The key step of biological deodorization is screening microorganisms, and it directly affect the removal efficiency.In this paper, the microorganisms being got from the biofilter can remove ammonia nitrogen and hydrogen sulfide efficiently. These microorganisms have been enriched, isolated and purified, and their deodorization performance also have been investigated, the following conclusions can be drawn:(1) After being enriched, isolated and purified, these microorganisms are four autotrophic bacteria Z1～Z4 and seven heterotrophic bacteria Y1～Y7. They have stable performance of removing H2S and NH3. According to the morphological characteristics, physiological and biochemical characteristics and the result of removal efficiency, the microorganisms could be identified to genus, the results are as follows:Zl is Nitrobacter, Z2 and Z4 are Thiobacillus, Z3 is Nitrococcus; Y1 and Y4 are Micrococcus, Y2 is Microbacterium, Y3, Y5 and Y7 are Pseudomonas, Y6 is Paracoccus.(2) The growth curve and pH value of heterotrophic bacteria have been analyzed, the results show that in the first 8 hours, heterotrophic bacteria are in lag phase and 8 hours to 24 hours are in logarithmic phase. As the consumption of nutrient, the accumulation of metabolite and the death of thallus, the pH value in nutrient increases. After 24 hours, the growth of bacteria begins to slow down, even leads to death.(3) In this paper, the effects on heterotrophic bacteria removal efficiency of H2S and NH3 have been investigated. In the conditions of the temperature 5 ℃～35℃, the pH value 5～9, the rotate speed 90rpm～210rpm, the inoculation amounts 1%～20%, the initial S concentration 1mmol/L～8mmol/L, the initial N concentration 100mg/L～1000mg/L, the C/N value 1/1～8/1 and the S/N value 1/1～8/1, the results show that the optimal conditions of microorganisms are temperature 28℃, pH value 7.0, rotate speed 150rpm, inoculum concentration 10%, initial S2- concentration 2mmol/L, initial NH4+-N concentration 200mg/L, C/N value and S/N value 2/1.(4) The growth curve and pH value of autotrophic bacteria also have been analyzed, the results show that in the first 12 hours, autotrophic bacteria are in lag phase and the growth of bacteria begins to slow down. From 12 hours to 48 hours, the bacteria are in logarithmic phase which the amount of microorganisms grows rapidly. The microorganisms in nutrient transforms ammonia nitrogen into nitrate and nitrite, sulfion into sulfate ion and lead pH value fall. After 48 hours, the growth of bacteria begins to slow down, even leads to death.(5) In this paper, the effects on autotrophic bacteria removal efficiency of H2S and NH3 have been investigated. In the conditions of the temperature 5℃～ 35℃, the pH value 5～9, the rotate speed 90rpm～210rpm, the inoculation amounts 1%～20%, the initial S concentration 1rnmol/L～30mmol/L, the initial N concentration 100mg/L～1000mg/L, the C/N value 1/1～8/1 and the S/N value 1/1～8/1, the results show that the optimal conditions of microorganisms are temperature 28℃, pH value 7.0, rotate speed 150rpm, inoculum concentration 15%, initial S2- concentration 5mmol/L, initial NH4+-N concentration 200mg/L, C/N value 4/1 and S/N value 2/1.(6) The influences of temperature, C/N value, S/N value, initial NH4+-N concentration, initial S2- concentration and inoculum concentration on removal efficiency have been investigated through the orthogonal experiment.Heterotrophic bacteria Y3 has been chosen as the objective bacteria, the results show that the significance order from big to small of the effects of each process parameters on removal efficiency in denitrification is initial NH4+-N concentration, initial S2" concentration, C/N, inoculum concentration, S/N and temperature. The significance order from big to small on removal efficiency in desulphurization is initial S2- concentration, temperature, inoculum concentration, S/N, initial NH4+-N concentration and C/N. In these factors, initial S2-concentration and initial NH/-N concentration are the main factors. Because NH4Cl and Na2S are not only the nutriment for microorganisms, but also the removal target in the experiment. So, the suitable concentration of initial NH4+-N and initial S2" are important. According to the results, the optimal conditions of heterotrophic strains in denitrification are temperature 25℃, C/N value 2/1, S/N value 4/1, initial N concentration 200 mg/L, initial S concentration 2 mmol/L and inoculation amount 10%, the optimal conditions of heterotrophic strains in desulphurization are temperature 25℃, C/N value 2/1, S/N value 2/1, initial N concentration 200 mg/L, initial S concentration 2 mmol/L and inoculation amount 10%.Autotrophic bacteria Zl has been chosen as the objective bacteria, the results show that the significance order from big to small of the effects of each process parameters on removal efficiency in denitrification is inoculum concentration, initial NH4+-N concentration, temperature, S/N, initial S2- concentration and C/N. The significance order from big to small on removal efficiency in desulphurization is inoculum concentration, initial S2- concentration, temperature, S/N, initial NH4+-N concentration and C/N. In these factors, inoculum concentration is the main factor. Because the suitable inoculum concentration could avoid the competition between bacteria. According to the results, the optimal conditions of autotrophic strains in denitrification are temperature 25℃, C/N value 4/1, S/N value 4/1, initial N concentration 200 mg/L, initial S concentration 5 mmol/L and inoculation amount 10%, the optimal conditions of autotrophic strains in desulphurization are temperature 25℃, C/N value 4/1, S/N value 2/1, initial N concentration 200 mg/L, initial S concentration 3 mmol/L and inoculation amount 10%.Due to the limitation of laboratory environment and experimental installation, the screened bacteria could not be used in real livestock farms to remove odor gases. And the DNA and biological assay for 4 autotrophic bacteria and 7 heterotrophic bacteria could not be tested. So, in the coming experiment, this part will become the key object, and it can provide the basis for future application.