| Air pollution derived from the odor of livestock and poultry farm has become a damage to the social environmental at present, it not only can cause environment depravation for humanity, but also has the serious influence on the poultry health in stock farm, so it is urgent to eliminate the pollution of odor caused by the livestock, biological deodorization is a broad deodorization method for the moment.In this paper, As a major environmental contaminant from many stock farms biological removal of ammonia odor has been investigated in a self-made bio-filter with membrane ceramsite、multi-faceted hollow balls and Pall ring. The better method of biological filter start-up、the effect of various experiment conditions on biological removal of ammonia odor also has been discussed and the removal kinetics of ammonia gas and the mechanism of biological degradation ammonia gas has been analysed. The conclusions are as follows:(1) The hanging biofilm of nitrobacterium has been investigated in this paper using a self-made bio-filter. Two kinds of start up methods of the reactor has been compared.The first one is called two-step method, the first step is sludge domesticated, and second step is biofilm hanging in packing. The second method is called biofilm hanging in packing and inleting air directly. The results show that the second method is better than the first method, in the reactor start time, ammonia gas removal rate, total nitrogen conversion.(2) The influence of initial pH value, the spraying amount of nutrient solution, temperature and the input of total gas on removal of ammonia gas are also investigated in this paper.At the condition of the spraying amount of nutrient solution80ml/min,30℃, the concentration of ammonia gas200mg/m3and the total gas input0.20m3/h, the impact of the initial pH value on ammonia gas removal rate has been discussed at the initial pH value condition of6.0,7.0,8.0,9.0, in order to find out the optimal initial pH value in experiment. The results show that when the initial pH value is7-8, the ammonia gas removal rate is the best, ammonia nitrogen and nitrate nitrogen conversion rate eventually can stabilize at90%, and the total nitrogen conversion rate even reaches100%. The optimal pH for the system is7-8in experimental conditions.At the condition of the initial pH value7.58,30℃, the concentration of ammonia gas200mg/m3and the total gas input0.20m3/h, the impact of the spraying amount of nutrient solution on a variety of conversion rate and removal rate of ammonia gas has been investigated at condition of20ml/min,40ml/min,60ml/min,80ml/min,100ml/min. In view of the total nitrogen conversion rate, ammonia nitrogen conversion rate and the removal rate of ammonia gas the nutrient solution spraying amount of80ml/min is optimal for ammonia removal.At the condition of the initial pH value7.74, the spraying amount of nutrient solution60ml/min, the concentration of ammonia gas100mg/m3and the total gas input O.25m3/h, the impact of the reaction temperature on ammonia gas removal rate has been discussed at temperature of20℃to35℃. The experiment results show that when the rection temperature is30℃, the removal rate of ammonia gas is the best, it is the most suitable for the growth of microorganism.At the condition of the spraying amount of nutrient solution60ml/min,30℃, the initial pH value7.72and the concentration of ammonia gas200mg/m3. The impact of the on ammonia gas removal rate also has been investigated at different the total gas input. When the total gas input changes from0.2m3/h to0.35m3/h, the removal rate of ammonia gas droppes, the removal rate of ammonia gas changes from100%to95%. The main reason may be that the resident time of ammonia gas in the bio-filter has shortened, which can result in that a part of ammonia gas haven’t enough time to be degraded by the microorganism.In condition of the spraying amount of nutrient solution80ml/min,30℃, the initial pH value7.7and the total gas input0.2m3/h. The removal rate of ammonia gas droppes obviously at ammonia concentration from200mg/m3to800mg/m3, it changes from100%to98%.When stopping inputting the ammonia gas and spraying the nutrient solution to reactor for a week, the bio-filter has been restarted in order to observe the removal effect, two days later the removal rate has resumed as before, When stopping inputting the ammonia gas and spraying the nutrient solution to reactor for half a month, four days later the removal rate had restored as before.(3) In this paper, the enzyme reaction kinetics equation is used to analyze the apparent degeneration of ammonia gas, through the linear regression, the parameters of equation is obtained, Ks is558mg/m3, Vm is3333.3g(H2S)/m3.d, the actual value of hydrogen sulfide degrading amount per day at unit reactor volume is lower than theoretical value Vm, it can be explained that there is big promotion space for the microbial degradation ammonia gas ability in reactor. Through analysing the chemical kinetics of ammonia gas, ammonia gas degradation is accorded with the first order reaction and reaction rate constant k is0.0269S-1.(4) The relationship between the mass of the microorganism degradating ammonia gas and the total mass of ammonia gas entering the bio-filter has been analyzed in experimental conditions in order to find the mechanism of degradating ammonia gas. In the process of removing ammonia gas, the total mass of ammonia gas which is inpoured into reactor is equal to the sum of the mass of the NO3--N and NO2--N in recycling nutrient solution and that of the un-degeneration NH4+-N. The experimental results indicates that most of the ammonia gas had been degraded into NO3--N and NO2--N by denitrification bacteria, a part of ammonia gas could exist in form of NH4+-N in recycling nutrient solution, the trace part of ammonia gas could exist as other forms.(5) Based on the experimental results the biodegradation process of ammonia gas in bio-filter generally should undergo requires three steps. The first step is the dissolution process of the ammonia gas from gas phase to liquid phase; the second step is ammonia gas migration process in liquid phase; the third step is the process of ammonia gas metabolismIn a word, the process of biological degradating ammonia gas has been carefully investigated in this paper, thus it could provide the theoretical foundation for industrialization. Due to the experimental limit, the removal kinetics and degradating mechanism are a primary discussion in the paper. There are many works to do in order to understand the degradating ammonia gas mechanism in the future. |
PDF Full Text Request