Study On Ammonia Biodegradation By Biological Technique

With the rapid development of industry and agriculture, the harm which attributes to the odors was more and more attracted attention by the public. The biofiltration and the biologic expanded bed techniques were adopted in succession to treat ammonia-contaminated gas streams, then the advantage and disadvantage of the two techniques were compared in detail, to overcome the shortage of the two techniques, a novel biological process for the treatment odors was established ,which was the result of the biofiltration and the biologic expanded bed technique's coalescent. The first ammonia gases were treated with gas phase biofilters, compost was used as biofilter packing media , the nitrifying microbe in the compost was enriched. The second, the biological expanded bed was inoculated with the filtrate from the compost filling used in biological filter, then the effects of different fillings, retention time, and inlet concentration of ammonia on the ammonia removal efficiency as well as the transformational law of different nitrogen species in the biologic reactor were studied. The third, the nitrifying microbe in compost filtrate and the biological expanded bed was screened, high-efficient nitrifying microbe would be found and isolated, and then the isolated nitrifying microbe would be introduced into the biological expanded bed fillings which have been disinfected under high pressure, the effect of different inlet concentration of ammonia on the ammonia removal efficiency was be studied. The last to be dead against the higher of pressure drop in the experimentation of the biological expanded bed technique, improvement have been made to the biologic technics, with depressing the liquor height and choosing filling afresh, the ammonia removal efficiency of the new technics was studied. The main results are as follows:(1) The biofilter had the high ammonia removal efficiency with compost adopted to be filling. The optimal inlet concentration of ammonia in which the biofilter runs well was 45.0mg/m~3～162.2mg/m~3, here the ammonia elimination capacity was from 36.86 g/m~3·h～136.07 g/m~3·h. However along with the study running and adding water to the compost filling, the fillings would be agglomerated, the another question was that the condition of carriers(pH, nutrimental substance) was difficult to control. Because of the change of the carriers' condition, the activity of microorganism would fall, accordingly the bioreactor' capability would drop.(2) The biological expanded bed technique had high rate of ammonia removal efficiency. The mixture of Ian-stone and compost was taken as fillings, and the volume ratio of this two media was 1/1. When the retention time was 28.6s, the influent gas concentration was below 100 mg/m~3, the ammonia removal efficiency was above 98%, the outlet concentration can meet the first level of national odor emission standard,the influx gas load was upto 127.39 g/m~3·h ,and the elimination load was upto 126.13 g/m~3·h .the activity was superior to the single fillings of compost. It was found that ammonia was nitrified to nitrate in the bioreactor mostly. Because of continual accumulation of nitrate, the pH in the bioreactor fell from 8.5 to 5.9.(3) 4 strains of nitrococcus(Y1～Y4) and 4 atrains of nitrifying microorganism(X1～X4) were screened and isolated by enrichment culture from compost and the liquid in the biologic expanded bed, with X2 being bacteria, X3 being actinomyces, the others being fungus. In the 4 strains of nitrous nitrifying microorganism, Y1 and Y4's ammonia transforming ability were higher, the nitrous nitrifying rate of them respectly achieved 26.94 mg /L·d and 16.54 mg /L·d; In the 4 strains of nitrifying microorganism, X2 and X3's nitrification activity were upper, the nitrifying rates respectly achieved 8.23 mg /L·d and 6.98 mg /L·d. The nitrous nitrifying rate of the mixed strains of Y1,Y2 and Y3 was 37.85 mg /L·d, the nitrifying rates of the mixed strains of X2 and X3 was 44.75 mg /L·d.(4) a novel bioreactor for the treatment of odors was established, which was the result of biofilter and biological expanded bed technique's coalescent, the novel bioreactor had a high rate of ammonia removal . When the air flow was 1.5 m~3/h, the retention time was 28.6s, the influent gas concentration was below 370 mg/m~3 , the removel rate of ammonia was held basically above 97%. Through an analysis of various forms of nitrogen's concentration in the solution and fillings, the experiment results were confirmed that ammonia was nitrified to nitrate, and the bioreactor had stratification phenomenon in ammonia removal over the bioreactor depth which meant that the different parts of the reactor had different weightiness in ammonia removal, the solution and the fillings at middle and lower layer played an important role for the ammonia removal.