Effects of different storage methods on manure utilization characteristics and main odorous gas emission of rural dry latrine
In order to explore the impact of different storage methods on the manure utilization characteristics and main odor-causing gas emissions of rural dry latrines,in this paper,we conducted experiments on this kind of dry sanitary toilet.By researching the dynamic changes in the physicochemical properties and odor emission of human feces in dry toilets under natural(open)storage and closed storage,we explored the effect of renovation of dry sanitary toilets on the agricultural potential and the emission of main odor.The results showed that compared with natural storage,closed storage had better nitrogen loss reduction with a decrease of total nitrogen loss by 20.24%and an increase of ammonia nitrogen content by 22.34%,while the loss of total carbon content and electrical conductivity diminished by 4.61%and 0.02,respectively,as well as a lower pH by 0.9.Throughout the experiment,the number of fecal coliforms decreased from 43 MPN·g-1 to less than 3 MPN·g-1 under the two storage methods,and the seed germination index value was 0,indicating that although the storage of human feces in dry toilet for half a year could achieve hygienically harmless,nevertheless,that still had toxic effects on crops when used as fertilizer directly.It was suggested that the addition of mulching material or filler into human feces was necessary to improve the maturity of manure to meet the agricultural utilization requirements.During the six-month experiment period,the ammonia concentration in closed storage was significantly higher than that in natural storage,with the highest being 279.29 mg·m-3 and the average being 129.75 mg·m-3.The average hydrogen sulfide concentration was 10.68 mg·m-3,which was slightly greater than that in natural storage,illustrating that the odor emitted in a closed septic tank after replacing them with dry sanitary toilets was mainly ammonia,which was slow and continuous,and there was a significant positive correlation with temperature.Therefore,in order to solve the odor problem in dry sanitary toilets,an exhaust pipe must be installed,and its height and inner diameter must be precisely configured to discharge the odor efficiently.
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