Optimization Of Acid Production And Gas Production Conditions For Anaerobic Fermentation Of Cow Dung

With the continuous improvement of economic living standards,people's demand for livestock and poultry products,such as meat,eggs and milk,is on the rise.The intensification of livestock and poultry raising industry is increasing rapidly,which leads to a large concentration of a large amount of livestock and poultry excrement,which brings great environmental pollution.Anaerobic fermentation technology can turn agricultural waste into treasure.The generated biogas can be used as clean energy for combustion,biogas slurry and biogas residue can be further processed into high-quality pollution-free fertilizers,biogas residue can also be further processed and added into feeding stuff for re-use,both economic,environmental protection,energy and many other benefits.So in recent years the use of animal manure as raw materials for anaerobic fermentation with harmless treatment has got more attention.Two-phase anaerobic technology has many advantages such as high effic iency,quick reaction,and strong stability.So in this paper,cow dung is selected as the raw material for anaerobic fermentation,to investigate the influence of temperature,HRT and TS on acidification in ac id producing phase and the effect of temperature and TS on gas producing in methanogenic phase during the two-phase anaerobic digestion of cow manure.In the condition optimization experiment of cow dung acidification,three parts of the experiment were designed:(1)Influence of temperature on the acidification effect of cow dung.This part of the experiment set three temperature levels of 18?,35?and 50?.(2)The effect of HRT on the acidification effect of cow dung.In this part of the experiment,five hydraulic retention times of 6,5,4,3,and 2 day were set,and tests were continuously conducted by gradually shortening the hydraulic residence time.(3)The effect of TS on the acidification of cow dung.This part of the experiment set up five TS levels of 2%,4%,6%,8%,10%,and the experiment is conducted in groups.The optimized conditions are:35?,HRT=4d,TS=8.Under this condition,the p H of the acid-producing phase can be stably maintained within a suitable range for acid-producing bacteria.The peak value of total volatile ac id concentration is 39.4 g/L,the average total volatile acid value is 23.83 g/L,and the average ratio of acetic acid and butyric acid is 69.79%.The whole process produces acid stable,and the ammonia nitrogen concentration is below 1500mg/L.If this is used as the feed of methanogenic phase,it will not have an inhibitory effect on methanogens at the beginning.The methanogenic phase experiments are continued using experimentally optimized conditions derived from acid production.Use the acidified material that come from previous step to test directly.To investigate the effects of different temperatures(35?,50?)and materials with different TS(TS=8%,10%)on gas production under strict anaerobic conditions.The results of the test are:The average daily gas production and pool capacity gas production rate of the fourth group(50?,TS=10%)are 633 mL and 0.528 m~3/m~3·d,and they are higher than the other three groups.The gas production gap between the second group(35?and TS=10%)and the fourth group is small.The final conclusion is that in the two-phase anaerobic digestion experiments,the optimum reaction conditions for the acid producing phase with cow dung as the fermentation material are:35?,HRT=4d,TS=8%.The optimum conditions for the methanogenic phase can be divided into two situations:Regardless of energy consumption,50?,feeding TS=10%are the optimal methanogenic phase reaction conditions;considering energy consumption,35?,feeding TS=10%are the optimal reaction conditions for methanogenic phase.