Adding corncob to enhance methane production during anaerobic digestion of dairy wastewater
The solid content and carbon nitrogen ratio are relatively low in dairy wastewater after solid-liquid separation,which restricts the digestion stability and methanogenic performance. In this paper,through batch anaerobic digestion tests,the digestion performance of dairy wastewater with corncob (0,4,8,12,16 g·L-1 dairy wastewater) was explored,and the system stability,methane pro-duction and energy balance were the key analyses. The results showed that corncob increased the concentrations of soluble chemical oxygen demand and the total volatile fatty acids during anaerobic digestion,and promoted the hydrolysis and acidification of substances. The pH and free ammonia in digestive systems with 12 and 16 g·L-1 corncob varied slightly,which was conductive to maintain stability. Adding corncob could delay the process of methanogenesis for 2-5 days,but increase the concentration of methanogenic gene mcrA,thus increase the total methane yields by 14.82％-51.65％,in which the average methane content of 12 g·L-1 reached 63.01％. According to the energy balance calculation,the energy input of anaerobic digestion with different concentrations of corncob was little different,but the energy output increased with the increase of corncob,which was 60.74-172.01 kJ higher than that without the addition of corncob. The addition of corncob increased the solid content and carbon nitrogen ratio of dairy wastewater,helped to maintain the stability of anaerobic digestion,and increased the total methane yields and energy output.
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