Research On Anaerobic Co-digestion Of Food Waste And Cow Manure And Promoting Factor

Anaerobic co-digestion method was adopt to solve the problem of foodwaste（FW）which was easy to acidify when anaerobic digested alone. And thenon biological promoting factor was also discussed at the same time.Food waste（FW）and cow manure（CM） were mixed in different ratio.Under the condition of35℃and sequencing batch, the anaerobic co-digestionefficiency on different ratio of food waste and cow manure were evaluated. Theresult showed that, the best FW and CM reaction ratio was3:1, and the total gasproduction was3750.5mL, which were there times of the single digestion of FW(T6). The content of methane gas was up to52.1%. At the later stage of reaction,pH kept at7.3-7.5, and the system did not acidify. The concentration of ammonianitrogen was maintained at2000-2200mg·L-1, and the maximum absorbancevalue of coenzyme F420was0.72. However, the acidification effect occurredwhen food waste was digested in anaerobic condition separately, and the reactionfailed to run. From the above results, adding CM can effectively inhibit thephenomenon that food waste anaerobic digested alone will easily acidify.In order to study the influence of single trace element on anaerobicco-digestion of food waste and cow manure, the sequencing batch was performedusing FW and CW at the ratio of1:1in weight. Different concentration of iron、cobalt、and nickel was added every day, respectively. The result indicated that,the addition of trace elements could promote the anaerobic co-digestion of foodwaste and cow manure, but the promotion effect was not obvious when theconcentration was too high. That is to say, adding moderate concentration traceelements can effectively promote anaerobic co-digestion of food waste and cowmanure. Among them, the promotion promoting effect of cobalt element onanaerobic co-digestion of food waste and cow manure is most obvious.Based on the single factor, the center combination design of three factorsand three levels, and response surface analysis method was adopt. The quadraticregression mathematics model was established, and regarding volatile fatty acids（VFAS） production as response composed the response surface and contour.The effects of concentration of trace elements and their interaction on volatile fatty acids （VFAS） production with mixed food waste and cow manure wereinvestigated. The result showed that, the optimal concentrations of three elementswas: iron1.00mg·mL-1, cobalt0.02mg·mL-1and nickel0.50mg·mL-1. Underthese conditions, the predicted volatile fatty acids（VFAS） production was3670mg·L-1, while the experimental value was3668mg·L-1which was correspondedto the predicted value. Therefore, it is feasible and reliable to determine theconcentration combination of adding iron, cobalt and nickel elements by responsesurface analysis method.