Enhancing the Performance and Stability of the Co-anaerobic Digestion of Municipal Sludge and Food Waste by Granular Activated Carbon Dosing

This study investigated the effects of granular activated carbon (GAC) dosing on the co-anaerobic digestion of municipal sludge and food waste. It was found that methane production increased in the GAC systems. The cumulative methane production in the 1 GAC system was 12.14% higher than the control. The 1 g.L-1 GAC system started very quickly at the initial stage of anaerobic digestion (AD) and reached the highest methane production per day on the 3rd day, while the control appeared on the 10th day. The maximum methane production per day of the 1 g.L-1 experimental group was 12.27% higher than that of the control. The pH of the 1 g.L-1 experimental group varied less during the entire AD cycle. The reduction in sCOD, TS, and VS of the 1 g.L-1 GAC system were 48.95, 23.26, and 10.20% higher than the control, respectively. The dominant bacteria in the GAC systems were Thermotogae, Firmicutes, and Bacteroidetes, and these bacteria play very important roles in the hydrolysis and acidification stages. The main methanogen genus in the control was Methanosarcina, and those in the experimental systems were Methanobacterium and Methanolinea (which are hydrogenotrophic methanogenic archaea). These results indicate that the addition of GAC can relieve the acidification, reduce the AD start-up time, and promote the activities and growth of microorganisms to improve methane production by enhancing direct interspecific electron transfer and interspecies hydrogen transfer.