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

Abstract

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 g·L–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.

Enhanced methane production by granular activated carbon: A review

“…The increase was attributed to enhanced DIET because of the enrichment of Geobacter and Methanobacterium on the surface of GAC. A 12.14% increase in biomethane production by GAC on food waste treatment was reported [59], where DIET participant Geobacter increased close to an order of magnitude. Enhancement of biomethane performance by GAC with Geobacter was found somewhere else, where 49.8% of the organisms on the surface of GAC were Geobacter species [60].…”

“…GAC can serve as a pH buffer because of its high adsorption capacity of VFAs and simultaneously promote the degradation of VFAs, thus stabilizing the pH variations and enhancing substrate production for methanogens. Wang et al demonstrated that 1 g⋅L -1 GAC in the AD system effectively stabilized the pH value, resulting in a 12% increase of methane production and reduced AD start-up time by about 5 days [59]. The pH buffering capacity of GAC was also observed at a concentration up to 20 g⋅L -1 , which showed the best performance that enhanced the methane production by 27% [97].…”

Acidogenic Fermentation of Food Waste in a Leachate Bed Reactor at High Organic Loading: Effect of Granular Activated Carbon (GAC) and Inoculum

“…(2008) operated an expanded granular sludge bed reactor packed with GAC at high volumetric organic loading to produce hydrogen from molasses-containing wastewater and showed high hydrogen production with better operational stability at a shorter fermentation time. Similarly, Wang et al (2020) reported 12.14% higher methane production by using GAC as a support media in anaerobic co-digestion of municipal sludge and food waste.…”

“…GAC can be derived by pyrolysis of the organic waste biomass with low production costs. Research studies have also reported the positive impact of GAC as a support media for microbial attachment in anaerobic bioreactors producing hydrogen, and methane (Bertin et al, 2010;Lutpi et al, 2015;Mohan et al, 2008;Guo et al, 2008;Wang et al, 2020). For example, Guo et al…”