Two-phase anaerobic co-digestion of food waste and sewage sludge

Abstract

The feasibility and performance of food waste and sewage sludge co-digestion were investigated to gain insight into their resource utilization. In this study, two-phase anaerobic digestion (TPAD) was operated under a total solids mixing ratio of 1:1 and different sludge retention times (SRTs). Results show that an acidogenic reactor with a 5-day SRT obtained the highest acidification efficiency, and its acetic acid content was dominant. The organic removal rate of a methanogenic reactor (MR) with a 20-day SRT and its corresponding TPAD system with a 25-day SRT were both the highest among the MRs and TPAD systems. Volatile solids and total chemical oxygen demand average removal efficiencies of the TPAD system with a 25-day SRT reached 64.7 and 60.8%, respectively. The MR with a 30-day SRT obtained the minimum ratio of volatile fatty acid to alkalinity (0.12). The methane content generated from the different MRs fluctuated at around 70%. All of the above results can provide reference for future research.

Importance of storage time in mesophilic anaerobic digestion of food waste

“…Therefore, optimum environmental and operational parameters influencing acid-phase digestion of food waste, including pH (Jiang et al, 2013;Lim et al, 2008;Wang et al, 2014), temperature (Jiang et al, 2013;Komemoto et al, 2009;Lim et al, 2008;Vanwonterghem et al, 2015), hydraulic retention time (HRT) (Lim et al, 2008;Wang et al, 2015a), inoculum-to-substrate ratio (Forster-Carneiro et al, 2008;Xu et al, 2012), and organic loading rate (Jiang et al, 2013;Lim et al, 2008), have been intensively investigated. Some studies have focused on the physical or chemical pretreatment of food waste in order to enhance the hydrolysis or to alter the properties of food waste and thus to facilitate subsequent methanization through processes such as microwave treatment (Marin et al, 2010;Shahriari et al, 2013), ultrasonication (Cho et al, 2013;Elbeshbishy and Nakhla 2011), mechanical grinding (Izumi et al, 2010), alkali treatment (Lin et al, 2013), thermal treatment (Li and Li and Jin, 2015;Wang et al, 2006), ozonation (Ariunbaatar et al, 2014), and enzyme treatment (Kim et al, 2006).…”

“…There are studies focusing on the fermentation time of food waste in a fermentation reactor using an inoculum. For example, Wang et al (2015a) used retention times of 1, 3, 5 days for an acidogenic reactor for food waste using mesophilic two-phase AD. They used a 1:1 inoculum-to-substrate ratio on total solids (TS) basis.…”