Acidogenic fermentation of blended food‐waste in combination with primary sludge for the production of volatile fatty acids

Abstract

The performance of a laboratory-scale anaerobic acidogenic fermenter fed with a mixture of blended kitchen food-waste and primary sludge from a sewage treatment plant was investigated for the production of volatile fatty acids (VFA). The operating variables for acidogenic fermentation were kitchen food-waste content (10 and 25 wt %), hydraulic retention time (HRT: 1, 3 and 5 days), temperature (ambient: 18 ± 2• C, and mesophilic: 35 ± 2 • C) and pH (varied from 5.2 to 6.7). The experimental results indicated that effluent VFA concentrations and VFA production rates were higher at ambient temperature than at mesophilic conditions. The net amount of VFA with 10 wt % food-waste increased up to 920 mg dm −3 with an increase of HRT, but contrasting results (a decrease of 2610 mg dm −3 ) were found due to the conversion of VFA into biogas in the case of 25 wt % food-waste, which increased significantly at HRT of 3-5 days. In terms of biogas composition (CO 2 and CH 4 ), the organic matter was converted into CO 2 through the oxidative pathway by facultative species at low temperature while mesophilic temperature and optimum pH (6.3-7.8) played a pivotal role in increasing rate of conversion of VFA into biogas by methanogenesis. Rates of VFA production and their conversion are dependent on the food-waste content in the mixture. Yet, the higher concentration of food-waste (25% compared with 10%) did not produce VFA proportionally due to the increased rate of conversion of VFA into gaseous products. The maximum VFA production rate (0.318 g VFA produced g −1 VS fed day −1 ) was achieved in the 10 wt % food-waste at ambient temperature and at a 5-day HRT.

Co-fermentation of waste activated sludge with food waste for short-chain fatty acids production: effect of pH at ambient temperature

“…3 Variations of total SCFAs concentration at different pH Leiyu FENG et al Co-fermentation of WAS with food waste for short-chain fatty acids production participation of SCFAs consumers, such as methanogen. In the literature, almost the same results were found by Min et al during the acidogenic fermentation of food waste in combination with primary sludge for the production of volatile fatty acids [8]. They found a decrease of 2610 mg COD$L -1 for SCFAs when hydraulic retention time was more than 10 d, which was attributed to the possible conversion of SCFAs into biogas of methane and carbon dioxide.…”

“…Additional advantages include the increased digestion rate and hygienic solubilization. Min et al reported the study of acidogenic fermentation of blended food-waste in combination with primary sludge for SCFAs production and found that the concentration of effluent SCFAs and its production rates were higher at ambient temperature than those at mesophilic one [8]. Ağdağ and Sponza presented the effect of co-disposal of industrial sludge with the organic fraction of municipal solid wastes (OFMSW) on anaerobic treatment of domestic solid waste and the leachate characteristics [12,13], showing that co-digestion of industrial sludge and OFMSW had a positive effect related to COD and SCFAs production and a synergistic effect between municipal solid wastes (MSW) and industrial sludge driven the degradation of organic matter.…”

“…In recent years, research on the acidogenic phase of anaerobic digestion where complex organic substances are converted into SCFAs and other low molecular weight soluble carbon compounds has increased considerably [3][4][5][6][7][8]. The acidogenic phase of digestion process may be a function of waste or wastewater characteristics, operational parameters, such as hydraulic retention time (HRT), solids retention time (SRT), etc., and environmental factors such as temperature, pH, reactor configuration, oxidationreduction potential (ORP), etc.…”

Benchtop Minimal-Intervention Anaerobic Digestion of Vegetarian Food Waste for pH and Methane Production: Conceivability and Control Study

“…blending) has a greater solids content than traditional wastewater digester feedstock, at 15% or higher (Li et al, 2011). Food waste also has a much higher COD (Min et al, 2005), which indicates a greater potential for producing methane (Droste, 1996). Anaerobic digestion of solid waste of all sources (e.g.…”

Small-scale Minimal-maintenance Anaerobic Digestion of Food Waste for Solids Reduction and Methane Production: Feasibility Study

“…blending) has greater solids content than traditional wastewater digester feedstock at 15% or higher (Li et al, 2010). Food waste also has a much higher COD (Min et al, 2005), which indicates a greater potential for producing methane (Droste, 1996). Anaerobic digestion of solid waste of all sources (e.g.…”