Investigation on the anaerobic co-digestion of food waste with sewage sludge

Abstract

In this laboratory-scale investigation on the applicability of the co-digestion of food waste with sewage sludge, evaluated were the effects of the single-stage versus two-stage operating modes at the hydraulic retention time (HRT) of 15 days, and the impact of HRTs: 15 days vs. 25 days, on the single-stage operation. An average volatile solid reduction (VSR) of 61% and methane yield of 314 ml/g-VS were achieved in the two-stage operation (HRT 15 days), while comparable VSR of 57% and the methane yield of 325 ml CH/g-VS could only be detected at a longer HRT at 25 days in the single-stage operation. The difference in the operating modes showed much higher influence on shaping the overall bacterial structures than the two HRTs of the single-stage operation. The one operational taxonomic unit (OTU) annotatable at the family level of Thermotogaceae was most abundant (> 10%) in all the methanogenic co-digestion consortia, and its dominant role was recognized to be independent of other OTU lineages in the community. OTUs in the phylum Proteobacteria were much more common as the persistent OTUs in the single-stage co-digestion consortia, while in the two-stage consortia, they were in the phylum Firmicutes. Annotation on the functional genes suggested that the phylum Firmicutes hosted the majority of pilus genes and hydrogenase genes that were reported to be essential for the syntrophic conversion of the high concentrations of alcohols and reduced fatty acids in the methanogenic reactor operated under the two-stage mode.

Biogas Production by Co-Digestion of Canteen Food Waste and Domestic Wastewater under Organic Loading Rate and Temperature Optimization

“…Excess ammonia and volatile fatty acid (VFA) accumulation are more common with anaerobic digestion of high solid content in food waste [13]. However, the composition of food waste varies, depending on the collection source [14]. Restaurant and canteen food waste accounts for 50% of the total amount of food waste, according to De Clercq et al [15].…”

“…Only the OLRs of 0.33 and 0.22 g VS L −1 d −1 likely ensured a high activity of methanogens, which are sensitive to environmental change and perform optimally in a pH range of 7-8 [39]. Wang et al [14] have suggested that when food waste is used for co-digestion with other substrates, one potential concern is that the more readily hydrolysable food waste might interrupt the established balance between hydrolysis and methanogenesis. A sharp pH drop and VFA accumulation in the digestion slurry would indicate such an interruption.…”

Acidogenic Fermentation of Brewers’ Spent Grain Monitored through Two-Dimensional Fluorescence Spectroscopy

“…28 In fact, taxa belonging to the Firmicutes and Proteobacteria phyla are reported to have more persistent taxa than the other phyla as well as an unexplained stability under anaerobic conditions. 29,30 Linkage between the Most Abundant Taxa and the Effluent FP Profile. To understand the relationship between the microbiome present in the UASB reactor and the FP produced, the temporal trend of the five most abundant taxa was related with the main FP obtained on each sampling day (Figure 3).…”

Thermophilic co-digestion of food waste and sewage sludge

“…Based on the food consumption pattern in Hong Kong, FW generally consists of 80% carbohydrates, 15% proteins and 5% lipids (Wang et al, 2015). Therefore, this distribution of organic matters in FW is adopted in this study and the FW is prepared accordingly for the experiment.…”