Two-Stage Anaerobic Digestion of Meat Processing Solid Wastes: Methane Potential Improvement with Wastewater Addition and Solid Substrate Fermentation
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Anaerobic digestion of slaughterhouse solid wastes (SSW) and wastewater (SWW) was investigated with different mixture ratios (M1: 25% SSW/75% SWW, M2: 50% SSW/50% SWW and M3: 75% SSW/25% SWW) in sequencing batch reactors at organic loading rates (OLRs) of 0.8, 1.6 and 3.2 kg VS m− 3 day− 1. The best methane production potential (MPP) and volatile solids (VS) removal yield of 0.38 m3 kg VSadded−1 and 86%, respectively, were obtained with the mixture M1 corresponding to the highest wastewater proportion. In fact, dilution improved the hydrolysis of organic compounds, which are hardly degraded by fermentative bacteria. For this reason, a biological pretreatment of the mixture M3 by solid substrate fermentation (SSF) using the endogenous microflora was performed. Therefore, the methanogens activity was improved significantly. At high OLR, the MPP and the VS removal yield increased by 52 and 22.7%, respectively. Results showed that the biological pre-treatment (SSF), using Bacillus and Lactobacillus bacteria, integrated to the anaerobic digestion process is an attractive strategy to improve the bioconversion of organic fraction of slaughterhouse wastes into methane.
KeywordsAnaerobic digestion Slaughterhouse wastes Biological pretreatment Ammonia inhibition
The authors wish to acknowledge the Ministry of Higher Education and Scientific Research in Tunisia, which has facilitated the carried work.
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