Comparative evaluation of the biochemical methane potential of waste activated sludge acetic acid and cellulose substrat
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Comparative evaluation of the biochemical methane potential of waste activated sludge acetic acid and cellulose substrates under mesophilic and thermophilic anaerobic digestion Getachew Dagnew Gebreeyessus1,2 Received: 8 March 2020 / Accepted: 18 August 2020 © Springer Nature Switzerland AG 2020
Abstract Knowing the biochemical methane potential of a substrate to biogas production is a preliminary to possible selection of the pre-anaerobic digestion technology and identifying the optimum reaction time. Following standard method to reactor assembly, feed preparation and monitoring of the specific methane yield, the two temperature systems are compared among substrates. As a result, the rate of biochemical methane yield from the waste activated sludge anaerobic digestion in the thermophilic case is much faster than the mesophilic. The specific methane yield and volatile solid removal of the waste activated sludge batch anaerobic digestion is 74% of the theoretical and 81% for the thermophilic while it is 57% theoretical and 76% for the mesophilic, respectively. However, the best methane yield is recorded for the acetic acid followed by the cellulose and sludge substrates, signifying the importance of sludge pretreatment to enhance degradability in anaerobic digestion. Also, the optimum reaction time for thermophilic and mesophilic systems is different. Keywords Waste activated sludge · Anaerobic digestion · Biochemical methane potential · Thermophilic · Mesophilic
1 Introduction Conventional wastewater treatments are so far preferred to manage the huge volume of sewage in an urbanized society and in different countries. However, the energy and economic inefficiencies are challenging them. In this regard, recovering the energy and other chemicals from such biowaste is accepted by most central wastewater treatment facilities across the globe [1–3]. Anaerobic digestion (AD) of biomass remains a robust technology to a renewable energy, soil nutrient and waste stability advantages. However, the performance of AD has to be evaluated mainly based on the recovered biochemical methane potential (BMP) of the biomass feed, which are achieved based on acceptable protocol. Therefore, performing the BMP test of the feed is essential, in fact, not
only for the later performance evaluation in terms of the energy recovered but also to judge the degradability status of the feed and thereby to determine the pretreatment required. For instance, degradability has been defined as the BMP divided by the theoretical methane potential which is calculated with the theoretical factor of 0.35 l of CH4 per unit gram of the chemical oxygen demand (COD) [4–7]. Generally, pretreatments are existing practices in wastewater treatment to enhance performance. However, the advantages and disadvantages the different pretreatment techniques should be considered with respect to cost, technology selection, energy and the resulting secondary waste [8]. Regarding of AD feeds, substrate pretreatments are being preferred for their outweighing advantages o
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