Abstract
Anaerobic Digestion Model Number1 (ADM1) was modified in order to predict accurately the impact of co-digesting bakery waste (BW) with municipal sludge (MS). BW is an industrial waste (300,000 gallons per day in USA) that contains a high concentration of organic matter (carbohydrates, low lipids and non-detected proteins). BW is an easily biodegradable substrate for creating a favorable microorganism growth environment, which enhances the biogas production needed for wastewater facilities. The modified ADM1 successfully predicted changes in pH, volatile fatty acids (VFA), propionic acid and methane gas production. The ADM1 outputs were compared to experimental batch reactor results of actual BW addition percentages in order to validate the model. Stability of the digestion process was achieved until the ratio range of 37-40% BW: 60-63% MS, and the digestion processes were inhibited at higher ratios of BW. This research provides an alternative to BW management through utilizing the BW to enhance methane production.
Highlights
The anaerobic digestion process is one of the oldest biological process technologies utilized by mankind
The model outputs were compared to the observed results from the full-scale digester at Central Weber Sewer Improvement District (CWSID)
Modification and validation were applied to the model in order to accurately predict the impact of adding the bakery waste (BW) to municipal sludge (MS)
Summary
The anaerobic digestion process is one of the oldest biological process technologies utilized by mankind. While anaerobic digestion is an attractive method for pollution control and energy recovery (Burton 2004), many factors may affect the balance between microorganisms or inhibit them in the anaerobic digester; for example, changes in temperature, retention time (related to loading), pH and toxic materials (Bitton 2011). Researches have been done to try to enhance methane gas production during co-digestion of food waste by combining it with other organic matter Wastes from food processers are high in organic matter and resulting in high methane gas production, but this same organic material can inhibit anaerobic microorganisms (Chen et al 2008). Co-digestion of certain food wastes such as meat waste will increase the accumulation of ammonia and volatile fatty acids (VFA); these two substances are potent inhibitors to anaerobic microorganisms in specific concentrations (Kayhanian 1999)
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