The effect of acid pretreatment on the anaerobic digestion and dewatering of waste activated sludge |
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Authors: | Devlin D C Esteves S R R Dinsdale R M Guwy A J |
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Institution: | University of Glamorgan, Sustainable Environment Research Centre, Upper Glyntaff, Pontypridd CF37 4AT, Wales, UK |
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Abstract: | Waste activated sludge (WAS) is difficult to degrade in anaerobic digestion systems and pretreatments have been shown to speed up the hydrolysis stage. Here the effects of acid pretreatment (pH 6-1) using HCl on subsequent digestion and dewatering of WAS have been investigated. Optimisation of acid dosing was performed considering digestibility benefits and level of acid required. Pretreatment to pH 2 was concluded to be the most effective. In batch digestion this yielded the same biogas after 13 days as compared to untreated WAS at 21 days digestion. In semi-continuous digestion experiments (12 day hydraulic retention time at 35 °C) it resulted in a 14.3% increase in methane yield compared to untreated WAS, also Salmonella was eradicated in the digestate. Dewatering investigations suggested that the acid pretreated WAS required 40% less cationic polymer addition to achieve the same cake solid content. A cost analysis was also carried out. |
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Keywords: | Biosolids Methane yield Oxitop Pretreatment Waste activated sludge |
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