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Energy Recovery from Residuals – Comparing Anaerobic Digestion with Combined Heat and Power to Drying Gasification

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During the summer of 2010, the Washington Suburban Sanitary Commission began a study comparing different biosolids management options at the Seneca, MD and Piscataway, MD Waste Water Treatment Plants with a focus on energy recovery from biosolids through the methods of drying followed by gasification and anaerobic digestion with combined heat and power generation. Both plants currently manage their biosolids with lime stabilization and Class B beneficial use. The study was set up as a three phase approach consisting of identifying and screening technologies, performing a detailed economic and noneconomic analysis of the short listed options and finally developing a concept design report for the selected option. Samples from both plants were analyzed for both energy potential and digestibility leading to the finding that the Seneca sludge was not suitable for conventional mesophilic anaerobic digestion alone. Several drying and gasification alternatives were screened but only close coupled systems were short listed for further analysis. Multiple anaerobic digestion configurations and pretreatment technologies were also screened leading to a short list of conventional mesophilic anaerobic digestion at Piscataway WWTP; acid-gas phase digestion for both WWTPs; 2PAD technology for both WWTPs and a combined digestion facility at Piscataway with thermal hydrolysis pretreatment. A detailed economic analysis led to drying and gasification along with a regional thermal hydrolysis and anaerobic digestion being the most favored options. Future work includes expanding the study to compare additional regional options in conjunction with other plants in Prince George's and Montgomery counties.

Keywords: Anaerobic Digestion; Beneficial Reuse; Biosolids; Class A; Energy Recovery; Gasification; Solids Processing; Thermal Hydrolysis

Document Type: Research Article


Publication date: January 1, 2011

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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