Anaerobic Sludge Digestion at Baltimore's Back River Wastewater Treatment Plant

摘要

This paper describes the evolution of the anaerobic sludge digestion process at the City of Baltimore, Maryland's 180-million gallons per day Back River Wastewater Treatment Plant through the twentieth century. Baltimore has consistently remained at the forefront of digester technology in the United States. Through much of the twentieth century, about 160-dry tons per day of sludge have been produced and digested at the plant. Back River WWTP was one of the first facilities in the United States in which sludge was treated in tanks separate from the main Wastewater liquid flow stream. By 1921, 20 above-ground, low-rate, digestion tanks were in use, including the Imhoff tank configuration. These were replaced by six 100-feet diameter below-ground tanks, which were converted to single-stage, high-rate, mesophilic digesters in the early 1970s. In the early 1990s, two three-million gallon egg-shaped digesters were placed into operation to supplement the high rate digesters. This was one of the early egg-shaped digester installations in the United States. In 2003, Baltimore City completed the construction of a 25-dry tons per day Process Evaluation Facility to assess the feasibility of converting to the two-phase (acid-gas) mesophilic anaerobic digestion process, which is an emerging technology with only a small number of installations world-wide.