BALTIMORE'S SUCCESSFUL EGG–SHAPED DIGESTER EXPERIENCE GUIDES THE FUTURE

In 1988 and 1989, the 180 million gallon per day (mgd) Back River Wastewater Treatment Plant in Baltimore, Maryland experienced numerous difficulties in its Sludge Management Program. This resulted in a State Complaint, a Consent Order, and a program of activities to correct the problems. Since then, operational changes, construction of a contract-operated sludge pelletizing facility, and construction of one of the first large-plant installations of egg-shaped digesters (ESDs) in the United States have drastically improved the plant's ability to properly handle the sludge solids produced. Additions and improvements to the sludge handling facilities continue today. A new sludge thickening facility has gone on line in the past year. A preliminary design for an expansion of the anaerobic digestion facilities has been completed. The success of the eggshaped digesters has guided and influenced current planning for the expanded anaerobic digestion facilities. This paper will present the lessons learned in this successful digestion program and how the operational information gathered to date has been used for future planning. This information will be of value to anyone considering egg-shaped digesters or modifications to an existing conventional digestion system.