Lessons Learned From the Design, Construction, and Startup of the First Denitrifying Biological Anoxic Filter (BAF) Providing Enhanced Nitrogen Removal in Connecticut

The 3.5 MGD Water Pollution Control Plant for the Town of Cheshire, Connecticut was facing significant expenditures to purchase nitrogen removal credits under the State of Connecticut's nitrogen credit trading program. The Town selected the construction of a separate stage denitrification filter as the long term approach to meeting the nitrogen limits contained in the statewide general nitrogen permit and also providing a local water quality benefit in the Quinnipiac River. An upflow biological anoxic filter employing the Biostyr process by I. Kruger was selected as the technology to be constructed to maximize the level of nitrogen removal. Construction of the filter project was completed in early 2006 and the filter has been operational since that time.This paper presents a description of the project, summarizes the operating data for the initial period of filter operation, describes some of the issues encountered during the initial operating period, reviews operating costs and chemical consumption, and presents some of the lessons learned during the implementation of the project.