O’Brien & Gere provided a wide range of professional services to Spotsylvania County (Virginia) to assist it in meeting the requirements of a consent order from the USEPA and upgrade the facility to achieve Biological Nutrient removal (BNR). O’Brien & Gere also supported plant operations in a post start-up optimization study to achieve Enhanced Nutrient Removal (ENR). The 8-MGD Massaponax Wastewater Treatment Plant has been on-line since 2003, and has consistently exceeded nutrient removal objectives. The plant could not comply with its discharge permit with regard to ammonia and total Kjeldahl nitrogen.

O’Brien & Gere provided services in the study phase, preliminary engineering, final design, engineering support during construction start-up, and post start-up process optimization services to achieve ENR.

The selected BNR process is a three-stage selector activated sludge process which is less costly and more compatible with existing operations than the alternatives. In addition to cost-effectiveness, the selector process provided lower energy use, better flexibility of operations, biological phosphorus removal and better compatibility with potentially more stringent effluent discharge limitations, which could result from the Chesapeake Bay Initiative.