LONG TERM BNR OPERATIONS - COLD IN MONTANA!

Ten years ago biological nutrient removal (BNR) was a unique concept, particularly in northwest Montana. It is precisely this area with its pristine lake and river systems considered to be at risk from phosphorus and ammonia discharges that warranted the acclaimed benefits of BNR. The new treatment process was unique, sophisticated and complicated for the operators. Learning experiences were at times self-generated, other times weather related, and sometimes inherent to the process. The experiences, solutions and operating results illustrate that a well designed BNR plant is not only manageable in the extreme climate of Montana but is a worthy recipient of many federal, state and local awards for its excellent effluent quality.The purpose of this paper is to share operational experience, solutions and the performance results of a highly automated BNR plant in the cold weather climate of northwest Montana.In addition, continuing economic pressure to reduce the operating cost of wastewater treatment has required innovative approaches in management and cost control. The operating costs of BNR for smaller wastewater treatment facilities approach 1,000 per day per mgd treated. Incorporating financial costs results in a total cost of 2,200 per day per mgd treated. Some ways used in Kalispell to reduce costs were process oriented, such as reducing dissolved oxygen set points, while other cost reductions were management directed.