Optimization of Nutrient Control in a Paper Mill Activated Sludge System, 1999 Environmental Conference Proceedings

Michael H. Foster

Environmental Business Specialists, LLC

Andrew Redmond & Steve Crozier

Willamette Industries

Activated sludge systems typically rely on monitoring effluent ammonia and orthophosphate residuals to maintain proper feed rates of nutrient formulations. While maintaining adequate effluent residuals is certainly a key component to proper nutrient control, it only provides part of the answer, particularly in systems prone to nitrification. Through the use of Chemical Oxygen Demand (COD) as a surrogate for Biochemical Oxygen Demand (BOD5) and a computer model to predict feed rates, a feed forward approach was implemented. This feed forward approach was utilized in conjunction with residual monitoring and monthly inventory tracking to ensure that adequate nutrients were routinely available for the biomass. The computer model is also used to make necessary adjustments in the N:P ratio of the commercial nutrient blend, thereby maintaining optimum product efficacy and cost performance.

Following the implementation of this control strategy, the mill was able to document:

1. A significant reduction in nutrient consumption and an associated 33% cost savings.

2. Lower effluent nitrate levels.

3. Improved biomass quality as measured by sludge volume index (SVI).