Canfor have been successfully employing the fast peCOD chemical oxygen demand (COD) method for improved effluent control and savings at the Prince George, BC Mills.
Having realized improved efficiency, the next step was to optimize nutrient feeds. Canfor have developed a PeCOD/BOD correlation for the basin inlet sample point to predict inlet BOD concentration. From there a BOD:N:P ratio of 100 : 2.5 : 1 is applied to determine the nutrient application rate. This ratio was chosen over the theoretical 100 : 5: 1 ratio that is typically used for Aerated Stabilization Basin (ASB) treatment plants as this is more easily obtained with our current nutrient mixture.
Changes to the nutrient feed are being made every 2 weeks to allow ample time for the basin to adjust prior to the next change. To date, there has been a reduction in Canfor’s nutrient application by approximately 40-50%. Nutrient application rates have an extra 5-10% added to them as a safety net, as this basin currently feeds residual nutrients to another basin. Our conservative estimate is showing a $150,000 – $175,000 annual savings by using BOD prediction via peCOD testing. PeCOD generates the result in less than 15 minutes.
The final step being developed is an automated nutrient application based on inputted laboratory PeCOD results, therefore, an ideal nutrient mixture can be formulated to better obtain an ideal application ratio. PeCOD vs BOD results will be presented along with nutrient optimization with corresponding financial savings.