Doing More with Less: Refining the Westbank Biological Nutrient Removal Process to Achieve Aerobic Granular Sludge While Enhancing Performance

AECOM partnered with the City of Penticton (Canada) to investigate various process modifications to its existing biological nutrient removal (BNR) process to promote the growth and retention of granular sludge. The continuous flow AGS demonstration pilot utilizes two completely independent trains, operated side-by-side. The pilot train configuration was modified to include an inDENSE hydrocyclone skid to selectively waste floccular biomass. The pilot train transitioned to a hybrid-floccular sludge, achieving an average SVI-30 of 70 -75 mL/g. Based on the particle size distribution analysis the average particle size in the pilot train was 210 µm vs 86 µm in the control train. Assuming the threshold size for granules is 200 µm, the granules composed approximately 12% in the control train vs 44% in the pilot train. The pilot also indicated that operating the last aerobic cells at low DO to maximize SND significantly reduced effluent TN by reducing nitrate concentration.