Mixing for Better denitrification with less energy - Case study
Achieving simultaneous nitrification & denitrification in the same basin
Topics: mixing, wastewater, activated sludge, energy savings, nitrification, denitrification
System Overview: This basin is part of an activated sludge treatment plant serving 17,000 residents with an average influent of five (5) million gallons per day.
Basin Build Information:
- Volume: 4 million gallons
- Type: Aeration Basin
- Dimensions (ft.): 370 X 37.5
- Depth (ft.): 11.5
Pre-Deployment Conditions: The anoxic portion of the basin was not able to achieve de-nitrification, effluent Total Nitrogen (N) was 15 mg/l.
Objectives: Reduce effluent Total N to 8 mg/l or less by converting the main basin to three (3) zones as follows:
- Zone 1: 0-1 mg/l DO for de-nitrification.
- Zone 2: 2 mg/l of DO for BOD reduction, nitrification.
- Zone 3: 0-1 mg/l DO for de-nitrification.Solution: Three (3) GridBee® GF Series Floating Wastewater Mixers (2013) to mix Zones 1 & 3.
Results: Effluent Total N was reduced from 15 mg/l to less than 5 mg/l. Aeration blower energy in Zones 1 & 3 were reduced by 55% resulting in an operational cost savings of-$5,000 per month.
The capital cost to the City for the entire project was less than $200,000 and they avoided spending $12,000,000 for a Moving Bed Biofilm Reactor (MBBR) system to achieve N compliance.
Update (2016): The City inquired about mixing options without a moving impeller in the water. One GridBee® AP Series Air-Powered Wastewater Mixer was subsequently deployed and later purchased.