Energy and Sustainability Consulting
Aeration Systems in Wastewater Treatment Plants
The Situation
A major city in California provides treatment services to its more than 100,000 inhabitants. The Water Reclamation Facility, a tertiary treatment facility, with
a capacity of 14 MGD and includes primary clarification, equalization basins, an activated sludge process designed for biological nitrogen nutrient removal, secondary clarification, tertiary filtration, and chlorination. This facility has a minimum requirement of 5 MGD estuary discharge, and produces recycled water for turf and landscape irrigation.
The Solution
Lincus engineers developed a benchmark analysis to identify potential energy savings for the facility which has an annual electric consumption of 8.0 million kWh. A typical urban wastewater treatment plant uses between 1,000 to 3,500 kWh/MG processed depending on the type of treatment. For comparison, this city’s treatment plant consumed an average of 2,357 kWh/MG processed.
1) Replace Secondary Aeration Blower
The existing secondary aeration blower process included three single stage centrifugal blowers that were 500hp each. Lincus determined that one blower should be replaced with a 300hp high-speed blower to improve the wire-to-air efficiency from 39.8% to 70%.
2) Pulse Air Mixers in Anoxic Zones
The facility’s anoxic zone included two tanks that both had two 15hp submersible pumps, one 4.4hp submersible mixer, and two other 2.7hp submersible mixers. Lincus advised that the existing mixers be replaced with a pulsair mixer system, which consists of stainless steel bubble forming plates and a 15hp air compressor.
3) Gridbee Mixers in Oxic Zones
The wastewater treatment plant had four aeration basins with
12 zones. Zones 1-9 are aerated with one 500hp blower, while
the air headers for zones 10-12 are closed for the anoxic zone.
Lincus recommended to install additional Gridbee mixers to
shut down the air headers for zones 7-9 to increase the
anoxic zone volume and decrease blower air being supplied
with fewer diffusers.
The Results
- Replacement of the Secondary Aeration Blower resulted in a 34% annual energy savings which provided an $80,571 reduction in annual utility costs (with a simple payback period of 4.9 years).
- By improving the Pulse Air Mixers in Anoxic Zones, the facility was able to reduce their energy usage by 71% and save $37,257 on their utility bills (with a quick payback period of 0.2 years).
- And, with installation of additional Gridbee mixers, savings resulted in a 14% annual energy reduction and a lowered annual utility bill by $28,561 (with a simple 0.3 year payback) .
Lincus’ Water Infrastructure and System Efficiency (WISE™) Program
The Lincus WISE program is a comprehensive turnkey solution for Water and Wastewater segment which offers engineering services, project support, and cash incentives. Lincus uses a holistic approach, combining existing pump tests, energy audits, and hydraulic modeling to evaluate how a water reclamation facility can optimize its performance. In this project, Lincus completed its review
of the system and an overall analysis in a single phase.
Lincus engineers conducted an onsite assessment to understandsystem operations, and then developed a
savings analysis to show the payback based
on improving blowers and mixers within the system.