Case Study: Lakota WWTP, Lakehaven Utility District, WA

High energy consumption and limited and inefficient operation

NAPA Sanitation District’s consultant QuEST and Herwitt Engineering conducted a study on replacing the plant’s Multistage Centrifugal blowers to address their inefficient operation, operational inflexibility and high energy consumption. Following the recommendation of the study, NAPA Sanitation District replaced their existing blowers with the High Efficiency turbo blowers which helped them secure a rebate by CalPOP.

Challenge
Like many wastewater treatment plants across the country today facing high energy costs and aging equipment, the Lakota Wastewater Treatment Plant sought options to address their challenges while moving towards a more environmentally conscious operation. The plant was equipped with two Positive Displacement Roots blowers (250 HP and 350 HP) used to supply air to the biological secondary treatment process. In service for almost 17 years, the 250 HP blowers were noisy and inefficient, consuming a lot of energy to meet plant’s air and pressure requirements. Due to its operational inflexibility, the 250 HP blower was unable to meet the low pressure aeration flow requirements of the plant, obliging the plant operator to turn on the second 350 HP blower, resulting in additional power consumption.

Solution
In 2008, the Lakota WWTP replaced the 250 HP P.D. blower with APG-Neuros’ 300 HP turbo blower. The blower replacement project was eligible for an Energy Grant from Puget Sound Energy (PSE). With APG-Neuros’ help, after thorough review of the estimated energy savings, and PSE agreed to finance 70% of the project capital cost, providing grant funds of over $156,000.

The APG-Neuros turbo blower saved the WWTP over $86,000 per year in power consumption (at 7.5 cents/kWh), which resulted in a payback period of 1.3 years (with grant funding from PSE). In addition to the energy savings, the turbo blower reduced the power demand by 1380 kWh/yr. The NX300 is able to supply all of the plant’s low pressure process aeration requirements that eliminate the need to run the 350 HP P.D. blower. Reducing operation from 2 units (250 HP and 350 HP) to one unit (NX300), demonstrates the operational flexibly with variable flow and pressure requirements. The plant PLC communicates with the blower’s built-in PLC to control its speed, to maintain a pressure set point, and adjust flow set point corresponding to the varying water depths and pressures. The plant PLC monitors the D.O. levels in each basin, regulating the motorized valves on supply headers to each section of tanks as needed, adjusting air flow to maintain the D.O. set points.
The APG-Neuros Turbo Blower provided an exceptional reliability with availability level exceeding 99.8% over four years and 35,000 operating hours.