Overview

The Frackville Area Municipal Authority (FAMA) sought to reduce its wastewater treatment plant (WWTP) operating costs through enhancements to their biological processes. We were retained to analyze energy usage and design system improvements for FAMA’s WWTP. After our analysis, FAMA chose to implement upgrades that retrofitted existing aerobic digestion tanks with covers, and installed new diffusers in the main treatment tanks. The projects minimized operating and capital costs while maximizing aeration and energy efficiency of the digestion process. In the first year of operation, FAMA’s energy usage decreased 15% or $18,000 from the new diffusers, and reduced sludge disposal costs by 58% or $15,000 annually.

Solution Details

FAMA’s existing aerobic digestion system contained dual, open air tanks with floor-mounted coarse-bubble diffusers. To contain heat and increase the speed of digestion, we designed upgrades that included tank covers, high-efficiency diffusers, and the rearrangement of the process flow to make the digestion tanks-in-series as opposed to parallel tanks. Retrofitting the existing tanks reduced capital costs, and the covers and diffusers allowed for maximum temperature control, while reducing energy demands and odors, and improving digestion. Improved digestion resulted from increasing the kinetic reaction speed, reducing solids retention time, and creating Class B stabilized sludge. The sludge was then able to be dewatered more effectively, reducing FAMA’s sludge tonnage disposal by 57%.

New high-efficiency diffusers were also installed in the main treatment tanks. High-efficiency Variable Frequency Drive (VFD) blowers were also installed, as part of both upgrades to the aerobic digesters and main treatment tanks. The VFDs allowed FAMA to deliver only the amount of oxygen needed, eliminating wasted energy from over-aeration, delivering significant energy savings to FAMA.

The upgrade projects were funded with a low interest PENNVEST loan, an H2O PA Grant, and Authority funds. Additionally, FAMA’s project costs were offset with over $55,000 in energy utility rebate programs. The upgrades were completed without interruption to the facility’s operation; FAMA is now enjoying significant reductions in energy, manpower, chemical use, and costs associated with dewatering and sludge disposal, as well as improved treatment plant efficiency.