Located in the Shenango Valley watershed of western Pennsylvania, the City of Hermitage's aging infrastructure began to collide with its growing treatment needs. Hermitage also undergoes heavy summer thunderstorms when wastewater volume can double or triple in a couple of hours. In 2005, sanitary overflow reached the point where the City entered into a Consent Order and Decree with the Pennsylvania Department of Environmental Protection to bring its treatment system into compliance.
The Hermitage Municipal Authority seized the mandate as an opportunity to leapfrog the compliance challenge and re-engineer the plant as the key to a more sustainable future for Hermitage. The vision included a plant that would maintain wastewater compliance and include an anaerobic digestion system that would accept residual waste from industries throughout the region, generate its own heat and electricity, and produce excess biogas and Class A biosolids for consumption, reducing landfilling to zero.
OMNIFLO SBR: Anchoring the Activated Sludge Process
The key to realizing this vision was Hermitage’s choice of an Evoqua OMNIFLO® Sequencing Batch Reactor (SBR) using Jet Tech technology for the new plant’s activated sludge process. "The SBR was the right choice for this application because it can handle large, sudden increases in wastewater volume," says RETTEW’s Jason Wert, part of the engineering team that designed the plant, "and Evoqua has the best SBR experience, especially in large-scale systems. In Hermitage’s case, the Authority split its upgrades into two phases. Phase I, completed in 2008, built new tankage and headworks facilities to reduce overflows, while Phase II, completed in 2014, converted the new tankage into fully-functional OMNIFLO SBR treatment facilities and upgraded the remainder of the facility. Along with its wastewater treatment, Hermitage also now converts its own waste activated sludge (WAS) and third-party residual waste into biogas and Class A Biosolids through anaerobic digestion. The digestion process uses Evoqua’s LO/PRO® multi-stage scrubber system to reduce odors, and Evoqua’s Dystor® Double Membrane Digester Gas Holders cap the digestion tanks. The sludge process uses Evoqua gravity belt thickeners and a dewatering press. The biogas produced generates electricity and heat for the site and separates remaining solids for reuse in agriculture and landscaping. By recycling the waste, more than 15,000 gallons of waste per week are no longer delivered to landfills, and the Hermitage plant operates at Net Zero waste biosolids.
The upgrades resulted in lifting the PA DEP’s consent order, as well as preparing the treatment plant for the next 40 years of use. In a move marked by bold vision and commitment to the community’s future needs, Hermitage has converted its wastewater treatment facilities from a system that experienced overflows to a system that is more than environmentally responsible: it accepts and processes residual waste from facilities throughout the region and neighboring states, converting waste to energy. The current self-sustaining operation meets its own power needs while meeting a community need for beneficial reuse of residual waste and expired food products. Today, Hermitage leadership is working on a process to use the system to provide fuel for the municipality’s transportation fleet and is on track for a ten-year payback on the biogas and biosolids investments.