The Rochester Area Joint Sewer Authority (RAJSA) has a $54 million construction project currently underway. The project is required to upgrade aging sewage conveyance and treatment infrastructure in order to comply with regulatory requirements and to ensure that reliable service can continue to be provided to RAJSA rate payers for at least the next 30 years.
RAJSA owns and operates combined sewer system interceptor sewers, three lifts stations and associated force mains, and a 1.4 MGD wastewater treatment plant (WWTP). These sewage facilities serve Rochester Borough, Rochester Township, East Rochester Borough, Freedom Borough, and New Sewickley Township, Beaver County. The interceptor sewers, lift stations and WWTP were constructed in the early 1960s. The original WWTP provided primary treatment, disinfection and sludge stabilization and dewatering.
In the mid 1970s the plant was upgraded to provide secondary treatment. The current plant processes include: aeration tanks, rectangular secondary clarifiers, gas chlorination for disinfection, aerobic digestion, and belt filter press sludge dewatering. The WWTP discharges to the Ohio River near the confluence with the Beaver River. The plant has no issues meeting all PA Department of Environmental Protection (DEP) effluent limits. Treatment of peak flows as high as 5 MGD, without issue, is possible.
The RAJSA conveyance system includes two permitted combined sewer overflows (CSO’s), one at the West Madison Lift Station and one at New York Avenue. The West Madison CSO discharges to the Beaver River near a boat dock. DEP has required elimination of this overflow since it is a “sensitive area.” While the New York Avenue CSO, which overflows to the Ohio River, can remain, overflow volumes must be significantly reduced to comply with the U.S. Environmental Protection Agency (EPA) CSO Control Policy 85 percent capture requirement.
Additionally, there are two non-permitted sanitary sewer overflows (SSO’s), one at the Freedom Lift Station and one at the Center Street Lift Station. DEP has required elimination of both of these SSO’s. RAJSA has a Consent Order and Agreement (CO&A) with DEP requiring completion of their Long Term Control Plan (LTCP) work. RAJSA worked with KLH Engineers, Inc., over the past four years, to complete project planning, design, and permitting for an upgrade of their conveyance and treatment systems to comply with their LTCP and CO&A requirements.
In addition to addressing regulatory requirements, it was RAJSA’s goal to ensure that another significant upgrade project would not be required during the design life of the proposed facilities. Given the age and condition of existing infrastructure, KLH developed upgrade alternatives considering remaining life of existing facilities and equipment.
Additionally, the proposed upgrade included provisions for potential future nutrient limits, including ammonia, total nitrogen, and phosphorus. The project includes:
- Upgrade of the WWTP design average flow from 1.4 MGD to 2.8 MGD
- Upgrade of the WWTP design peak flow from 5 MGD to 15 MGD
- Upgrade of West Madison Lift Station peak capacity from 1.8 MGD to 25 MGD to eliminate the “sensitive area” CSO
- Upgrade of the Freedom Lift Station peak capacity from 1 MGD to 9 MGD to eliminate the SSO
- Construction of 1.5 million gallon flow storage tank to accommodate CSO flows from the West Madison Lift Station and New York Avenue Construction of an overflow sewer from the New York Avenue CSO to a new pump station, which will pump to the flow storage tank
- Construction of new force mains for both the West Madison and Freedom Lift Stations
New mechanical bar screens are proposed upstream of each lift station. A grit removal system, rectangular clarifiers, and chlorine contact tanks, all rated for a peak flow of 15 MGD, will be constructed at the WWTP. Gas chlorination system is being converted to sodium hypochlorite to accommodate short duration high chlorine feed rate during peak flow events.
The WWTP design average flow and peak flow are increasing by two and three times respectively, without construction of new aeration tanks. This upgrade is being accomplished by converting the existing complete mix extended aeration process to a plug-flow, step feed Modified Ludzack-Ettinger (MLE) process. The new aeration process has a design hydraulic retention time of 12 hours vs. 24 hours for the existing extended aeration system, thus allowing for the design average flow to double. The process peaking factor is 5.3 with respect to design average flow of 2.8 MGD and over 10 with respect to annual average flow. The high peak flows are accommodated through the design by:
- Construction of four new rectangular clarifiers. Only two of the clarifiers will operate during normal dry weather conditions. As wet weather flow increases additional clarifiers will automatically be brought online. The MLE process includes: one anoxic zone and three aerobic zones for each of the two trains. Under normal dry weather conditions all return activated sludge (RAS) and influent flow will enter the process at the anoxic zone of each train. As flows increase during wet weather, the influent flow will be automatically redirected to the last aerobic zone. This mode of operation will keep the biomass in the aeration tanks and prevent the clarifiers from being overloaded.
- The large clarifiers increase potential for denitrification and associated rising sludge. Inclusion of the anoxic zone will allow for controlled denitrification within the MLE process instead of in the clarifiers. The MLE process also will enable the plant to meet potential future total nitrogen limits. The existing WWTP property is confined by railroad tracks, Beaver River, Ohio River, and Borough roads, creating significant challenges for construction. A detailed sequence of construction was developed, including construction of temporary facilities, to allow for the proposed plant to be constructed while the existing plant remains fully operational.
The project was bid as five contracts: WWTP General, WWTP Electrical, Lift Stations General, Lift Stations Electrical, and Force Mains. Construction notice-to-proceed was issued in February
2020 and work is currently underway. The contact time is two years.
The total project cost is $54,635,471, with $53,402,959 being fully funded by PENNVEST. The PENNVEST funding includes a $1,592,241 grant and a $51,810,718 loan at 1.0% for 30 years.