Weston performed an alternative analysis for the Delaware County Regional Water Quality Control Authority (DELCORA) to determine the best approach to managing the Rose Valley borough wastewater system. The purpose of the analysis was to determine the most cost-effective solution to address upcoming, more stringent National Pollutant Discharge Elimination System effluent limits for phosphorous and other nutrient limits. Several alternatives were considered, including upgrades to the existing wastewater treatment plant and plant decommissioning and pumping the wastewater off site for treatment.
We evaluated the treatment technologies extended aeration process and membrane bioreactor. Unit processes for each technology were sized based on evaluation of plant flow records for the past 5 years and establishing peaking factor from collection system meters. Weston reviewed the influent loading data, such as 5-day biological oxygen demand (BOD5), chemical oxygen demand (COD), Total Suspended Solids (TSS), total Kjeldahl nitrogen (TKN), and tailings pile (TP) and established future effluent limit criteria to size and select unit process and equipment. Each technology included headworks with grit separation, UV disinfection, and chemical precipitation to meet phosphorus limits.
The plant decommissioning alternatives included siting new pump station(s) and force main routing. This alternative required an understanding of the sewersheds within the Rose Valley system and where they discharge. Weston prepared sewershed mapping of the system, and based on the mapping we were able to establish two viable options. Each option involved sending the wastewater to DELCORA’s Western Regional Treatment Plant (WRTP) for treatment. Pump station capacity, type, location(s), constructability, and utilities were considered for the evaluation as well as force main routing and construction methods. The alternative recommended and ultimately selected was decommissioning the existing Rose Valley wastewater treatment plant. Further, we would construct a new pump station on the site and pump the wastewater to Middletown Township Sewer Authority, which ultimately is pumped to DELCORA’s WRTP. This alternative had several benefits both for DELCORA and the residents of Rose Valley. The solution had the lowest cost and shortest schedule as compared to the other options. Access to the treatment plant was through a residential neighborhood; therefore, this alternative eliminated the vehicular traffic to the plant. The installation of the new force main will use trenchless technology for minimal disruptions to the nearby residents. Lastly, this alternative eliminated a wastewater treatment plant, which provides for a cleaner and safer environment.