Large processing room with a series of inclined steel plates.

Yardley Water Treatment Plant Upgrades

Our Client’s Challenge

The Yardley Water Treatment Plant (WTP), a half-century-old facility located in Yardley Borough, is owned by Pennsylvania American Water, a subsidiary of the largest investor-owned water utility in the state.

Serving more than 13,000 homes and businesses, portions of the WTP were outdated and well past their useful life. As part of a robust $400 million capital improvement program, Pennsylvania American Water reserved $22.6 million to implement significant upgrades to multiple treatment processes at its Yardley facility.

Adding these new, state-of-the-art water treatment processes enabled the client to meet the U.S. Department of Environmental Protection’s (DEP) Long-Term 2 (LT2) Enhanced Surface Water Treatment Rule and improve drinking water quality and safety as well as reliability of water service for customers in Yardley, Lower Makefield, and Falls Township.

Our Solution

To reduce viruses and bacteria that could be present in surface water sources, Pennsylvania American Water engaged Gannett Fleming to design a new ultraviolet (UV) disinfection system at the Yardley WTP. Pre-treatment improvements included a sodium permanganate feed system at the raw water pump station and a new carbon feed building at the WTP to improve the quality of raw water entering the WTP.

Gannett Fleming also implemented a new pre-treatment process building that includes a carbon contact basin, flocculation tanks, and plate settler sedimentation tanks to replace an aged lamella clarifier system.

Designers also included a new addition to the WTP building to house the new UV disinfection system and two new chemical systems. Improving worker safety, sodium hypochlorite and liquid ammonium sulfate chemical systems replaced the existing chlorine gas systems, and all emergency safety showers were upgraded to circulate tempered water per OSHA regulations.

Pennsylvania American Water incorporated several residuals handling improvements, which included replacing the sludge collection system within the existing wastewater basins, adding a new thickener tank to improve solids removal, and replacing the pump associated with the facility’s sludge collection and recycling systems.

To support these new upgrades, the design team modified the existing main distribution switchboard and installed a new sub-distribution panel (SDP). Redundant ‘A’ and ‘B’ feeds connect the main distribution switchboard and SDP to downstream distribution and process equipment, including motor control centers in the new pre-treatment building, allowing system maintenance while retaining plant operations.

Analysis of existing load data indicated that the current service capacity is sufficient. However, the existing standby emergency generator was deemed inadequate and replaced with a more powerful unit to ensure continued plant operation during a utility power outage.

Key Features

  • New UV disinfection system.
  • Sodium hypochlorite and liquid ammonia systems replaced existing gas systems.
  • New sodium permanganate feed system at the raw water pump station.
  • New collection system and thickener tank to improve sludge removal.
  • New pre-treatment building to replace existing sedimentation system.


  • UV disinfection strengthens protection against pathogens and microorganisms in the source supply.
  • Sodium hypochlorite and liquid ammonia sulfate provide a safer work environment for employees.
  • Pre-treatment upgrades enhance water quality by removing more solids, thus improving water treatment.
  • Improving sludge collection improves recycled water quality and reduces sludge hauling costs.
  • Facility is fully compliant with LT2 requirements.


Pennsylvania American Water


Yardley, Pa.



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