History of Sweeney Water Treatment Plant

Sweeney Water Treatment Plant: A History of Improving Water Quality


1943: Sweeney Water Treatment Plant, named after John H. Sweeney Sr., Chief Engineer for the City of Wilmington, is put into service. With two pumps and seven filters, the plant is capable of producing 7 million gallons of water per day (MGD). Treatment at the plant consists of dry alum for flocculation and sedimentation, filtration through sand filters, chlorination and treatment with lime. Ammonia also is used to raise chlorine residual, and carbon was added to improve taste and reduce odors.

1958: More filtering units and basins are added, bringing the total capacity to 12 MGD.

S Plant Basins
Control Panel

1982: The plant, equipped with a 1250 horsepower motor, is capable of producing 15 MGD. Upgrades to the electrical system include two General Electric switch gears and a 12-million-gallon pump at the Kings Bluff Pump Station. A gas chromatograph and an atomic absorption spectrophotometer improve testing. The new instruments also are be used to conduct research on the effectiveness of new chemicals in purifying river water.

1998: A project begun in 1995 reaches completion and includes a state-of-the-art facility with increased treatment capacity of 25 MGD. It also introduces the use of ozone as a primary means of disinfection, making Sweeney Water Treatment Plant one of only 250 in the nation to use this method. 

Ozone facility at Sweeney Water Treatment Plant.

2012: A $68 million expansion and upgrade project incorporates the latest, most innovative water treatment technologies and increases total plant capacity to 35 MGD. The new facility includes a newly constructed administration and maintenance building, a UV treatment facility, an upgraded residuals system, five new filters, two new Super Pulsator treatment trains, and a new finished-water high-service pump station.

SWTP 2012

2015: Clear well rehabilitation and installation of aerators help reduce disinfection byproducts.

2017: CFPUA works with Black & Veatch, a world-class engineering firm, to conduct pilot studies evaluating options to filter PFAS. The study examines three technologies: granular activated carbon (GAC), ion exchange, and reverse osmosis. GAC emerges as the best long-term solution for CFPUA and its customers, offering reduction of a broad range of PFAS and other compounds, flexibility, and cost-effectiveness.

GAC Ben Kearns Slide 15

2018: Work begins on design of eight new deep-bed GAC filters.

Filter Media

October-December 2018: CFPUA begins the first phase of an interim step to replace GAC in seven of 14 existing filters as a short-term measure to reduce PFAS. Media in the remaining seven are replaced the following spring This phased replacement will continue until the new deep-bed filters become operational in 2022.

September 11, 2019: CFPUA Board approves $35.9 million contract to build eight new deep-bed GAC filters at Sweeney.

October 2022: GAC filters at Sweeney come online. Water sampling shows that PFAS have been reduced to at or near non-detectable levels in treated drinking water.