March 2007, Vol. 19, No.3

Plant Profile

Milford, Del.


Kent County Regional Wastewater Treatment Facility Location: Milford, Del.
Startup date: Oct. 6, 1973
Service population: 125,000
Number of employees: 45
Design flow: 16.3 mgd (61,700 m3/d)
Average flow: 10.5 mgd (39,700 m3/d)
Annual operating cost: $8.5 million

The Kent County Regional Wastewater Treatment Facility is an award-winning, trend-setting treatment facility located in Milford, Del. In addition to providing secondary treatment with nutrient removal for its 125,000 customers, the facility is also
one of two publicly owned wastewater treatment plants currently in the U.S. Environmental Protection Agency’s National Performance Track program. The program is a partnership that recognizes top environmental performance among participating U.S. facilities of all types, sizes, and complexity, public and private.

Additionally, the facility’s environmental, health, and safety management system is certified to the Occupational Health Safety Assessment System (Macclesfield, Cheshire, England) 18001 program, an international occupational health and safety management system specification. The facility also is certified to the International Organization of Standardization (Geneva, Switzerland) 14001 standard and the National Biosolids Partnership (Alexandria, Va.) environmental management system programs. It is currently the only wastewater facility in the country certified to all three systems. The goals of the program are to reduce the environmental footprint of facility operations and improve employee health and safety.

Kent County Regional Wastewater reatment Facility (Milford, Del.) staff hold the National Biosolids Partnership’s (NBP; Alexandria, Va.) banner showing the facility is NBP-certified. Pictured are Michael Berry, Keith Powell, Karen Lewis, William Pennell, Patrick McPhail, Keith Schwamberger, Allen Kearn, Reinhold Betschel, Sherry Barker, and Jack Schulties. (Photo by James Newton) About 25% of the facility’s flow comes from local industries, but this percentage is declining due to a county water conservation program and some industries closing. Residences are the primary source of influent, with commercial operations also contributing some flow. A unique aspect of the facility is that the collection systems in Dover, Smyrna,
Milford, and Camden–Wyoming are controlled by their respective municipalities, and the municipalities pay per-gallon treatment fees to the treatment facility.

The wastewater treatment system includes influent screening and grit removal. The wastewater is then treated in two 10-million-gal (38-million-L) activated sludge extended aeration basins utilizing the Parkson Biolac® biological nitrogen reduction system operating in the Wave-Ox© mode. The plant hosts visitors from around the world to showcase the Parkson system. Four clarifiers enable solids to settle from the water. After settling, chlorine disinfects the water, and sulfur dioxide removes excess chlorine. The effluent is discharged through a man-made ditch to a tributary of the Murderkill River.

Solids removed from the clarifiers are stored in two large concrete tanks before being treated. Treatment consists of belt filter pressing followed by lime addition for stabilization. A series of thermal dryers dries the material to 60% solids. The Class A material is stored under cover, and then land-applied as Kentorganite on several county-owned farms and many large and small private farms located throughout the state.

Kentorganite is a highly prized soil amender to adjust soil pH. Nutrients are considered a minor component of the material. About half of the Kentorganite is transported by county-owned vehicles to local farms and applied by county personnel for a nominal fee. There is no charge for the Kentorganite if residents and local farmers pick up the material at the facility. There is currently a greater demand than supply for Kentorganite.

The facility is under expansion. Two new grit chambers are being added, as well as chemical storage and feed facilities for nutrient reduction in the aeration basins. Two existing concrete tanks also are being modified to act as aerobic digesters for the treatment of grease-trap waste.

Moreover, in 2010, the facility is planning to expand its aeration basin capacity by 50%, as well as add a clarifier, a microfiltration system, and an innovative disinfection system. In addition, the facility is working with a local energy company to install a renewable energy park at the facility that will combine wind, solar, biomass, and hydroelectric generating units. The energy park is intended to make the facility nearly energy self-sufficient and reduce air pollution.