Enhancing WWTPs

Maryland’s Bay Restoration Fund will generate nearly $1 billion over the next six years, enabling the State to implement enhanced nutrient removal processes at major wastewater treatment plants, such as Mattawoman in Charles County.

Nitrogen pollution is one of the most serious threats to the health of the Chesapeake Bay, fueling algae growth, clouding water, depleting oxygen levels, and creating “dead zones” for fish, blue crabs, oysters, and other marine life. With discharges from wastewater treatment plants (WWTPs) accounting for as much as 20% of the nutrient pollution reaching the Bay, Maryland is investing in biological or enhanced nutrient removal (BNR/ENR) programs at large sewage processing facilities.

The Maryland Department of the Environment (MDE) has estimated that upgrading 66 of the State’s 272 WWTPs would reduce the level of nitrogen loading from all plants by 95%. By eliminating 7.5 million pounds of all the nitrogen reaching the Bay each year, Maryland moves one-third of the way closer to meeting nitrogen level goals outlined in the multistate Chesapeake 2000 Agreement. The 2004 Bay Restoration Fund will provide more than $1 billion in funding over the next six years to upgrade WWTPs, septic systems, and sewage holding tanks while also providing money for farmers to implement nutrient management plans. MDE will allocate grants for upgrading wastewater facilities to meet ENR goals on a priority basis, initially targeting those facilities with capacities greater than 500,000 gallons per day.

Mattawoman WWTP—In Charles County, MD, KCI Technologies has been providing process, mechanical, electrical, structural, and geotechnical designs for ENR upgrades at the Mattawoman WWTP, the largest Maryland facility discharging effluent into the Potomac River. When the project is completed, Mattawoman will be one of the first wastewater treatment facilities in the State to meet the new ENR discharge goals of 3 mg/L total nitrogen and 0.3mg/L total phosphorus.

“KCI has been working at Mattawoman for nearly 20 years, so we really understand the facility,” explained KCI Project Manager Priyali Sen, PE. “We designed the plant’s Phase I expansion in the early 1980s and have worked on all of the major upgrades since then. Now, we’re partnering with GMB in a joint venture to further enhance the plant’s nutrient removal processes and overall capacity.”

By January 2003, the project team had completed the BNR upgrade design for the 15 million-gallon-per-day (MGD) facility, when the Charles County Department of Public Works negotiated with MDE to expand the plant’s capacity to 20 MGD and to incorporate ENR systems into the final design. “The County wanted to accomplish the upgrade without adding significant cost, so we looked at creative ways to increase the efficiency of the aeration basins to treat wastewater,” said Sen. In considering preliminary design alternatives, the project team selected a process that reduced the plant’s required aeration capacity.

In the final design, engineers developed plans for converting the existing activated sludge process to a four-stage system using oxidation ditch technology with chemical phosphorus removal, while adding a fifth process train to achieve a 20 MGD operating capacity. The project team also designed a new 130-foot-diameter primary clarifier, two 100- foot-diameter secondary clarifiers, a gravity sludge thickener, an aeration system for the sludge holding tanks, a septage receiving
station, an ultraviolet disinfection process, and a plant automation system. In addition, the team delivered rehabilitation plans for two existing clarifiers, the belt thickeners, and the effluent sand filters.

KCI also prepared a life-cycle cost analysis and developed operational alternatives for digestion options in the plant’s sludge processing facilities. Engineers added thickening equipment to address odor and septic concerns, while maintaining the existing lime stabilization process. Currently, the project team is providing construction phase engineering and inspection services.

“We were able to help the County reach its operational and environmental performance goals,” said Sen, “and deliver systems that are reliable, cost-effective, and operator-friendly.”

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