January 2008, Vol. 20, No.1

Problem Solvers

Enhanced Nutrient Removal Achieved

Problem: Difficulty in meeting consistent BOD removal; need to increase capacity.
Solution: Compact reactor process system.

The city of Fruitland, centrally located on Maryland’s lower Eastern Shore, needed to expand the capacity of its wastewater treatment plant while upgrading its level of treatment to include enhanced nutrient removal. The existing wastewater treatment facility utilized a high-rate, single-stage trickling filter preceded by primary sedimentation and anaerobic digestion of raw and secondary settling-tank solids.

The facility needed to increase capacity from 1893 m³/d (0.5 mgd) to 3785 m³/d (1.0 mgd) because of population growth in the city and surrounding counties while at the same time protecting the Chesapeake Bay Watershed. Treated effluent from the plant is discharged directly into the Wicomico River, approximately 1.6 km (1 mi) from the facility.

The facility also experienced difficulty in meeting consistent biochemical oxygen demand (BOD) removal required by the 30–30 BOD–TSS (total suspended solids) National Pollutant Discharge Elimination System permit. Effluent quality also interfered with the chlorine disinfection process.

The Chesapeake Bay Initiative requires that nitrogen and phosphorus levels be controlled to protect the resources and quality of life in the Chesapeake Bay area. The City of Fruitland entered into an agreement with the Maryland Department of the Environment to install a new facility that complies with reducing nitrogen levels to 8 mg/L and phosphorus levels to 2 mg/L on a monthly basis.

To remedy these problems, the city chose the OMNIFLO® sequencing batch reactor process from Siemens Water Technologies (Warrendale, Pa.) because of its compact footprint and ability to achieve enhanced nutrient removal within a two-tank layout. The system is a fill-and-draw, nonsteady-state activated sludge treatment process in which one or more reactor basins are filled with wastewater during a discrete time period and then operated in batch treatment mode. The reactor process accomplishes equalization, aeration, and clarification in a timed sequence in a single reactor basin.

The system installed for Fruitland includes the VARI-CANT® jet-aeration system from Siemens, as well as a monitoring and control system that has a modem interconnection to allow remote access, observation, and troubleshooting. The plant also has installed a traveling bridge filter and an ultraviolet disinfection system to improve operation and produce higher-quality effluent.

The system went on-line in December 2002. Since that time, the process system has been successful in meeting nitrogen levels less than 3.5 mg/L and phosphorus levels less than 1 mg/L. The average consistently exceeds the wastewater treatment design levels of 8 mg/L for nitrogen and 2 mg/L for phosphorus on a monthly basis. The plant operators have been able to control the process from many different parameters, optimizing the success of the plant.

The Fruitland facility received the Environmental Excellence Award from the Salisbury Area Chamber of Commerce in 2004, earned first place in the Clearest Wastewater Finale Effluent Competition from the Maryland Rural Water Association (Woodbine) in 2003 and won the association’s Wastewater System of the Year Award in 2004.

Two of the operators also have received the Wastewater Operator of the Year Award from the Maryland Rural Water Association in 2004 and 2006. George, Miles & Buhr LLC (Salisbury, Md.) provided process, civil, architectural, and structural design of the plant. The firm also coordinated geotechnical testing, wetlands, erosion and sediment control, stormwater management, and forest conservation permitting. Gipe Associates (Easton, Md.) provided the electrical and mechanical design. 

For more information, contact Kevin Bunting, eastern region technical sales manager in the Edwardsville, Kan., office of Siemens Water Technologies (Warrendale, Pa.) at  (913) 422-7600  or kevin.bunting@siemens.com . Contact George Calloway, superintendent of the Fruitland plant, at  (410) 548-2806  .