March 2007, Vol. 19, No.3
East Coast Treatment Plant Helps Improve Chesapeake Bay Water Quality
Problem: Increasing population challenges plant to meet effluent discharge limits.
Solution: Increase plant capacity with space-saving design that allows for nutrient removal process.
The ski resort community of Massanutten is located at the headwaters of Quail Run in Rockingham County, Va. In 1998, Quail Run, a tributary in the Chesapeake Bay watershed, appeared on the state’s Clean Water Act Sec. 303(d) list for violating the general standard for aquatic life designated use. The Sec. 303(d) designation is given to waterbodies and pollutants needing total maximum daily loads (TMDLs).
A stressor analysis in a TMDL study in 2003 submitted by the Virginia Department of Environmental Quality identified effluent from the Massanutten Sewage Treatment Plant (STP) as the primary contributor of ammonia and residual chlorine into Quail Run. The area’s steadily increasing population, especially during high tourist season, had strained the plant’s ability to comply with effluent discharge limits, given its antiquated lagoon treatment process.
By the time the TMDL study was complete, the Massanutten STP was already building a new treatment facility designed for biological nutrient removal. In 2001, a private utilities company that owns and operates the Massanutten Public Service Corp. STP entered into a contract with Siemens Water Technologies (Warrendale, Pa.) to provide and construct the majority of this new facility.
Two problems were presented to the designers of the upgrade. The new facility had to treat to a higher effluent quality, especially with the drastic seasonal fluctuations. It also had to incorporate all treatment equipment within the site’s tight land allowance.
The commissioning and initial startup of two field-erected circular steel treatment plants was completed in early 2003. The two mirror-image plants, operating in parallel, increased the treatment capacity to 5678 m3/d (1.5 mgd). A 5-stage biological nutrient removal process achieves biochemical oxygen demand (BOD) reduction, nitrification, denitrification, and biological phosphorus removal.
The new field-erected plants’ innovative process hydraulic configuration enabled them to fit this complex enhanced nutrient removal process into the restrictively small and mountainous site. This space-saving design incorporates the anaerobic, anoxic, aeration, post-anoxic, reaeration, and clarification zones into a single tank, making the most of the available land.
The new facility also includes two deep-bed filters followed by a Gravisand® XCELL traveling bridge filter and an ultraviolet-light disinfection system.
The Massanutten facility has reduced the ammonia drastically and eliminated the residual chlorine discharged into Quail Run which, in turn, has significantly improved water quality. However, the State of Virginia has yet to enforce the total nitrogen and total phosphorus standards of the facility’s effluent discharge permit. These stricter nutrient standards are expected to be in place during the next few years. Massanutten STP can easily optimize the biological process operation to achieve effluent discharge levels of 5 mg/L BOD, 5 mg/L total suspended solids, 3 mg/L total nitrogen, and 1 mg/L total phosphorus, once the new effluent standards are in place.
As a proactive measure, the Massanutten STP is conducting a pilot study to further reduce total nitrogen in its effluent discharge. The deep-bed filters, which are currently operated simply as a tertiary solids removal process, will be converted to NxClear™ denitrification filters. This modification is part of the Massanutten STP’s commitment to achieve the goals outlined in the Chesapeake Bay Initiative to improve the water quality and quality of life in its community.
For more information on Siemens Water Technologies, send e-mail to firstname.lastname@example.org, or see www.enrsolutions.usfilter.com.