Wastewater Treatment Process
Hall Creek Wastewater Treatment Plant
The Hall Creek Wastewater Treatment Plant (formerly called Emory-Meadowview) is located adjacent to Highlands Business Park and Hall Creek near Glade Spring.
The plant began operating in 1996 and provides sanitary sewer service to the Washington County communities of Emory, Meadowview and Glade Spring, as well as the Washington County Industrial Park (Exit 22), Highlands Business Park and Emory & Henry College. The plant’s collection system consists of gravity and force main lines, along with 11 pump stations.
The plant is authorized to discharge under the Virginia Pollution Discharge Elimination System (VPDES) and the Virginia State Water Control Board. It is permitted by the Virginia Department of Environmental Quality to discharge to Hall Creek, which is part of the Middle Fork Holston River watershed. Originally designed to treat an average flow of 315,000 gallons per day (gpd), the plant was upgraded in 2000 and can now treat 630,000 gpd.
Wastewater enters the plant through a single 12-inch pipe. It travels through a channel equipped with a mechanical screen that filters out large items. Wastewater then travels through an open channel grinder pump to reduce the size of the material that passed through the mechanical screen. Wastewater is then pumped into a manhole, where it travels by gravity through a grit removal channel to remove additional debris from the waste stream. If needed, the wastewater can bypass the grit removal channel.
The wastewater then travels to the oxidation ditch, which serves as the primary treatment for the wastewater and consists of three oval basins with a total capacity of approximately 526,000 gallons. Wastewater flows into the three basins, where air is added to provide oxygen, mixing and movement within the basins, which allows microorganisms to treat the wastewater stream.
From the oxidation ditch, the waste stream travels to two secondary clarifiers. These large, concrete, open-top tanks allow additional time for debris that remains in the waste stream to settle out. Aerobic digestion is used to stabilize the secondary waste from the secondary clarifiers. The waste stream is then disinfected with chlorine and travels to holding tanks, where it is held to allow for adequate disinfection time. Once it is ready to be discharged into Hall Creek, the waste stream is dechlorinated using sulfur dioxide.
Sludge from the treatment plant is sent to the solids dewatering process through a belt press. Here, sludge is pressed to remove water. The sludge is then removed by truck for offsite disposal at an approved location.
Obtaining a satisfactory final effluent, prior to the stream discharge, depends to a large extent on developing and maintaining a healthy biological bio-mass in the activated sludge process. It is imperative that plant operators employ continuous monitoring, laboratory testing and evaluation of the operational parameters for the activated sludge process. VPDES requires that the wastewater treatment plant be staffed 8 hours/day, 7 days/week and 365 days/year. Licensed operator requirements are Class II Wastewater Operator.
If the WCSA receives waste that is not designed for the plant and its microorganisms, it can reduce the effectiveness of treatment or, even worse, kill all of the bugs and result in regulatory violations. It is for this and other reasons that we maintain a Sewer Use Ordinance and Sewer Use Rules and Regulations.
Damascus Wastewater Treatment Plant
The Damascus Wastewater Treatment Plant provides sanitary sewer service to the Damascus area of Washington County.
The treatment plant has a capacity of 250,000 gpd. The plant uses an extended aeration activated sludge treatment process to treat the wastewater. Currently, the entire wastewater system is gravity flow, meaning there is no pump station within the system. Wastewater enters the plant and travels through a channel equipped with a mechanical screen that filters out large items of debris. Wastewater then travels through an aerated grit removal channel to remove additional debris from the stream.
The wastewater then travels to parallel activated sludge reactors. The activated sludge reactors serve as the primary treatment for the wastewater and consist of parallel concrete tanks, each divided into two compartments. Wastewater flows into the concrete tanks, where air is added to provide oxygen, mixing and movement within the basins, which allows the microorganisms to treat the wastewater stream.
From the activated sludge reactors, the wastewater stream travels to two secondary clarifiers, each with a capacity of 47,451 gallons. These clarifiers are large, concrete, rectangular, open-top tanks that allow additional time for the remaining sludge in the stream to settle out. The wastewater stream is then disinfected with chlorine and travels to a holding tank, where it is held to allow for adequate disinfection time. Once all treatment is complete, it is ready for dechlorination and discharged into the South Fork of the Holston River.