Wet Weather Improvements

In 2007, the Western Virginia Water Authority completed work to upgrade the Regional Water Pollution Control Plant and 900 miles of sewer main to the benefit of the community and the environment. These improvements represented a $50M investment by the community to protect the Roanoke River.

The primary goal of this project was to greatly reduce the possibility of sewer collection system overflows. Although the plant is designed to treat only sanitary sewer, rain water can infiltrate the collection system during wet weather events and dramatically increase the volume of flow that enters the facility. With these improvements, the permitted daily treatment capacity increased from 42-million gallons of wastewater per day to 55-million gallons per day and the facility’s wet weather treatment capacity doubled.

The improvements were put to the test in November and December 2009 as both month’s average flows exceeded the highest monthly averages ever recorded at the plant; however, treatment removal met permit conditions with 99.9% removal of biochemical oxygen demand (BOD) and above 97% for all other parameters. A peak daily flow of 146 mgd was recorded in May 2017.

The project improved the treatment process, enhanced safety and reliability and renovated aging pipes and equipment in the plant and throughout the distribution system.

Peak Flow Enhancement Project

In February 2013, construction began on the Peak Flow Enhancements Project at the Regional Water Pollution Control Plant.  Completed in the Fall of 2015, the project involved construction of a new chlorine contact basin, new effluent screw pumps and modifications to the Biological Aerated Filter (BAF). Haren Construction Company of Etowah, TN performed the work on this $16M project.

After the improvements made as part of the 2007 Wet Weather Improvements, the focus shifted on moving more treated water out of the plant. As the receiving river would rise during flood events, pushing the treated water into the river became increasingly difficult and river water would make its way into the plant. Four Archimedes screw pumps, each with 40mgd capacity, were installed at the effluent pump station to lift the treated water into the river during high flow events.

The Biological Aerated Filter (BAF) capacity and treatment efficiencies are also being improved as part of this project. Flow from the facility’s existing equalization basin will enter the BAF and allow for operation of the unit as a single or two stage treatment process. Additional mechanical and equipment modifications to the existing process will also be considered to improve operations and reliability of the unit. By utilizing the BAF during peak flow events, an additional 12 million gallons of flow per day will be able to be treated at the Regional Water Pollution Control Plant.

Digester Improvements and Biogas to Renewable Natural Gas

During FY22 and 23, five of the seven digesters were rehabilitated.  New digester roofs were constructed, structural repairs were made inside the digesters, and new mixing equipment was installed.  These improvements will allow the plant's permitted capacity to increase to 62mgd.

The second phase of the digester improvement project involves a cooperative agreement with Roanoke Natural Gas to produce commercial quality renewable natural gas, or RNG. Roanoke Gas constructed a gas conditioning system and interconnect facility to allow clean biogas to be injected into the Roanoke Gas pipeline.  Biogas, also known as digester gas in wastewater treatment, is a mixture of methane (63%) and carbon dioxide (37%) that is produced as a by-product of the anaerobic digestion treatment process as bacteria consume the organic solids that are removed earlier in the wastewater treatment process. 

Utilizing an advanced membrane separation system, raw digester gas is refined to commercial quality natural gas for use within the greater Roanoke community, creating the potential for the protection of the environment and complete recycling of waste at a level only imagined a decade ago.  This cooperative project is an example of another area for energy recovery beginning to be realized within the wastewater treatment industry and will have far reaching benefits within our community and beyond. This new supply source will provide enough natural gas to heat 500 homes on a cold, winter day.  

Learn more about the Biogas to Renewable Natural Gas Project