$500 Investment Helps Elk County Community Improve Water Quality, Save Money

A $500 investment recommended by the Department of Environmental Protection wastewater outreach technical assistance staff will save an Elk County community approximately $30,000 a year in energy and chemical costs at its wastewater treatment plant while improving water quality by reducing the total nitrogen discharged from the facility.

Staff from DEP's wastewater outreach technical assistance program held regular meetings with the staff of the Borough of Ridgway’s wastewater treatment plant. Ridgeway already was working to reduce energy costs by addressing lighting, HVAC and other projects. A review of their process and loadings showed that the process was a three-ring (in series) oxidation ditch system and the facility had relatively high concentrations of ammonia nitrogen to remove. Average daily flow for this system is approximately 0.9 MGD.

The process of nitrification (converting ammonia nitrogen into nitrate nitrogen) consumes large amounts of oxygen and alkalinity. The nitrification process can double energy costs for many treatment plants. DEP suggested that Ridgway consider denitrification to reduce energy and chemical usage.

The process of denitrification provides energy savings through the beneficial uptake of nitrate, in fact savings can amount to 60 percent of the energy required for nitrification. The process of denitrification also releases alkalinity and can reduce supplemental alkalinity addition by up to 50 percent.

In order to achieve denitrification, the facility would have to set up an anoxic zone. It was decided to use the outer ditch as the anoxic zone and the inner two ditches as aerobic zones. This was accomplished by changing shims (about a $500 investment) on mixing rotors and adjusting return activated sludge rates.

The combined energy and chemical savings amounted to more than $30,000 per year. That is a 6,000 percent return on investment. Additionally, the quality of the effluent discharged from the facility improved by reducing total nitrogen discharged. It is estimated that the facility has removed 68,000 of total nitrogen per year through this process.

For more information, visit DEP’s Water and Wastewater Outreach Assistance Program webpage.