Mosier WWTP Update

PROBLEM: The City of Mosier’s Wastewater Treatment Plant (WWTP) currently utilizes a damaged outfall pipe that sends secondary treatment water directly to the Columbia River in a shallow, kiteboarding, swimming and windsurfing recreation area. The State may require the City to replace the outfall in the future to meet new more stringent regulatory standards. In addition, it is increasingly difficult and expensive to find appropriate disposal sites for WWTP biosolids as required by the State for nutrient management and reuse. The treatment plant currently cannot remove nutrients such as phosphorous and nitrogen. Nutrient treatment is expected to be required by regulation in the near future.

SOLUTION: New Tertiary Treatment Outfall and WWTP Treatment Improvements – In 2020, the City developed a WWTP Facilities Plan Update. This Plan includes the following objectives: • Reduction of nutrient pollution through innovative treatment • Elimination of substandard and hazardous outfall pipe with a tertiary wetland treatment system. • Reduction of the plant’s carbon footprint by installing energy efficient equipment. • Replacement of aging and outdated equipment • Reduction of solids produced at the treatment plant to eliminate tanker transportation needs and the cost to land apply biosolids