Wastewater Treatment Plant

The wastewater treatment plant is considered tertiary in nature. The district uses spray irrigation during the summer and stream discharge to the South Yuba River during the winter, when storm flows are high enough that there are appropriate levels of discharge dilution. The treatment plant generally consists of the following processes:

1. Wastewater is directed to a flow equalization tank, which provides constant flow through the plant, wastewater collection during peak flow periods, and metering to keep the plant at appropriate flow levels.
2. Wastewater goes through a pre-treatment comminutor, or grinder system, which makes the water and solids consistent.
3. The wastewater is distributed through two packaged sewer treatment plants at 0.22 and 0.30 million gallons per day (mgd). The treatment process uses an activated sludge processor, secondary clarification, gravity filtration, and aerobic digestion.
4. Wastewater goes through a chemical treatment process including chlorination and dechlorination, as well as other chemical treatment to render the liquid effluent to acceptable discharge standards.
5. Solids are directed to a sludge storage tank during the winter months and are dried in sludge beds during the summer months. Sludge is then transported to the landfill in Lockwood, Nevada.

The treatment plant operates under a waste discharge permit from Central Valley Regional Water Quality Control Board, allowing a monthly average of 0.52 mgd. A tank provides storage for peak flows and meters effluent pumped to spray irrigation areas during summer months. The actual flows to the plant have ranged between 0.05 mgd during the lowest point, up to a maximum of nearly 1.0 mgd during peak weekend visitor periods. The treatment plant is meeting its waste discharge quality requirements, based on daily, weekly and monthly averages.