Regional San Nitrifying Sidestream Treatment Project

Aerial of Regional San Wastewater Treatment Plant | Nitrifying Sidestream Treatment Project

Regional San Nitrifying Sidestream Treatment Project

Cost-Effective Solution for Reducing O&M Costs

The Sacramento Regional County Sanitation District, or Regional San, was required to upgrade its 181-million-gallon-per-day Sacramento Regional Wastewater Treatment Plant by 2021 to comply with a new permit that included nitrogen removal and California Title 22 filtration and disinfection. A new nitrifying sidestream treatment facility was included as one of many projects in Regional San’s EchoWater Program to reduce ammonia loads in the sidestream and thereby reduce effluent ammonia in the discharge. 

The nitrifying sidestream treatment facility is a cost-effective solution that drastically reduces plant operations and maintenance costs for a quick return on investment. Having a nitrifying sidestream treatment facility at the plant meant that the new biological nutrient removal facility could be designed smaller at a lower construction cost and carbon footprint, because the “loading rate” is much lower and peak ammonia loading events from sidestreams are avoided. Nitrifying sidestream treatment operations reduced the required aerobic capacity of biological nutrient removal by approximately 10%, resulting in savings of about $20 million on the biological nutrient removal project. 

Implementation of the nitrifying sidestream treatment facility allows nitrates produced in the facility to be sustainability applied to the influent, reducing the purchase of other inorganic nitrate chemicals, and significantly reducing the purchase of chlorine and the chemical Bioxoide®. The sustainable use of nutrients for odor control has reduced the sodium hypochlorite demand by about 8,500 gallons per day and is now saving Regional San about $2.4 million a year in chemical costs because the nitrifying sidestream treatment’s nitrate-rich effluent is successfully mitigating odors. This sustainable use reduces greenhouse gas emissions by reducing the trucking of chemicals into the Sacramento region, and eliminates the energy used by chemical manufacturers for producing the avoided liquid chlorine and nitrate chemicals. 

After all the projects at the Sacramento Regional Wastewater Treatment Plant are completed, the plant will be able to produce high-quality Title 22 water that can be used for water recycling. Using recycled water helps preserve our precious water supplies, especially during drought conditions.

Aerial of Regional San Wastewater Treatment Plant | Nitrifying Sidestream Treatment Project
Sacramento Regional County Sanitation District (Regional San)

Sacramento, CA
United States



Merit Award (2022)
Engineering Excellence Awards
American Council of Engineering Companies of California
Project of the Year (2021)
Environment, Over 200,000 Population Served, $10 to $50 Million Construction Value Category
American Public Works Association, Sacramento Chapter
Outstanding Water Award (2020)
American Society of Civil Engineers, Sacramento Section