Partial Denitrification Anammox (PdNA) Demonstration in a Tertiary Biological Aerated Filtration Pilot

Presentation Description: Partial denitrification anammox (PdNA) presents a useful tool in addressing stringent nutrient limits, spatial constraints, and budgetary issues through its decreased carbon and energy requirements and potential for intensification. Thus, a $4 million U.S. Department of Energy (DOE) PdNA study was designed to help further understanding and acceptance of PdNA through implementation at six water resource recovery facilities (WRRFs) nationwide. This project tests various parameters including media types, carbon sources, and utilities with different treatment trains and nutrient loading conditions. Hydraulic conditions including head loss, mixing requirements, and fill ratios are also being evaluated to lessen the impacts of retrofitting and/or new construction of PdNA processes and increase interest in adoption of this technology.

Over the last year, this project has been established across five installations in various PdNA configurations. Secondary PdNA processes are currently being tested at DC Water, HRSD, and Prince William Water. A tertiary pilot, at the Linda County WRRF in California, was initiated in May 2025 with plans to continue through March 2026. This is a 1 gpm tertiary PdNA pilot process in a biological aerated filter (BAF) using secondary effluent supplemented with additional ammonia (at a ratio of 0.5 ammonia to nitrate). Two testing periods are planned, one with glycerol as a carbon source and the other with methanol, with ideal carbon to nitrogen ratio for operation. An average of approximately 80% ammonia removal rate has been observed following the initial startup period, and it is expected to increase as operation stabilizes. Maximum anammox activity testing will be conducted to understand anammox rates in the BAF process.

PdNA implementation is a potential solution for California utilities seeking to increase capacity or are considering implementing water reuse. PdNA can be retrofitted into existing facilities without significant construction, allowing capacity increases, and tertiary PdNA in a BAF offers a solution for achieving effluent total inorganic nitrogen and total suspended solids limits with minimal upstream infrastructure modifications.

PdNA represents a cost-effective method for expanding capacity, reducing operation and maintenance costs, and transitioning to water reuse, making it a valuable solution for California utilities.