Project #4884

Estimating the Comammox Contribution to Ammonia Oxidation in Nitrogen Removal Systems

Principal Investigator
Research Manager
Ms. Stephanie Fevig, PE
Northeastern University
Biological Nutrient Removal


Unlike the two-organism nitrification that is the basis for nearly all nitrogen removal processes, complete ammonia oxidizing (i.e., comammox) bacteria alone can completely convert ammonia to nitrate. This has implications for shortcut nitrogen removal processes that rely on limiting the oxidation of ammonia to nitrite. Thus, understanding and managing comammox bacterial activity may be critical to ensure that the energy and resource-saving benefits of shortcut nitrogen removal processes are realized. This project aids the understanding of the prevalence of comammox bacteria across mainstream and sidestream nitrogen removal systems, and quantifies the effects of process and environmental variables on their abundance. This project identifies nitrogen removal process configurations that are particularly vulnerable to comammox proliferation and what strategies may be deployed to effectively manage them. In the long-term, an accurate and clear understanding of nitrogen biotransformation in wastewater treatment systems is critical toward realizing sustainable and cost-effective nitrogen removal. Published in 2021.

 Originally funded as WERF project U4R16.