title: Anammox Polishing in Mainstream Wastewater Treatment to Meet Stringent Ammonia and Total Nitrogen Limits
Creators: name: Holgate, Rebecca Mary
Publisher: name: Old Dominion University Libraries
Year: 2014

description: As nitrogen discharge limits are becoming more stringent there is a need for new processes that are sustainable and cost effective. Since anaerobic ammonia oxidizing bacteria (anammox) were discovered in the mid 1990s, there has been considerable success implementing anammox in many wastewater treatment plants to treat internally generated nitrogen rich waste streams (e.g. centrate). Recently, there has also been discussion of implementing anammox in mainstream wastewater treatment to exploit the benefits of autotrophic nitrogen removal.

A two stage A/B pilot study was conducted that included a high-rate activated sludge (HRAS) process followed by a two-stage de-ammonification process incorporating nitrite-shunt and a fully-anoxic anammox moving bed bioreactor (MBBR) polishing process. Anammox polishing is a novel concept that could prove to be highly effective to meet very low nitrogen limits. The cornerstone for anammox polishing is the ability of the nitrite-shunt B-stage to produce approximately equal parts of ammonia and nitrite.

Currently, attached growth de-ammonification processes are implemented mainly in concentrated side-stream treatment process. These processes incorporate both anammox and ammonia oxidizing bacteria (AOB) growing and working together in unison. Therefore, there is a lack of information in terms of kinetics for designing a fully anoxic, anammox-only process in mainstream applications with lower temperatures (approximately 12-30 °C) and concentrations.

The anammox polishing MBBR was in operation for almost one and a half years. High nitrogen removal rates were measured, with TIN removal rates ranging from 0.053 - 0.26 g TIN/m2/day, with the system being typically limited on influent nitrite concentrations. Throughout the entire study due to limiting nitrite conditions, effluent nitrite values remained less than 0.25 mg NO2--N /L, with the last phase of the study producing an average effluent of 0.09 mg NO2--N/L. Batch activity tests were conducted on a weekly basis to determine maximum anammox removal rates. A maximum TIN activity removal of 1.5 g TIN/m2/day was observed at 24°C.

Nitrite breakthrough performance was conducted to determine the maximum nitrite removal that could be sustained by the system. A maximum value of 15.4 mg NO2--N/L was fed to the system and an effluent of less than 1 mg NO2--N/L was measured in the effluent. Near the end of the data collection period, a limited amount of acetate {2.8 ± 1 mg/L COD) was fed to the reactor to reduce nitrate in the system to nitrite. This produced significant results that added to even more TIN removal in the system with an average ratio of COD added/TIN removed of 0.9 ± 0.4.

Overall, this thesis presents the kinetics and operational limitations of anammox in a mainstream MBBR. As plants are shifting focus and implementing NOB suppression throughout their process, there is the need to remove the residual ammonia that remains in the system for effective NOB suppression. The use of an anammox MBBR as a polishing process can assist plants in cost-effectively meeting their future more strict permit limits, such as an ammonia limit or a total nitrogen limit.