June 22, 2016
DNA of Anammox Bacteria used for Shortcut Nitrogen Removal
POSTED BYDaniel Hardin, P.E.
Anammox bacteria is the active “ingredient” for shortcut nitrogen removal or deammonification. The anaerobic ammonia oxidizing bacteria (“AnAOB” or “anammox”) convert ammonia directly to nitrogen gas, which is a shortcut method to traditional methods that require additional steps such as oxidizing ammonia to nitrite and nitrate (nitrification) followed by nitrate and nitrite reduction to nitrogen gas (denitrification). Because the deammonification depends on anaerobic conditions, there is a reduction in energy used for aeration demand. Additional savings are achieved through reductions in supplemental carbon sources needed (e.g., methanol or glycerin) and reductions in sludge production. Successful deammonification depends on conditions that favor the slow-growing anaerobic ammonia oxidizing bacteria to outperform and limit the growth of nitrite oxidizing bacteria.
Researchers have recently attempted to study the microorganisms to better understand exactly how anammox works. One of the first reactors to use anammox was installed in The Netherlands in 2006. The reactor has a great performance record and is an ideal place to study the physiology of bacteria responsible for the anammox reactions. New laboratory techniques such as genome-resolved metagenomics were used in the study. The study was published in the journal Nature Communications in April 2016. According to Daan Speth, a researcher from the department of microbiology at Radboud University (Njimegan, The Netherlands), “DNA sequencing chemistry and tools for analysis have greatly improved over the past years, to the extent that our study would have been nearly impossible a few years ago.”
A fraction of aerobic ammonia oxidizing bacteria was found to be present in places where the anammox bacteria was missing. If there is an ideal ratio of the two types of bacteria working in tandem, then there is potential to increase reactor performance. A mysterious genome was also uncovered during the study and was referred to as “microbial dark matter” because the organisms look like bacteria but are missing essential genes. One theory is that the “dark matter” organisms may be parasites – and although not abundant in the reactor – a better understanding of their role with the anammox bacteria may help improve performance. Researchers hope that the findings of the study will further advance wastewater nutrient removal technology as the deammonification process has become more widely known as an alternative to conventional biological nutrient removal techniques.
Water Environment and Technology (www.wef.org/magazine), May 2016, “What Every Operator Needs to Know about Shortcut Nitrogen Removal”, Adam Rogensues