Anammox for Sidestream Treatment of Wastewater Effluent

Pepper, I.3, Field, J.,1 Sierra, R.,1 Prevatt, J.,2 Foster, A., and 3 Ikner, L.,31University of Arizona, Department of Chemical & Environmental Engineering, 2 Pima County Regional Wastewater Reclamation Department, 3University of Arizona, Water & Energy Sustainable Technology (West) Center, USA



Following wastewater treatment, dewatering of biosolids at Tres Rios WWTP in Tucson Arizona results
in ≃ 0.5 mgd of effluent with high concentrations of NH4 (1000 ppm). This effluent is returned to the
head works, and the high NH4 concentration results in a need for extra oxygen to be pumped into the
effluent to enhance nitrification. This results in significantly enhanced energy costs (= 30% total energy
costs). Therefore, there is a need to remove the NH4 prior to re-entry into the head works. This project
evaluates an alternative method of removing the NH4 from the effluent – namely anaerobic oxidation of
ammonia or anammox. Anammox relies on a consortium of autotrophic bacteria to oxidize NH4 utilizing
nitrite as a terminal electron acceptor. We are evaluating the efficacy of anammox as an alternative side
stream treatment of effluent, and also determining the influence of anammox on human pathogenic
virus inactivation.

anammox, novel nitrogen removal, planctomycetes


A relatively recent discovery is that ammonium oxidation can occur under anaerobic conditions using
nitrite as the terminal electron acceptor (Kuenen, 2008). This process, known as anammox, is the
bacterial oxidation of ammonium using nitrite as the electron acceptor resulting in the production of
nitrogen (Eq. 1).
(see paper)
Anammox was first discovered in a bench-scale wastewater treatment reactor. Since then it has been
observed in a wide variety of both aquatic and terrestrial ecosystems with naturally low levels of oxygen.
These include marine and freshwater sediments and anoxic water columns, anoxic terrestrial
environments, as well as a number of managed systems including wastewater treatment plants,
aquaculture, and landfill leachate treatment systems (Thamdrup, 2012). All anammox bacteria identified
are associated with the phylum Planctomycetes. This phylum is characterized by extremely slow growth
rates, and in addition has internal membrane-bound structures. In anammox bacteria, one such
structure is the “anammoxosome”, the organelle where the ammonium oxidation and energy generation
reactions take place.

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