Partial Nitritation/Anammox Applications for Sidestream Nitrogen Removal: Experience from a Pilot-Scale Reactor
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PublisherThe University of Arizona.
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EmbargoRelease after 05/27/2022
AbstractWastewater streams containing high ammonium and low organic carbon concentrations present challenges for safe and effective wastewater recycling or discharge. Traditionally, ammonium is removed through biological nutrient removal (BNR) processes such as nitrification/denitrification (N/DN). In recent years, an alternative biological process, anaerobic ammonium oxidation (Anammox), has become more widely researched, due to the advantages of the Anammox metabolism that allows ammonium and nitrite to be converted directly to nitrogen gas. This process is an attractive alternative to conventional N/DN methods. Anammox applied as a technology with limited aeration to partially convert ammonium to nitrite, known as partial nitritation/Anammox (PN/A), requires less aeration and the need for an electron donor is eliminated. This allows for a more sustainable process, as less chemicals and energy are required when compared to N/DN. One of the most popular applications of Anammox is in nitrogen removal of sidestream municipal wastewater. This thesis analyzes the performance of a pilot-scale expanded granular sludge bed (EGSB) Anammox bioreactor. This reactor was monitored over the course of approximately 18 months to examine the removal efficiency of ammonium from sidestream sludge digestion centrate. The performance of the reactor, quantified as nitrogen removal efficiency and Anammox activity, varied over its operational lifetime, with nitrogen removal efficiencies ranging from 18.4% - 90.9%. Ultimately, it was found that Anammox bacteria within the EGSB reactor were sensitive to nitrogen (N) inhibition at concentrations of 2100 mg N L-1 or higher, which caused severe disruption in reactor performance (up to 75.9% loss in nitrogen removal efficiency) when operated as an Anammox only process. When operated as a combined PN/A process, fluctuation in performance was also investigated due to potential toxicity of constituents present in centrate. Laboratory scale activity assays conducted to measure the specific Anammox activity (SAA) showed a 56% reduction in SAA when Anammox were exposed to centrate as opposed to synthetic wastewater of the same nitrogen concentration. It was also observed that reactor pH of 5.7 or below, or 8.9 and above led to nitrogen removal efficiency to decrease by a factor of 63.9% and 63.2%, respectively. However, the reactor was able to recover any removal efficiency and Anammox activity lost due to nitrogen or pH shocks within 5 – 10 days given remediation of the issue. Ultimately, further experimentation will be needed to more definitively determine whether Anammox is a feasible solution for the removal of sidestream ammonium in wastewater treatment plants in Pima County, Arizona.
Degree ProgramGraduate College