Anammox Polishing in Mainstream Wastewater Treatment To Meet Stringent Ammonia and Nitrogen Limits

Authors:

  • Rebecca (Becky) Holgate - Hazen and Sawyer
  • Pusker Regmi - Brown and Caldwell
  • Mark W. Miller - Virginia Tech
  • Charles B. Bott - Hampton Roads Sanitation District

A two stage A/B pilot study is being conducted that includes a high-rate activated sludge (HRAS) process followed by a two-stage deammonification process incorporating a nitrite-shunt suspended growth reactor with a clarifier followed by a fully-anoxic anammox moving bed bioreactor (MBBR) polishing process.

Anammox has been implemented in sidestream treatment with remarkable success over the last decade. But, as effluent permit limits become more stringent, there is an incentive to implement more cost efficient wastewater treatment for nitrogen removal. In order for plants to meet their changing permits, many plants are shifting towards utilizing chemicals to assist in removing the final concentrations of nitrogen in their system, which is very costly. The use of anammox as a polishing process can eliminate the need for these chemicals and create a more economical treatment process. 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.

The vision of employing anammox in mainstream treatment is a compelling possibility with the associated reduction in cost of treatment compared to conventional biological nutrient removal technologies. However, this seemed a daunting challenge due to the slow growth rate of anammox and the perceived potential for difficulty achieving low effluent TN concentrations using anammox (based on only sidestream experience to date).

This study demonstrated the feasibility of implementing anammox in mainstream wastewater treatment as a polishing step. This anammox polishing MBBR was successful following a nitrite shunt process in which the NOB were out-selected and the effluent (influent to the MBBR) contained an equal blend of both ammonia and nitrite. Utilizing anammox in an MBBR process allows the ample solids retention time needed for anammox growth and stability. With such a simplistic design, along with minimal process control required, the anammox MBBR polishing process can be implemented in current treatment plants at minimal costs.

For more information, please contact the author at rholgate@hazenandsawyer.com.

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