High Nitrogen Recycle Streams

High Nitrogen Recycle Streams

A significant nitrogen load can be generated internally in a wastewater treatment facility. These internal side streams include supernatant liquid from sludge digesters, and the centrate/filtrate return stream from sewage sludge dewatering processes.

AOx-DN™

Ammonia Oxidation-Denitrification Over Nitrite

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AOx-DN™ is a process for nitrogen removal from a high ammonium concentration waste stream that minimizes the quantity of both the air and the supplemental electron donor (organic carbon).  This is achieved by intermittently aerating the bioreactor to accomplish ammonium oxidation to nitrite and then denitrification over nitrite.

The bioreactor is operated so that the aerobic contact time only allows for the oxidation of ammonium to nitrite. The intermittent aeration creates environmental conditions which inhibit the nitrite oxidizing bacteria (NOB).  This is likely due to the NOB oxygen half-saturation coefficient (Ks) of 1.1 mg/l as compared to 0.3 mg/l for ammonia oxidizing bacteria.  The result is a very stable reaction to nitrite only

The recovery of alkalinity during denitrification typically sustains the alkalinity requirement of the ammonium oxidizing reaction. This eliminates the need for chemical addition to maintain the alkalinity and pH level.

AOx-DN Process advantages:

  1. Extremely stable reaction to nitrite only, with no dependence on temperature
  2. Nitrogen removal via the nitrite route requires 25% less oxygen
  3. Denitrification from nitrite requires approximately 40% less supplemental carbon
  4. High biomass concentration results in relatively small area requirement for reactor
  5. Ease of operation

AOx-PD™

Ammonia Oxidation-Pipe Denitrification

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AOx-PD™ is a process for nitrogen removal from a high ammonium concentration waste stream that minimizes the quantity of air and eliminates the need for a supplemental electron donor (carbon). This is achieved by intermittently aerating the bioreactor for ammonium oxidation to nitrite. The intermittent aeration creates environmental conditions (i.e. low DO), which inhibit the nitrite oxidizing bacteria (NOB).

AOx-PD™ takes advantage of the environmental conditions within the influent piping system and headworks of a typical municipal wastewater treatment plant by introducing the partially treated (high nitrite concentration) recycle stream into the collection system. Therefore, the collection system and headworks are utilized as a denitrification reactor.

AOx-PD™ Process advantages:

  1. Extremely stable reaction to nitrite only, with no dependence on temperature
  2. Nitrogen removal via the nitrite route requires 25% less oxygen
  3. No supplemental carbon is required with sufficient residence time within influent piping
  4. Denitrification occurs within the pipe reducing the carbonaceous load to the treatment plant
  5. Odor suppression within the influent pipe due to the addition of nitrite
  6. High biomass concentration results in a relatively small area requirement for reactor
  7. Ease of operation

High Nitrogen Literature: