key details:

Technology: SAGR™ post-lagoon cold-water nitrification

Key advantages:

  1. Reduces Total Ammonia to <1 mg/L year-round, even in <0.5°C water
  2. Polishes cBOD to <5 mg/L, TSS to <10mg/L, and provides partial effluent disinfection
  3. O&M requirements similar to an aerated lagoon


  • Nitrification in any climate
  • Post-lagoon polishing
  • Airport de-icing fluid treatment
  • Decentralized wastewater treatment
  • Water reuse applications

Associated Case Studies:

Your challenge: Post-lagoon ammonia removal

Reduce TAN to <1mg/L: You need to achieve  effluent Total Ammonia-Nitrogen levels down to <1 mg/L, even in the cold of winter, something your existing lagoons just can’t do.

Save space, time, and money: You'd like to do it on a compact footprint, and as usual, the simpler to operate and more inexpensive the solution, the better.

Our technology:


Nexom is the exclusive source for the SAGR, a simple, powerful tool for fully nitrifying lagoon effluent in any climate. The SAGR consists of a clean stone bed that is fully aerated. In a typical configuration, water flows through the substrate horizontally, and a layer of insulating wood chips, mulch or shredded tires at the surface prevents ice formation in the bed, allowing the system to treat wastewater that is near freezing (<0.5°C).

Why do you need a SAGR? Lagoons are incredibly powerful ecosystems that cost-effectively, naturally remove a host of wastewater’s most harmful components with a minimum of operations or maintenance requirements. But lagoons often struggle to remove ammonia in winter for four reasons:

  1. If a facultative (un-aerated) lagoon freezes over, access to atmospheric oxygen is cut off, which is needed by nitrifying bacteria.

  2. Nitrifying bacteria require a surface to grow on, something that is not plentiful in a lagoon.

  3. The heterotrophic bacteria that consume cBOD5 tend to dominate nitrifying bacteria, meaning cBOD5 needs to drop below 25mg/L before nitrification can begin in earnest. Cold temperatures slow the metabolism of the heterotrophs. More of the lagoon retention time is required for BOD removal, reducing the available HRT for nitrification.

  4. Both the reproduction rate and the metabolism of the nitrifiers themselves slow as the water temperature drops. The low reproduction rate means that new biomass does not form quickly enough to make up for the reduced consumption of ammonia that occurs due to the lower metabolism.