Nutrient Recovery

Wastewater streams are often rich in nutrients such as nitrogen and phosphorus. Our nutrient recovery technologies unlock this potentially valuable nutrient source, which can be converted into ecologically friendly fertilisers and other uses.

NAS anammox technology

Many sectors produce highly polluted wastewater, with nitrogen being one of the main pollutants. Removing nitrogen can be very expensive.

NAS®, the innovative anammox technology developed by Colsen, is an energy-efficient wastewater treatment method based on anammox bacteria. This cost-saving technology is used for industrial and municipal wastewater treatment plants.


Our robust NAS® anammox technology reduces the operating costs of conventional water treatment methods by cutting energy consumption and sludge disposal costs. NAS® systems are equipped with a clarifier or MBR (Membrane Biological Reactor) but can be fully configured to the customer’s needs.

If you work in the municipal sector, try NAS®-ONE technology. It is suitable for sidestream treatment after mesophilic or thermophilic sludge digestion, with or without thermophilic pressure hydrolysis (TPH) pre-treatment. NAS®-ONE technology is a highly efficient wastewater treatment method based on high-load anammox bacteria that removes high levels of nitrogen from sludge filtrate, even at high organic and solid concentrations.


Anammox micro-organisms allow for efficient nitrogen removal by short-cutting the conventional nitrogen cycle. These bacteria are autotrophic, which means they do not need any organic pollution to work as intended. They use ammonium and nitrite as substrates and work optimally at mesophilic temperatures (35-37°C) in the absence of oxygen. All NAS® technologies are equipped with our proprietary aeration control, which ensures that part of the ammonium is converted to nitrite. Depending on the NAS® application in question, the aeration phase is carried out in the same tank or a separate one.


Low energy consumption, reduced sludge production and the absence of a carbon source mean that NAS® systems can help cut water treatment operating costs by 40%.

AMFER nitrogen recovery

In certain waste and wastewater flows, high quantities of nitrogen occur in the form of ammonium, such as in digestate or centrate produced by a digester, in manure processing flows or in industrial wastewater. In such cases, nitrogen recovery is more efficient and cheaper than nitrogen removal.


Nitrogen recovery with AMFER® is incredibly interesting for waste and wastewater flows with high levels of ammonium. Thanks to the proprietary stripper design, AMFER® can process highly polluted flows and the technology can be applied directly to (thin) manure or digestate without having to dewater or pre-treat these flows.


AMFER® technology is a batch process and consists of just one process step. CO2 and ammonia (NH3) are successively removed from the substrate in a stripping column. The stripping air is passed through a gas scrubber, where ammonium sulphate or ammonium nitrate is produced.

The stripping tank features a proprietary aeration field and distribution system, allowing it to process thick flows with high quantities of dry matter, such as manure and digestate, or heavily polluted wastewater.


AMFER® technology has several advantages:

  • Energy-efficient way to process large quantities of nitrogen
  • Low energy consumption compared to nitrogen oxidation
  • Produces valuable artificial fertiliser
  • Increases capacity of feeding high-nitrogen co-substrates to digesters
  • Easier discharge of residual flows in manure processing and biogas systems
  • Pasteurisation in the same system

AMPHOS phosphate recovery

Phosphate is a crucial component of artificial fertilisers, but the main mining areas are being depleted, which makes phosphate recovery all the more important. That’s why we developed ANPHOS® technology.

Today, chemical addition in wastewater treatment is a convenient way to remove phosphate, but it also produces additional sludge, increasing operating costs. Capturing phosphate in a sub-stream by promoting struvite formation lowers those costs and creates a valuable product.


ANPHOS® technology can be used in both the industrial and municipal sectors, as the phosphorus recovery process can take place in the main flow (industry) or in a sub-flow, such as the filtrate of a digestate dewatering system (municipal STP), by means of controlled struvite formation.


ANPHOS® technology is a batch process and consists of two process steps: a stripping tank and a reaction tank. In the stripping tank, CO2 is stripped from the wastewater, increasing its pH level. The water is then pumped to the reaction tank, where magnesium is added to set the controlled struvite formation process in motion. The struvite settles in the reactor and is transported to a dewatering or struvite recovery system. The overflow of the reaction tank is the effluent of the struvite system, which can either be treated further or discharged.


  • Controlled struvite formation
  • Prevents struvite formation further down the line
  • Produces valuable struvite
  • Only requires a source of magnesium
  • Reduces sludge production in subsequent systems