Anaerobic water purification systems for nutrient removal and recovery - Water and Wastewater

Companies and municipalities have to remove nutrients from their effluents - such as nitrogen and phosphate - before they can reuse the water. There are also strict discharge limits on the nutrients levels that must be met. Paques has a number of technologies that can deal with these requirements.

  • Reject water treatment from sludge digestion
  • Post-treatment of anaerobic effluent
  • Effluent polishing at (municipal) wastewater treatment plants

If nitrogen limits in the final effluent of the wastewater treatment plant exceed regulations, it is an option to remove ammonia from the reject water from the sludge digestion, rather than to increase the nitrogen removal capacity of the main plant. Typically 15-25% of the total nitrogen load of a municipal wastewater treatment plant derives from the reject water. Paques ANAMMOX® technology removes ammonia in a cost-effective and sustainable manner. Because of a shortcut in the nitrogen cycle, ammonia is removed without the use of an external carbon source such as methanol. This requires 60% less energy compared to conventional treatment.

Effluent from anaerobic reactors still contains low levels of BOD and possibly ammonia and phosphate. Paques offers several technologies for post-treatment of anaerobic effluents.

The CIRCOX® reactor is a very efficient aerobic system for the treatment of anaerobic effluents. It uses biofilm on a carrier material in an airlift reactor. This compact system is a fully closed aerobic system with outstanding purification performance, as the purified effluent can be directly discharged to surface water. BOD removal can be combined with total nitrogen removal (nitrification/denitrification) in one reactor system.

The combination of PHOSPAQ™ and ANAMMOX® recovers and removes phosphate and ammonia cost effectively and energy efficiently. Contrary to conventional nitrification/denitrification, the ANAMMOX® process does not need a carbon source for denitrification. This leaves the full potential of BOD in the wastewater to be used for the production of biogas. Furthermore, ANAMMOX® requires 60% less energy to operate. PHOSPAQ™ recovers phosphate as struvite that can be used as fertilizer.

To raise the effluent quality of (municipal) wastewater treatment plants, a treatment stage can be added to reduce concentrations of nitrogen, BOD, phosphate and TSS. The ASTRASAND® continuous sand filtration technology has proven to be very effective for the final removal of ammonia and nitrate. It also removes phosphates, TSS and BOD effectively. The removal of different components can be combined in a single filter. The ASTRASAND® filtration process removes total nitrogen and phosphate to levels below 2 mg/l and 0.15 mg/l respectively.