Shortcut nitrification in activated sludge process treating domestic wastewater- key technology for low-carbon and clean wastewater treatment

The aim of this Project is to create an innovative Technology that will allow to achieve mainstream shortcut nitrification/denitrification via nitrite at municipal wastewater treatment plants (WWTPs). Achieving this objective will significantly reduce oxygen and organic carbon demand for nitrogen removal process, improve effluent quality and increase digester gas production. This Technology also includes a development of separate reactor for sludge disintegration with nitrous acid to aim easy biodegradable organic carbon for denitrification process improvement, which is usually limited by organic carbon available in raw wastewater.

Achieving mainstream shortcut nitrification/denitrification will be possible due to:

  • inhibition of nitrite oxidizing bacteria (NOB) by nitrous acid in a separate reactor (selector) fed with the acid and recirculated activated sludge from the main technology line,
  • use of mainstream aeration system control algorithms which promote growth of AOBs.

Nitrous acid for mainstream augmentation will be produced in a sidestream shortcut nitrification reactor treating reject water from sludge dewatering. Sludge disintegration will be conducted in another reactor fed with combination of waste or digested sludge and nitrous acid. Each of the Technology components will be operated by an advanced control system developed during this Project.

Further increase in biogas production will be tested by application of co-digestion with fish sludge and thermophilic mode of AD (anaerobic digestion). In order to close the loop and in accordance to circular economy the digestate properties will be investigated.

Project SNIT (NOR/POLNOR/SNIT/0033/2019-00) is financed by Programme “Applied research” under the Norwegian Financial Mechanisms 2014 – 2021/POLNOR 2019.

Project duration: 01.10.2020 to 30.09.2023

Project budget: 1 717 640 EUR

Project promotor: Wrocław University of Science and Technology


  • Municipal Water and Sewage Company Wrocław
  • Silesian University of Technology
  • Aquateam COWI AS