Positive results obtained from nitrate removal process

A European EIT Raw Materials project, ‘NITREM‘, has achieved positive results from a pilot scale implementation at LKAB’s Kiruna mine and is planned to be scaled up to full-scale. Nitrate concentrations of around 70 mg/litre in the leachate from waste rock piles was reduced to less than 10 mg/litre (an efficiency of 77%) after passing through a bioreactor. Nitrate is formed from the residual of ammonium nitrate-based explosives used in mining, and causes unwanted growth of algae leading to autrophication of waterways.

The bioreactor is a passive design, requiring little intervention. An oblong pit is constructed, the walls sealed with a geomembrane, and filled with wood chips and a dose of activated sewage sludge containing nitrogen-reducing bacteria. The bioreactor is covered an operates under anaerobic (oxygen-free) conditions. The bacteria utilise carbon from the wood chips to transform the nitrate to nitrogen gas, while the leachate flows through the reactor.A trial during 2019 recorded an average nitrate removal efficency of 77% with input nitrate contents of 61 – 87 mg/litre. During the operating period the average temperature was 3 °C, confirming that the microbial process is suited for use in cold climate conditions.

The process is proposed to be scaled up and implemented at further mining sites to reduce the impact on the environment. Further details are available at the NITREM project webpage. The project consortium consists of Uppsala University, WSP Sverige AB, Cedervall Arkitekter, Agencia Estatal Consejo Superior de Investigaciones Centificas, Boliden Mineral, LKAB, LTU Business and the Swedish University of Agricultural Sciences.

Schematic diagram of the NITREM nitrate biorector system
NITREM nitrate removal process, from https://nitrem.eu

Passive wastewater treatment systems have been widely reported for the reduction of heavy metals, a review is given here. These results that the technology is also suitable for reduction of anions such as nitrate in the wastewater.

Call for papers

A Call for Papers has been issued for a Special Issue of the Journal of Water & Climate Change, with the topic of “Integrated assessment and adaptation to climate change impacts in cold regions”. The Special Issue is related to the 6th IAHR (International Association for Hydro-Environment Engineering and Research) EUROPE Congress – at which Hanna Virpiranta is scheduled to present results from the Kolarctic CBC SEESIMA project. Tiina Leiviskä is one of the Guest Editors of the Special Issue. The submission deadline is 31 March 2021, with expected publication in October 2021.

This Special Issue will cover the following topics:

  • Data sources and acquisitions (e.g. observations, reconstructed, reanalysis, models, remote sensing data).
  • Data calibration, verification and sensitivity analysis.
  • Use of state-of-the-art research methods (e.g. machine learning, hydrological model, climate model simulations).
  • Natural hazards and risk assessment (e.g. urban flooding, snow avalanches, rockfall, landslides, debris flows).
  • Future climatic and hydrological simulations and projections.
  • Changes in the hydrological cycle and heat and energy transfer.
  • Water pollution control and quality management.
  • Innovative wastewater treatment processes, waste management and resource reuse.
  • Impacts of climate change on the total environment.
  • Mitigation and adaptation options (e.g. blue-green solutions, nature-based solutions, and performance assessment, social-economic value and multi-benefits, etc). 
  • Rehabilitation and repairing technologies of structural defects and the use of new materials and new construction methods.
  • Other aspects of hydro-environmental research and innovation topics.

The link to the call for papers is here.