Hydrated Oil Shale Ash Mitigates Greenhouse Gas Emissions from Horizontal Subsurface Flow Filters for Wastewater Treatment

Kuno Kasak, Riho Mõtlep, Marika Truu, Jaak Truu, Margit Kõiv-Vainik, Mikk Espenberg, Päärn Paiste, Kalle Kirsimäe, Ülo Mander*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


Previous pilot-scale studies have shown outstanding levels of efficiency in phosphorus removal by using hydrated oil shale ash (HOSA) sediments in horizontal subsurface flow (HSSF) filters with low greenhouse gas emissions. However, no long-term full-scale experiment has been conducted using this material. From September 2013 to December 2015, two HSSF filters with different hydraulic loading regimes (NH1 with a stable loading regime and NH2 with a fluctuating regime), used to treat municipal wastewater, were analysed to estimate greenhouse gas (GHG) fluxes and to develop a treatment system with minimised GHG emissions. The fluxes of CO2, CH4 and N2O, as well as their emission factors were significantly lower when compared with studies where regular filter materials (sand, gravel, etc.) are in use. The fluctuating loading regime significantly increased CO2 and N2O fluxes (median values of −3.3 and 2.6 mg CO2−C m−2 h−1, and 5.7 and 8.6 μg N2O−N m−2 h−1 for NH1 and NH2 regimes, respectively), whereas no impact could be seen on CH4 emissions (median 93.3 and 95.6 μg CH4−C m−2 h−1, for NH1 and NH2, respectively). All GHG emissions were strongly affected by the chemical composition of the water entering into the system. The water purification efficiency of the system was satisfactory for most water quality parameters and excellent for phosphorus. Thus, the HOSA-filled filters have a good potential for municipal wastewater treatment with low GHG emission.

Original languageEnglish
Article number320
JournalWater, Air, and Soil Pollution
Issue number9
Publication statusPublished - 1 Sept 2016

Bibliographical note

Publisher Copyright:
© 2016, Springer International Publishing Switzerland.

Copyright 2017 Elsevier B.V., All rights reserved.


  • Carbon dioxide
  • Methane
  • Mineral carbonation
  • Nitrous oxide
  • Reactive filter material


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