General Cleanup Technology

Ash sediments for improving the water quality of mining lakes

As part of this project, the project partners examine the use of alkaline suspensions to improve water quality of sulphuric post-mining water bodies formed from the remainders of opencast mines with additional CO2-mineralisation. Following the cleaning-up of mining lakes, this allows to derive economic benefit of it, as well as to recycle ash sediments, and lignite filter ash from power plants.


As a result of mining activities, both ground as well as surface water become acid. When mining activity decreases, the groundwater table rises and forms a lake in the hollow pattern left behind. The resulting quality of the water often precludes achieving the planned usage objectives (tourism and scenic lakes). The sanitation concept of balance neutral flooding undertaken up till now at the post-mining lake Burghammer (Lausitz, Saxonia) showed that the required volume of water could not be made available. Therefore, the present study examines technological aspects of water management using carbon dioxide (CO2) to improve water quality. Additionally, the potential for additional CO2-mineralisation as a long-term strategy to save climate-relevant by-product was determined.  Both studies require an alkaline solid matter (ash sediment, lignite filter ash) and inorganic carbon (CO2 from emissions). In this way, the potential of ash sediments to improve water quality, as well as to save CO2 in the mining lake Burghammer was determined. The tests were thereby conducted at varying levels (shake, batch, and pilot plant trials).


  • The suitability of ash sediments to improve water quality and CO2-mineralisation was shown.
  • Ash sediments can be used for treating lake water, as well as for continuing mineralisation of CO2 (strategy for lowering CO2 emissions).

  • In sequential extractions, it was shown that large amounts of calcium and magnesium can be mobilised from ash sediments.
  • The water quality of the sulphuric mining lake of Burghammer could be significantly improved through the incorporation and repositioning of sediments.  It was possible to produce neutral effluent that was free from iron, aluminium and manganese.

  • By using CO2, the specific generated alkalinity could be increased to >1 mol/kg.
  • Although CO2-balance turns in favour of CO2-mineralisation on using suction dredger, technology costs exceed costs generated from CO2 -certificates.
  • On the basis of the investigations conducted it can be shown that a contamination that has an impact on the environment does not occur by using ashes.
  • An increase in concentrations of micronutrients in the treated water could not be found; the co-concentration fell to 10-70 µg/l.

Project Participants

Implementing Institutions

Dresden Groundwater Research Centre (DGFZ e.V.)


Promoting Institutions

Federal Ministry of Education and Research (BMBF)

Promotional Program


More Project Information

Project title: Verbundprojekt UR: CDEAL, Vorhaben: Bench- und Pilot-Scale Process-Modellierung - Sonderprogramm GEOTECHNOLOGIEN

Project number: 03G0628B

Project period: 2005 - 2008

Project region: Germany (Saxony)

Project contact:

Herr Dr. Bilek

+49 0351/4050 674

View Publication

Source: German National Library of Science and Technology Hannover (TIB)