State Water Resources Research Institute Program

Project Id: 2010SD174B
Title: Investigation of Arsenic Removal from Water by Microbiologically Induced Calcite Precipitation
Project Type: Research
Start Date: 3/01/2010
End Date: 2/28/2011
Congressional District: SD First
Focus Categories: Toxic Substances, Treatment, Water Supply
Keywords: Arsenic, Arsenic Removal, Water, Bioremediation, Bacteria
Principal Investigators: Davis, Arden D (S.D. School of Mines and Technology); Bang, Sookie S; Dixon, David J.
Federal Funds: $ 13,983
Non-Federal Matching Funds: $ 27,966
Abstract: This research will focus on improvement of the efficiency of a limestone-based process for removal of arsenic from water, through the encapsulation of arsenic in limestone waste during microbiologically induced calcite precipitation. In previous work by the principal investigators, limestone-based material has clearly shown the ability to remove greater than 90% of arsenic from drinking water, with the additional benefit of low-cost disposal of a stable waste product in ordinary landfills. The means of arsenic removal is believed to be the formation of a calcium arsenate precipitate on the surface of limestone, but the surface chemistry is not well understood, and the efficiency of the method should be improved if it is to achieve commercial viability.

Microbiologically induced calcite precipitation is a process that uses bacteria to create an environmentally friendly calcium carbonate cement. In this process, a common soil bacterium, Sporosarcina pasteurii, is fed a solution of urea and calcium chloride. The bacteria hydrolyze urea, forming carbon dioxide and ammonia as end products. In the presence of water, the ammonia reacts to form ammonium hydroxide, which raises the pH, creating a basic environment with an abundance of carbonate ions. These react with calcium ions to induce precipitation of calcium carbonate, commonly known as limestone.

Dissolved arsenic in water has a known affinity for limestone, as demonstrated in previous work by the principal investigators. Microbiologically induced calcite precipitation shows great promise for improving the efficiency of arsenic removal by using bacterial enhancement to increase the reaction rate. If bacteria are involved in the formation of a calcium arsenate precipitate during arsenic removal by limestone-based material, it could constitute a major advance in the field, with the added benefit of encapsulation of arsenic within precipitated calcium carbonate.

The objectives of this research are:

  1. Develop and test a process for arsenic removal from water during microbiologically induced calcite precipitation, by using a solution with a low (approximately 100 parts per billion) concentration of dissolved arsenic.
  2. Investigate the efficiency of the process by determining arsenic removal rates during bacterially enhanced calcite precipitation.
  3. Determine levels of tolerance of Sporosarcina pasteurii for dissolved arsenic in solution, by testing solutions with different arsenic concentrations ranging from 10 parts per billion to 1 part per million or greater.
  4. Determine the stability of the encapsulated arsenic through leaching tests.

Potential benefits of the work could be extended to aquifer remediation, industrial applications such as waste streams, and mine drainage water.

Progress/Completion Report, 2010, PDF

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