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# Process and Apparatus to Accelerate Restoration of Acidified Water by Pretreatment with Carbon Dioxide

| **Introduction**
Industrial, chemical, and mining processesresulting in acid deposition in streams andlakes have had a significant negative effecton aquatic resources in North America,including the loss of important commercialand recreational fisheries.  Direct effects ofacidification on fish include acute mortality,reproductive failure, altered growth rates,and chronic impairment to body organs andtissues.  Negative indirect effects ofacidification include fish habitatdegradation, increase in concentrations ofsoluble toxic metals, such as aluminum, andchanges in predator-prey relationships.  
Within the coal deposit regions ofAppalachia and the Ohio River Basin, acidmine drainage contributes significantly toacid deposition in surface waters.  Given theseverity of the problem and associatedenvironmental/economic ramifications, theBiological Resources Division of the 
U.S. Geological Survey (USGS), signed thestatement of Mutual Intent for "Restorationand Protection of Streams and WatershedsPolluted by Acid Mine Drainage fromAbandoned Coal Mines," put forth by theOffice of Surface Mining and theEnvironmental Protection Agency.  Workhas been done to increase the understandingand application of the best technologiesavailable for remediating and preventingmine drainage and to support thedevelopment of new technologies.  
**About the Process**
A variety of processes and apparatus designsusing calcium carbonate have beendeveloped in an attempt to treat effluentacidity. In addition, a variety of apparatusdesigns have been used to dose acid minedrainage with calcium carbonate.Researchers at the USGS have invented animproved process and apparatus usingcarbon dioxide pretreatment of the effluentto accelerate limestone (calcium carbonate)dissolution with subsequent recycling of thecarbon dioxide gas stripped or recoveredfrom water exiting the apparatus.  Thisinvention is a method of using anintermittently fluidized (pulsed) limestonebed system incorporating carbon dioxidepretreatment to enhance restoration ofacidified water from acid mine drainage andchemical industrial processes. ****
**Advantages**
The main advantages of this method are acceleration of  limestone dissolution ratesby increasing dissolved carbon dioxideconcentrations and reduction of  treatmentsystem sensitivity to limestone armoring byintermittent fluidization of  limestone beds. Other advantages include the ability to:-  allow for sidestream treatment. Sidestreaming eliminates the need to dam theentire flow and reduces significantly the sizeof the reactor and plumbing required fortreatment, thus reducing capital and sitepreparation costs, enhance rates of biological productivity inacidified impaired waters, improve the efficiency and reduce the costof limestone beds for the treatment of aciddrainages, 
- to increase the hardness and alkalinity ofvery soft waters,   make acid drainage suitable fordevelopment of aquaculture production, and obtain the release of calcium ions fromcalcium carbonate to reduce the toxicity ofcertain dissolved metals.
**For More Information**
For more information about licensing of thisand other patents and for cooperativeresearch opportunities with the USGS,please contact:
U.S. Geological SurveyBranch of Business Development12201 Sunrise Valley Drive, MS 500Reston, VA 20192Tel: (703) 648-4344FAX: (703) 648-4706Email: Branch of Business Development
For information about the technical detailsof this invention please contact the inventor:
Barnaby J. WattenU.S. Geological SurveyLeetown Science Center1700 Leetown RoadKearneysville, WV 25430Tel: 304-724-4425FAX: 304-724-4435E-mail: barnaby_watten@usgs.govPrivacy StatementDisclaimerAccessibilityFOIAU.S. Department of the Interior | U.S. Geological Survey              URL: http://www.usgs.gov/tech-transfer/factsheets/FS-105-97.html              Maintainer: Technology Transfer                            Last modified: Monday, 06-Oct-2003 10:28:41 EDT                            |
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