Acidity and Alkalinity in Mine Drainage: Practical Considerations

Cravotta, Charles A.; Kirby, C.

doi:10.21000/jasmr04010334

Cited by 22 publications

(29 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Even though metals were not speciated except to differentiate Fe II from Fe III , the calculated acidity produced by Equation 9 matched several hundred measured Hot Acidities reasonably well, although less well at higher acidities (Hedin et al, 1994). Hedin et al (1994) suggest that even at low pH (2.7), H + acidity is only a minor component (compared to metals) of total acidity based on Equation 9.…”

Section: Calculation Of Theoretical Aciditymentioning

confidence: 84%

“…Stumm and Morgan (1996) Acidity from the alkalinity gives a net alkalinity result that is incorrect and can result in inadequate addition of alkaline materials such as lime or limestone in mine-drainage treatment. Hedin et al (1994) …”

Section: Laboratory Definitions Of Alkalinity and Aciditymentioning

confidence: 99%

“…The definition of calculated acidity from Hedin et al (1994) given in Equation 9 and the recent definition of net acidity given in Equation 11 (Hedin, this volume) (Hedin et al, 1994). Hedin (2003, pers.…”

Section: Calculation Of Theoretical Aciditymentioning

confidence: 99%

See 2 more Smart Citations

Acidity and Alkalinity in Mine Drainage: Theoretical Considerations

Kirby¹,

Cravotta²

2004

JASMR

Self Cite

View full text Add to dashboard Cite

Acidity, net acidity, and net alkalinity are widely used parameters for the characterization of mine drainage, but these terms are not well defined and are often misunderstood. Incorrect interpretation of acidity, alkalinity, and derivative terms can lead to inadequate treatment design or poor regulatory decisions. We briefly explain derivations of theoretical expressions of three types of alkalinities (caustic, phenolphthalein, and total) and acidities (mineral, CO 2 , and total). Theoretically defined total alkalinity is closely analogous to measured alkalinity and presents few practical interpretation problems. Theoretically defined "CO 2 -acidity" is closely related to most standard titration methods used for mine drainage with an endpoint pH of 8.3, but it presents numerous interpretation problems, and it is unfortunately named because CO 2 is intentionally driven off during titration of mine-drainage samples. Using the proton condition/massaction approach and employing graphs for visualization, we explore the concept of principal components and how to assign acidity contributions to solution species, including aqueous complexes, commonly found in mine drainage. We define a comprehensive theoretical definition of acidity in mine drainage on the basis of aqueous speciation at the sample pH and the capacity of these species to undergo hydrolysis to pH 8. We demonstrate that "net alkalinity" is a valid mathematical construction based on theoretical definitions of alkalinity and acidity. We demonstrate that, for most mine-drainage solutions, a useful net alkalinity value can be derived from: 1) alkalinity and acidity values based on aqueous speciation, 2) measured alkalinitycomputed acidity, or 3) taking the negative of the value obtained in a standard method "hot peroxide" acidity titration, provided that labs report negative values. We recommend the third approach; i.e., Net alkalinity = -Hot Acidity.Additional Key Words: calculated and measured acidity.

show abstract

Section: Calculation Of Theoretical Aciditymentioning

confidence: 84%

Section: Laboratory Definitions Of Alkalinity and Aciditymentioning

confidence: 99%

See 1 more Smart Citation

Acidity and Alkalinity in Mine Drainage: Theoretical Considerations

Kirby¹,

Cravotta²

2004

JASMR

Self Cite

View full text Add to dashboard Cite

show abstract

“…The equivalents of acid used to decrease pH to 4 are subtracted from the equivalents of base added in titrating to pH 8.3, making the result essentially a net acidity. Cravotta and Kirby (2004), Cravotta (2005a, 2005b) and Hedin (2006) showed that a reliable net acidity can be obtained from the hot peroxide acidity (Standard Methods, 1998), or by calculation from the pH, Fe, Al, Mn and alkalinity concentrations:…”

Section: Aciditymentioning

confidence: 99%

“…Cravotta and Kirby (2004) urged labs and others to use the Standard Methods (1998) procedure and to report negative acidities when obtained.…”

Section: Aciditymentioning

confidence: 99%

Advances in Passive Treatment of Coal Mine Drainage 1998-2009

Rose¹

2010

JASMR

View full text Add to dashboard Cite

Abstract. This report updates the review of passive treatment prepared by the Acid Drainage Technology Initiative (Skousen et al., 1998). Important advances since that report include: 1. Measured and calculated acidities are net acidities that are robust measures of this parameter. 2. Removal rates of Fe at pH>5 can be enhanced by CO 2 degassing, by catalysis by solid Fe phases and by specialized aerators; at pH<5, low pH Fe oxidation by bacteria can be helpful in treating high-Fe acidic discharges. 3. For low-Fe-Al AMD, oxic limestone drains can be effective for treatment, but effectiveness declines over years owing to accumulation of precipitate. 4. For high Fe or Al AMD, limestone beds with timed flushing devices can remove large amounts of metals, though eventual cleaning of the limestone may be needed. 5. Addition of limestone sand or lime to streams can be a cost-effective method of restoring watersheds 6. Vertical flow ponds (VFP's, SAPS) can be sized using a loading factor of 25-35 g of acidity/m 2 /d. 7. Manual flushing of VFP's removes only a few percent of accumulated Al precipitate, but timed flushing can be much more effective. 8. Common problems of VFP's include inadequate size, accumulation of Fe precipitate on compost, deterioration owing to Al coatings, and construction defects. 9. Sulfate reduction in passive systems involves a complex community of microbes, with long-term rates dependent on cellulose degrading microbes. Mixtures of fresh organic matter with high-cellulose material appear to provide good performance in lab tests, but more data on longer-term behavior is needed. 10. Sulfate-reducing bioreactors process Al better than older VFP's. 11. Steel slag and chitin hold promise for effective treatment of AMD. 12. A relation for sizing of limestone beds for Mn removal has been developed. 13. Fe precipitate from sludge is being successfully sold for pigment production, and Mn-rich concentrate has been recovered from limestone beds. 14. A revised flow chart for selection of treatment method has been prepared, and the AMDTreat computer program allows easy costing of passive treatment.

show abstract

Passive Treatment of Acid Mine Drainage (Wetlands)

Rose

2004

Water Encyclopedia

View full text Add to dashboard Cite

show abstract

Acidity and Alkalinity in Mine Drainage: Practical Considerations

Cited by 22 publications

References 31 publications

Acidity and Alkalinity in Mine Drainage: Theoretical Considerations

Acidity and Alkalinity in Mine Drainage: Theoretical Considerations

Advances in Passive Treatment of Coal Mine Drainage 1998-2009

Passive Treatment of Acid Mine Drainage (Wetlands)

Contact Info

Product

Resources

About