Summary #
Neutralizing acid in AMD-impacted water involves adding alkalinity, typically through limestone or other carbonate sources. This page covers the chemistry behind acid neutralization — how alkaline materials dissolve, react with acid, and raise pH. For information on treatment systems that neutralize acid, see the Neutralizing Acid section under AMD Treatment.
Neutralizing Acid
Some information compiled using “A handbook of Technologies for Avoidance and Remediation of Acid Mine Drainage” Prepared by J. Skousen, A. Rose, G. Geidel, J. Foreman, R. Evans, W. Hellier, and Members of the Avoidance and Remediation Working Group of the Acid Drain Tech. Initiative (ADTI).
AMD is often acidic, which lowers the pH in receiving streams. Fewer living things can tolerate the harsh conditions associated with a low pH, and a stream is effectively dead when pH is below about 4.5.
Treatment systems add alkalinity when AMD is acidic in order to neutralize this acid before it reaches a waterway. Adding limestone is often the least expensive, safest and easiest way to add alkalinity. It can be utilized in many ways, including lining a trench, pond or stream bed with limestone, or applying crushed limestone on or near the surface of a stream or pond. Alternatively, certain types of wetlands may be used to neutralize acid without limestone.
When installing a treatment system to treat an acidic discharge, you must first determine how much alkalinity must be added to neutralize the level of acidity. This assessment can be done by a consultant specializing in Acid Base Accounting (ABA). With a plan of action you and your group will have an easier time gaining funding and completing a successful remediation project.
External link: Alkalinity and Acidity http://www.hartwick.edu/envirsci/Courses/chem315/Lab/Lab-Alkalinity.htm
External link: An Alternative Alkaline Addition for Direct Treatment of Acid Mine Drainage (Jennifer S. Simmons and Paul Ziemkiewicz, National Mine Land Reclamation Center)
http://www.ott.wrcc.osmre.gov/library/proceed/sudbury2003/sudbury03/141.pdf
Sources/Links (as provided in the source text):
- http://www.hartwick.edu/envirsci/Courses/chem315/Lab/Lab-Alkalinity.htm
- http://www.ott.wrcc.osmre.gov/library/proceed/sudbury2003/sudbury03/141.pdf
Related Pages #
- Buffering — Natural alkalinity in watersheds
- Removing Metals (Chemistry Concepts) — The other half of treatment chemistry
- Neutralizing Acid Overview (AMD Treatment) — Treatment systems
- Anoxic Limestone Drains (AMD Treatment)
Source and Last Reviewed #
Source: AMR Clearinghouse (amrclearinghouse.org). Migrated to AML-Connect. Last Reviewed: 2026-03-13.
[Admin note: Some external links in this article may be outdated. Verify before relying on them. Flag dead links for removal or replacement.]
Tags: amd, alkalinity, acidity, passive-treatment, education
