Summary #
Anaerobic (compost) wetlands treat acidic AMD by passing water horizontally through organic compost and limestone. Bacteria in the compost remove oxygen and sulfate, while limestone adds alkalinity. This page explains how anaerobic wetlands work and how they differ from aerobic wetlands.
Although similar in appearance to aerobic wetlands, anaerobic wetlands are used to treat AMD that is acidic or that has high sulfate concentrations.
In an anaerobic wetland (also called a “compost wetland”), water flows horizontally through organic compost and limestone (either in layers or mixed together). Bacteria in the compost remove oxygen and sulfate from the water. The bacteria also help to reverse the normal chemical reactions by which AMD creates iron oxide, and in doing so, some of the acid in the water is neutralized (see Sulfate-Reducing Bioreactors). The limestone adds even more alkalinity to neutralize acid.
Related Pages #
- Sulfate Reducing Bioreactors — Related bacterial treatment approach
- SAPS and Vertical Flow Reactors — Combines ALD and wetland concepts
- Treatment Strategies — Choosing the right treatment approach
- Neutralizing Acid (Chemistry Concepts)
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[Admin note: Some external links in this article may be outdated.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: passive-treatment, alkalinity, o-and-m, practitioner
