Biochemical reactors (BCRs) treat mining-influenced water (MIW), which is water that has been contaminated by mining or mineral processing activities. MIW is typically acidic and contains metals, sulfate and other inorganic contaminants. During BCR treatment, the contaminated water moves through one or more treatment cells filled with a mixture of natural materials, such as wood chips, mushroom compost, hay, manure and limestone. These materials cause biological and chemical reactions that reduce acidity and sulfate levels. The materials also decrease concentrations of metals in the water or convert them to safer forms.