Abstract: A system for treating groundwater contaminated with acidity or other contaminants is disclosed. The system involves excavating a trench into the aquifer in the path of the contaminant plume, and placing a body of active material in the trench. The active material depends on the particular contaminant: organic carbon may be used when the contaminant is ferrous sulphate, or hexavalent uranium oxide, or dissolved nitrate; pyrite or elemental iron may be used when the contaminant is eg chromium oxide. The active material causes the contaminant, by chemical reaction, to change its oxidation-reduction state, and to precipitate harmlessly in the body of material.

Abstract: A system for treating groundwater contaminated with acidity or other contaminants is disclosed. The system involves excavating a trench into the aquifer in the path of the contaminant plume, and placing a body of active material in the trench. The active material depends on the particular contaminant: organic carbon may be used when the contaminant is ferrous sulphate, or hexavalent uranium oxide, or dissolved nitrate; pyrite or elemental iron may be used when the contaminant is e.g. chromium oxide. The active material causes the contaminant to transform or break down by chemical reaction into harmless precipitates and substances.

Abstract: Nitrate-polluted run-off water from a field is conveyed via land drains to a reservoir. The reservoir is large enough to contain excess quantities of storm water from the field. From the reservoir, the run-off water enters a tank which contains wood or other organic carbon material. The wood is kept under water, i.e. under anaerobic conditions, whereby the nitrate is broken down by bio-chemical action. Sufficient wood is provided, and the flow rate is so adjusted, that the nitrate-polluted water spends many hours in contact with the wood.

Abstract: Mine tailings containing iron sulphides can cause acidity in groundwater travelling down through the tailings, if the tailings ever become exposed to the air. In the worst case, if only an upper level of the tailings becomes exposed, the amount of acidity produced is as if the whole body of tailings were exposed, because ferric ions in the water seeping down from the vadose region to the still-unexposed anaerobic regions tend to cause oxidation of the sulphides below, as if they too had become exposed. A layer of organic carbon (in the form of wood chippings, seaweed, etc) is added to the body of tailings, just below the (stabilized) water table. Water seeping down from the vadose region encounters the carbon before reaching the anaerobic sulphides, and most of the oxidation-producing tendency of the ions in this water is dissipated on the carbon, by bacterial action, leaving the anaerobic sulphides below unchanged.