Denitrifaction of septic tank effluent

Abstract From the Canadian patent

Water draining from a septic tank contains ammonium which traditionally is, oxidised to nitrate in an aerobic soakaway. When the effluent enters the groundwater, the resulting nitrate concentration can be troublesome. A body of organic carbon, eg wood chppings, is provided and the nitrate-laden, effluent is passed through the carbon. The carbon is placed in the ground so as to be anaerobic: for example, the carbon may be placed below the water table; or the carbon may be mixed into a layer of fine silt which is maintainedin a state of tension-saturation by the affluent. Under anaerobic conditions the nitrate is reduced by micro-biological action. The carbon is located such that the effluent …