The AQUAMEND Denitrification Unit, or ADU, has been designed and implemented using a patent pending process that provides significant advantages over other types of denitrification technologies. There are few technologies designed to deal specifically with nitrate for on-site wastewater treatment. One approach for reduction of nitrogen that is at a fundamental disadvantage in terms of reaching very low nitrogen levels is to cycle between aerobic and anoxic conditions. The BOD that is present in the water is used as the carbon source that is required for the denitrification zone, but the water will always contain some amount of either nitrate or ammonia, which can be later converted to nitrate in the environment. Another approach that has been used is to provide an over-abundance of a carbon source following a purely aerobic treatment system. Although this system is capable of reaching very low nitrogen levels, there is little control on the amount of carbon released, and thus an excess of BOD is likely to result. It is for these reasons that the ADU was designed to meet very low nitrogen and BOD levels.
ADUs are installed following aerobic treatment units, where virtually all the nitrogen is converted to nitrate. This influent is then passed through a highly efficient fixed-film denitrification region where the nitrate is removed. ADU Liquid Carbon (ADU LC) is added to the water in controlled excess. This ensures there is more than enough carbon to achieve essentially complete removal of nitrate. Once the nitrate is removed, the water is transferred to an aerobic fixed-film region where the excess of Liquid Carbon is removed, thereby preventing an overall increase in the BOD. Because the process is fixed-film, the suspended solids are retained in the reactors until such time that they are removed in a controlled fashion through an air sparging event. Approximately once every 3 to 6 months, a portion of the biomass in the reactors is dislodged and returned back to the septic tank of the treatment system. This results in very low total suspended solids (TSS) in the final effluent. Finally, due to the highly efficient design, the contact time required is very low. The denitrification process requires a design contact time of 2 hours based on the average flow, or 1 hour based on the peak flow, whichever is greater. The aerobic process requires half this time.