Background European rivers are often the subject of a process of eutrophication – an ‘over-productivity’ of an ecosystem that is usually the result of an increase of chemical nutrients, typically compounds containing nitrogen or phosphorus, most often from the release of sewage effluent or industrial wastewater. Eutrophication generally promotes excessive plant growth and produces a severe deterioration of water quality. As a result, there is a crucial need to reduce the concentrations of nitrates coming from industrial discharged across the EU. The regions of Flanders and Brussels, and the river basins of the Meuse and Scheld in the Walloon region, have been designated "sensitive areas" under the Urban Wastewater Directive. This meant that these areas had to implement tertiary wastewater treatment (nutrient removal of up to 15 mg/l) by 2005. Currently, the reduction of nitrate ions is generally achieved by biological processes - electrodialysis or reverse osmosis. However, these treatments have the disadvantages of incomplete removal and the production of by-product pollution. However, on a laboratory scale, the Catholic University of Leuven (UCL) and Laborelec had developed and tested an innovative technique to eliminate both nitrates and ammonia in a single step via an electro-destruction cell with zero environmental load. Objectives The project aimed to demonstrate Elonita, a sustainable wastewater treatment technology in power plants that removes nitrates down to a level of to zero percent and prevents the generation of sewage sludge. The project was to show the efficiency of a prototype of a zero-emission nitrate and ammonia electro-destruction system for the treatment of the industrial effluents of a power plant. The effluents to be treated resulted from ion exchange resins and vacuum pumps and contained concentrations of approximately 500 mg/l of nitrate ions and 1 g/l of ammonia ions – a level of ions that matched discharge norms (15 mg/l nitrate by 2005 and 0.5 g/l ammonia). This was due to their toxicity to aquatic life and humans. Electro-destruction will contribute to a sustainable reduction of nitrates and ammonia ions in surface waters and to the prevention of producing sludge as a by-product. Results The electro-destruction of toxic nitrate and ammonia ions has not yet been used on an industrial scale for wastewater treatment. The technology thus was entirely new. In the end, the expected results of the Elonita water treatment were far better than those from the more commonly used treatment. Furthermore, there was no production of sludge (as there is with biological treatment) or concentrated stream (as with reverse osmosis or electro-dialysis) The technology has been assessed from the point of view of its environmental performance, or its technical requirements and its costs. It has in particular been compared to the best alternative, biological treatment of waste water. In terms of its success in removing nitrates, nitrites and ammonium from waste water, the Elonita system achieved concentrations of less than 20 mg/l for nitrates, 0.2 for nitrites and 5 for ammonium. This is sufficient to satisfy environmental regulations. On the other hand, the process generates AOX, NOx, chlorine derivatives and gaseous ammonia, which is admittedly a significant drawback. Further processing of the effluents may be required. From a technical point of view, Elonita seems to be complementary to its main competitor. It requires high conductivity and high concentrations of Cl- ions, is more effective at higher concentrations, but does not function if the water contains suspended solids or organic matter. Limited tests were carried out with other effluents than those resulting from resin demineralisation in power plants. The following have shown promise: tests on reverse osmosis concentrate, on effluents of the biological treatment from the food industry, and effluent from incinerator flue gas cleaning. Compared with the biological treatment of wastewater, the investment costs required by the technology are much higher at low levels of throughput, but they are similar at higher levels of throughput. At a rate of 15kg of NO3- per day, the Elonita system cost €722,000 for compared with €200,000 for biological treatment. At 100 kg/day, Elonita cost €735,800 compared with €735,000 for biological treatment). It was not possible to estimate how many industrial plants might usefully and cost-effectively be equipped with Elonita systems. Only the actual commercialisation process would provide the answer to that question.