Background The treatment of wastewater with metal salts (e.g. iron chloride) is the most commonly used method for phosphorus removal in the wastewater treatment plants of the food industry in Europe. The process has a high chemicals input (iron chloride). Furthermore, the process generates a waste stream of sludge containing iron phosphates. This sludge can only be disposed of in landfills, by incineration or by dumping at sea. Furthermore, with these commonly used processes, the phosphorus is not reintegrated into the biological cycle and is a threat to the quality of surface water. The struvite process consists of treating the phosphorus with magnesium oxide and forming a magnesium ammonium phosphate (MAP) sludge. The MAP can be used as a fertilizer in agriculture, and this results in a closed phosphorus cycle. The struvite process has already been applied to effluents from an aerobic treatment plant for liquid manure and for sewage water. An industrial research project (partly funded by the Dutch Ministry of Environment) has confirmed that this process works for anaerobic effluent as well. Objectives The project aimed to apply the struvite process in anaerobic conditions to industrial effluents resulting from potato processing. The chemical composition of these industrial effluents is very different from those to which the technology was previously applied on a smaller scale. The struvite process will achieve the removal of both phosphorus and nitrogen (in NH4 form). By performing this demonstration project, LWM aimed to contribute to the development, the use and the spread of a new technology that would prevent phosphorus from polluting surface waters, and that would encourage the reuse of, and the recycling of phosphorus from, industrial waste waters. The objectives of the project were: 1. Demonstration of the economic, social and environmental benefits of the struvite process in industrial wastewater treatment with the first trial at industrial scale of this de-phosphorisation process of anaerobic effluents. 2. Obtaining of reliable data (measurements) on the operating conditions. 3. Informing the food industry and other relevant actors about the struvite process. Results The project was successful in achieving its broad objectives through the innovative use of the struvite process to replace treatment of waste water with metal salts. In terms of the economic, social and environmental benefits, the demonstration of the struvite process on an industrial scale achieved considerable cost savings and reductions in the environmental impact of the plant. It was found that removal of over 80 percent of the initial phosphorus load could be achieved, and that wastewater can be re-used after treatment (a problem was encountered in this respect because of scaling, but it is expected that this can be solved). The project has therefore contributed to reducing surface water pollution by producing higher quality effluent. Furthermore, using the process employed, the production of large amounts of sludge contaminated with heavy metals is avoided. It was hoped that the struvite produced by the project could be supplied to the company Thermphos in Vlissingen. This company would use it in the production of pure MAP. However, this option was not judged economically viable. The beneficiary is looking into opportunities to market the struvite as a fertiliser for agricultural purposes, which should be possible as the process avoids the production of large amounts of sludge contaminated with heavy metals. Residue levels of heavy metals present in the struvite are within legal limits. In the short term, the introduction of the struvite process is expected to lead to new jobs at the companies that supply process equipment and know-how. In the long term, the yearly operating costs for the struvite process at the beneficiary's site will be considerably lower than for conventional phosphorus removal – €107,500/year instead of €257,000/year during the project. This calculation includes the increase of the biogas production in the anaerobe reactor (before the struvite process) and the reduction of the sludge production in the aerobic reactor (after the struvite installation). During the monitoring period (March 2004 to May 2005), reliable measurements of the operating conditions were gathered. This data will enable the beneficiary to define exactly the limit of the process at industrial scale. These advances will enable the process to be implemented in two other Lamb-Weston/Meijer plants. Several other operators in the potato industry have also shown an interest in implementing the technology, with the LIFE demonstration project contributing significantly to the choice of a struvite installation instead of a conventional one. These factors have demonstrated the sustainability of the project. Furthermore the test installation has remained in operation beyond the end of the project, and the struvite process is part of the daily operation of the wastewater treatment of the beneficiary. The results of the project can also be directly applied in other food processing industries with waste water streams with high phosphorus loads: potato processing, starch, milling and sugar. In summary, the specific results from the process were: A decrease in the output of phosphate from 0.30 kg/ton to 0.05 kg/ton potato processed (expected result: 0.24 kg/ton). Phosphorus decrease in effluent of around 75 percent on average, and up to 90 percent (expected result 90 percent). Estimated recycling of 75 percent of effluent, equal to 1,450,000 m³/ year (equivalent to the expected result). Legal constraints were experienced in development of sludge for use as fertilizer, which had been one expected result of the project. Estimated annual operating costs at the end of the project were €107,500 (operational costs were expected to be reduced from €275,340 to €203,800 per year). This project has been selected as one of the 21 "Best" LIFE Environment projects in 2005-2006