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Smart Flow in Reiderland (RAS)
Date du début: 1 déc. 2000, Date de fin: 30 nov. 2003 PROJET  TERMINÉ 

Background In the past the sewerage system of the Municipality of Reiderland did not meet statutory sewerage requirements. There was a fair degree of leakage and secondary facilities were needed to back up the overflows. Consequently, the sewerage system led to the pollution the ground and surface waters. The result of a combined (rain water, household water) system was that water treatment had to deal with a large amount of clean rainwater and consequently peak supply and over dimensions of the treatment plant. Objectives A solution to the abovementioned problem was a separated effluent system. However, building a separated system in existing residential areas posed a number of difficulties mainly with regard to the interference with private properties (houses) and the risk of misconnection of the different water lines. This is why the municipality of Reiderland developed the new Smart Flow technology, jointly with BV Wavin KLS and Arcadis. In practice, this means that the present main sewerage system will be retained but will function after implementation as a rainwater drainage system. Any leakage from the present system will not be harmful, since it will contain only clean rainwater, which will be allowed to drain into the soil. The original domestic connections would continue to exist, but the new Smart Flow system would function as a dry-weather discharge, collecting the household sewage. This effluent would then be transported to the waste water treatment plant. Smart Flow would create the following situation. Wastewater would flow via the dry weather drainage system to the wastewater treatment plant. In the case of rainfall the dry weather drainage system would be closed using Smart Flow and the rainwater would disappear via the rainwater drainage system. The first rainwater, however, would drain into the dry weather drainage system. This is the so-called first flow, containing pollution from e.g. roof gutters and streets. The rainwater system would discharge all the collected and transported water directly into the surface water. The Municipality of Reiderland would be the first to use this entirely new technology. The objective of this LIFE project was to: 1. Optimise and implement the ‘Smart Flow’ system under several village and semi-city conditions; 2. Demonstrate and transfer the Smart Flow technique and its related experiences 3. Disseminate the Smart Flow technology to a national and international audience; 4. Allow long-term unemployed workers to get working experience via this demonstration project. Results The Smart Flow system was developed before the project, but the practical testing of the prototype in a real situation was carried out in the village of Drieborg. Based on these tests the design was adapted and further tested. The prototype system was then monitored on-line for an initial period of 6 months, which was extended by 3 more months due to insufficient rainfall in the summer period. The initial tests showed unacceptable high concentrations of nutrients and BOD. Only after detailed studies of the system a solution was found. Therefore, a slight change of operational approach, in which the first flow of rainwater (containing a relatively high concentration of nutrients from litter, leaves, road dust) was discharged to the sewage system (dry weather discharge); after this (enriched) water had been discharged the rainwater was discharged to the (clean) rain water line. This approach proved to be acceptable to the Water Board. Following these successful tests, the Water Board granted permission for implementation of the system in the municipality of Reiderland. This approval was somewhat unique in the development of Dutch sewer technology. After completion of the testing, the Smart Flow system was subsequently implemented in several villages in the municipality of Reiderland: Drieborg, Nieweschans and part of Finsterwolde. In total 11 km of Smart Flow sewer pipes, with about 800 Smart Flow sumps have thus been successfully implemented. A preliminary evaluation has shown that the system was a cost-effective approach, with limited technical problems. Initial calculations, based on work recently carried out in Nieuweschans and Finsterwolde, demonstrated the following cost comparison: • Traditional solutions, such as building a separated sewerage system, with work that had to be done on private ground, measured a additional price of € 50, per linear metre. • The average price of the Smart Flow solution for Nieuweschans and Finsterwolde was € 270, per linear metre. Based on current experience, it could be concluded that using the Smart Flow system produces a 15 % reduction in costs. Dissemination of the project results was firstly directed towards the inhabitants of the respective villages where Smart Flow would be implemented. The system was explained, and the benefits of implementation, including the environmental aspects were addressed. A communication plan was prepared based on the preliminary evaluations. Dissemination was then carried out nationally (towards other municipalities, at national conferences) and internationally (notably towards the bordering municipalities in Germany, and one international related conference). Furthermore, the results of the project were disseminated on two internet sites (that of the municipality and Arcadis, the implementing consultant); brochures on the system were prepared and distributed towards the general public and to the water/effluent sector. Finally, several specialist articles were prepared and submitted to scientific journals for publication. The objective of providing work for four long-term unemployed was only partly addressed. It took great efforts to find suitable workers that were sufficiently capable and motivated to receive dedicated training and work experience to continue in full employment. Only in the second half of the project 5 candidates were selected. They were due to start a training course in early 2004, beyond completion of the EU funded project.


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