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The Syndicat des Eaux d'Ile de France (SEDIF), which is responsible for water distribution in the Parisian suburbs, built a large-scale NF unit in M¿ry-sur-Oise to improve its total production capacity and the quality of the distributed water. This NF unit with a production capacity of 140,000 m3.d-1 (37 MGD) was started up in September 1999. In order to document the impact of NF on distributed water quality, a large survey was conducted 18 months before the modification of the treatment was performed in the distribution system fed by the plant. Physico-chemical and bacteriological water quality was followed in 15 stations of the distribution system.Based on results obtained before NF (1998-1999) and since NF was in service (2000-2002), the objectives of the study were: to directly appreciate the impact of NF on THMs, bacteria numbers; and,to estimate the relative influences of variables influencing water quality in distribution systems, such as temperature, oxidant residual (i.e. free chlorine), BDOC, and TDC at the inlet to the system. The M¿ry-sur-Oise water treatment plant (MWTP) treats Oise River water and has two trains: a conventional train; and, the NF treatment train. Up to September 1999, the distribution system was supplied only by the conventional train. The new train was started up in September 1999 and reached its full capacity in April 2000. From this point onwards, the water feeding the distribution system has been a mixture comprising 30% coming from the conventional train and 70% coming from the NF train. The water currently produced by both treatment trains is blended, adjusted for pH and dechlorinated. The NF unit is composed of 8 independent files. Each file is composed of three filtration stages, all of them designed to filter half of the inlet flow, with a total yield of 85% in water. Each file has a production of 17,500 m3 d-1 so that the total production capacity of the unit is 140,000 m3.d-1. Each file is composed of 190 tubes with 6 modules of NF membranes. (Molecular Weight Cut-off: 200 Daltons, theoretical DOC removal: 90%). The total surface membranes is around 340,000 m2. The distribution system supplied with MWTP water covers 31 cities in the northern suburbs of Paris, and supplies water to over one million people. There are 9 one line storage tanks (all covered) and 12 booster chlorination units. The distribution system is divided into 3 main pressure zones. The average residence time is 40 hours, storage tanks not included. The majority of DS pipes are cast iron pipes, although mains are concrete pipes, and PEHD is now used for small diameter pipes. Six sampling campaigns were done each year, with exception of 2002 (only 3 sets of results are available). 15 Sampling stations were chosen in order to represent various situations in terms of residence time and hydraulic characteristics, including the plant outlet, the in- and outlet of the largest one line storage tank. For each sampling, the water was collected after a flush at low flow over a period of 5 minutes in order to discharge stagnant water. Samples were sent to the laboratory immediately after collection. Includes 12 references, table, figures.

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Edition: Vol. - No. Published: 11/01/2002 Number of Pages: 11File Size: 1 file , 290 KB