Wastewater treatment
This paper provides a brief discussion of the state of municipal wastewater treatment in France and Quebec. It then presents some important changes that have developed over the last ten years in the world and their potential influence on the future. In France, 95% of towns of more than 10 000 residents have a wastewater treatment plant. Construction of new plants reached 730 installations in 1976, but has since declined to less than 300/year. Among 11 310 sites of more of 200 inhabitants, 5 % utilize only primary treatment and 50 % utilize the activated sludge process which represents 60 % of the treatment capacity.In order to satisfy the European directive of May 21st 1991, approximately 36 billion French Francs should be invested between 1994 and 2005. This investment represents new wastewater treatment facilities for 17 million people. In Quebec, construction of wastewater treatment plants occurred mainly during the 80's and 90's. Today, nearly 80 % of the population is served by wastewater treatment plants, which represent approximately 4,9 million residents. This accounts for a flow rate of 5,3 million cubic meters per day.Among 450 municipal treatment plants, those of the urban communities of Montreal and Quebec represent nearly 60 % of the total wastewater treatment capacity of Quebec. Physico-chemical treatment plants are the most significant (6 plants for 2,28 million residents) followed by activated sludge process plants (40 plants for 0,69 million residents) and plants using biofilter technologies (9 plants for 0,75 million residents). A total of approximately 320 small treatment plants, serving an average of 3 500 residents, use the aerated lagoon treatment. Over the past decade technological developments have resulted in an evolution that will modify the design and operation of wastewater treatment plants in the future: - the more widespread use of techniques developed for the elimination of nitrogen and phosphorus; - the realization of the importance of polluting charges transported by pluvial waters; the beginning of the resultant wastewater treatment plant adaptations; - the limited development of anaerobic treatments that have survived the energy crisis; - the valuable development of biological fixed-culture systems for wastewater treatment and most notably, the biofilters; - the appearance of promising membrane technology in wastewater treatment systems, which could facilitate the definition of new treatment objectives; - the consideration the global reliability of the wastewater treatment systems instead of only peak performance; - a more integrated vision for the prevention of pollution in industry (clean technologies) as well as in the domestic environment (integrated management of sewerage system and wastewater treatment plant)