USE OF ARTIFICIAL WETLANDS FOR THE TREATMENT OF RECREATIONAL WASTE-WATER

In June 1990 the City of Montreal opened a beach on an artificial lake where a wetland was built to maintain water quality. Occupying an are a of 20 000 m2, the wetland consists of four ponds of varying depth wh ere more than 100 000 aquatic plants of different native species were introduced. Intake pipes draw 140 1 sec-1 of water into the first pond and water then circulates by gravity through the three remaining pond s. During 1990 and 1991 several parameters were monitored in order to evaluate the efficiency of the system. The ponds proved to be very goo d traps for O-PO4 and NO-3. A good interception of soluble phosphorus and suspended solids was also observed. Removal of faecal coliforms ho wever, seems uncertain and long-term effectiveness is also uncertain.