Wastewater disinfection - Montréal chooses ozonation

    MONTREAL, Jan. 30 /CNW Telbec/ - The Mayor of Montréal, Gérald Tremblay,
is pleased to announce that a major step has been taken to improve the quality
of the St. Lawrence River water for the benefit of Montrealers and residents
downstream from Montréal. Mayor Tremblay explained that after years of
analyses and experiments, the executive committee has approved ozonation as
the only appropriate technological choice to treat Montréal wastewater.
    The Montréal administration accepts the recommendations of a tripartite
committee of experts made up of representatives of the city's wastewater
treatment department, the Québec ministère du Développement durable, de
l'Environnement et des Parcs (MDDEP) and ministère des Affaires municipales et
des Régions (MAMR). This committee, which was created in 1997, had the mission
to examine the challenges posed by wastewater disinfection at the Montréal
treatment plant, carry out a comparative analysis of the various disinfection
processes and develop an action plan containing the steps necessary to
implement the process.
    "I am pleased to announce a major breakthrough for Montréal and Québec in
the fields of the environment and water management. Today, my administration
is acting responsibly in favour of the River and, more globally, for the
environment. We had committed to carrying through wastewater disinfection in
Montréal. Today, I can tell you that we are going forward with the ozonation
technology," said Mayor Tremblay.
    "The committee's recommendations are highly documented and supported by
reliable pilot tests and impact studies. The additional research work that we
have authorized means that the solution that we have chosen to disinfect
through ozone meets the city's specific wastewater requirements, in addition
to being the technology capable of treating emergent products. In fact, we are
proposing an innovative solution that will make Montréal a leader in the field
of wastewater disinfection through ozonation," said Mr. Sammy Forcillo, member
of the Montréal executive committee responsible for infrastructures, roads and
water management.
    The Montréal wastewater treatment plant processes 2.5 million cubic
metres of wastewater daily, or approximately 50% of Québec's wastewater. The
disinfection process to be used is part of a long-term vision and takes into
account the elimination of virus and bacteria, new emergent compounds,
including pharmaceutical products, as well as surface-active agents, such as
    In developing a solution to improve water quality in the St. Lawrence
River, Montréal had set up a laboratory to develop a wastewater environmental
toxicology follow-up program at the treatment plant, in association with the
Institut national de la recherche scientifique (INRS-Armand-Frappier) and
Environment Canada's St. Lawrence Centre. The program was set up to determine
the effects of the plant's wastewater on the aquatic fauna's endocrine system.
Later, the analyses were combined with the pilot project to determine the most
"environmentally desirable" technology in terms of disinfection alternatives,
in a follow-up and sustainable development perspective.
    The city administration supported the analyses listing the advantages and
disadvantages of each disinfection systems (ozone and UV), which were
conducted by the tripartite committee. After comparing the relatively similar
costs of the two disinfection methods and examining the environmental benefits
of ozonation, the ozonation method was chosen for wastewater disinfection at
the Montréal treatment plant.


    Since its beginnings, the Montréal wastewater treatment plant has used
chlorination as a disinfection process, before flushing it into the
St. Lawrence River. The MDDEP prohibited this process at the end of the 1980s,
because chlorine had a negative impact on the aquatic fauna and was a public
safety hazard. Now, the MDDEP allows two disinfection methods for large
cities. They are: ultra-violet irradiation and ozonation. Lagooning is also
used for small urban areas.
    Over the years, Montréal developed partnerships with various university
organizations and research institutes to determine a method that would meet
the specifics of the city's industrial waters and address the issue of
emergent products, such as pharmaceutical materials. Pilot tests have been
conducted since 2005 to determine the effectiveness of the two disinfection
technologies. At the same time, environmental toxicology tests were conducted
to determine the effects of these methods on the aquatic fauna. Results are
meaningful with the ozonation process, because it doesn't harm the flora or


    The tripartite committee's report will be tabled before the urban
agglomeration's standing committee on sustainable development and submitted to
a public hearing in the winter of 2008. The committee will then make its final
recommendations taking into account the public documents presented as part of
the consultation.
    Additional tests will be conducted to determine the design and
implementation criteria for the ozone injection system, as well as the
financing package to secure funding agreements with the government of Québec.
The estimated cost of the project is approximately $200 million. The
anticipated annual cost for ozone disinfection could reach approximately
$9 million.
    "We are going forward for the entire Montréal community. Our decision to
invest in a disinfection system will have a major impact on all our riverside
municipalities and their residents. I am also thinking of future generations
who will benefit from a healthy river," said Mayor Tremblay.

For further information:

For further information: Philippe Sabourin, Chargé de communication,
Division des relations avec les médias, (514) 872-5537; Source: Renée Sauriol,
Cabinet du maire et du comité exécutif, (514) 872-4894

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Ville de Montréal - Cabinet du maire et du comité exécutif

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