13 million cubic meters of untreated water will be discharged into the river
Work on the future ozonation unit at the Rivière-des-Prairies wastewater treatment plant should begin shortly. While it promises to eventually reduce more than 99% of the bacteria discharged into the river, it will however lead to the discharge of 13 million cubic meters of untreated water during its construction, including water from the sanitary sewers. A situation reminiscent of the “flushgate” of 2015.
A $93.2 million contract with Pomerleau for the construction of the ozonation plant located at the J.-R.-Marcotte water treatment plant was authorized this Wednesday by the executive committee . Its commissioning is scheduled for 2025.
However, overflows into watercourses during major periods of rain or snowmelt are expected during the construction period. The reason: The processing capacity of the plant will be reduced for two periods of 6 months in 2022 and 2023.
Maja Vodanovic, elected head of water on the executive committee, however, assures that the situation would not however be comparable to that of the “flushgate” of 2015. At the time, approximately 4.8 M cubic meters of wastewater had dumped directly into the river over a four-day period.
“In 2015, it was continuous, and it was just waste water. (…) Here, 65% will be rainwater. It's much more diluted.”
Even if this still means that 4.5 M cubic meters of wastewater will indeed end up in the river, this water will be discharged over a much longer period.
The period overflow is expected between November 1, 2022 to April 30, 2023, and from November 1, 2023 to April 30, 2024. During this period, the 13 M cubic meters of water will be released at certain times of the day, extending over 44 days.
Reduce nearly 100% of viruses
The ozonation process promises to reduce bacteria in treated discharge water by more than 99.9% and enteric viruses by 96% to more than 99%, according to the city. It would be 75% to 85% of the pharmaceutical residues which will thus be eliminated, in the long term.
In this context, the spills expected during the work are worth the effort, believes Ms. Vodanovic. “It will be so much better afterwards. Right now out of the factory, it's a million fecal coliforms per 100 milliliters. At the end of the work, there will be just 9,000,” she illustrates.
The RDP plant currently treats all of Montreal's sewage and 45% of domestic water in the province.
Promised for several years, the wastewater ozonation unit project had been estimated at over of $210 million in 2005 by the administration of Gérald Tremblay.
Several years later, the budget had to be revised upwards. It reached more than $350 million under the Coderre administration. The delivery of the project had been promised for 2018, but “technical problems” had delayed its commissioning.
The budget is currently estimated at $696.2 million. A total of 8 contracts are planned for the entire project.
“Since then there has been inflation. But apart from inflation, it is also the technological challenge of the installation. We are the first in the world to do so in such a broad way, ”says Ms. Vodonovic.