Montreal wastewater treatment | 3.7 billion to invest in the purification plant

The bill to deal with the contents of Montrealers’ toilets is about to explode: after paying nearly a billion for an ozonation plant, which is still not in operation, the City plans to spend 3, 7 billion more within 10 or 15 years, to burn the sludge – our excrement – ​​in a less polluting way and add treatment before discharging the wastewater into the river.

Where is the construction of the ozonation plant?

Ozone disinfection of water from sewers across the entire island of Montreal will begin at the end of 2028, if there are no further delays. The ozonation plant project, started in 2015, was to last three years and cost 200 million. Nearly 10 years later, it is still not finished and the bill has reached 942 million. Ozonation will be the last step to disinfect wastewater before its discharge into the river, at the Jean-R.-Marcotte treatment plant, in Pointe-aux-Trembles. The project includes the construction of an oxygen production unit and a new electrical substation on the site. It is the largest ozone disinfection unit in the world, which will treat nearly 50% of Quebec’s wastewater. “We are well placed to meet the deadline,” assured the director of the City of Montreal’s water service, Chantal Morissette, while presenting her budget to the elected officials of the Commission on Finance and Administration, there a few weeks. Good news: the bill estimate has not increased since last year. A third of the project’s costs will be covered by grants, and the City is trying to obtain more from higher levels of government, said Ms.^me Morissette.

What is ozonation used for?

By injecting a large quantity of ozone into the water before releasing it into the river, we destroy bacteria, viruses and almost all emerging particles, such as medications (anovulants, antibiotics, antidepressants), traces of which are found in watercourses. Montreal will thus be able to comply with the standards established by the Quebec Ministry of the Environment. “The benefit of this project is also for the St. Lawrence River, for biodiversity, for the towns downstream” which obtain their drinking water from the river, notes Chantal Morissette.

What is the next project?

The project to replace incinerators that burn dried sewage sludge is scheduled to begin in 2028 and last six years. It will cost even more: 1.2 billion, according to the current estimate. And by 2023, it was estimated at 682 million. The four current multiple hearth incinerators, powered by natural gas, date from 1988 and are expensive to maintain and repair. “They emit 30% of the greenhouse gases produced by the activities of the City of Montreal,” explains Chantal Morissette.

How will the new incinerators be better?

The new sludge treatment and valorization plant (UTVB) will reduce greenhouse gas emissions by 61%. “The old incinerators will be replaced by three technologies: new incinerators, biomethanization and thermal drying,” indicates Chantal Morissette. The objective is to increase our capacity to recover sludge, and in addition, we will produce renewable natural gas. » Incineration residue can be used in agriculture.

And then there will be more work?

Despite all these improvements, it will be necessary to add another stage to the treatment of wastewater, with an even steeper bill: 2.5 billion, revealed the director of the water service, during the presentation of her budget. “It is a secondary treatment to remove organic matter and nitrogen, to comply with the regulations on wastewater sanitation of the Quebec government,” says M.^me Morissette. All cities in Quebec will have to adapt their wastewater treatment facilities to meet the new standards. The Ministry of the Environment set the deadline for 2030, but Montreal, which chose treatment by biofiltration, requested a delay until 2040.

Why do we need to add additional treatment when the wastewater will already be disinfected with ozone?

The current treatment stages – screening, desanding, coagulant injection and decantation – do not make it possible to reach the new standard, even when ozonation is added, explains Professor Yves Comeau, specialist in wastewater treatment at the Polytechnic School. “Logically, the City should have first installed a secondary treatment [la biofiltration] before planning disinfection [l’ozonation]. However, when the decision was made, there were not the same requirements imposed by the Ministry of the Environment,” notes Mr. Comeau.

Why are these treatments so expensive?

For the ozonation plant, whose costs more than quadrupled compared to initial estimates, municipal officials explained that it was cutting-edge technology and that there was nowhere in the world of similar installations. There have also been several glitches on the site, few companies interested in bidding and an explosion in construction costs in recent years. For example, in 2018, a major technical problem paralyzed the project for months: teams feared that a huge wave would form in the water pipes after ozonation. For secondary treatment by biofiltration, the sum of 2.5 billion is only a first estimate, warned Chantal Morissette. “It may seem like a lot, but in Quebec, the cost that citizens pay is much lower than elsewhere in the world, including Ontario, the United States, Europe and elsewhere,” also underlines Professor Yves Comeau. . There is a real investment deficit in water infrastructure. »