Upgrades at the Sainte-Angelique drinking water treatment plant in Saint-Lazare, Quebec, aimed to double water production capacity to 19 MLD without enlarging the plant building and staying within budget.


  • Saint-Lazare, Quebec

Project Value

  • $8,000,000

Project Status

  • Complete


  • Dube Matte Architects

The Sainte-Angelique water treatment plant was commissioned in 1994 in order to reduce the iron and manganese contained naturally in the groundwater. WSP’s services were required to upgrade and increase the capacity of the plant from 10.5 MLD to 19 MLD. WSP performed preliminary studies, treatability pilot testing, detailed design, and contract administration for the upgrade and expansion.

The pilot testing included the physical/chemical removal treatment process, as well as the biological removal process of iron and manganese from underground water. Based on the outcome of the pilot testing, a chemical-free treatment was selected to be the preferred treatment approach. The transformation of the existing oxidation/greensand filters into biological filters allowed water production capacity to almost double, reaching 19 MLD, without enlarging the building. Other important benefits brought by the new technology were the significant savings on filtered water used for the backwash of the filters, and the interruption of potassium permanganate usage -- a hazardous chemical.

The drawings and specifications were prepared in compliance with the requirements of the new drinking water treatment design guidelines. Value engineering was performed in order to meet the client’s budget, which included the participation of the pre-selected biological filtration equipment supplier. One of the biggest challenges was maintaining the drinking water production at all times during this work, especially during the transformation of existing filters.

Quantity of Wells
7 7
Rated capacity
19 MLD 19 MLD
Population served (2025 Horizon)
20,500 20,500
Approximate drinking water saved per year
200,000 m3 200,000 m3
Approximate potassium permanganate saved per year
3,500 kg 3,500 kg
Capacity of the new clearwell
3.4 ML 3.4 ML


  • Construction of a new raw water room in the plant.
  • Transformation of existing oxidation/greensand filtration process into biological filtration process for iron and manganese removal.
  • Construction of a new chemical room.
  • Replacement of the gaseous chlorination system with a sodium hypochlorite dosing system.
  • Expansion of the drinking water clearwell, including the addition of baffles in the existing reservoir.
  • Replacement of two 20 HP fixed speed pumps by two variable speed distribution pumps of 75 HP each.
  • Replacement of entire control system and instrumentation, including the addition of a telemetry system at the wells.
  • Addition of a 450 kW stand-by power system.


After the upgrades, the Sainte-Angelique plant became one of the largest plants using a biological iron and manganese removal system, and one of only a few in the entire province to use this kind of chemical-free technology.

For every 100 L of filtered water, the biological filtration system requires 2 L of wash water, compared to the old greensand filtration system, which required 10 L. This allows the Municipality to save more than 200,000 m3 of drinking water per year, which is equivalent to 80 Olympic-size swimming pools.

Instead of a compressor, an aerated cascade was designed to supply oxygen to biological media.

In order to expand without enlarging the building, the plant upgrades were designed in 3D to optimize the concepts.