public works – Geeky Girl Engineer

The F.J. Horgan Water Treatment Plant was one of my top two reasons for coming to Doors Open Toronto. Sadly, no wastewater treatment plants were open for the event, as I find them more interesting than water treatment plants. However, water treatment plants are still interesting. This plant was even more interesting than I initially thought it would be because I am fairly this is the first water treatment plant I have been to where they use ozone for the initial disinfectant. This is the second water treatment plant I have visited in Toronto. The first Doors Open Toronto I came to, I visited the absolutely magnificent R.C. Harris Water Treatment Plant. F.J. Horgan Water Treatment Plant is not as beautiful, but it is interesting none the less.

The plant’s water intake is from pipes in Lake Ontario over 2 km from shore. It is then pumped to the plant and then up from the pipes which are (I think) nine stories below the surface. The plant sits on cliffs high above the water surface. Ozone is added to the water. Ozone disinfects the water. The ozone is made at the treatment plant from liquid oxygen. Before the water leaves the tanks where is contacts ozone, sodium bisulfite is added to remove any left over ozone.

Ozone generation unit from liquid oxygen and electricity

Coagulant is then added to the water. Coagulant causes certain ions and tiny particles to start to come together to make bigger particles, which are easier to filter out. The water is pumped to sediment filters. The filters have a lower sand layer topped with a carbon layer. The filter tanks are huge, but so are the pipes in the building.

Gigantic water pipe conveying water (I think) to the filter tanks

This is a horrible photo because is taken through glass with wire lining, but that is water in the filter tanks. The filters are at the bottom, and I think blue plastic thing is the trough where the backwash goes when the unit is backwashed.

Another horrible photo taken through glass, but on the left side is an empty filter tank, and on the right side is a filter tank with water.

Low pressure air pipes in the filtration gallery

Gigantic air pipes running through the main part of the building

After the water has been cleaned, chlorine is added. The water has already been disinfected at this point, but a residual disinfectant is needed to kill any bacteria the water may encounter in the distribution system on its way to customers.

As part of Doors Open Toronto, I toured the R.C. Harris Water Treatment Plant, which is not only the most beautiful water treatment plants I have ever visited, it is one of the beautiful buildings I have ever visited period. Colored stone and brass are everywhere. It was built in Arts Deco style, and in my opinion as an engineer, lays tribute to the importance of what the plant does, providing clean water to Toronto. It has two galleries with huge windows to allow viewing of the filtration chambers. In front of these windows are gorgeous stone tables with simple bronze control levers. The plant itself sits on hill overlooking Lake Ontario, where it gets its supply of water to clean.