Here are some pages taken from the “City of Ottawa” water treatment plant website.
Water purification and treatment
On an ordinary day, the human body loses about two litres of water through breathing, perspiration and excretion. It’s important that we replace that lost fluid with clean, safe water. While the waterborne transmission of typhoid fever, diphtheria, cholera and several other intestinal diseases has decreased by over 98 percent in Canada during the last 50 years, our water still needs to be purified and treated before we drink it.
Constructed in 1874, Ottawa’s original water supply system was located in the Fleet Street pumping station. This station used the hydraulic energy of the Ottawa River’s Chaudiere Falls to pump untreated river water into the distribution system. In 1915, an electric motor-driven pumping station was constructed on Lemieux Island followed by a complete water purification plant in 1932. The Britannia water purification plant began operations in 1961. Today, these plants are part of a system that produces and distributes an average of 341 million litres of water a day.?
The system draws water from the Ottawa River then, using the most effective processes and equipment available, treats it to remove colour, suspended particles, algae, vegetation, bacteria and viruses. Our water-purification processes are continuously monitored, ensuring that high-quality water is pumped out of the plants and maintained as it travels through the distribution system.
Central water supply system
Every day, the City of Ottawa’s central water supply provides drinking water to approximately 750,000 customers. This quarterly report is published to give water quality information to the public and to meet the requirements of the province’s new Drinking Water Protection Regulation. It summarizes water quality results and other information collected during the period October through December 2002.
Water supply in Ottawa
The source of our city water is the Ottawa River, an abundant supply of clean, soft water that is high in natural colour. Extensive testing confirms that the Ottawa River as a source of raw water is essentially free from contamination. Where urban or industrial discharges exist, there is the potential for pollutants to enter the watershed and impact drinking water quality. For the Ottawa River watershed, these are limited to the Chalk River Laboratories and a pulp and paper plant at Portage-du-Fort. Intensive monitoring for radioactive and trace organic substances are carried out to ensure the safety of our raw water supply.
The river water (raw water) is treated at two purification plants: Lemieux Island (constructed in 1931) and Britannia plant (1961). Both plants use an identical water treatment process and have undergone significant expansion and modernization over the years. Raw water enters the treatment plants through large intake pipes that extend into the main flow of the river.
- The treatment process makes use of the “multiple barrier” principle. A series of treatment steps successively remove undesirable substances such as colour, suspended particles, algae, bacteria, and viruses from the water. The purification process in Ottawa consists of the following steps:
- primary disinfection (chlorine)
- coagulation (alum)
- flocculation (silicate)
- filtration (sand/anthracite)
- pH correction (lime)
- secondary disinfection (chloramine)
During the final treatment step, fluoride is added for prevention of dental cavities, and chloramine is added to preserve water quality as it travels through the vast water distribution system.
After the treatment process, water is pumped through the distribution network of watermains (over 2400 km of watermain piping) to reach water customers over an area roughly 25 km by 50 km. Treated water from both the Britannia and Lemieux Island water plants is blended as it travels through the distribution system. Pressure and storage requirements are met through the operation of 20 pumping stations and reservoirs located throughout the system. The total volume of water stored in reservoirs is 270 Million Litres, about 2/3 of daily water production.
Drinking Water Standards
Health Canada has established the “Guidelines for Canadian Drinking Water Quality” which lists 80 maximum acceptable concentration (MAC) values for various substances that are of health concern, as well as aesthetic guidelines for substances that affect consumer acceptance such as taste, odour, colour, and hardness. The Ontario Ministry of Environment has established “Ontario Drinking Water Standards” (ODWS) with MAC levels adopted from the Health Canada guidelines, as well as standards for several additional parameters.
Health Canada and the Ontario Ministry of Environment maintain that adherence to these standards will result in drinking water that is safe and protective of public health.
Some of our cities still discharge raw or partially treated sewage with metals, grease and toxins into rivers, lakes and oceans. In the United States, most cities, even small ones, are required to perform at least secondary sewage treatment (see “Waste matters,”). In addition to treatment?plant discharges, overflows from combined sewers and dirty storm water are huge sources of water pollution in most Canadian cities. Although the technologies exist to solve these problems sewer separations and chemical recycling and other source controls to keep toxics out of the sewer system to begin with no consistent regulations require cities to clean up.
An Environment Canada working group is considering a national strategy for dealing with municipal wastewater effluent. Its report is expected this fall. But don’t hold your breath waiting for real regulations. Says group member Michael Guilcher, Environment Canada’s manager of pollution reduction in Halifax, “It takes about two years to get a new regulation through the system.”
Revisions to the THM [trihalomethane, a by?product of chlorination] guideline were debated for seven years,” echoes Health Canada engineer David Green, recorder for the federal?provincial subcommittee on drinking water (see ” Can we drink the water?”). While there is a federal guideline for THMs, there are none for PCBs or dioxins in drinking water, to name just a couple of surprising omissions.