Around Nov. 7, the city is adding another chemical besides chloride and fluoride to your drinking water.
It’s orthophosphate, and its purpose is to adhere to pipes as a protective coating your drinking water passes over on its way to your home tap. But some of it will end up in your glass of water.
An average person would need to drink 330 glasses of water to get the same amount of phosphate that is in one glass of milk.
Why is it needed?
To control corrosion on the remaining old lead pipes in the water distribution system. Orthophosphate is one of the most common methods used for control, says Andrew Grice, director of Hamilton Water.
This is needed because the lead that corrodes and leaches into the drinking water from lead pipes is bad for people.
“Consumption of even very small amounts of lead is harmful to human health, especially in infants, young children, and pregnant woman,” said Grice in a report to council last month. “There is no recommended level of lead ingestion that is considered safe.”
OK, but is orthophosphorus safe?
Yes, according to the city.
It is a form of phosphorus — and phosphorus, found in human bones and teeth, is an essential mineral for growth and repair of body cells. We need it, in low levels, to survive.
Orthophosphate is being added on or around, Nov. 7, depending on equipment checks, in the form of food-grade phosphoric acid that is a clear, odourless liquid.
By the time drinking water reaches your tap, “only a minimal amount remains,” says Grice.
An average person would need to drink 330 glasses of water to get the same amount of phosphate that is in one glass of milk.
Do other cities do this?
Yes. Orthophosphate is used in Toronto, Winnipeg, Halifax, New York City, Detroit, Chicago, and Washington, D.C., among others.
The United Kingdom started treating water with it over 30 years ago. It is now used in 95 per cent of drinking water systems there.
But why not just replace old lead pipes?
Any lead water mains that existed have been replaced. But the city is still replacing pipe connections to private properties ad hoc. And unless homeowners have replaced their own incoming lead pipes in homes built before the mid-1960s, they exist there too.
What else is added to our drinking water?
Chlorine, fluoride, aqueous ammonia and poly aluminum chloride.
Chlorine disinfects and kills harmful bacteria. Fluoride reduces tooth decay, and aqueous ammonia keeps the chlorine from losing its power as it goes through the distribution system.
Is that it, for making drinking water safe?
No. It’s more involved than that, but put simplistically:
Water is drawn from an intake pipe in Lake Ontario, 900 metres offshore from near Barangas on the Beach restaurant on Van Wagner’s Beach Road. A chlorine injection is given as needed in summer to prevent lake zebra mussels from clogging the intake pipe.
The lake water is drawn into a “low lift” pumping station building across from Hutch’s restaurant, also on Van Wagner’s Beach Road. A large screen captures debris coming in with the water.
Then a pipe going under the Queen Elizabeth Way carries the water to the treatment plant on Woodward Ave. Poly aluminum chloride is added to bind particles like clay, silt, sand and bacteria so they sink into sediment tanks.
Hamilton’s drinking water treatment plant is on the same site — but on opposite ends — as the main sewage treatment plant which discharges into Hamilton Harbour near the Windemere Basin.
Once clay and other particles settle out, the lake water is moved through filter basins where carbon filters, acting much like a Brita filter, remove organic material, improve taste and eliminate odour.
Once passed the filters, the water goes into clearwells (large underwater storage tanks). It is at this point that chlorine is added, then fluoride — and coming soon, orthophosphate.
As the treated water is then pumped out, aqueous ammonia is added to help the chlorine stay in the system.
The water is sent out through high lift pumps and distributed to 21 water pumping stations, 13 reservoirs, and seven water towers throughout the city before ending up at household taps.
The city’s water system of pipes, reservoirs and water towers amount to an asset of $3.2 billion.
Drinking water enters the distribution system through a series of large pipes ranging in diameter from 1,200 mm (48 in.) to 2,250 mm (88 in.)
The water treatment plant can treat up to 909 megalitres per day, the equivalent of 350 Olympic swimming pools.
What about people who get their city water from wells?
Only chlorine is added to the city’s four wells at Carlisle, Freelton, Lynden, and Greensville. Orthophosphate will not be added — any lead in the system is so minor it is not an issue.
Isn’t adding orthophosphate to lake water counterproductive?
The city must remove phosphate when converting sewage and wastewater into an effluent that can be discharged.
High levels of phosphorus can promote the growth of algae that decreases sunlight and oxygen levels for fish and other aquatic life.
While some of the added orthophosphate will go down the drain to the sewage treatment plant, Grice says “We’re talking a very small percentage that comes through … It’s a drop in the bucket.”
“We are adding a bit (in drinking water), but we can remove it at our sewage wastewater treatment facility.” Phosphorus levels in the discharge is not at zero, but the city does meet regulatory targets, he said.
(The city has two sewage treatment plants — the main one at Woodward, and a smaller one in Dundas that empties through the Desjardins canal into Cootes Paradise.)
What does adding orthophosphate cost?
Construction of the orthophosphate building and equipment is in the $4.5 million range. The cost of adding orthophosphate is estimated at about $300,000 a year.
How many lead pipes are left in the system?
20,000, scattered throughout Hamilton, although most are in the lower city and on older parts on top of the Mountain.
The average cost estimate for a homeowner to replace theirs is around $4,000 — but the city has a loan program to help.
What do experts say?
Drinking water researcher Clare Robinson says there is good scientific literature showing orthophosphate has been successful at reducing lead levels in drinking water.
The Western University associate professor in environmental engineering says the only other option is to replace the lead pipes, which is very expensive for private property owners.
“A lot of them don’t want to fork out the money to replace the pipes, so orthophosphate is a more cost feasible option (and) really the best alternative…it’s going to be a lot less harmful than the lead”, Robinson said.
Source: City of Hamilton
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