Winnipeg hopes new water-treatment chemical will reduce brown water

Winnipeg is testing out a new coagulant at its water-treatment plant in the hopes of reducing complaints about discoloured drinking water next year.

The city receives as many as several hundred complaints each month about brown water and no fewer than 1,200 calls for service a year related to the discoloration, water services manager Tim Shanks told city council's water and waste committee on Monday.

After a rash of brown-water complaints in 2013, the city determined the discoloration is due to manganese. That metal, naturally present in tea, leafy greens and groundwater, started to build up in city water pipes after the city began operating its $300-million water-treatment plant in the RM of Springfield in 2009.

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In 2014, an external consultant concluded the manganese was a byproduct of materials used to manufacture ferric chloride, a coagulant used in one of the key treatment steps at the city plant. Changes in water pressure in the city's pipes, caused by either water main breaks or construction, caused manganese concentrations in drinking water to spike, especially during the summer.​

The city is now trying out a different coagulant, ferric sulfate, which contains about 90 per cent less manganese, Shanks said.

Engineers are testing out the efficiency of this coagulant in a number of conditions, including different temperatures, he said. If all goes well with the experiment, the city will replace ferric chloride with ferric sulfate in 2018, Shanks said.

The results in water quality should become noticeable within months, he said.

While brown water due to manganese is not considered a health risk, the discoloration has made it difficult for residents to wash clothes and has sparked thousands of complaints to 311 since 2013.