June 25, 1914: Engineering News article. A Novel Water-Filtration Plant for Toronto. “It is not often that a city takes up a novelty in water filtration or in any other class of engineering work on so large a scale as the proposed 72,000-U. S.-gal. “drifting sand” filtration plant for which the city council of Toronto awarded the contract on June 8. It is true, as stated elsewhere in this issue, that two plants of a few hundred thousand gallons capacity are already in operation elsewhere and that contracts for two other and much larger plants are well under way. It is also true that a working unit was tested for 33 days at Toronto under the direction of the local medical officer of health and city analyst, and that this same test plant has been under observation for over a year. Nevertheless, the fact remains that the drifting-sand filter is as yet in the working-scale experimental stage, with few data yet available regarding its efficiency and less to be had regarding operating costs.
The drifting-sand filter may be described as a deep mechanical filter with reversion to the early type in the way of absence of coagulation basins and rate-controllers and with the addition of continuous washing and replacing of filter sand. It is claimed that this added feature makes up for the lack of a coagulating basin. To what extent this claim will be made good by experience at Toronto and on different waters at other places, it will be interesting to learn a few years hence.”
Commentary: The filter plant was built in 1917 and used until 1981 by the City of Toronto. No other large-scale filtration plants adopted this unique design.