May 25, 1806: Letter from Thomas Telford discussing design of the filtration works at Glasgow, Scotland. Glasgow was the third city in the world to receive filtered water (after Paisley, Scotland and Paris). Delivery of water by pipes to customers began in 1807.
“Thomas Telford, who later founded and served as first president of the Institution of Civil Engineers, was engineer for the Glasgow Water Works Co. Correspondence between him and Boulton & Watt (13) affords meager data regarding his plans for the earliest filter at Glasgow. In a letter dated May 25, 1806, he said that “if there is any difficulty in getting the water [from the Clyde] to subside or filtrate so as to be perfectly good-then instead of one reservoir 6 ft. in depth, it will be advisable to have two of 3 ft. in depth each-and each one acre in superficial area.”
About forty years after the works were completed, Donald Mackain, engineer of the company then supplying water to Glasgow (14), described how Telford proposed that water be pumped from the Clyde at a point two miles above the city to three reservoirs each holding a day’s supply. These reservoirs were to be so placed, wrote Telford, in a report no longer available, “that the water in passing from one to another shall be filtrated.” Telford’s plan was followed, says Mackain, but in times of flood the river brought down alluvial matter that did not soon subside, followed by water from sources higher up which had a deep brown color. Telford’s filter yielded water differing little from that of the river.
Again what a pity that Telford and Mackain made only vague references to filters built so early. Neither Telford in his autobiography (15) nor Sir Alexander Gibb in his recent biography of Telford (16) mentions Telford’s filters at Glasgow.
James Simpson, in a discussion (17) of Mackain’s paper, describes Telford’s filters as “a series of cells, filled with sand” through which the water passed in succession. When the water was at its worst it was little changed after passing through the first filter, but at times the filters worked satisfactorily.”
Reference: Baker, Moses N. 1981. The Quest for Pure Water: the History of Water Purification from the Earliest Records to the Twentieth Century. 2nd Edition. Vol. 1. Denver, Co.: American Water Works Association, 80-1.