April 18, 1912: Municipal Journal article. Water Purification at Trenton. By Howard C. Hottel. “As a result of investigations made by the New Jersey State Board of Health, the city of Trenton, on November 9, 1911, started to purify its drinking water supply, raw Delaware River water, by the use of calcium hypochlorite.
Previous analysis of the water had shown that there was more or less constant pollution, liable to increase under certain weather conditions, and at the time that the plant was ready to start operation there was a typhoid epidemic in progress at Trenton.
The chemical purchased when tested was found to have 35 per cent available chlorine and treatment was begun with a strength of about 0.4 to the million of available chlorine. This was found to be insufficient and on November 28 the dose was raised to 0.8 and has since then varied from 0.8 to 1.0 part per million, with a daily pumpage of about 20,000,000 gallons. In commercial terms this means that from 20 to 25 pounds of calcium hypochlorite are being added to every million gallons of water that is being pumped.
After the chemical had been increased the intestinal bacteria began to disappear, as shown by tests made by the State Board of Health. Inasmuch as the pipe area is rather large it took some time before the tap water gave negative tests for B. coli.
There has been considerable complaint from the taxpayers, who claim that the chemical gives a slight taste to the water. In fact, some would seem to prefer taking chances with typhoid rather than purification by treatment with calcium hypochlorite. The treatment, however, will probably continue until a permanent purification plant is established. Plans are already being drawn for the erection of a mechanical filtration plant, with the expectation of having the same completed within a year.
Shortly after the hypochlorite treatment was begun the typhoid dropped abruptly and a few statistics may prove interesting. During the month of November, 1911, there were 82 cases of typhoid reported, and during December 49. For the first three months of 1912 there has been a total of only 15 cases; in 1911 for the same three months there were 52; in 1910, 47.”
Reference: Hottel, Howard C. 1912. “Water Purification at Trenton.” Municipal Journal