Disposal and purification of factory wastes or manufacturing sewage / by H. W. Clark.

Date:
1910
Catalogue details

Licence: In copyright

Credit: Disposal and purification of factory wastes or manufacturing sewage / by H. W. Clark. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    organic and mineral matter present in the liquor is often from one hun- dred to three hundred times as great as is seen in ordinary domestic sewage, the necessity for an excessive use of precipitants is to be expected. There is, too, the difficulty due to the large amount of dirt. Much of the fatty matter in the liquor, furthermore, is in a state of semi-emulsion, and lighter than the water in which it is held; hence, any coagulation tends to gather this matter into masses containing a smaller percentage of water than before coagulation, and this coagulum, by reason of its buoyancy, carries some of the precipitants to the surface instead of being carried down by them. The experience at Lawrence has been similar to that at other places in the purification of such liquors by precipitation. At Bradford, Eng., the center of the English woolen trade, where it is calculated that 8 per cent, by volume of the sewage of the city comes from wool-washing establishments, it has been shown that from nine to twelve times as much precipitant is needed when treating week-day sewage as when treating Sunday sewage, free from this waste. Straining through Coke and Cinders. Experiments have shown that a considerable clarification can be ob- tained by passing these liquors to beds of coke or cinders; in fact, if the liquor is to be considered a sewage, and passed into the sewers of a town or city1', the most successful method of treatment is undoubtedly by the combination of settling tanks and coke strainers, the mixture of the clar- ified effluent with the domestic sewage being passed to an ordinary filter bed. At a fourth factory the liquors came from the processes of scouring wool, washing yarn, cloth-washing and dyeing, and the total volume amounted to 30,500 gallons per day, divided as follows: 21,000 gallons from wool-scouring, 2,100 from yarn-washing, 400 from cloth-washing and 7,000 from dyeing. Acid Treatment. Many examinations and experiments were made at the station with these liquors, and it was estimated from the analyses that the organic matter in them was equal to that in 200,000 gallons of domestic sewage such as flowed to the area to which it was proposed to pass these wastes. It was found that only about 20 per cent, of the organic matter in sus- pension would settle out in twenty-four hours; that the use of 25,000 pounds of sulphuric acid per million gallons of liquor treated caused good coagulation of the fatty matters and left the organic matter in such a condition that it could be filtered or strained easily, leaving a clear