Cantor lectures on bacterial purification of sewage / by Samuel Rideal.
- Rideal, Samuel.
- Date:
- 1899
Licence: Public Domain Mark
Credit: Cantor lectures on bacterial purification of sewage / by Samuel Rideal. 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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![the depth should not be less than 5 feet. At Lichfield the first layer, over tlie drain pipes, is A-in. cube coal, then a little ]-in., afterwards 2^ feet of i-8th inch cube, and 2A- feet of i-i6th inch, ending with 6 inches of 3-i6th coal dust. The liquid is supplied con- tinuously for 12 hours, with 12 hours rest, and the rate is 1,000,000 gallons per acre per day. The effluent is said to be bright and clear. He adds that as a result of 12 months working the efficacy of the coal has in- creased. At first it would appear that the action is a chemical one, because the oxygen absorbed is at once directly affected; after- wards, however, nitrates are produced in con- siderable quantities, so that probably there is then a double action, chemical and bacterio- logical. The interior of the filter, after many months, has nothing but a slight earthy smell. This filter was introduced by Mr. Garfield in the summer of 1896. Mr. Fowler, in his report of the Davyhulme experiments, in 1897, confirms the results of previous observers that coal and burnt clay filters, when worked continuously, rapidly become clogged, and that improved results are obtained with intervals for rest and aera- tion. He considers coal to be superior to burnt clay. In the experiments with Manchester sewage the liquid dealt with was usually an effluent which had been treated with chemicals, such as lime and sulphate of iron or alumina, a pro- cedure which robs the liquid of its natural bacteria, or inhibits their action. The work of bacteria is repeatedly recognised, and yet, even where, as at Accrington, Oldham, and other places, a treatment is adopted which is called biological, merely as a supplement to chemical and mechanical processes, we meet with such phrases as Both the tank efHuent and the cinder filtrate were tested for nitrites and nitrates practically without result (Oldham); There is practically no formation of nitrates in the filters at Swinton; at Accrington, nitrification in final filter none; at Salford, the large excess of lime present acts as a temporary sterilising agent.'' We cannot be surprised, therefore, that nearly all the effluents were found liable to subsequent putrefaction, or at the result that the anaerobic changes which had been suspended by the treatment, are resumed imperfectly and ir- regularly in the Ship Canal or the rivers. Jn l^ecembcr, 1897, a Rivers Sub-Committee of the Manchester City Council visited repre- sentative sewage works at Barking, Friern Barnet, Sutton, Oldham, Swinton, Chorley, Glasgow, Salford, Hendon, and Accrington. In March, 1898, their rcpoit was approved and a deputation was appointed to wait on the Local Government Board. The conclusions of the Committee arc shortly:— 1. That filtration by land is altogether im- practicable. 2. That no practicable system of precipita- tion by chemicals alone has been laid before them which will meet the requirements of the Mersey and Irwell Joint Committee. 3. That the method most reasonably practic- able and available is the biological filter or bacteria bed, such as may be seen in operation at many of the places visited. After some delay and correspondence, two bacteria beds of coke breeze were completed at Davyhulme on September 14, 1898, under the superintendence of the three experts appointed— namely, Baldwin Latham, Percy F. Frankland, and W. H. Perkin, junr. The working capacity of each filter is 5,000 gallons, and the liquid to be purified is taken direct from the sewer and passed into a settling tank for an hour before proceeding to the first or coarse filter. After remaining in the latter for one or two hours, according to circum- stances, the partially purified sewage is transferred to the fine filter, where it again rests for a period of one or two hours. Each filter requires three-quarters of an hour for filling, and the same time for emptying. Samples are taken every five minutes during emptying, and mixed for analysis. The figures show, as in other cases, that an improvement occurs as the filters mature. At first, the beds were filled once a day with settled sewage and twice with crude, and under these conditions the capacit)' of the coke filter remained constant. With regard to trade refuse, Mr. Fowler reports that iron pickle (ferrous chloride), dye refuse, carbolic acid, and sulphocyanides from gas liquor, are all removed or oxidized, that in no case has the presence of manufacturing refuse showed a marked tendency to make the purification less effective (an opinion also shared by Dr. Perkin), though it is probable that with purely domestic sewage the yield of nitrate would be larger. The three experts also state in their report that the bacteriological system, without the use of any chemicals, notwithstanding the peculiar nature of the Manchester sewage, will purify that sewage, and yield an effluent which will comply with all the requirements of](https://iiif.wellcomecollection.org/image/b24398639_0016.jp2/full/800%2C/0/default.jpg)
