242 SEWAGE AND ITS PURIFICATION 



organisms was proved repeatedly in the Massachusetts experi- 

 ments, when the temperature of inception of active nitrification 

 was found to be 39° F. A number of bacteria, however, are not 

 affected by cold : in the L.C.C. Report of the Barking filter, it 

 is said that it " was able to do its work satisfactorily during the 

 exceptionally severe weather in January and February, 1895. 

 A thin coat of ice was formed on the surface, but the filtration 

 proceeded without intermission, the only noticeable change being 

 the decreased production of nitric acid. Macfadyen and Rowland 

 showed that Proteus vulgaris, B. coli communis, and several 

 other bacteria were not killed in ten hours by a temperature of 

 - 250° C. (liquid hydrogen).^ 



The idea of increasing the activity of organisms by raising 

 the temperature was also applied in 1898 by Whittaker and 

 Bryant in their " Thermal Aerobic Filter," at Accrington. The 

 plant included an open septic tank, the effluent of which was 

 distributed over a filter-bed of 2 feet broken stones, and 6 feet 

 gas coke, with 12 inches limestone chippings on the top, by 

 means of an automatic revolving sprinkler. A small jet of 

 steam was blown into the sewage just as it arrived at the 

 sprinklers " to raise the sewage, and thereby the whole body of 

 the filter to the required temperature." The added heat also 

 promotes the circulation of air in the filter, so that better 

 aeration was claimed to be produced in this way. 



In their patent. No. 4,460 of 1899, the filters consist of 

 several circular or polygonal chambers containing filter- 

 material, with shafts between through which air can be drawn 

 or forced, and preferably a central air-shaft in each chamber. 

 On the sloping bottom of each filter were laid perforated pipes, 

 forming channels leading to the air-shafts, to secure free and 

 uniform aeration. The filters were filled with ordinary un- 

 broken gas coke, well forked, to remove all the smaller material, 

 and were 61 feet diameter and 9 feet deep, each capable of 

 dealing with 200,000 gallons of open septic tank effluent per 

 day, the area covered being 958 square yards. 



Whittaker beds were tried at Leeds, and the purification was 

 found to be maintained during severe frost, as the action of the 

 pulsometer raised the temperature of the septic effluent going 

 on to the bed, a few degrees above that of the sewage. Good 

 results were obtained with an open septic tank effluent, and the 

 small amount of suspended matter passing the filter was readily 



^ Proc, Roy. Soc, 1900, Ixvi., 488. 



