294 SEWAGE AND ITS PURIFICATION 



II. Moving Distributors. 



In Nos. I to 5, 7 and 8 of the following, the principle is that of 

 "Barker's Mill"; or of the still more ancient " ^^^olipile " (des- 

 cribed by Hero of Alexandria about 200 B.C.) — rotary motion 

 produced by the recoil from jets of fluid issuing from holes on 

 one side of suspended and balanced tubes. 



1. Candy - Caink " self-propelled revolving sprinkler and 

 aerator" (International Purification Syndicate). This form 

 was installed at Reigate, Southampton, and Southwold, where 

 the sewage, after passing a catch-pit, or after a first anaerobic 

 treatment, was distributed by the sprinkler over aerobic beds. 

 Mr. Caink seems to have been the first person to introduce 

 revolving sprinklers into sewage treatment. 



2. Candy - Whittaker Sprinklers (Patent Automatic Sewage 

 Distributors, Ltd.). In the smaller sizes the arms are attached to 

 a revolving cylinder suspended from an overhead ball-bearing 

 attached to a fixed central column. The sewage enters the 

 cylinder through ports in the column, and then flows into the 

 perforated arms. The patent joint between the moving cylinder 

 and the fixed standard is formed with a trap of mercury, so as 

 to be water-tight and almost frictionless. Variations in water 

 pressure are guarded against by a check ring. Oscillation of 

 the distributor arms in a vertical direction is guarded against 

 by a ball-bearing in combination with the mercury seal, and 

 precautions are taken to render the bearings as moisture-proof 

 as possible. Variations in flow are dealt with by the usual 

 device, by means of which two additional perforated arms come 

 into action as soon as the level of the liquor in the cylinder is 

 sufficient. For large sprinklers the weight, which may be as 

 much as 2 or 3 tons, is carried by means of a circular buoy 

 floating in a small tank of water in the centre of the bed. This 

 method is said to require only a fourth of the power (as com- 

 pared with ball-bearing distributors) to set it revolving. There 

 are two of these buoyant distributors of 120 ft. diameter at 

 Harrogate and Birmingham, and six of 200 ft. diameter are in 

 course of construction for Worcester. Non-buoyant distributors 

 of 80 ft. diameter are at work at Redhill, Wednesbury, and 

 elsewhere, and smaller ones of 8 ft. diameter and upwards are 

 made. The average price may be taken as 20s. for each foot 

 diameter of bed, exclusive of an automatic flusher, which is 

 usually supplied (see Fig. 43). 



