288 



SEWAGE AND ITS PURIFICATION 



from holes. It consisted of a number of gutters arranged at 

 right angles to the supply channel, provided with a series of 

 points on their under surface, from which the overflowing 



sewage or tank effluent fell in a series 

 of fine drops. 



It is said to work with only three 

 inches of head, and to be unaffected by 

 accidents such as a discharge of sludge 

 or continued frost. Suspended matter 

 settling in the troughs of the distributor 

 is removed by a brush from time to 

 time. 



A later form of the Stoddart Con- 

 tinuous Sewage Filter is made in one 

 piece of corrugated iron sheeting fixed 

 just clear of the surface of the filter bed 

 and filled with septic effluent from 

 transverse fixed troughs. The edges of 

 the corrugation are notched every few 

 inches, and as the hollows fill up they 

 overflow through the notches and the 

 sewage falls from points attached to 

 the under surfaces of the hollows. In 

 this way, if the corrugated sheeting is 

 kept absolutely true and horizontal, a 

 good and uniform distribution can be 

 effected. The difficulty is to keep the 

 ridges absolutely true and level and to 

 prevent inequalities due to changes of 

 temperature, sinking of the supports, 

 or displacement due to high winds. 

 The improvements are intended to 

 reduce these difficulties (Figs. 35 to 37). 

 Fig. 36 shows the triangular projections 

 on which the corrugated sheeting is sup- 

 ported (the inner surfaces only of the 

 ridges are carried), and Fig. 35 the 

 sheeting in position. The distributors 

 are constructed in sections of 2 sq. yds 

 each, so that any desired area can be built up. Mr. Stoddart 

 prefers to limit beds to 500 square yards. The cost of the 

 apparatus averages 15s. per section. An advantage pecuhar 



