XX. J. DAVIS. 



15 tons a day. At present, however, the quantity is not more 

 than three or four tons. 



This amount is greatly reduced by pressing, five tons of wet 

 sludge from the tanks producing only one ton of sludge cake ; 

 the difference represents the liquid portion which is extracted 

 by the presses. Fully 90 per cent, of bulk of the wet sludge is 

 water, but the percentage in the cake after pressing is only 55. 



The value of the cake as manure is not as well-known 

 or appreciated as in countries where intense cultivation is 

 practised, and it was deemed inadvisable to rely solely for any 

 demand for the product as a means of disposal. On the other 

 hand burning was a method readily available, and, after all, the 

 most efficacious. 



After the sewage has passed through the filter beds it is 

 collected in its purified state by the underdrains, which are of 

 perforated pipes laid in coke breeze. These converge into an 

 outfall pipe 2 1 in. in diameter, which discharges into Willoughby 

 Bay slightly above mean spring tide level. 



When drain pipes in sand filters have been made sufliciently 

 porous to admit of the effluent passing freely into them, difficulty 

 has been experienced in keeping the sand out. 



As the success of the filter beds depended upon both the 

 effluent getting into the pipes and the sand being kept out, before 

 finally deciding the mode to be adopted at Willoughby Bay it 

 was deemed advisable to carry out experiments. 



Three tanks were constructed, each 4 ft. deep, and having a 

 combined area of 0'9 of a yard. At the bottom of each tank a 

 glazed perforated pipe was placed, and surrounded with 6 in. of 

 fine breeze coke, the perforations being -J in., T 3 g- in., and J in. 

 diameter respectively. The boxes were then filled with sand 

 to within a few inches of the top. Each tank formed a miniature 

 sand filter, and as no sewage was available, the city water was 

 laid on to them. 



The water, which was measured by meter, was turned on at 

 3.30 p.m. on Friday, 10th December, 1897, and at 11.12 a.m. 

 on Saturday the meter recorded 2,245 gallons as having been 



