672 



PROCEEDINGS OF SECTION I. 



Table IV. — Table showing Percentage Reduction in Organic Matter 



Effected in Tanks and Filters, Separately and Combined. 



North Sydney Outfall. 



CHATSWOOD OUTFALL WORKS. 



The scheme was taken over by the Board in February, 1902, after 

 the Department of Public Works had conducted the same for about 

 six months. Up to that time tanks Nos. 1 and 2 had only been used 

 for sewage, but No. 3 had been filled with city water, and a few water 

 hyacinths were growing feebly in one corner of it. In May, 1902, 

 some of this water was run out and sewage turned in to fill the tank. 

 Hyacinths began to thrive at once, and in two months had completely 

 covered the surface of the tank. In September, 1902, as the scum 

 was not forming on tanks Nos. 1 and 2, it was decided to place some 

 hyacinths in them, and in a month the tanks were covered with the 

 growth. 



The installation consists of three open tanks and four contact 

 filters ; in addition a small silt bed is in existence, but up to the present 

 it has not been found necessary to use it, because the sewage is found 

 to carry but little detritus. By means of a flume the sewage is con- 

 ducted across this pit into the main carrier which feeds the three tanks. 

 The tanks are provided with submerged inlets and outlets, so arranged 

 that the entrance and discharge is 4ft. below the surface. Each tank 

 is 41ft. 9in. wide by 70ft. long by 6ft. Sin. deep, and contains approxi- 

 mately 120,000galls. A collecting channel at outlet end of tanks 

 receives the tank effluent, which is conveyed from this point by means 

 of an iron flume to the automatic gear regulating the distribution on 

 to the filter beds. Each filter bed is 64ft. long, 39ft. 3in. wide, and 4ft. 



