684 PROCEEDINGS OF SECTION H. 
designed basins, on account of the sewage having to pass under 
the bed of a navigable river by asyphon. The sludge is dredged 
from these basins, and together with extraneous matter, which is 
caught on the screens, is taken to the farm and dug in. 
The farm is situated on a neck of land at the junction of Cook’s 
River with Botany Bay. The formation is drift sand overlying 
clay, which is at a considerable depth. 
The sewage, after passing under the bed of the river, is 
conveyed across the farm by a concrete carrier, on each side of 
which is laid out the storm-water tanks and irrigation areas. 
The irrigation areas lie between the main carrier and Cook’s 
River. They are formed in terraces, and the sewage is applied 
to the land by sluices in the main carrier and ordinary earth 
channels, with subsidiary sluices made of timber. The daily 
sewage is applied to the irrigation areas, the tanks on the opposite 
side being reserved for storm-water. 
The irrigation plots have been planted with sorghum, barley, 
cabbages, swede turnips, and other vegetables, all of which thrive 
very well and find a ready sale. Some of the storm-water tanks 
have been planted with lucerne, the crop being watered with the 
storm-water, which is turned into the tanks ; the growth has been 
beyond expectation, considering the nature of the soil prior .to 
being irrigated, the crop being capable of being cut once a month. 
From a sanitary standpoint, the disposal of the sewage has 
proved successful, the effluent water being analysed by the 
Government Analyist every quarter. Appended hereto are 
reports of Mr. Hamlet for July and September, 1889. 
The question of disposal of sludge has to be considered in any 
system of sewage disposal. This difficulty has been met in many 
ways, viz.—l. By allowing the matter in suspension to precipitate 
in specially-designed tanks, drawing off the supernatant water, 
and allowing the sludge to dry, and afterwards dealt with; 2. To 
precipitate the suspended matter by chemicals and sludge, dealt 
with as above; 3. To carry out precipitation by either of the 
above processes, and treat the sludge by “filter presses,” the 
resultant being sludge cake. This has the advantage of the sludge 
being easily handled if there is any demand for this description 
of manure by farmers, market gardeners, or other agriculturists. 
The simplest and best means of disposal of sludge is to dig it into 
the ground if the land is available ; where such cannot be obtained 
the question of disposal becomes more expensive, and the cost has to 
be faced, as experience has demonstrated that no laboratory value 
of the sludge can be obtained from those who are likely to use it. 
The mode of disposal adopted at the Botany Sewage Works is 
to precipitate the suspended matter by lime, the supernatant 
water being lifted from the tanks to the syphon-well by an 
“ejector.” The sludge is dredged out by a dam-dredger, and 
deposited in trucks and conveyed to the farm and used as a top- 
dressing and manure. 
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