86 SEWAGE DISPOSAL. 



by any accident, as in the case of excessive storms, the tops of the beds become charged with sewage 

 before proper treatment in the septic tanks, the top layer of coke requires raking over or possibly renewing, 

 but the material can be used again after &quot; resting &quot; several days. It is important that the effluent from 

 the septic tanks be properly distributed over the bacteria beds. To secure this a small collecting chamber 

 is made between the last septic tank and the bacteiia bed, fitted with a siphon, which discharges the liquid, 

 about forty gallons at a time, and distributes it over the bed by means of perforated wooden troughs. 

 Where the purity of effluent, either from the chemical or bacteriological point of view, does not reach a 

 sufficiently high standard after contact with a single bacteria bed, a second bed should be installed. The 

 first bed is called the primary and the second the secondary bed, and the secondary contact produces a 

 great improvement. It can be reasonably assumed that the primary bacteria bed will reduce the number 

 of bacilli contained in the crude sewage up to twenty-five per cent., and the secondary contact up to sixty 

 per cent. 



There remains the question of the ultimate disposal of the effluent. In this matter each individual 

 case requires to be considered on its merits, as local circumstances have an important bearing, and the 

 ultimate means of disposal has a direct influence upon the design and construction of the bacteria beds. 

 The effluent has excellent fertilising properties, and provided it is possible to utilise it in the garden, 

 beneficial results will accrue. It is desirable, however, that the liquid should be spread over the ground 

 by means of movable troughs or other suitable arrangements, as if discharged for any long period in one 

 place the ground will become sodden and sour. If consideration be given to other ways of nourishing 

 gardens, any prejudice against the utilisation of the effluent for garden purposes will be quickly dispelled. 

 The liquid should be utilised in a fresh condition, without resort to storage, except in exceptional 

 circumstances. Whether the effluent is discharged over the garden or into a ditch or other channel, it 

 is necessary that the course should be kept clear of vegetable matter, such as fallen leaves, etc. Ditches 

 need to be kept quite clean, and all bacteria beds should be covered with small-mesh galvanised wire 

 movable screens. 



No matter what the method of disposal of the effluent, it is necessary, alter passing through the 

 bacteria beds, that it should be given the maximum opportunity to aerate properly. This can be secured 

 by separating the fluid, by passing it over steps with &quot; baffles &quot; inserted, and if the installation is of 

 sufficient size, a small apparatus for spraying may be installed. It is beneficial if a portion of the conduct 

 channel is paved with hard bricks or other similar material. Undoubtedly aerobic action continues in the 

 effluent after its discharge, this either being helped or retarded according to the manner of its disposal. 

 There are certain other fittings not mentioned in detail, which should always be of the simplest kind, of 

 strong make, and such as can be easily replaced if necessary. 



As previously mentioned, no sewage disposal works are absolutely automatic ; but with a little 

 systematic and intelligent attention the cost of maintenance of a septic system with its necessary bacteria 

 beds is trifling. The system known as &quot; broad irrigation &quot; has not been dealt with here, as it seems an 

 impossible method for private works. As can be readily understood from the foregoing, the cost of a suitable 

 septic tank and bacteria bed installation depends a very great deal upon the circumstances of each case ; 

 but assuming the disposal works have to provide for a population of sixty, with reasonable requirements, 

 the cost would be from forty pounds to one hundred and thirty pounds. The cost of all maintenance, 

 including labour for attention, for such an installation should not exceed four pounds to fifteen pounds 

 per annum. A. AI.BAN H. SCOTT. 



