Sewage disposal means the getting rid of the foul water contained in the sewerage system of any community.
Where a dry method is in force for the collection of the excrementitious matters it is called “interception”; the following are some of the systems which effect it:—
Privies, ashpits, middens, cesspools, pails, troughs, the “Rochdale,” the “Eureka,” the “Goux,” Fosses Permanentes, Fosses Mobiles, and Moule’s, Taylor’s, and Phillip’s earth closets.
The collection and disposal of the mass of excrement under these dry systems is found to be a very troublesome matter, and they are at their best but inferior substitutes for water carriage, nor must it be forgotten that sewers and drains are necessary even if a good interception process is in force. I shall therefore confine my remarks to the disposal of water-carried sewage.
Many books have been written, many valuable reports have been prepared and issued, lengthy papers and discussions have been frequent at the meetings of scientific societies, and almost innumerable pamphlets have been published upon this important sanitary subject. Some millions of money have also been spent in trying to deal satisfactorily with this question, not only with a view to the purification of the effluent of the sewage, but also to endeavour to make a profit out of the residuals.[187] The result of this literature, discussion, and experiment has led to the following conclusions:
No hard and fast lines can be laid down as to the best method to be adopted for the disposal of the sewage of any town, but the peculiar circumstances of each case must be considered before advice could be given on the subject: geographical position, physical arrangement, habits of the population, and the character and quantity of the sewage of the town being some of the most important.
In any case it is necessary that the transmission of the sewage to the outfall should be effected as speedily as possible, and that the position of this outfall should be such as to cause no nuisance. The contents of the sewers should, if possible, be emptied by gravitation, as pumping is a constant expense, and economy with efficiency must of course be studied.
Up to the present time the following are the methods adopted in this country for the disposal of sewage:
(1.) Passing the sewage in its crude state into the sea or tidal river.
(2.) Passing the sewage in its crude state over large tracts of land; this is called broad irrigation.