sludge, being the foulest part of town sewage, ought to receive primary and earnest attention if we desire to improve the condition of our watercourses.
When town sewage is pumped through a long rising main, it can often be spread on the land in its really crude state, and if the soil is clay ploughed up to receive it the sludge is most beneficial to its texture.
But in every other case we must face the nuisance of extracting the sludge, and its desiccation in one of the following ways.
1. On a farm at some distance from roads and houses, the cheapest plan is to form a bank of earth about 18 inches high, enclosing a rectangular area into which the wet sludge can be run or pumped out of depositing tanks, and left alone until dry enough for cartage, when it can be used on the farm or sold to neighbouring farmers for a shilling or two a load.
2. A wall of farmyard long manure may be used instead of earth, and trench 5 feet wide dug on each side of the longer sides of the rectangle, leaving 3 feet of ground between the wall and trench, on which men can stand to scoop the sludge over the wall when it has consolidated a little in the trench; the latter is then ready to receive the sludge from another tank emptying, which is again scooped over the wall on to a thin coating of farmyard manure, which has been scattered over the last layer of sludge in the rectangle; and thus in a year’s time a solid mass of the mixture is raised four or five feet high, and is in capital order for putting in drills for a crop of mangold wurtzel.
This is the plan in use at the Camp Farm; it occupies little ground and smells only like rotten dung does during the few days carting to the mangold field.
3. Pressing by compressed air forcing a liquid mixture
of sludge and lime into the interstices between cloths supported by vertical iron plates on a horizontal frame; and such pressing is a very expensive process, only resorted to when the sewage works are in a confined populated district where no accumulation of sludge can be tolerated.
Expert examination of neighbourhood a very necessary preliminary to any sewage scheme.
Before any sewage scheme is conceived a very careful survey of the neighbourhood ought to be made by a person who knows the requisites of a site for sewage disposal, especially if land irrigation is intended, because natural advantages of site both for tanks, main carriers, roads, etc., may make all the difference in the world in expense and efficiency not only in first cost of works but also in their use afterwards.