ABSTRACT
IT is usually preferable for any sewage treatment works to be at the lowest point of a sewerage system, and for all sewage to flow to that point by gravity. This is, however, often not possible, and it may be necessary either to pump the flows from small, isolated sections into neighbouring higher sewers or, where the district is very flat, it may be necessary or more economical to pump the sewage as an alternative to the construction of very deep gravity sewers. It is not economical to lay a very deep trunk sewer merely to serve a few low-lying areas en route.
