In on-site treatment, collection is simply a matter of directing the wastewater a short distance to the wasterwater treatment unit. In off-site treatment, collection is usually achieved by a network of pipes, known as sewers. Sewer systems were a major contributor to improved public health in the developed world in the late 19th and early 20th century (see W).
Sewer design
An innovative low-cost method of sewerage in the W
- involves narrow piping, much more affordable than regular large diameter pipes.
- small chambers for collection of solids before the sewage enters the pipes. This allows the use of small diameter pipes without blocking.
This is less than ideal from a public health point of view, as the waste must be handled by collectors, and however careful they are some spillage is inevitable. However, as an appropriate technology it is a vast improvement over the previous situation of sewage in the streets, and was able to be paid for by the residents of a poor slum community.[verification needed]