The removal of urban solid waste from stormwater drains

1. Urban drainage systems fal into two categories: “separated” systems where stormwater and sewage is reticulated in separate reticulation systems; and “combined” systems where the same pipes are used for both. The report deals exclusively with the urban litter problems associated with the stormwater conduits and streams in a country where the stormwater and sewage are always (theoretically at any rate) separated. Where combined systems are used, much of the litter can be trapped and removed at the wastewater treatment works. On the other hand, combined sewer overflows (CSOs), which generally occur as a result of heavy downpours, become a particular problem as both litter and effluent ends up in the rivers. Combined sewers are something of an anathema to anyone from a water scarce region. Why would anyone want to pollute a valuable resource – stormwater–with effluent?!