Complex sentence: In many older cities collection of sanitary sewage, the sewage that emanates from homes or businesses, was collected by a single sewage system that also collected the stormwater runoff from the streets and roofs.
Split into simpler sentences: In many older cities, the collection of sanitary sewage--the sewage that emanates from homes or businesses--was collected by a single sewage system. This system also collected the stormwater runoff from the streets and roofs.