Urban runoff

As rainfall travels over roofs and the ground, it may pick up various contaminants including soil particles and other sediment, heavy metals, organic compounds, animal waste, and oil and grease
Some jurisdictions require storm water to receive some level of treatment before being discharged directly into waterways
Treatment processes used for storm water include retention basins, wetlands, buried vaults with various kinds of media filters, and vortex separators (to remove coarse solids)

Ways for Treatment

Sewage Treatment can be done in two ways-

1. Sewage can be treated close to where it is created, a decentralised system (in septic tanks, bio filters or aerobic treatment systems)

2. Sewage can be collected and transported by a network of pipes and pump stations to a municipal treatment plant, a centralised system (sewerage and pipes and infrastructure)

Centralized System