Effluents: qualitative aspects
Sewerage of agglomerations - General principles and Effluents present

Water in clouds accumulates dissolved gases, suspended particles and dissolved substances as it passes through the atmosphere. It can also be loaded with harmful substances over large industrial agglomerations, as well as bacteria.

When rainwater falls on impermeable surfaces such as pavements, sidewalks and roofs, it cannot infiltrate the soil. As a result, it runs off these surfaces, collecting various pollutants before reaching drainage systems...