Water purification plants are composed of a set of parts, generally in reinforced concrete, each with its specific function, which purify civil and industrial wastewater.
Usually, a wastewater treatment plant has two different flows: the water line and the sludge line.
The water line treats raw fluids from sewers and usually has three stages:
• primary treatment: a physical treatment used to remove sedimentable organic solids from the fluid, by means of grilling, sanding, degreasing, and primary sedimentation;
• secondary treatment: a biological process used to remove organic solids (sedimentable and non-sedimentable) from the fluid. This includes aeration and secondary sedimentation;
• third stage treatment: treats the fluid exiting the secondary sedimentation stage to increase the level of purification. Includes special treatments for reducing the content of substances not dealt with by the primary and secondary stages.
The sludge line treats the sludges produced during the sedimentation stages of the water line process.
The purpose of the line is to eliminate the large amount water contained in the sludge and reduce its volume, as well as to stabilise the organic material and destroy any organic pathogens, so as to make final disposal less costly and environmentally damaging. The final treated effluent is conveyed in a line called the outlet, which delivers it to bodies of ground water (water courses, the sea, etc.), underground channels or the surface.
The final effluent may also be used for irrigation or for industrial applications.