The wastewater produced by the villages, towns, cities and industrial estates is taken away via the drainage and sewage systems. General interceptor sewers then channel it to the wastewater purification plants.
During the regulation phase, the first runoffs that are the direct result of storms are contained and controlled. This rush of water is handled using specific devices known as spillways and retention chambers that return all additional water to the transportation network in a controlled manner.
The wastewater is channelled along Interceptor Sewers (these run alongside natural river courses) with the flow being controlled by Pumping Stations. Manholes enable the pipelines and conduits to be accessed for checking and cleaning purposes.
Finally, the wastewater arrives at the Wastewater Purification Plants where, via a complex purification system, all harmful substances are eliminated before it is returned to the natural environment in optimum condition.
The purification process begins with the capture and entry of untreated water from the sanitation network. The untreated water is first channelled into the filtering well where the heaviest foreign bodies settle to the bottom and the largest are retained.
Next, the now partially treated water is subjected to a rough filtering process to eliminate any «coarse» and «fine» solids, which are then tipped onto conveyor belts and finally deposited in skips for transportation to the waste disposal site.
After the wastewater has been rough filtered, it is subjected to a process that removes the grit and oils, fats and grease it contains. Due to the fact that it is heavy, any grit settles to the bottom.
Any oils, fats and grease rise to the surface by floatation, a process helped by air bubbles produced by compressors and delivered by submerged nozzles.
During this phase most of the sediments and floating matter that could not be removed during previous phased are separated off.
This is achieved using a natural physical settling process for the suspended solids and a natural floatation process for the less dense particles. The solids fall to the bottom, while the less dense particles are removed using revolving sieves mounted on the surface. The resulting water is then transferred to a channel that takes it to the biological treatment plant.
Once most of the solids have been removed via sedimentation, the water is taken to the biological reactors to be subjected to a process the fundamental purpose of which is to remove any organic matter by allowing it to be degraded via the action of a series of micro-organisms.
The biological reactors are divided up into two different areas:
During the final phase of the purification process, the treated water is separated from the biological sludge formed during the previous treatment. This process is carried out in the secondary settling tanks where the sludge sinks to the bottom and the purified water is piped off into rivers or the sea in compliance with the current legislation governing wastewater disposal.
Throughout the wastewater purification process a significant volume of sludge is generated, which in turn has to be treated in order to make it safe to be later transported as waste and disposed of at authorised waste disposal sites.
Currently, research is being done into the reuse and recycling of this sludge.
Having been subjected to the aforementioned purification process at the Wastewater Purification Plants, the wastewater is returned to the rivers, thereby completing the integral water usage cycle.
Know the processes of a W.P.P (Wastewater Purification Plants) through this video.
All of the processes carried out at the Wastewater Purification Plants are either manually or automatically controlled in order to guarantee the correct functioning thereof. Likewise, and at regular intervals, all necessary analyses are carried out in the laboratories attached to the purification plants in order to ensure that the water returned to the rivers and seas is of the required quality.
The transportation and regulation networks are controlled by way of remote information systems that enable the purification plants to interact over long distances with the main installations of the network (pumping stations, spillways, etc.).