Opening the faucet and, almost instantaneously, getting out of the water is a process that seems simple, but it has several steps behind it. From the collection of water to its arrival at the Water Treatment Plant (ETA), passing through a filtering and analysis process, there is a lot of work to be done. Alcantarilha, with its ETA, is one of the “bastions” of water that comes out of taps throughout the Algarve, a region where this natural resource even has a quality certificate.
At the Alcantarilha ETA, there are noisy rooms, large tubes, a smell of chlorine, but also laboratories equipped with the latest technology. From there, the treated water goes to the municipalities of Albufeira, Aljezur, Lagoa, Lagos, Monchique, Portimão, Loulé (West and North), Silves and Vila do Bispo.
Even so, it is not at the ETA that the whole process begins, but… at the Odelouca Dam, where the water comes from. Then there is, therefore, a first stage: the pre-oxidation, with ozone, of the substances present. «This way we can immediately start to disinfect the water», explains Helena Lucas, director of the operation of the supply subsystem, to Sul Informação, which followed, in a report, the entire water treatment process.
From there, the water goes to a chemical coagulation process. In tanks, a coagulant is poured, but also coal. The goal: to eliminate unwanted substances, such as those associated with smell and taste.
To these is added another purple flocculant that will give a clearer color to the water. «At the Odelouca dam, the water has a brownish hue», explains Helena Lucas, as she visits each of the sections through which the water passes until it reaches the taps.
The treatment of the (few) solids present in the water is the next step. But the "quality of the water in Odelouca" is such that "there are hardly any solids that decant" but that float.
Thus, in this process it is possible to see small yellowish colored foams floating in the tanks. For the future, there is even a project revealed by Helena Lucas to our newspaper: «build a floating unit».
Then comes the time for filtration, which will remove the particles still present in the decanted water. «The water comes to us with a turbidity of 2 units. In the decantation, it has 0.4 and the law says that the water is ready for consumption when it has 1 unit», explains the director of operation of the supply subsystem.
Although, at this point, the water is legally able to be distributed, the process has not (yet) finished.
In a dark tunnel, the final disinfection is carried out with chlorine. And the addition of this substance does not change the quality of the water? Helena Lucas is authoritative in her answer: «Chlorine has nothing to combine. When we turn on the faucet and fill a jug with water, after 30 minutes there is no longer any chlorine. It was only harmful if combined with some organic matter».
And the process… is finished. Or rather: almost finished, because the water is still to be pumped by the two pipelines of the system to the reservoirs. It is in this process that “most of the ETA's electricity” is used: around 60%. The next connection, from the reservoirs to the houses, for example, is in charge of the municipalities.
In this true “water cycle”, supervision is constant. This is because, in the laboratories, everything is monitored, as well as in the “Operations Room”, where there is always someone on duty at all hours.
In the laboratory, at each stage, water samples are collected to be analyzed. One of the people in charge of this work is Sandra Ribeiro who explained to the Sul Informação some of the parameters that are measured: “aluminium, manganese or iron”.
All this is done using "specific equipment", he added. Once the analysis is done, the results are facilitated and it is decided whether it is necessary – or not – to make an adjustment to the treatment.
The fact that the company Águas do Algarve, which also has another ETA in Tavira, where the treatment process is identical, is “the only one in Europe” with water with a HACCP quality certificate, requires extra attention – and precautions – to be redoubled. Helena Lucas proudly says that this distinction is due "to a set of good practices from construction to maintenance".
“We manage everything in a secure way. I'll give you an example: all our material must be approved by a laboratory in order to be in contact with water. Imagine that there is a pipeline or a break: we do not put it back into service without disinfecting this section», he explains.
And for the future, the objective is not to lower quality. As such, Águas do Algarve participated in an international project – the My Hemb – whose idea is to prevent problems that might happen. In a room, next to the water pumping area for the reservoirs, there are now two machines with different purposes.
One simulates the water treatment that is carried out by the company Águas do Algarve, the other simulates a treatment with new technologies. “This way, we can already test possible future contaminants that may appear in the water and how we can treat them”, explains Helena Lucas.
These potential contaminants can come from, for example, "droughts or climate change", he says. The conclusions, for now, are that the machine that uses new technologies "removes more contaminants if we had high concentrations of drugs or pesticides, but would use a lot of coal", revealed the operation director to the Sul Informação.
With or without advances (or future contaminants), for now what is certain is that the water leaves the Alcantarilha ETA with a neutral pH (of 7) and a turbidity of 0.1.
And the complaints that sometimes the water has muddy and limestone tones are in no way due to the company Águas do Algarve, guarantees Helena Lucas. “If there is a low water collection and the pipe is put back to work without being washed, that can happen”, he explains. But such a situation is “the responsibility of the municipalities”.
After visiting the entire treatment process, it's time to enjoy a glass of tap water (as expected). Between sips, Helena Lucas concludes: «unfortunately, in Portugal we still have the wrong idea that tap water is not good».
Photos: Pedro Lemos | Sul Informação
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