Rafael Mujeriego, professor of Environmental Engineering at the Polytechnic University of Catalonia (UPC), is a great defender of the use of reclaimed water from treatment plants to gain resources and combat water deficits in the Barcelona region. And in this sense, he sees it as feasible to reuse the water from the Besòs (Sant Adrià) treatment plant, reusing it for domestic uses once regenerated, among other possibilities. In this way, the flow that is now discharged into the sea with a submarine outfall would not be lost.
Mujeriego believes that it is possible to carry out a reuse of the purified water from the Besòs in a similar way to what is being done now in the Llobregat river.
He stresses, however, that this water should be previously taken to a regenerative plant. And for this, an adequate physical space would have to be found. He maintains that the quality finally obtained would be even higher than that of conventional drinking water. Once purified, it could be used to be injected into the Besòs aquifer (and gain reserves), or be transported to the Cardedeu water treatment plant (for distribution to the network) or even taken directly to the same Trinitat reservoir, at the entrance in Barcelona
“Having a regeneration station in the Besòs treatment plant would allow, among other options, to implement a project similar to the one that is currently being carried out in the Llobregat river,” he stresses.
And what uses would it have? A first possible use would be to feed the ecological flow in the final stretch of the Besòs. But another alternative, which he deems “as valuable or more”, would be the advanced regeneration (or purification) of the treated water at the Besòs station in Sant Adrià and its delivery to a suitable storage place (reservoir or aquifer). This flow would be considered pre-potable water and would be available for the Ter-Llobregat system.
“This option -he clarifies- would require an adaptation of the Besòs treatment plant, with an adapted discharge control, and above all the construction of an advanced water regeneration station (purification)”, emphasizes Mujeriego.
“It is the most avant-garde and effective option. It is something that is being considered at this time in places like southern California, a territory of about 50,000 km2, with a climate like that of Murcia and Almería, and in which some 20 million inhabitants live, without sufficient water resources ” , he argues.
Mujeriego answers that the best-known direct reuse project in the world is the one in Windhoek (capital of Namibia), where a high-quality regenerated flow is introduced into the drinking water distribution network. The purified flow is mixed in a proportion of between 20% and 40% with drinkable surface water. “It’s the most iconic project in the world, along with the one practiced by astronauts on the International Space Station,” she says.
The Windhoek project was implemented in 1968, its facilities have been expanding (up to a current capacity of 14,000 m3/day: 5 hm3/year) and with it an excellent sanitary quality is guaranteed for the population (verified by international entities). which also enjoys great international prestige
The professor endorses this use. He argues that the planned indirect water reuse project that is being carried out in the Llobregat river can be considered “identical” to the one that occurs “incidentally, unplanned, in all the rivers of the world.” This is the circumstance that occurs when the used and treated waters of the inhabitants of the upstream areas “are discharged into the river, mixed with the circulating flows and are later captured by the inhabitants who reside in downstream areas for their use, including its purification and human consumption”.
The peculiarity of the indirect reuse project in the case of the Llobregat river lies in the fact that “this is a planned project, with the advantages that this entails in terms of supervision and control of its activities”. In addition, “the water that is discharged into the river is not a purified effluent, but reclaimed water of a higher quality” than that which comes out of the treatment plant, since it is subjected to a treatment similar to that of a water treatment plant at the foot of a river. .
In this way, mixing proportions of “reclaimed water/circulating water” from one to three are achieved, and foreseeably with a higher ratio, depending on the needs derived from the rainfall irregularity. This proportion is, in any case, higher than that recorded “incidentally” in the world’s rivers, which is usually less than 10% effluent.
Mujeriego maintains that the experience developed in California in this field can be very useful for Catalonia, since this North American State bears a great climatological, orographic, demographic and hydrological similarity with the Mediterranean areas. “What is happening there from the point of view of rainfall and the management of water resources should inspire us to adapt to the “new rainfall normality” that we are experiencing at the moment.
The climate of California, like that of the Mediterranean, is characterized by irregular rainfall, and long periods of dry and sunny weather, interspersed with short periods of rain, which at certain times generate avenues and floods.
“The most outstanding forecast of the climatological studies associated with climate change is that this traditional rainfall irregularity will intensify in the coming years: dry periods will be prolonged and rainfall will be concentrated in time and space, which will increase the risk both of droughts as well as floods and floods ”, adds the professor. “Dry periods will be prolonged and rainfall will be concentrated in time and space, which will increase the risk of both droughts and floods and floods,” adds the professor.
“In reality, that future has already become the present, especially in California and also in our territories recently,” he explains.
The case of California is especially relevant because it is “an early example of this new rainfall normality.” The area registered an intense drought of 5 consecutive years between 2012 and 2016, and is now about to end a second period of 3 consecutive years of drought that began in 2021, simultaneously with the one affecting us now in the Mediterranean.
