Ana Tuñas Matilla |
Valencia (EFE).- Reducing the presence of nutrients in the wastewater that is discharged into the natural environment is essential to avoid the eutrophication of water masses such as the Mar Menor, in which the lack of oxygen caused by the proliferation of algae practically impossible the existence of other forms of life.
In this context, Life Renaturwat, a project co-financed with European funds, tests the potential of using water treatment sludge to filter water and “trap” pollutants and nutrients, with preliminary results revealing 80% reductions in terms of phosphorus.
In addition, other contaminants are significantly reduced, such as fecal Escherichia coli or emerging bacteria (medications, pesticides, etc.), and the biological quality of the water is improved.
The tests are carried out in treatment plants based on artificial wetlands in the Valencian town of Carrícola, with 200 inhabitants, and in the Los Monasterios urbanization (Puçol, Valencia), where some 2,000 people live.
In both, lagoons have been built in which to compare the quality of the outgoing water from the wetlands built with dehydrated sludge in the framework of the project and that coming from existing treatments.
The excess of nutrients, such as ammoniacal nitrogen or phosphorus, causes the proliferation of algae, a phenomenon called eutrophication and considered one of the major processes of contamination of rivers, lakes, reservoirs, ponds, etc.
These algae and the organisms that accompany them consume the dissolved oxygen in the water, making the existence of other forms of life practically impossible and generating a great loss of biodiversity.
In the lagoons where the water filtered by these sludge reaches, the phosphorus concentrations are below 2 milligrams per liter in Carrícola (100 inhabitants) and 1 mg/L in Los Monasterios (2,000).
Results superior to those of any other system
“In both cases, we would be within what the European directive requires for much larger populations and well above the results that would be obtained with any other system,” according to the project coordinator, Miguel Martín, from the Institute of Water Engineering and Environment of the Polytechnic of Valencia.
With the artificial wetlands installed to date, built with gravel, the phosphorus reductions are only 15 or 20%, added the researcher from the institute Carmen Hernández.
The peculiar thing about the sludge from a water treatment plant is that it contains traces of aluminum from the coagulant used to treat the water and which gives it highly adsorbent properties.
“The phosphorus that is in the form of phosphates in the wastewater reacts and chemically precipitates on that aluminum, which adsorbs it and remains trapped there.”
In addition to lower concentrations of nutrients, in the lagoon that receives the filtered water with sludge, a greater reduction of pollutants is also observed, while insects and aquatic invertebrates proliferate “indicating a very good water quality.”
“The algae do not grow explosively as they do in the other lagoon (…). It is very important to avoid eutrophication of water because eutrophic aquatic ecosystems run out of oxygen (…). In Spain we have several examples of very important aquatic ecosystems that are highly eutrophic, including the Albufera de Valencia or the Mar Menor”, he recalled.
Portugal, interested in replicating the project
“Renaturwat has great potential in terms of application in Portugal. It is a very simple and very natural solution that allows a reduction of contaminants in wastewater”, stressed Ana Rita Ferreira, a technician from Aguas de Portugal-Valor, a partner in the project.
In addition, it allows us to go one step further in the country’s commitment to the circular economy, since it would be applying what is now treated as waste, and it could be very useful to help renaturalize water from industries such as textile, very present in Portugal, stood out during a visit to the facilities where the project is being developed.