Humanity demographic and social growth and the development of sanitation and water treatment infrastructure are closely linked. Thanks to them, we live in healthy environments and minimize the impact on the environment around us and from which we supply ourselves.
Although this type of infrastructure was built by societies like the Roman, it was not until 1827 when James Simpson built the first modern and effective system used for water treatment: a sand filter for the purification of drinking water.
We had to wait more than a century, until 1931, to address the project for the construction of the first urban wastewater treatment plant in Spain, in Madrid. It aimed to solve the problem of pollution of the rivers of Madrid, which also being used for irrigation of crops caused death by typhoid fever of many inhabitants.
Today, and almost another century later, wastewater treatment is facing a new qualitative leap, a paradigm shift. Many of the pollutants in our waters – organic load, nitrogen, metals, cellulose of paper, grease and oils, etc. – are only possible resources for obtaining other products of high value, such as energy, bioplastics or fertilizers. Water treatment plants, both urban and industrial, thus begin to evolve from points where we treat our waters towards recovery centers and obtaining resources. The growing environmental awareness, the scarcity of renewable resources and the development of new technologies push WWTPs towards this change, and in the not too distant future they may become urban mines from which to extract environmentally sustainable resources. In a source of economic wealth.
The treatment plants, an inexhaustible source of resources
The application of circular economy strategies in treatment plants is not new. The most common example is urban sewage sludge, a byproduct frequently revalued in agriculture. In the vision of the WWTP as a center for obtaining resources, it goes a step further. The revaluation of the waste generated in a conventional WWTP is not only sought, but the wastewater treatment processes are designed and operated from the beginning, seeking both the purification of the incoming waters and the recovery and obtaining of secondary raw materials.
The secondary raw materials to be obtained vary greatly from the type of water treated by the WWTP – the waters of a dairy industry, for example, will be rich in fats, proteins, or lactic acids, among others, while those of a municipality will be rich in nitrogen in the form of ammonia and ammonia, in phosphorus, or in materials such as cellulose from toilet paper. However, whatever their typology, all treatment plants have resources in large quantities and variety, pending the implementation of the technologies and processes necessary for their new inclusion in industrial value chains.
CETIM, as a Technology Center with extensive experience in water treatment technologies, is currently working on several lines of research for the recovery and / or obtaining of resources. These works, alienated with national and international innovation trends in the water sector, are consortium research where we combine efforts and knowledge with the main agents of the water value chain. Some of the current lines of action in which CETIM investigates for the development of treatment plants such as Water Treatment and Resource Recovery Centers are:
- Membrane technologies
During secondary treatment, using membrane technologies – such as direct osmosis, or membrane contactors in the REC4Agua project – or through combined technologies – such as anaerobic membrane bioreactors in LIFE GREEN SEWER – we investigate the concentration and extraction of nutrients from wastewater -nitrogen and phosphorus, mainly – while generating quality water for reuse and biogas.
- Biosorption / adsorption technologies
Thanks to the use of this type of technologies it is possible to retain the resources present in aqueous streams. Currently, in CETIM we develop innovative biotechnological processes, based on microorganisms, fungi and enzymes, to carry out in projects such as H2020 Biorecover the selective biosorption of metals with high economic value present in these currents.
In addition, we also apply adsorption technologies based on novel materials, such as biochar, for the recovery of other metals of interest.
All previous applications have a common point: the recovery of existing resources in wastewater. But it is also possible to obtain resources that, even without being present in the waters, can be generated from them. The sewage sludge consists mainly of bacterial biomass, which is rich in organic biomolecules such as proteins, carbohydrates, lipids, etc. From CETIM, through projects such as LIFE ULISES, we transform these biomolecules through an enzymatic hydrolysis process into peptides and amino acids, which are a source of organic nitrogen, which can be used in agronomic fertilization.
Similarly, by means of specific bacteria that accumulate PHAs as carbon and energy reserves, we can transform currents with a high content of biodegradable organic matter into bioplastics. Waters of different types – such as dairy, forestry or wine – are some of the examples with which CETIM investigates, in projects such as Conecta PEME BIOPOL or H2020 REWAISE through direct collaboration with companies and involving the entire value chain for obtaining products based on these biopolymers.
- Electrochemical technologies
Electrochemical technologies have a high potential for the recovery of ions present in different types of residual aqueous currents. Likewise, they are respectful with the environment since the addition of large quantities of reagents to the medium is avoided and they allow the recovery of metals without a subsequent phase of separation, since the precipitate of the metal of interest will be found on the surface and in the vicinity of the electrode. From CETIM we investigate in the development of electroprecipitation processes for the recovery in the form of hydroxides of metals of economic interest such as the Magnesium present in landfill leachates. Likewise, since 2020 we will investigate the electrochemical recovery of brine lithium thanks to the H2020 REWAISE project.
In all cases, these are lines of applied research launched with national and international tractor entities, of the entire water value chain – technology developers, town halls and other Public Administrations, industries, plant operators, platforms and clusters, etc. Clients and collaborators such as Aqualia, Espina and Delfín, COPASA, EMALCSA, Universitat de Barcelona, EnergyLab, Universidad de Almería, INDUTEC Ingenieros, DairyLac, INTACTA Medioambiental, GESTÁN Medioambiental, MAGTEL, SOCAMEX, and a long list of companies make possible Centre’s researches and its application in industry.