Significant help in dealing with the problem of treating wastewater containing organic residues (from food waste, livestock manure, grass and dry leaves, waste wood, etc.) could come from a special type of purple bacteria, defined as phototrophic, i.e. capable of extracting energy from light (in a similar way, in certain aspects, to what plants do through photosynthesis). These microorganisms, if stimulated properly, could “capture” almost 100% of the (carbon-based) organic molecules found in waste, transforming them into hydrogen, bioplastics and possibly also proteins to be reused for animal food: notably this very important result is achieved without producing carbon dioxide, responsible for the greenhouse effect (which on the other hand is the case in traditional treatment systems). These conclusions were reached by researchers from the University Re Juan Carlos, Móstoles (Spain) and the University of Alcalá, who published the results of an experimental study in the scientific journal Frontiers in Energy Research.
In particular, the Spanish researchers supplied weak electronic currents to the bacteria, modifying their metabolism and making them capable of recycling organic substances. At the end of this “activity” (which is rather complex, from a chemical and physical point of view), the purple bacteria transformed these substances into easily-reusable molecules, also simultaneously releasing hydrogen, as we have already said, which can be used for the production of electricity (using various techniques).
The study by the Spanish researchers can also be used in much broader scenarios: it is in fact possible that with different manipulations (for example, adjusting the intensity of the light or the temperature) the same bacteria could digest and transform other types of substances, thus becoming true and proper treatment and biological recycling plants, in systems that have been redefined as bio-electrochemical.