Wastewater Recycling Technology Offers

University of Vigo posted this:

Many industries, such as those belonging to the textile, wine, and paper industry, consume huge volumes of water and, as a result, generate a large amount of contaminated water containing persistent colour pollutant compounds. These compounds represent an environmental and health threat due to their well-known associated problems, such as carcinogenicity, toxicity and mutagenicity. Furthermore, they entail a great environmental impact when discharged in aquatic environments, perceptible at very low concentrations, creating an undesirable visual impact, which, in many cases, does not meet the degree of conformity under the current directives on the wastewater treatment for industrial effluents (Directive 91/271 / EEC). The solution proposed by the research group Chemical Engineering at the University of Vigo, is the use as adsorbent of peat, or a similar lignocellulosic material, immobilized in calcium alginate beads. This process is efficient, cheap and environmentally friendly, unlike other processes and technologies. In fact, the utilization of peat instead of activated carbon as industrial adsorbent has the advantage that peat requires no activation, unlike activated carbon, reducing operating costs. In addition, the low cost of the adsorbent would be translated into significant economic benefits. Moreover, depending on the contaminant removed from the waste effluent, the exhausted adsorbent may be used as soil fertilizer at its end of life.

Universidad de Cádiz posted this:

UCA researchers have developed a new process for the treatment of waste waters by using microalgae, specifically for the removal of nitrogen and phosphorus. This process is based on applying three fundamental findings made by the research group: • Before the microalgae start to grow, they are already consuming nitrogen and phosphorus when cultivated in waste waters. • The microalgae accumulate nutrients internally in such a way that the assimilation of nutrients commences before the growth phase, and at a rate that is considerably faster than the rate during the generation of biomass. • The initial elimination of nutrients prior to the growth of biomass takes place at a similar rate both in darkness and in the presence of light. To exploit this phenomenon, a procedure has been designed in which the two phases take place separately in two reactors: the first phase for elimination of nutrients from the waste water in darkness (known as ‘luxury uptake’) and the second for the growth of biomass under illumination. What this achieves is not only the efficient removal of the nutrients from the waste water but also, by means of a simple change of the mode of operation of the process, nutrients can be eliminated at night using the excess of biomass generated during daylight hours. To implement this advance, the research group has conceived a process for the separation of the biomass from the culture medium in both phases, by means of membrane technologies. The treatment plant can operate with cellular retention times very much longer than the hydraulic residence times. This, in turn, allows the same flow volumes of waste water to be treated in smaller reactors. • It enables waste waters to be treated at night without the need for a luminous phase. This cannot currently be done with the processes that employ existing photosynthetic organisms. • Simplicity of operation and reduction of costs in comparison with conventional technologies. It avoids the production of more solid residues, i.e. sludges, which require disposal. • The use of microalgae allows the treatment of waste waters with high levels of nitrogen and phosphorus but low content of organic matter (a characteristic of the waste waters of steelworks), since autotrophic organisms are involved. Thus the proposed process avoids the need to add organic matter from an external source, as is the case of other biological processes. • With the possibility of generating energy and capturing CO2, the biomass generated in the process represents value added in terms of energy consumption and environmental protection