Solar technologies for urban wastewater treatment, reuse, and recovery of extracted resources

An increasing scarcity of clean, safe water is a serious worldwide problem, particularly in arid and semi-arid areas. Ongoing research is needed to identify new water treatment methods for the removal of pollutants to achieve reductions in costs, energy consumption and the use of chemical products. Conventional water decontamination and disinfection treatments are generally very expensive in terms of chemicals, energy and operating costs

Advanced oxidation processes (AOPs) promote the generation of hydroxl radicals that degrade the majority of organic molecules, and, therefore, pollutants, most of which are organic compounds.

These processes include heterogeneous photocatalysis and homogenous photocatalysis by means of photo-Fenton type processes. These processes are based on the use of semiconductors and the addition of hydrogen peroxide to iron salts, respectively, as well as the irradiation of these systems with UVVis light. Both processes are of particular interest because solar light can be used as a source of UV radiation, with consequent reductions in operating costs.

The use of photo-reactors is required to carry out-photocatalysis-based AOPs.. The
most commonly implemented photo-reactors for these applications are those known as compound parabolic collectors (CPC), (Figure 1), which are static non-concentrating systems. This design is advantageous in that it results in stationary reactors with an optic that provide the greatest efficiency to collect direct and diffuse radiation, without the need for solar tracking. Because the photo-reactor is tubular, it provides a turbulent flow that favours homogenous mixing, and because these are enclosed systems, there are no volatile compound losses. As a result, maintenance is cheap and easy, and these systems can be easily scaled.

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Article published in: FuturENVIRO #39 April 2017