277 This vulnerability is especially pronounced in peri-urban areas of Lima. While residents in central Lima receive water from the public utility at an approximate cost of USD 0.8 per cubic meter, those in periurban zones pay between USD 5 and 7 per cubic meter—up to eight times more—for water of inferior quality and reliability. These households often have access to only 30 liters per person per day or less, compared to the virtually unlimited supply available in formal urban areas. Moreover, the water is frequently unsafe due to precarious transport and storage in unsuitable containers, and residents must wait between 0.5 and 1 hour daily to receive it. In rural areas, a critical challenge is the lack of knowledge regarding water quality. For instance, hydrogeological activity in the highlands of Tacna has been shown to contaminate the Sama and Locumba basins [2]. Similarly, some artesian wells in the Peruvian jungle contain polymetallic ions—such as arsenic and manganese—that exceed maximum permissible limits due to natural geogenic conditions [3,4]. In this context, there is an urgent need to develop water treatment technologies suited to rural and peri-urban communities, where access to economic resources, energy, chemical supplies, and skilled technical personnel is limited. Such technologies must be efficient, robust, easy to implement, and simple to maintain. Fortunately, Peru’s geographical location—extending up to 18°20' south—provides high-intensity solar radiation throughout the year [5], offering a valuable opportunity to leverage solar-based solutions adapted to the country’s complex terrain and limited transportation infrastructure. 2. METHODOLOGY 2.1. Experimental Setup and Reactor Configurations Three distinct types of solar photoreactors were developed and evaluated to test photocatalytic efficiency under different irradiation conditions and scales. 2.2. Non-Concentrating Flat-Plate Reactor A flexible, portable reactor was constructed using polyethylene (PE) sheets thermally fused at the edges to form a flat reaction chamber. Two configurations were tested with working volumes of 25 L (50x50x10 cm3) and 120 L. The system was equipped with inlet and outlet valves, a recirculation pump, and an integrated activated carbon filter to reduce suspended particles. A thin film of TiO2 photocatalyst was immobilized on the bottom inner surface of the reactor to maximize solar exposure. 2.2.1. PET Bottle Reactors (Low-Cost Disinfection) For simplified point-of-use experiments, standard polyethylene terephthalate (PET) bottles were utilized. These were modified to contain composite pellets of Activated Carbon (AC) and TiO2. The bottles were sealed and exposed directly to solar radiation to evaluate the synergistic effect of adsorption and photocatalysis. Additionally, variants containing Fe3+ and citric acid were employed for arsenic removal assays. 2.2.2. Solar Concentrating Reactors (Parabolic and CPC) To evaluate higher-intensity irradiation, concentrating solar reactors were employed using borosilicate glass tubes as the receiver elements. The setup consisted of cylindrical Compound Parabolic Collectors (CPC) and parabolic troughs. Catalyst Support: TiO2 was immobilized via sol-gel deposition onto frosted glass cylinders (30 mm diameter, 250 mm length) positioned along the longitudinal axis of the reactor tubes (97 mL useful photoreactor volume). Alternatively, modified catalysts such as cellulosesupported TiO2 and Ruthenium complexes on silicone strips were tested. The pilot setup consisted of three independent systems driven by 12 W electrical pumps with a recirculation rate of 12 L/min. Two systems operated with a two-tube configuration (treating 12 L), used to test the supported TiO2 and Ru-complex catalysts. The third system operated with a single tube (treating 10 L) and served as a photolysis control (solar radiation without catalyst).
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