Reclamation of grey water for non-potable purposes using pilot-scale solar photocatalytic tubular reactors

Abstract

Application of pilot-scale slurry-type tubular photocatalytic reactor was tested for the decentralized treatment of actual grey water. The reactors were fabricated by reusing the locally available materials at low cost, operated in batch recycle mode with 25 L of grey water. The influence of operational parameters such as catalysts' concentration, initial slurry pH and addition of HO on COD abatement were optimized. The results show that Ag-decorated TiO showed a two-fold increase in COD abatement than did pure TiO. Better COD abatement was observed under acidic conditions, and addition of HO significantly increases the rate of COD abatement. Within 2 h, 99% COD abatement was observed when the reactor was operated with optimum operational conditions. Silver ion lixiviate was also monitored during the experiment and is five times less than the permissible limits. The catalyst shows good stability even after five cycles without much loss in its photocatalytic activity. The results clearly reveal that pilot-scale slurry tubular solar photocatalytic reactors could be used as a cost-effective method to treat grey water and the resulting clean water could be reused for various non-potable purposes, thus conserving precious water resource. This study favours decentralized grey water treatment and possible scaling up of solar photocatalytic reactor using locally available materials for the potential reuse of treated water.

Identifying Key Design Criteria for Large-Scale Photocatalytic Hydrogen Generation from Engineering and Economic Perspectives

“…Over a decade ago, the capacity for designing and constructing pilot-scale suspended photocatalytic systems was demonstrated where tubular reactors and parabolic concentrators were used for photocatalytic water detoxification (Figure a and b). − More recently, Domen et al demonstrated the upscaling of their SrTiO 3 :Al photocatalyst panel into a 100 m 2 photocatalytic water-splitting reactor for H 2 generation containing 1600 panels . A maximum H 2 production rate of 3.6–3.7 mL/min (average 0.5% solar-to-hydrogen efficiency) was achieved under natural sunlight with solar radiation of approximately 0.9 kW/m 2 during autumn.…”

Application of visible light active photocatalysis for water contaminants: A review

“…Graywater is a highly reclaimable water source. Saran et al ( 2019 ) prepared TiO 2 ‐Ag for a pilot‐scale slurry‐type tubular photocatalytic reactor to treat actual graywater, with the addition of H 2 O 2 a 99% COD abatement was achieved within 2 h. Tsoumachidou et al ( 2017 ) used commercial TiO 2 ‐P25 with H 2 O 2 and Fe 3+ to treat graywater, which achieved an almost 64% DOC removal rate in a pilot‐scale slurry fountain photoreactor. Olga Sacco et al ( 2018 ) set a pilot‐scale test for real wastewater disinfection and MB removal using nitrogen‐doped TiO 2 particles (N‐TiO 2 /PS) immobilized on polystyrene spheres.…”

Water reclamation and reuse

“…A cost-effective slurry-type tubular photocatalytic reactor with the Ag-TiO 2 catalyst was tested at a pilot scale for its application in the decentralized treatment of gray water (Saran, Arunkumar, Manjari, & Devipriya, 2019). At an optimum operating condition (i.e., catalyst concentration of 220 ppm, initial pH of 2, and addition of 5 mM H 2 O 2 at a flow rate of 15 L under 1 mW/cm 2 solar irradiation), 100% organic pollutants were degraded, and 99% COD was removed within 2 hr, producing water available for various nonpotable use.…”