Photo-catalytic reactor and detention pond integration: a novel technique for surface water quality enhancement via nano-TiO₂

Integration possibility and performance of a fixed-bed photo-catalytic reactor, merged with a detention pond, were examined at scale model. The focus of this study is to overcome the key issues of the conventional detention ponds and provide an enhanced surface water quality via nano-TiO₂ as a novel hybrid technology. Photo-degradation of detained water nutrients in newly designed fixed-bed reactor pond (FRP) was studied to observe the impacts of heterogeneous reactions under ultraviolet irradiation. Immobilization of nano-titanium dioxide as catalyst, covering the FRP internal surface, was practiced for comparison and control. Rutile with anatase forms of TiO₂ nano-powder (P25) was replaced in cement (white cement as well as Portland) at three dosages (30, 10, and 3%) for optimization purpose. Biodegradable pollutant elimination capability of FRP underpinned by the results for lower nitrate (16%), orthophosphate (25%), and COD (18%) in 2 days retention time, comparatively. Within 21 days, detaining time 26%, 58%. and 47% higher elimination was achieved, respectively. Improved catalyst surface area to reactor volume as well as an optimized retention time, based on streamflow pollution level, were achieved via splitting the FRP into two parts using a divider. FRP inlet was equipped with a flow switcher to capture and detain the first flush from the stormwater separately, while the balance is directed to the second part with a different required holding period. The divider walls were coated with cement-based nano-TiO₂ and it also retrofitted applying filter media inside, for sediment-bound pollutant omission which the technique emerged with a greater TSS removal potency of up to 43%.