Assessing the environmental sustainability of light emitting diodes and conventional blacklight lamps for the treatment of bisphenol-A in water

Abstract

Ultraviolet (UV) water treatment techniques currently employ blacklight (UV-BL) lamps, which are energy intensive, short living and contain toxic materials, damaging the environment. Light emitting diodes (UV-LEDs) can offer an environmentally friendly alternative to UV-BLs, however their environmental impacts for water treatment have not been quantified yet. This study aims at investigating the environmental sustainability of UV-LEDs for removing bisphenol-A from water and compare it with UV-BL lamps. The life cycle assessment (LCA) methodology was utilised to estimate the process' environmental footprint. The functional unit adopted was the treatment of 1 L of water with initial 7.5 mg/L bisphenol-A concentration and 125 mg/L of titanium dioxide (TiO2) acting as a catalyst. UV-LED/TiO2 was found to have an environmental footprint of 61% less than UV-BL/TiO2. From a sensitivity analysis the environmental hotspots of the treatment process were the energy consumption and the photocatalytic reactors used. Therefore, three alternative scenarios investigating the use of solar photocatalysis, a renewable electricity mix and recyclable materials were explored to enhance the environmental performance of the treatment process. The results overwhelmingly favoured solar photocatalysis as the most environmentally sustainable treatment, leading to a 87.2% and 78.6% decrease of the environmental footprint of the UV-LED/TiO2 and the UV-BL/TiO2 treatment process, respectively. Using a renewable electricity mix, representative of Scotland's renewable output, a decrease of 41.5% (from 198.3 to 116.0 μPt) and 15.7% (from 517.2 to 435.9 μPt) for the UV-LED/TiO2 and UV-BL/TiO2, respectively, was observed. Beginning with the most environmentally sustainable, the treatment processes ranked in the following order: solar/TiO2 > UV-LED/TiO2 renewable electricity mix > UV-LED/TiO2 > UV-BL/TiO2 renewable electricity mix > UV-BL/TiO2, indicating that UV-LED systems driven by renewable electricity could be feasible for 24/7 large-scale wastewater treatment systems.