Environmental life cycle assessment of UV-C LEDs vs. mercury lamps and oxidant selection for diclofenac degradation

This study is the first environmental comparison between a UV-C LED lamp (emitting at 265 nm) and mercury
lamps employed in a lab-scale photoreactor for water treatment purification purposes, using the removal of
diclofenac as a case study. Ex-ante life cycle assessment (LCA) methodology was used as a robust method to
identify hotspots and recommendations at the early stage of the UV-C LEDs technology. The functional unit was
defined as “the treatment of 1 L of polluted water with 20 mg L􀀀 1 of diclofenac to achieve a 90% removal of the
contaminant”, while the system boundaries include the production and the operation of the photoreactors,
following a cradle-to-gate approach. Several scenarios were explored, and overall, the UV-C LED lamp shows a
promising environmental performance, with less or similar potential impacts than the mercury lamps in the 16
categories selected from the Environmental Footprint (EF) method. In particular, it reveals less impact in “human
toxicity non-cancer” and “resource use minerals and metals” and presents electricity as the main source of
impact. Given the higher efficacy of the UV-driven advanced oxidation processes compared to the UV irradiation
alone, and since no studies have previously been conducted on the sustainability of free chlorine (FC) as an
oxidant in water treatment, a comparison between UV-C, UV-C/H2O2, and UV-C/FC while employing the 265 nm
UV-C LED lamp was also assessed. UV-C/H2O2 was more sustainable than UV-C/FC for the same treatment time,
but both led to an overall impact reduction of 35% and 30%, respectively. To increase sustainability, employing
cleaner energy sources such as photovoltaic or wind energy also resulted in an 80% and 93% reduction in the
“climate change” category. Overall, this study demonstrates that using UV-C LEDs and the selected oxidants for
water purification is beneficial and encourages the scale-up of the system.