Life-cycle assessment of a coupled advanced oxidation-biological process for wastewater treatment:: Comparison with granular activated carbon adsorption

A comparative Life Cycle Assessment (LCA) concerning two strategies for coupling advanced oxidation processes (AOPs) with biological treatment, namely solar-driven photo-Fenton and ozonation, is performed. In addition, these emergent technologies are compared to a reference technology, namely granular activated carbon (GAQ adsorption. The study is based on pilot plant and laboratory tests using alphamethyl-phenylglycine (MPG) as a target substance. The system under study includes production of infrastructure for the solar plant, chemicals, electricity, transport of all these materials to the plant site, management of the spent catalyst by landfilling and spent GAC by regeneration, as well as treatment of the obtained effluent in a conventional municipal wastewater treatment plant (MWWTP) and excess sludge treatment by incineration. Nine environmental impact categories are included in the LCA: global warming, ozone depletion, human toxicity, freshwater aquatic toxicity, photochemical ozone formation, acidification, eutrophication, energy consumption, and land use. The experimental results obtained in the pilot plant show that both AOPs are able to obtain a biodegradable effluent, while GAC is able to adsorb almost 100% MPG. The results of the LCA show that none of the treatment options appears as preferable at the same time in all nine impact indicators. Nevertheless, in six of these indicators solar-driven photo-Fenton coupled to biological treatment obtains the lowest impact. From a weighted life cycle impact assessment (LCIA) results perspective, solar-driven photo-Fenton appears as the most environmentally friendly alternative, even in locations with relatively low solar resources.