Life cycle assessment of sequential and simultaneous combination of electrocoagulation and ozonation for textile wastewater treatment

Abstract

Electrocoagulation (EC), ozonation (O3) and their combination have attracted the interest of researchers for textile wastewater treatment. However, the lack of an exhaustive comparison among the different approaches, including also the evaluation of their impact on the environment, has hampered full-scale application. As a result, in this study, environmental impacts of simultaneous (-) and sequential (→) combination of EC and O3 were analyzed and compared to EC and O3 alone processes. The effect of type of electrode (Fe or Al) was evaluated in the EC process. The processes were investigated at lab scale and compared through Life Cycle Assessment (LCA), using ReCiPe midpoint and endpoint methods. EC process with Al electrodes resulted in the lowest impact for all the environmental categories due to the lower energy consumption, while O3 process resulted in the highest impact being an energy- and oxygen-intensive process. In particular, when the processes removed COD below 60 mg/L, the higher CO2 emission as the key midpoint method indicator was expected for O3 (81.4 g CO2 eq), while the lower was measured for EC(Al) (1.4 g CO2 eq). Moreover, the higher effect on Human Health, as the key endpoint method indicator, was obtained for O3 (6.65E-6), and the lower one was for EC(Al) (1.35E-7). The environmental impact of simultaneous combination (EC-O3) is still high due to high ozonation time. In sequential combination option (EC→O3), O3 treatment time was very short and environmental impacts decreased significantly besides high purification performance (approximately 50% COD removal). It is worthy to note that the environmental impacts of all processes are strongly related to energy and chemical consumption, that emphasize the importance of optimizing operation conditions. LCA showed that the sequential combination of EC and O3 is the most sustainable solution for textile wastewater treatment among the investigated processes and it can be successfully applied at industrial scale.