Treatment of mature landfill leachate by electrocoagulation followed by Fenton or UVA-LED photo-Fenton processes

The main objective of this study is to optimize a two-step treatment for mature landfill leachate consisting of electrocoagulation (EC) followed by Fenton or UVA-LED photo-Fenton processes aiming to provide a more efficient and feasible alternative treatment strategy that also increases biodegradability and decreases conductivity. Although 5 mA cm−2 EC is cheaper than 10 mA cm−2 EC per kg of removed COD (0.63 vs. 0.89 € kgCOD−1), it achieved the half total COD removal (13% compared to 26%), and the low residual iron concentration (100 mg L−1) that remained at the end of the process made necessary a long treatment time to perform the posterior Fenton (48 h) or UVA-LED photo-Fenton (6 h) process. When EC was performed at 10 mA cm−2, the residual iron concentration (220 mg L−1) was high enough to reduce treatment time by one half for both Fenton processes. Consequently, treatment cost decreases from 5.91 to 3.48 € kgCOD−1 for the EC + UVA-LED photo-Fenton ([H2O2]/COD = 1.063) treatment combination; whereas it slightly decreases from 1.68 to 1.61 € kgCOD−1 for the alternative EC + conventional Fenton combination. In both cases, total COD removal was around 87%. In addition, SUVA removal was >40%, conductivity was reduced about 20–30%, and biodegradability (BOD5/COD) increased over 0.3.