Electrocoagulation vs. coagulation–flocculation applied to real wastewater and set up to pilot/full scale

Abstract

ABSTRACT Electrocoagulation (EC) and coagulation – flocculation (CF), have been employed for the treatment of different organic contaminants present in aqueous solutions owing to their efficiency. This review article reports the results obtained by different authors in the last 5 years, where EC, CF, and their coupling with other processes, are employed at the laboratory, pilot plant, and industrial scales. The evaluation of operating conditions, efficiencies, applications, limitations, and opportunities that arise in scaling both processes are presented. In this way, the present paper is novel because it presents evidence on the advantages and disadvantages of EC and CF technologies implemented at pilot/full scale to treat real wastewater, which has not been collected and synthesised in previous studies. The average elimination percentages (%COD) were evaluated at a pilot/industrial plant scale, where EC (%COD = 70%) presents higher efficiencies compared to CF (%COD = 60%). In CF, the %COD increases when using longer times, contrary to EC (%COD = 75% at t = 10 h in CF and %COD = 80% at t = 0.33 h in EC). Achieving neutral conditions in treated wastewater promotes high efficiencies and low energy consumption, causing costs to be reduced. The origin and composition of the wastewater also influence the pH and efficiencies. EC is the most studied method at laboratory scale, however, its development at an industrial level is minimal, unlike CF, where more studies are reported on a pilot and industrial scale. In both processes, the use of oxidising agents and ultraviolet energy favours the formation of metal radicals and the transformation of contaminants, increasing removal efficiencies.