The Water-Energy Nexus: Electrocoagulation and Energy Conservation

Electrocoagulation is a multiple-purpose process re-emerging nowadays as a low-energy solution to water treatment and pollution control problems. This paper describes the development of electrocoagulation-flocculation (ECF) treatment processes of water and wastewater that could be a potential hydrogen gas source and reduce operational costs as well. ECF coupling with ultrafiltration (UF) for organics removal and flux enhancement and, with granular filtration (GF) and constructed wetland (CW) for P removal from secondary effluents are examined. Bench-scale experiments of ECF-UF and ECF-UF configurations and ECF-GF-CW pilot tests had been performed. Analysis of ECF mechanisms leads to energy conservation potential via (a) hydrogen co-generation, (b) low voltage application, (c) reduced chemicals transportation (which is also helpful in less developed cold areas where and when roads are blocked) and (d) hybridization with other low energy treatment processes such as constructed wetlands or SAT. A model developed for energy minimization is found to play a major role in process selection. It is also concluded that ECF as pretreatment for UF and MF improved filtrate quality and reduced the fouling, particularly by reducing cake influence. And, complementing CW treatment with a physicochemical process of ECF reduces soluble and particulate phosphate, and removes organic matter and nitrogen compounds.