Experimental and Modelling study for Electrocoagulation Cell Used to Remove High Organic Loads in Wastewater

Electrocoagulation is a very promising technology for cleaning wastewater with high organic content, furthermore, in most of the published papers, experimental studies are performed in beakers with magnetic stirrers, unfortunately this type of laboratory scale, as such may not be scale-up. In this work, a laboratory scale electrocoagulation cell has been designed to operate in batch and continuous flow mode, which can be scale-up to processing larger volumes of effluents with high organic matter content of the food and liquors industries, which are difficult to treat by biological methods. The laboratory scale electrocoagulation cell (CEEL-TUU01) [1] is built in polycarbonate with carbon steel electrodes 1018 with thickness of 1/8". The main objective of this work is to develop a modeling and experimental methodology to establish the operating conditions for this cell. The methodology consisted of: a) physicochemical characterization of the effluent, b) microelectrolysis studies, c) chemical coagulation, d) thermodynamic analysis, e) kinetic studies of electrode dissolution and gas generation (H₂ and O₂), f) for cell operating in batch mode, the effect of the inter-electrode gap on pH changes was studied, g) to find the flow cell operating in continuous mode, experimental studies of the residence time distribution (RTD) were conducted, Finally, h) macro electrolysis studies were performed using food and liquors effluents. Using the methodology here propose the operating conditions of the electrocoagulation cell for to clean effluents of the food and liquors industries (98% COD removal and almost 100% removal of the effluent turbidity) were establish. The RTD curves were approximated with two no ideal reactor design mathematical models: i) N-tanks in series (N-CSTR) and ii) axial dispersion model (MDA), likewise to detect local deviations of the flow pattern within cell, computational simulation studies of hydrodynamics (Comsol Multiphysics 4.2 software) were carried out. The generation of gas bubbles (hydrogen) in the cathode positively modify the liquid flow pattern and the axial dispersion model (MDA) could be considered as the design equation for the liquid phase cell. The hydrodynamic simulation results helped to identify punctual defects in the geometric cell design. Finally, the strategy developed aid in the design and re-design of an electrocoagulation cell.

[1] A. Torres-Mendoza, P. E. Mendoza-Campos, I. Rodríguez-Velázquez, P. Benítez. M. R. Cruz-Díaz, E. P. Rivero , I. González. Extended Abstracts of XXXII Encuentro Nacional y 1^er Congreso Internacional de la AMIDIQ. 3 al 6 de mayo del 2011, Riviera Maya, Quintana Roo. p 3109-3115