Concurrent multiresponse multifactorial screening of an electrodialysis process of polluted wastewater using robust non-linear Taguchi profiling

Abstract

Electrodialysis is an important chemical process that separates pollutants from wastewater pools to produce clean water for consumption and irrigation. Initial wastewater concentration of chemical elements always differs. Chemical components are strongly dependent on the efflux origin and treatment. To optimize an electrodialysis process is congruent to improved key water quality characteristics. To predict optimal electrodialysis performance there will always be a need to conduct a small number of structured experiments. This is because wastewater conditions are usually different in each situation thus requiring reliable evidence-based design decisions to be delivered timely and low-cost. We study a real example from crucial dessert wastewater operations that aim to supply clean water for irrigation. Several issues are scrutinized that are often overlooked when carrying out multi-response multi-factorial statistical optimization in environmental screening. Programming fast-cycle trials with Taguchi-type factorial recipes reaps quick information for new development and improvement projects. But it also introduces phenomena such as saturation, unreplication and non-linearity that could undermine the optimization effort. The showcased paradigm uses popular Taguchi methods to organize a rapid and short round of trials in order to investigate the behavior of four electrodialysis controlling factors: 1) the dilute flow, 2) the cathode flow, 3) the anode flow and 4) the voltage. The three monitored water quality indices are: 1) the percentage of removed sodium cations, 2) the sodium adsorption ratio and 3) the sodium ratio. We discuss the intricacies that emerge from the synthetic type of the electrodialysis data: non-normality, non-linearity and messiness. We propose a robust and agile method to conduct the multi-response multi-factorial optimization for electrodialysis of polluted wastewater. It is based on super-ranking and distribution-free profiling. Comparison with other profiling methods is provided and main advantages are commented from a chemical engineering perspective.