Application of a multiple criteria analysis for the selection of appropriate radical based processes in treatment of car wash wastewater

Abstract

In this study, the treatment of car wash wastewater was investigated by radical based hybrid/combined processes. Proposed processes, (Microwave (MW) + persulfate (PS) + Electrocoagulation (EC)), (ozone (O3) + PS + EC) and (MW + PS + O3), were optimized with Taguchi orthogonal array technique for maximum COD removal. The COD removal under optimum conditions was obtained to be 84%, 64.9% and 61.4%, for (MW + PS+ EC), (O3 + PS+ EC) and (MW + PS+ O3) processes, respectively. Operating costs for (MW + PS + EC), (O3 + PS + EC) and (MW + PS + O3) processes have been calculated as 0.2614, 0.1335 and 0.2653 €/L wastewater under optimum operating conditions. Pareto analysis showed that MW time and PS dose are very effective parameters but especially ozone related parameters have no significant effect on COD removal. Processes were evaluated with the PROMETHEE approach in terms of treatment efficiency, operating cost, sludge formation, and preferability criteria to determine the most suitable among the three alternative processes. As a result, the preference order of the processes for the treatment of car wash wastewater with radical based treatment processes was found as (MW + EC + PS) > (MW + O3 + PS) > (O3 + EC + PS).

Electro-Persulfate Processes for the Treatment of Complex Wastewater Matrices: Present and Future

“…The inter-electrode gap ranges between 1 and 4 cm for the different studies presented. The influence of this operational parameter in the electro-persulfate activation process was only assessed by Durna and Genç (data not presented in Table 2 ), while treating a car wash wastewater [ 34 ]. No significant difference was observed in the results by the increase in the inter-electrode distance from 1 to 3 cm, which led the authors to conclude that, despite this being an effective parameter in the electrocoagulation process, it is insignificant in the combined metal-activated persulfate with simultaneous electrocoagulation.…”

“…Durna and Genç [ 34 ] have treated a car wash wastewater by PDS electro-activation through aluminum anodes, using microwaves (MW) to pre-activate PDS, and adding O 3 during the experiments. PDS/COD ratios between 1.5 and 3 were assayed at very low applied current densities (0.0159 or 0.0319 mA cm −2 ), when compared to others studies.…”

“…Current density is another important variable that influences pollutants degradation rate, since the increase in current promotes the increased Fe 2+ production and persulfate activation, and more radicals are available to attack organic pollutants. Although the different works performed, with the objective of studying the influence of current density on the COD removal rate, very different current densities were assayed, most of them have found an optimum current value that, in general, was not the highest assayed [ 11 , 12 , 13 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. In fact, higher currents may slow down the organics degradation rate, since an increase in current leads to an increase in ferrous ion in solution, which can act as a sulfate radical scavenger (Equation (34)).…”

Carwash wastewater treatment using the chemical processes

“…However, considering the characteristics of wastewater and the ability of each treatment method is efficient in integrated system to achieve the desired efficiency. As an example, Durna & Nevim (2021) reported the 84% reduction efficiency of COD in using the combined process of microwave þ persulfate þ electrocoagulation versus the 64% reduction efficiency of COD in using the combined process of ozone þ persulfate þ electrocoagulation for the same wastewater. Selecting the appropriate integrated method based on recognizing the characteristics of wastewater and the capability of chemical treatment methods, in addition to achieving appropriate efficiency can also be effective in reducing treatment costs.…”

“…Selecting the appropriate integrated method based on recognizing the characteristics of wastewater and the capability of chemical treatment methods, in addition to achieving appropriate efficiency can also be effective in reducing treatment costs. durna and Genc stated that the use of ozone instead of electrocoagulation in the combine process with microwave þ persulfate, increased the cost of wastewater treatment by 0.04 euros per liter, and reduced the efficiency from 84 to 61% (Durna & Nevim 2021).…”