This study compares the effects of pulsed and continuous ultrasound at two frequencies (28 and 40 kHz) on hybrid electrocoagulation (EC) systems for the treatment of compost wastewater, combining zeolite addition with different electrode pairs (Al/Al, Fe/Fe, Zn/Zn, and Al/Fe). The experimental investigation addressed four complementary aspects: (i) effluent quality and treatment efficiency evaluation through solution parameters monitoring, (ii) electrode degradation assessment through mass loss measurements and surface analysis, (iii) sedimentation analysis, and (iv) operational costs evaluation in terms of electrode and energy consumption. Process optimization was conducted using a mixed Taguchi L8 design to quantify the combined influence of electrode pairs, ultrasound mode and frequency, zeolite addition, and treatment time on pollutant removal and electrode wear. Operational cost calculation demonstrated that electrode material, ultrasound mode, and frequency, along with applied current and voltage, collectively govern electrode wear and Faraday efficiency, with pulsed ultrasound at 40 kHz and Al electrodes minimizing anodic mass loss and energy consumption. The Taguchi analysis revealed that zeolite addition is the most influential factor negatively affecting COD and turbidity. Meanwhile, the optimal operational parameters for overall performance were identified as an Al/Al electrode pair, a 40 kHz ultrasound frequency, pulsed mode, a 10 min treatment time, and the absence of zeolite. These findings provide practical guidance for designing hybrid pulsed ultrasound EC processes that are both effective and economically sustainable for complex wastewater treatment.
Čule et al. (Fri,) studied this question.