TAGUCHI-BASED OPTIMIZATION OF AIR-GAP MEMBRANE DISTILLAT

This study investigated the optimization of the performance of an Air Gap Membrane Distillation (AGMD) system using the Taguchi orthogonal experimental design method. Four operating parameters were evaluated: feed water temperature (T₁), cooling water temperature (T₂), feed flow rate (V₁), and cooling flow rate (V₂). Process performance was assessed using three response variables: distillate flux, distillate mass, and product electrical conductivity. Materials and Methods Experiments were conducted using a laboratory-scale AGMD unit at PURA-Lab (PSA, CIEMAT, Spain) equipped with a flat-sheet hydrophobic PTFE membrane with a 3 mm air gap. Feed and coolant streams circulated in a counter-current configuration, while temperatures were controlled using thermostatic baths (±0.5 °C). Process optimization was performed using an L8 Taguchi orthogonal array. The investigated operating ranges were T₁ = 70–80 °C, T₂ = 20–25 °C, V₁ = 100–150 L/h, and V₂ = 100–150 L/h. Distillate flux, distillate mass, and product conductivity were statistically analyzed. Results The experimental results showed that the distillate flux ranged from 36.72 to 122.11 L/h, distillate mass from 0.158 to 1.328 kg, and product electrical conductivity from 1.23 to 3.69 μS/cm. Taguchi analysis identified feed water temperature (T₁) as the dominant operating parameter, accounting for 56.4% of the variation in distillate flux and 69.8% of the variation in distillate mass. Increasing T₁ from 70 °C to 80 °C reduced both distillate flux and distillate mass by more than 60%. The optimal operating conditions were T₁ = 70 °C, T₂ = 20 °C, V₁ = 150 L/h, and V₂ = 100 L/h, yielding a maximum distillate flux of 118 L/h with high product quality (1.3 μS/cm). Conclusion The Taguchi experimental design method proved to be an effective tool for optimizing AGMD operating conditions. Feed water temperature was identified as the most influential parameter affecting system performance. Proper optimization of operating conditions significantly enhances distillate production while maintaining excellent product quality.

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