Highly alkali caustic discharges recovery using tubular and disc type of ceramic membranes and its applicability as a near zero liquid discharge opportunity in the textile industry

Ceramic membrane technology is a good alternative for the recovery of highly alkaline and heavily concentrated caustic discharges through textile causticization processes since their high robustness. Recovery of causticization processes discharges with ceramic membrane technology has not been considered in detail in previous studies. In this study, highly alkaline and heavily polluted caustic discharges was assessed recovery and reuse potential using laboratory scale disc and tubular types of ceramic microfiltration, ultrafiltration and fine ultrafiltration membranes (0.2 µm, 300 kDa, 50 kDa, 15 kDa, 3 kDa and 1 kDa). Causticization discharges characteristics can be defined as 13 ± 0.2 pH, 21.2 ± 1 g NaOH/L, 27.9 ± 9 g COD/L, 1 ± 0.3 g TSS/L and 1785 ± 1568 Pt-Co based on long term wastewater characterization period. Required minimum MWCO membrane and membrane filtration process configuration based on permeate quality with minimum NaOH loss, membrane geometry affect, membrane fouling mechanism and economical assessment of caustic solution recovery were studied. Achievable optimum and acceptable permeate results obtained with two stage ceramic membrane filtration, 0.2 µm microfiltration followed by 15 kDa ultrafiltration permeate can be reused in the causticization process again. Steady state flux values were around 7–43 LMH at 1 bar and main fouling mechanism was the physically removable resistance according to resistance in series model, flux recovery 74% and up to 99% more after chemical cleaning and tubular type of membranes shows more fouling tendency compared to disc types. Proposed two stage ceramic membrane filtration not only provides comparable less chemical consumption but also Textile BREF documents’ caustic discharge criteria might be met with near zero liquid caustic discharge.