Valorization of Nixtamalization wastewaters (Nejayote) by integrated membrane process

• Nejayote was fractionated by membrane separation technologies.
• The water permeabilities of the membranes were almost completely recovered.
• High rejections on TSS, TSC, turbidity, TOC and total carbohydrates were achieved.
• A concentrated fraction enriched in carbohydrates was obtained.
• A clarified fraction enriched in total polyphenols was obtained.

The purpose of this study was to analyze the potentiality of an integrated membrane process for the treatment of Nixtamalization wastewaters (well known as Nejayote). In particular, a sequence of one microfiltration (MF) pre-treatment step followed by two ultrafiltration (UF) processes was investigated on laboratory scale operating in selected process conditions. The performance of selected membranes in terms of productivity, fouling index, and water permeability recovery was evaluated and discussed.The produced fractions were analyzed for their total soluble solids (TSS), total solids content (TSC), pH, electrical conductivity, turbidity, total polyphenols, total carbohydrates and total organic carbon (TOC). The rejection toward compounds of interest was evaluated. On the basis of experimental results, an integrated membrane process for the treatment of Nejayote was proposed. The conceptual process design permitted to achieve three streams as valuable products: a fraction enriched in carbohydrates, a fraction with high content of calcium components and clear fraction enriched in phenolic compounds. The obtained solution enriched in carbohydrates is of interest for preparing formulations to be used in food industry. Besides, the solution enriched in polyphenols can be used in cosmetic or pharmaceutical applications. Finally, the integrated membrane process used in this study can be used to fractionate Nixtamalization wastewaters as well as avoid the water and environmental pollution by the effluent.