Treatment of real textile wastewater by coagulation/flocculation integrated with direct contact membrane distillation

ABSTRACT

This study investigated the water recovery of real textile wastewater by Coagulation/Flocculation (CF) integrated with Direct Contact Membrane Distillation (DCMD). The proof-of-concept tests were studied with synthetic solutions of reactive and disperse black dyes at different concentrations, and real textile wastewater from the discharge machine and the equalization tank. Results showed that CF-DCMD exhibited higher permeate fluxes (up to 40%) than single DCMD and maximum color rejection rates (100%). Moreover, CF-DCMD enabled water reclamation from cotton and polyester dyeing wastewater which was not possible by MD (Membrane Distillation). The integrated system showed excellent chemical oxygen demand removal capacity, total suspended solids, turbidity, conductivity reduction, and removed any signs of toxicity from the tested wastewater. The coagulation/flocculation process prior to the MD reduced the fouling factor for all wastewater, highlighting the equalization tank where a reduction of around 72% was observed, achieving the goal of reducing fouling and increasing the efficiency of the MD. Membrane characterization indicated that CF-DCMD confirmed less fouling of membranes than single DCMD. Thus, this study allows to understand the potential and robustness of the CF-DCMD process in the treatment of textile wastewater and that it is possible to develop alternative technologies to treat complex wastewater effectively.

GRAPHICAL ABSTRACT

KEYWORDS:

• CF-DCMD
• integrated processes
• pretreatment
• textile industry
• fouling

Acknowledgments

The authors are grateful to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001, to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), and to Universidade Federal de Santa Catarina (UFSC) for the financial and technological support granted.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data used to support the findings of this study are included within the article and its Supplementary material.

Statement of novelty

The novelty of our work resides in real textile wastewater treated by coagulation/flocculation integrated with membrane distillation producing high-water quality. This hybrid separation technology was not studied until now for this industrial sector. This introduces a proposal for wastewater treatment and water reclamation from complex streams that cannot be treated with membrane distillation (due to wetting) and are not effectively treated with conventional processes. Physicochemical characterization and toxicologic evaluation (usually not presented in this kind of study) add knowledge that high-quality water could be obtained for textile industries, essential to reuse in this sector, which demands rigorous water requirements in their process.

Additional information

Funding

The work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico [--]; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior [--].