Abstract
Treating wastewater from textile plants using membrane distillation (MD) has great potential due to the high-salinity wastes and availability of waste heat. However, textile wastewaters also contain surfactants, which compromise the essential hydrophobic feature of the membrane, causing membrane wetting. To address this wetting issue, a custom-made membrane consisting of a hydrophilic layer coated on hydrophobic polytetrafluoroethylene (PTFE) was tested on textile wastewater in a pilot MD setup, and compared with a conventional hydrophobic PTFE membrane. The test was carried out with a feed temperature of 60 °C, and a permeate temperature of 45 °C. The overall salt rejection of both membranes was very high, at 99%. However, the hydrophobic membrane showed rising permeate electrical conductivity, which was attributed to wetting of the membrane. Meanwhile, the hydrophilic-coated membrane showed continually declining electrical conductivity demonstrating an intact membrane that resisted wetting from the surfactants. Despite this positive result, the coated membrane did not survive a simple sodium hydroxide clean, which would be typically applied to a membrane process. This brief study showed the viability of membrane distillation membranes on real textile wastewaters containing surfactants using hydrophilic-coated hydrophobic PTFE, but the cleaning process required for membranes needs optimization.
Highlights
The need for more sustainable industries that can capture waste and recycle clean water from their existing saline effluent drives the need for new desalination technologies
membrane distillation (MD) was previously limited by the availability of membranes, but with the recent availability of high-performance hydrophobic microfiltration membranes, MD may find practical application alongside the highly efficient reverse osmosis, and mature conventional thermal technologies
This paper presents the outcome of a pilot trial of MD for processing textile wastewaters, which was carried out before a three-month trial that was fed with wastewater from the existing biological treatment process [19]
Summary
The need for more sustainable industries that can capture waste and recycle clean water from their existing saline effluent drives the need for new desalination technologies. High-efficiency and low-cost thermal processes are an important part of solving some of our most important water problems. One technology that may help achieve this is membrane distillation (MD) [1]. The concept of MD emerged in the 1960s, and was a topic for researchers exploring new membrane materials and systems with high thermal efficiency, but MD literature reported few full-scale installations. MD was previously limited by the availability of membranes, but with the recent availability of high-performance hydrophobic microfiltration membranes, MD may find practical application alongside the highly efficient reverse osmosis, and mature conventional thermal technologies (e.g., multi-stage flash).
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