Removing Fluoride from Industrial Wastewater Using Hybrid-Membrane Technology
Peterson, Joel*; Madole, Jim
(Geomatrix, Scottsdale, AZ. Nalco, Phoenix, AZ )
Removing Fluoride from Industrial Wastewater Using Hybrid-Membrane Technology New fluoride [F] discharge limits are forcing many industrial sites to employ [F] treatment. Past [F] limits, when imposed, were lax but now limits of 10-25 ppm are common with some set at drinking water levels, < 4 ppm. Many [F] removal systems are unable to achieve these limits. However, emerging membrane technology is proving capable of meeting these limits while improving efficiency and operating costs. The semiconductor industry proved an ideal place to test the treatment of small concentrated streams, such as HF baths/rinses, and the large dilute ones, such as combined process effluent. Pilot testing of a Vibratory Shear-Enhanced membrane Process, VSEP, has shown great success in both cases. VSEP technology was integrated into a chemical process to remove calcium fluoride solids in a single filtration step. Feed concentrations of 5K–25K ppm [F] were used to simulate a range of waste streams and were filtered through a UF membrane (200K MWCO, ~ 0.1 um). Effluent [F] ranged from 8-17 ppm, resp., with lower levels achieved using co-precipitation reagents. The VSEPs high resistant to fouling is due to vibratory-induced shear forces imparted directly at the membrane surface. The hybrid VSEP concentrates solids 10X, creating a zone of reactive solids above the membrane surface. Contaminated water passes through this zone, where collision efficiency is elevated, and exits the membrane as high quality permeate at ~90% recovery. The VSEP can use most membrane materials, and pretreatment can be tailored to address various/multiple contaminants and problematic waste streams. The result is superior performance in terms of removal efficiency, chemical/waste reduction, treated water quality, reliability and operating costs.
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