Removal of anionic detergents from water and treatment of gray water by micelle–clay composites

Shortage of water has resulted in attempts to purify contaminated water. This study demonstrates removal of anionic detergents from synthetic water, well water, and gray water (GW), and the removal of pathogenic microorganisms from GW. The complex of montmorillonite with micelles of the organic cation, octadecyltrimethylammonium, was expected to yield efficient adsorption of anionic detergents and microorganisms on account of its large surface area, positive charge, and existence of large hydrophobic domains. The removal of anionic detergents, total suspended solids, and bacteria was tested by column filters packed with micelle/montmorillonite complexes mixed with excess sand. Efficient removal of anionic detergents was demonstrated for synthetic water (130 and 30 ppm), well water (from 1.35 to below 0.3 ppm) and from two domestic laundries. A model that considers convection, adsorption, and desorption yielded adequate simulations and predictions for the above kinetics of filtration. GW from showers and sinks included several million of fecal coli per 100 mL, indicating health hazard in using the water without proper treatment. The second column of two in series removed all pathogenic bacteria after the passage of 30 L, whereas activated carbon yielded poor removal. The micelle–clay filter can adequately purify such GW for reuse in irrigation and toilet flushing.