AWWA WQTC60798

Magnetic ion-exchange (MIEX®) has been shown to be effective for reducing the concentration of dissolved organic carbon (DOC) from water. MIEX® is a high capacity ion exchange resin that is used as a continuous feed suspension in a stirred contactor. The magnetic component of this resin aids in settling by aggregating particles for more rapid settling. In this investigation, MIEX® was evaluated for removal of several endocrine disrupting chemicals (EDCs) and pharmaceuticals. Both static benchscale and dynamic pilot-scale tests were completed using Colorado River water spiked with over 60 different EDCs and pharmaceuticals, which include compound classes such as antibiotics, steroids, flame-retardants, analgesics, pesticides, and x-ray contrast media. For bench-scale testing, MIEX® was dosed at 5, 10, 15, and 20 mL/L with contact times of 10 and 20 minutes. Bench-scale results show, in general, that removal is related to polarity (log Kow) with higher removal related to lower polarity (higher log Kow). For instance, most compounds with log Kow values greater than 3.5 were removed by greater than 40% (i.e., oxybenzone, triclosan, polycyclic aromatic hydrocarbons, and some organochlorine pesticides). However, some exceptions were noted. For instance, the pharmaceutical diclofenac has a log Kow of only 0.7, yet it was well removed by MIEX® (>70%). The removal of diclofenac is dominated by ion exchange since it exists as an anion at ambient pH. Furthermore, excellent dose response curves were obtained, showing that removal is directly related to MIEX® dose. Contact time seemed to be less important as the 20 minute contact time generally improved removal by only 20% or less. Pilot-scale tests were conducted at 10 gallons per minute with a spike feeding 100 ng/L of the target compounds. For pilot-scale tests, a MIEX® dose of 20 mL/L with a contact time of 20 minutes was utilized. Results from the pilot-scale were similar to results from the bench-scale. MIEX® proved to be of limited use for the removal of EDCs and pharmaceuticals, as most compounds were not well removed. However, for specific compounds and multibarrier processes, MIEX® may be applicable. Includes tables, figures.