1 Solids Retention Time, Influent Antibiotic Concentrations, and Temperature as Selective Pressures for Antibiotic Resistance in Activated Sludge Systems MAJID NEYESTANI 1,2 , ERIC DICKENSON 3 , JEAN MCLAIN 4 , VICTORIA OBERGH 5 , OSCAR QUINONES 3 , CHANNAH ROCK 5 , DANIEL GERRITY 1 * 1 Department of Civil and Environmental Engineering and Construction, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, NV 89154-4015, United States 2 Greeley and Hansen, 1120 N. Town Center Dr., Suite 120, Las Vegas, NV 89144, United States 3 Applied Research and Development Center, Southern Nevada Water Authority, 1299 Burkholder Blvd., Henderson, NV 89015, United States 4 Water Resource Research Center, University of Arizona, 350 N. Campbell Ave., Tucson, AZ 85719, United States 5 Department of Soil, Water & Environmental Science, University of Arizona, 1177 E. 4 th St., Tucson, AZ 85719, United States * Corresponding author. Mailing address: Department of Civil and Environmental Engineering and Construction, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Box 454015, Las Vegas, NV 89154-4015, United States. Phone: (702) 895-3955. Fax: (702) 895-3936. Email: Daniel.Gerrity@unlv.edu. Electronic Supplementary Material (ESI) for Environmental Science: Water Research & Technology. This journal is © The Royal Society of Chemistry 2017