Many water utility professionals are concerned about meeting a proposed drastically lower MCL for arsenic. This AWWA Research Foundation report provides the latest findings about water treatment processes that will meet such a new regulation. Several technologies were tested and compared for arsenic removal. The technologies that are presented include conventional processes (coagulation, Fe/MN removal, and softening), sorption processes (ion exchange, activated alumina, and iron-oxide-coated sand), and membrane processes (nanofiltration, ultrafiltration, and microfiltration). Studies were conducted at bench scale, pilot scale, and full scale. The report also provides guidance on residual management and costs.