Pilot-scale studies of arsenic removal with granular activated carbon and zero-valent iron

Studies on arsenic removal by zero-valent iron (ZVI)-based system have focused mostly on batch or small scale tests. In this research, pilot-scale studies were carried out on arsenic removal by technologies developed in rapid small-scale column tests (RSSCTs). Pilot-scale studies can provide significant information on final scale-up to full-scale operation, which RSSCT inherently was not able to provide. In addition, comparison between pilot column and RSSCT breakthrough profiles could help validate RSSCT design, especially RSSCT for arsenic. Results from pilot studies indicate that arsenic removal by a system of ZVI plus iron-tailored granular activated carbon showed significant promise for practical applications. The best performance was achieved when ZVI worked together with carbon pretailored by an iron-salt evaporation method. In addition, the similarity in arsenic breakthrough curves between RSSCTs and pilot studies serves to confirm that it is appropriate to assume proportional diffusivity for arsenic oxyanions in RSSCT design.