AWWA WQTC60627

This paper presents an outline of the distribution, solid-phase speciation, and desorption/dissolution of As in iron-based treatment media. Objectives include: define the solid phase speciation of As on drinking water (DW) treatment media; examine the desorption of As and solution speciation from Fe-media over 50 days while minimizing microbial effects; assess the desorption and solution speciation of As as a function of pH; and, compare results from desorption experiments with results from TCLP extractions. Materials and methods included: two Fe-based media from pilot scale studies sampled at 0"-1", 1"-4", 4"-7", and 7"-10" from top of bed (granular ferric hydroxide and E33); and, media sampled under N₂ and analyzed for total As by EPA Method 3051, solid-phase As speciation by X-ray absorption spectroscopy (XAS), desorbed As in H₂O under anoxic conditions at 4°C over 50 days in batch experiments, and desorbed As as a function of pH in continuous stir tank reactors. Includes table, figures.