| Disposal of arsenic (As) concentrates that result from drinking water treatment procedures is a problem that must be considered when developing such procedures. A simple and low cost solution is to land apply the Arsenic concentrates with the municipal wastewater effluent. To examine the extent of arsenic wells across the continental United States that exceed the 10 parts per billion (ppb) maximum contaminant level (MCL), and to select a study site, a geographic information system (GIS) study was performed. Kinetic batch experiments were carried out on three diverse soils collected from a land application facility in New Mexico. Arsenate [As(V)] solutions, in buffer or wastewater effluent, ranging from 5 mg L-1 to 100 mg L-1 , were equilibrated with the soils for 12 to 504 h. Finally, As(V) column breakthrough curve (BTC) experiments were performed on the same three soils in the presence and absence of wastewater effluent, at pore-water velocities of 0.7 and 1.4 cm h-1. One-site and two-site kinetic models were fit to each BTC to determine As(V) sorption over time, and to obtain solute transport parameters including dispersion coefficient (D), retardation factor (R), and partition coefficient (Kd). The GIS study found that 60% of the continental U.S. "high arsenic" wells (> 10 mug L -1 As) were located on farmland, and that these high arsenic wells were located in all regions of the country. The presence of wastewater effluent decreased the sorption of arsenic (decreae of Freundlich Kf values) for As(V) on all soils at all reaction times. Furthermore, wastewater effluent caused the % As(V) sorbed over time to remain low, for all three soils, regardless of the initial As(V) concentration. The presence of wastewater effluent decreased sorption (R) of As(V) for each soil column and pore-water velocity (PWV). Furthermore, wastewater effluent caused the mass recovery of As(V) from all columns to exceed 100%, and may be responsible for desorbing preexisting arsenic from the soils. Thus, it appears that while soil is typically an effective sorbent for As(V) in dimple aqueous solutions, when the contaminant is added with wastewater effluent, its sorption is decreased, and its mobility through soil is increased. |
