Arsenic Immobilization From Iron Based Waste Water Treatment Residuals in Pilot-Scale Columns Simulating a Bioreactor Landfill.

Iron based wastewater treatment residuals were incorperated with simulated waste products (aluminum cans, plastic, paper, yards waste, and dog food) and placed in large columns (1 m by 3 m).  The initial material was wet to 50% moisture capacity and leachate from the columns was monitored for pH, ORP, conductivity, dissolved oxygen, and a sweet of elements (As, Fe, Al, NA, Ca, Mg, Cl, Mn, Ni ,Cu, Zn, and Pb).  Solid samples were collected after two and half years and analyzed by X-ray absorption spectroscopy for As and Fe.  Results indicate the initial Fe-hydroxide phase was dissolved and/or transformed to either a siderite, Fe(II) oxide or iron sulfide phase depending on the location within the column and the column temperature.