NAMS 2002 Workshop - ICOM 2008

Nanofiltration and Reverse Osmosis III - Applications – 5
Friday July 18, 11:45 AM-12:15 PM, Maui
Treatment of the Groundwater Contaminated by High Concentration of
Arsenic
M. R. Alizadehfard (Speaker), WorleyParsons, Australia -
reza.alizadehfard@worleyparsons.com
M. H. Alizadehfard, Curtin University, Bentley, Australia
Arsenic classified as Group 1 carcinogenic substance to humans based on
powerful epidemiological evidence. Arsenic cannot be destroyed; it can only be
transformed into different forms or combined with other elements to be converted
into insoluble compounds. Therefore, there is a tremendous demand for
developing expense efficient methods for arsenic removal from contaminated
groundwater and drinking water. In this work, the removal of arsenic from
contaminated groundwater by Membrane and Ligand technologies were
investigated. The suspended solids in contaminated groundwater were removed
by a 1 micron bag filter. Organic compounds in the contaminated groundwater
were removed by adsorption onto granular activated carbon. The Arsenic in the
groundwater, with the average initial concentration of 450 mg/l, was concentrated
by rejecting through a thin film composite reverse osmosis (RO) membrane unit.
The arsenic concentration in the final RO permeate was reduced to 2 mg/l by
passing two times through the two stages RO membrane pilot unit. The arsenic
concentration in RO concentrate was increased to 2500 mg/l prior to
Electrochemical (Ion Exchange membrane) unit. RO permeate was captured by
passing through a thin bed of zirconium hydroxide media. The arsenic
concentration in the final treatment was reduced to 0.05 ppm. Then, the
arsenite/arsenate mixture was removed from the media with an alkaline solution
forming sodium arsenite and sodium arsenate. This solution was treated by a
proprietary electrochemical process in a specially designed cell to plate the
arsenic as metalloid onto a cathode.