Removal of arsenic from drinking water by fungal biomass and biological filtration

Arsenic contamination of fresh water resources and the associated health risks have created mounting pressure on water agencies to find cost-effective arsenic removal technologies. Arsenic concentration in drinking water is limited to 10 mug/L by the World Health Organization, Health Canada, the United States Environmental Protection Agency, and the European Commission.;Another objective of the present research was to examine the potential of fungal biomass (Aspergillus niger) to remove arsenic. Studies on the potential of fungal organisms to adsorb anionic metal ions including arsenic are limited. It was found that non-viable A. niger biomass (autoclaved) and certain treated [H2SO4 , NaOH, acetic acid/NaOH, cationic surfactants (propyl trimethoxy silane and cetyl trimethyl ammonium bromide except polyethylamine), and polyelectrolyte (zetag)] biomass only achieved less than 20% removal of arsenic from the water. The iron oxide-coated A. niger biomass was determined to be the best among all the modifications to remove arsenic [greater than 95% of As(V) and 75% of As(III)] from aqueous solutions, so this biomass was used for all of the detailed studies. Desorption of arsenic varied according to the arsenic species and the solution pH.;The thermodynamic study showed that arsenic was chemisorbed onto the iron oxide-coated biomass and that the surface charge of the biomass did not have a direct correlation with its arsenic removal efficiency. The presence of cations (Ca2+, Mg2+ and Fe2+) enhanced the removal of both As(III) and As(V), whereas the presence of anions (SO42-, NO3-, and Cl -) did not influence the arsenic adsorption process. The fixed bed column study showed that iron oxide-coated biomass could treat approximately 5021 and 5437 bed volumes of As(III) and As(V) contaminated waters respectively before the column was exhausted.;Biological sand filters were found to be effective in removing arsenic from 100 mug/L to below 5 mug/L when the ratio of iron to arsenic in the influent was 40:1. Iron was found to be less than 0.1 mg/L in the effluent. The depth of the filter sand had less influence on the removal process. Iron-related bacteria were active in the sand filtration column.;Biological filtration for arsenic removal in conjunction with iron removal seems a promising technology. Two biological filters were evaluated earlier for their effectiveness in removing arsenic from natural groundwater in Swift Current, Saskatchewan, Canada. This groundwater contained 6.4 to 8.4 mg/L of iron and 14.5 to 27.2 mug/L of arsenic. Iron was found to be nearly absent in the effluent, and arsenic in the effluent was well below 2 mug/L. The presence of iron may have played a major role in the effective removal of arsenic. Iron and manganese ions often coexist in natural groundwater with arsenic ions, although this may not always be the case. The external addition of iron to the water could be one of the options to remove arsenic from a contaminated source with no iron. One objective of the present research was to find a proper ratio of iron to arsenic that would be required to achieve an effluent arsenic concentration of 5 mug/L or less in a biological filtration system.