SIMULTANEOUS OXIDATION/CO-PRECIPITATION OF As(III) AND Fe(II) WITH HYPOCHLORITE AND OZONE

The aim of the study was to investigate oxidative precipitation of As(III) with ozone and sodium hypochlorite in Fe(II) containing water. As guideline value was achieved with both ozone and hypochlorite for 100 mu g/l of initial As(III) concentration. High As removal efficiencies were achieved by dosing 2.5 and 5 times the stoichiometric amounts of hypochlorite in the presence of 10 mg/l of initial Fe(II). When the dose of hypochlorite was increased to 10 and 50 times the stoichiometric amount, similar. removal efficiencies were achieved with 2.5 and 5 mg/l of initial Fe(II) concentrations. When ozone was dosed at 10 times the stoichiometric amount, 2.5 mg/l of initial Fe(II) presence was sufficient to meet As standard. Simultaneous oxidation and co-precipitation results gave an almost perfect fit to Langmuir isotherm for ozone (r(2) approximate to 0.99). The value of r(2) was found as 0.87 for hypochlorite. It was concluded that simultaneous oxidation of As(III) and Fe(II) by ozone and hypochlorite was an effective option to remove low level As(III) from water. As guideline value was not achieved either by ozone or by hypochlorite for high As(III) concentration, even with 10 mg/l of initial Fe(II) existence. Supplemental Fe(II) addition can be taken into consideration to overcome this limitation.