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    Performance of nanofiltration and reverse osmosis membranes for arsenic removal from drinking water
    (Taylor & Francis Inc, 2016) Elcik, Harun; Çelik, Suna Özden; Çakmakçı, Mehmet; Özkaya, Bestamin
    The removal of arsenic was investigated by four types of thin-film polyamide nanofiltration (NF) (NF270, NF90) and reverse osmosis (RO) (XLE, BW30) membranes in a flat-sheet module. The influence of membrane types, pressure, pH, and pre-oxidation step on the removal of arsenic (As(III)) was investigated. Initial As(III) concentration was 100g/l for all of the experiments. Flux was determined over a pressure range of 3.5-10bar for both NF and RO membranes. Experiments were conducted at pH 3.5, 5, 7.5, and 10 to evaluate the effect of pH on As(III) removal. The impact of pre-oxidation and oxidant concentrations on As(III) removal were also evaluated. It was found that the percentage of As(III) removal of RO membranes were in the range of 97-99 for all transmembrane pressure applied. In the range of operating conditions, As(III) and As(V) rejection were found almost equally good by RO membranes. RO permeate met the WHO and Turkish standard for arsenic. Pre-oxidation step improved the rejection performance of NF. Nevertheless, NF permeate did not meet the standards in the range of operating conditions.
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    Simultaneous oxidation/co-precipitation of as(Iii) and fe(ii) with hypochlorite and ozone
    (Scibulcom Ltd., 2016) Elcik, Harun; Çelik, Suna Özden.; Çakmakçı, M.; Şahinkaya, E.; Özkaya, Bestamin
    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 µg/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 (r2 ? 0.99). The value of r2 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. © 2016, Scibulcom Ltd. All rights reserved.
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    SIMULTANEOUS OXIDATION/CO-PRECIPITATION OF As(III) AND Fe(II) WITH HYPOCHLORITE AND OZONE
    (Scibulcom Ltd, 2016) Elcik, Harun; Çelik, Suna Özden; Çakmakçı, M.; Şahinkaya, E.; Özkaya, Bestamin
    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.