Abstract
In the present study, several pre-polymerized coagulants of iron and aluminum were tested for their efficiency towards As(V) and As(III) removal from water sources. The results showed that the pre-polymerized coagulants of iron, such as poly-ferric sulfate and poly-ferric silicate chloride, were very efficient for As(V) removal. With regard to As(III) removal, among all examined coagulants, including the conventional ferric chloride, only the poly-ferric sulfate (PFS) was able to reduce As(III) to concentrations below the drinking water regulation limit of 10 μg/L. In contrast, all tested composite coagulants based on aluminum were not capable of removing efficiently both species of arsenic. PFS addition in water containing 4 mM of alkalinity and 25 μg/L of As(V) and As(III) (i.e., total arsenic concentration 50 μg/L) resulted in finished water with less than 5 μg/L arsenic, only by dosing 5 mg Fe-PFS/L at pH 7, whereas, simultaneously, the residual iron concentration was found well below its drinking water regulation limit of 200 μg/L. The use of PFS could provide a viable alternative for As(III) and As(V) removal at household treatment level for application in vulnerable communities, without the need of any additional treatment, such as oxidation of As(III) to As(V).
Highlights
Arsenic contaminated groundwater is a major threat to human health when used as a drinking water source and concerns millions of people worldwide
In Southeast Asia, more than 500 million people are exposed to arsenic concentrations over the WHO recommended concentration of 10 μg/L, and this was identified as a major cause of skin lesions and cancer
There are still areas in several countries of Europe and several millions of people in Asia, who are still exposed to elevated arsenic concentrations, i.e., in remote areas without access to community piped treated drinking water [2,4]
Summary
Arsenic contaminated groundwater is a major threat to human health when used as a drinking water source and concerns millions of people worldwide. There are still areas in several countries of Europe and several millions of people in Asia, who are still exposed to elevated arsenic concentrations, i.e., in remote areas without access to community piped treated drinking water [2,4]. Arsenic is usually present in polluted waters with both major inorganic forms of pentavalent arsenate—As(V)—or trivalent arsenite—As(III) [5]. In aerated waters, such as in surface water bodies or in swallow aquifers, the ionic species H2AsO4−/H2AsO42− of As(V) are the main existing forms. As a result, regarding the efficient As(III) removal, the pre-oxidation of As(III) to the As(V) form is always practiced, which is commonly performed by employing ozonation, chlorination, or manganese oxides [2,4]
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