Removal of arsenic and natural organic matter from groundwater using ferric and alum salts: A case study of central Banat region (Serbia)

摘要

This paper presents a comparison of the efficacy of three different coagulants (polyaluminium chloride (PACl), Aluminium sulphate (Al_2(SO_4)_3) and ferrous chloride (FeCl_3)) for natural organic matter and arsenic (As) removal from groundwater. Coagulation efficacy was evaluated for the coagulants alone and for combinations of them (PACl/FeCl_3; Al_2(SO_4)_3/FeCl_3), on the basis of changes in dissolved organic matter (DOC) and arsenic content. For single coagulants, PAC1 (30 mg Al/L) showed optimal efficacy for DOC removal (57%, relative to raw water). The highest arsenic reduction (<5 μg As/L in coagulated water) was achieved when a very high 300 mg/L dose of FeCl_3 was used. However, if PACl (30 mg Al/L) and FeCl_3 (10 mg FeCl_3/L) are combined, the efficacy of DOC removal increases compared to PACl and FeCl_3 alone under similar doses (66% decrease in DOC relative to raw water). The DOC and As contents of the coagulated water after application of these doses were 2.26 mg C/L and 9.7 μg/L, respectively, compared to 6.44 mg C/L and 60.5 μg As/L measured in the raw groundwater. The combination of Al_2(SO_4)_3 and FeCl_3 did not show any improvement in DOC and As removal efficacy relative to using those coagulants alone.