Arsenic removal to < 1 μg L~(-1) by coprecipitation with in-situ generated pe(III) precipitates with and without advanced pre-oxidation

摘要

The aim of this study is to investigate removal of low As concentrations from groundwater at a Drinking Water Treatment Plant (DWTP) in The Netherlands in order to achieve <1 μg L~(-1) As in produced drinking water.Two iron based emerging technologies,both relying on in-situ generated Fe(III) precipitates for As adsorption,were investigated.These include:1) Advanced Oxidation-Coprecipitation-Filtration (AOCF) and 2) Coprecipitation prior to ultrafiltration (C-UF).We show that most of the As removal occurs in the top half of a Rapid Sand Filter (RSF) bed.In this part we also observe the conversion of As(IIl) into As(V).The mechanism of As(III) oxidation to As(V) in the RSF is still not understood,however we hypothesize that either the manganese oxides or the biological activity in the filter bed may be responsible for this conversion.In agreement with this observation,we also notice that drinking water only contains As(V) and that the levels of As(III) are negligible.The experiments have shown that both AOCF and C-UF are promising emerging technologies to reduce arsenic levels to below 1 μg L~(-1) which is the agreed target in The Netherlands between the Dutch water companies.