Full‐Scale Removal of Arsenate and Chromate from Water Using a Limestone and Ochreous Sludge Mixture as a Low‐Cost Sorbent Material

Abstract

The oxyanions arsenate (AsO43−) and chromate (CrO42−) are major freshwater contaminants. Arsenate is a problematic contaminant in drinking water reservoirs, and chromate limits the use of urban stormwater runoff. High‐capacity, low‐cost, energy‐efficient treatment technologies are required for the removal of these toxic anions from freshwater sources. Using a 50‐m‐long dual porosity filter, with limestone as filtering grains, treating stormwater runoff from Copenhagen, Denmark, we tested if addition of the waste product ochreous sludge can improve the removal of arsenate (As) and chromate (Cr) without compromising the calcite's removal affinity towards metallic cations. Upon on‐site embedding of the ochreous sludge, removal of arsenic and chromium was improved greatly, and copper (Cu) removal remained high. Steady‐state effluent concentrations were reduced from 31 to 2 µg As/L, 127 to 1.5 µg Cr/L, and 18 to 9.6 µg Cu/L upon mixing with the ochreous sludge. Limestone‐ochreous sludge represents a promising low‐cost oxyanion and cation sorbent operating at neutral pH without pH control.

Assessment of Existing Roadside Swales with Engineered Filter Soil: II. Treatment Efficiency and in situ Mobilization in Soil Columns

“…at low or neutral pH. Increased amounts of such metal oxides were also shown to increase the sorption of anionic elements such as chromate and phosphate (Richard and Bourg, 1991; Cederkvist et al, 2010). Thus, addition of aluminum and iron oxides may have significantly positive effects on both heavy metal and DOC retention, but a potential increase in pH as well as introduction of monovalent cations counteracts the positive effects (Lombi et al, 2003; Grolimund and Borkovec, 2005).…”

Dual Porosity Filtration for treatment of stormwater runoff: first proof of concept from Copenhagen pilot plant

“…To improve the removal efficiency of the DPF-pilot plant towards Cr and Cu a limestone -iron oxide mix was tested as filtering material in the DPF-6-layers with promising first results (Cederkvist et al 2010). …”

“…The amount of limestone is three times as high in DPF-18-layers as in DPF-6-layers. Experiments with a limestone-ochreous sludge mixed sorbent are reported inCederkvist et al (2010) DPF-6-layers and DPF-18-layers refer to the two versions of a DPF-filter being compared in the pilot piant.…”

Synthesis and characterization of bifunctional mesoporous silica adsorbent for simultaneous removal of lead and nitrate ions

“…2,3 Among these techniques, adsorption is very popular owing to its simplicity and low cost. 4,5 Considering that most adsorbents only adsorb either a type of cationic or anionic ion, it is necessary to develop bifunctional adsorbents that can remove both cations and anions simultaneously, thereby simplifying the treatment of toxic ions-containing wastewater. Porous materials have been selected as the most potential bifunctional adsorbents because of their intrinsic high specific surface area and stable interconnected frameworks with an active pore surface for easy modification.…”