Influence of Aquifer Heterogeneity on Cr(VI) Diffusion and Removal From Groundwater

Abstract Previous studies show aquifer heterogeneity has an important influence on removal of Cr(VI) in groundwater, but little research has revealed the role of aquifer heterogeneity in Cr(VI) migration and how effective using emulsified vegetable oil is for Cr(VI) removal in groundwater. We simulated a laboratory sand-packed box over a 50-day period to research the effects of aquifer heterogeneity on Cr(VI) diffusion and also injected emulsified vegetable oil (EVO) into the permeable reactive barrier (PRB) filled with compost to investigate the influences of aquifer heterogeneity on Cr(VI) removal from groundwater, with fixed conditions of simulated true water temperature of shallow groundwater (19±0.5 ℃), hydraulic gradient (3‰), the Suzhou coal mining area (Anhui, China). The results show that aquifer heterogeneity had the significant impact on Cr(VI) diffusion with an overall diffusion direction of Cr(VI) that was from the upper left corner to the lower right corner along the direction of the groundwater; permeable reactive barrier would effectively remove Cr(VI) from groundwater in heterogeneous aquifer due to the vertical movement of microorganisms between different aqueous media; coarse sand and medium sand showed high performance in Cr(VI) diffusion, with a slight superiority to fine sand; following a one-time EVO injection, a considerably stable and uniform effective remove zone similar to the shape of ∑ was formed in the heterogeneous aquifer, and its Cr(VI) removal efficiency was over 95%.

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Permeable reactive barrier of waste sludge from wine processing utilized to block a metallic mixture plume in a simulated aquifer

Water Science & Technology ◽

10.2166/wst.2021.440 ◽

2021 ◽

Author(s):

Shui-Wen Chang Chien ◽

Yi-Pei Li ◽

Cheng-Chung Liu

Keyword(s):

Competitive Adsorption ◽

Heavy Metal Contamination ◽

Fine Sand ◽

Underground Water ◽

Permeable Reactive Barrier ◽

Sand Layer ◽

Processing Waste ◽

High Concentration ◽

Reactive Barrier ◽

Waste Sludge

Abstract Heavy metal contamination in underground water commonly occurs in industrial areas in Taiwan. Wine-processing waste sludge (WPWS) can adsorb and remove several toxic metals from aqueous solutions. In this study, WPWS particles were used to construct a permeable reactive barrier (PRB) for the remediation of a contaminant plume comprising HCrO4−, Cu2+, Zn2+, Ni2+, Cd2+, and AsO43− in a simulated aquifer. This PRB effectively prevented the dispersals of Cu2+, Zn2+, and HCrO4−, and their concentrations in the pore water behind the barrier declined below the control standard levels. However, the PRB failed to prevent the diffusion of Ni2+, Cd2+, and AsO43−, and their concentrations were occasionally higher than the control standard levels. However, 18% to 45% of As, 84% to 93% of Cd, and 16% to 77% of Ni were removed by the barrier. Ni ions showed less adsorption on the fine sand layer because of the layer's ineffectiveness in multiple competitive adsorptions. Therefore, the ions infiltrated the barrier at a high concentration, which increased the loading for the barrier blocking. The blocking efficiency was related to the degree of adsorption of heavy metals in the sand layer and the results of their competitive adsorption.

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