Low-cost laterite-laden household filters for removing arsenic from groundwater in Vietnam and waste management

Abstract

This study evaluated the performance of a low-cost natural laterite from Thach That (NLTT), Vietnam, for its arsenic (As) removal capacity in a household filter with contaminated groundwater. The NLTT was initially tested in a laboratory column trial lasting 800 h. The breakthrough curves were found to fit the Thomas model very satisfactorily with adsorption capacities of 0.06 and 0.20 mg/g at a flow velocity of 0.85 m/h for the influent As(V) concentrations of 0.1 and 0.5 mg/L, respectively. In household filters at four sites, the median As concentration in groundwaters (0.04-0.19 mg/L) dropped to 0.026-0.054 mg/L after traditional sand filtration. However, after the subsequent NLTT filtration through columns (14 cm inner diameter, 65 cm height) at 0.65 m/h flow velocity, it fell to below the Vietnam and WHO drinking water standard (0.01 mg/L) during seven months of continuous operation.Portland cement and lime were tested as binding agents for the exhausted NLTT waste in a solidification/stabilization process at different ratios. The best ratio of exhausted NLTT: Portland cement: lime for restraining mobility of As from this waste was 3: 1: 0.5. The concrete brick products revealed a suitable compressive strength for using it as building materials in construction work.

The Removal of As(III) Using a Natural Laterite Fixed-Bed Column Intercalated with Activated Carbon: Solving the Clogging Problem to Achieve Better Performance

“…Among all of these approaches, adsorption has been proven to be the most promising method because of its high efficiency, ease of handling, and the availability of several types of adsorbent materials. Among these adsorbents, natural laterites have been the subject of many investigations since they were shown to have potential applications in arsenic removal from groundwater [18][19][20][21][22][23][24]. In our context, natural laterites are widely available in the country and can be used for low-cost arsenic removal.…”

“…In our context, natural laterites are widely available in the country and can be used for low-cost arsenic removal. Indeed, many studies have documented arsenic removal by adsorption on natural laterite using the batch mode, as well as fixed-bed column systems [18][19][20][21][22][23][24]. In an effort to develop an efficient, low-cost, and easily applied method, our previous research focused on As(III) adsorption in the batch mode using local natural laterites [21,22].…”

“…It is worth noting that there is little published information on the hydraulic conductivity of laterite soils in Western Africa [26]. After carrying out an exhaustive literature review, we noted that the percolation treatment process for arsenic adsorption using fixed-bed column percolation has been improved upon by several authors, who proposed various column configurations that combine laterite layers and adsorbent/inert materials to solve shortcomings in the operation of the system [12,18,20,23,24]. Even though the column designs are different, the most current approach consists of one or two laterite layers integrated in a column configuration of successive layers of inert and/or adsorbent materials [12,18,20,23].…”

“…Even though the column designs are different, the most current approach consists of one or two laterite layers integrated in a column configuration of successive layers of inert and/or adsorbent materials [12,18,20,23]. A lot of studies have addressed the fixed-bed column adsorption of As(III) on laterite soil [12,19,20,23,24]. The technical details of these configurations are given in (Supplementary Information (SI1)).…”

“…Clogging can be related to different modes, such as cake formation and pore blockage by fine particles [30]. It has been reported that nanomaterials, which exist as small particles in a fine powder form, cause hydraulic problems by clogging column-based filters [24].…”