Arsenic treatment technology for groundwaters

Abstract

The new United Kingdom drinking water standard of 10 μg/l arsenic will become a statutory obligation in 2003. To comply with the new standard, Severn Trent Water will require a new treatment process to be installed at 17 groundwater sites. The Company embarked on a development programme in 1995, with pilot studies commencing in 1996. Investigations have covered a range of potential treatment technologies including coagulation, ion exchange, reverse osmosis and adsorption. Adsorption with granular ferric media was found to be the best available technology for treating groundwater in Severn Trent. The paper details the development work undertaken, which has focused on the evaluation of aluminium and ferric based granular medias. This has enabled the design and construction of the first arsenic adsorption plant in the UK, with an output of 20 Ml/d.

Improved removal of arsenic from groundwater using pre-corroded steel and iron tailored granular activated carbon

“…Much research has focused on developing iron-based arsenic adsorbents such as granular ferric hydroxide (GFH) (Driehaus et al 1998;Selvin et al 2002;Westerhoff et al 2005). GFH removes both As (V) and As (III) from aqueous solutions and can be used for a wide range of pH (pH , 9).…”

“…GFH removes both As (V) and As (III) from aqueous solutions and can be used for a wide range of pH (pH , 9). GFH is reported to have a high treatment capacity of from 50,000-300,000 BVs to a 10 mg/L breakthrough level (Driehaus et al 1998;Selvin et al 2002;Westerhoff et al 2005). However granular ferric oxide is physically weak and can crumble and disintegrate when employed for prolonged use.…”

Inorganics Removal

“…A comparison of the two media is shown in Figure 11.4 where at natural pH 190 000 bed volumes were treated with GFH before the outlet concentration reached 10 g l −1 , over 15 times greater than AA under the same conditions (Selvin et al, 2002). It is a simple process, has a reasonable bed life, produces minimal process residuals and the arsenic is strongly bound to the media, allowing safe disposal.…”

Scoping candidate minerals for stabilization of arsenic-bearing solid residuals

“…All of these technologies generate arsenic-bearing solid residuals (ABSRs) that must be safely disposed [2,3]. The regulatory leaching tests, the Toxicity Characteristic Leaching Procedure (TCLP) and the California Waste Extraction Test (CA-WET), underestimate the leaching of arsenic from the residuals [4], and consequently arsenic leaching from ABSRs disposed in mature Municipal Solid Waste (MSW) landfills.…”