Number

268-EN

Section

General Section

Use

Abstract

Arsenic in ground water is very hazardous and is a serious problem for poor communities that use it as drinking water. An electrochemical, cost effective method for arsenic removal is presented and compared to the method using activated alumina regenerated with sodium hydroxides. Other methods are mentioned and compared briefly.

Substituted substances

Reliability of information

Internet information: data are from an internet document and only a basic and partial evaluation could be performed

Reason substitution

CMR
skin/respiratory sensitizing

Hazard Assessment

Substance to be substituted: Activated alumina (a form of aluminiumoxide) may include crystalline silica that is a category 1 carcinogen (IARC) as listed in the Substance Database according to SUBSPORTplus Screening Criteria (SDSC). Sodium hydroxide is not listed in the SUBSPORTplus Database. Alternative substance: The alternative uses iron electrodes that are nontoxic.

Description of Substitution

Arsenic in drinking water is a problem in many parts of the world but it affects especially the less developed regions. There, cases of arsenic poisoning are acknowledged with effects ranging from lesions to cancer and child morbidity. In such regions where money and technical expertise is lacking, solutions to lower the risk for everyday life need to be effective, affordable, simple and safe. The University of California Berkley National Laboratory proposed a technical solution named ECAR-ElectroChemical Arsenic Remediation. ECAR uses a battery with iron electrodes emerged in the water set to be treated. Dissolved iron ions, from the anode, form iron hydroxide (rust). Trivalent arsenic is oxidised in the anode area to its pentavalent form that binds to the rust and settles at the bottom of the treatment basin, removing arsenic and iron from the water. Advantages, as presented by the alternative provider, include: -low costs for consumables (approx. 200g iron/person/year) -low waste volume (approx. 300g/pers./year) -low maintenance -does not need hazardous chemicals as reagent or as auxiliary materials. The disadvantage is that the method needs an electricity source. Intermittent source is enough but even this may be problematic in some areas. ECAR is compared by the authors to other methods like activated alumina (regenerated with sodium hydroxide), ferric chloride and sodium hypochlorite (both corrosive), solar oxidation (exposure to sun radiation) or MIT Kanchan (a combination of layers of brick chips, iron nails, sand and gravel). Effectiveness of ECAR is comparable to that of methods using activated alumina or ferric chloride and bleach. The ease of use was better than for all the other methods. ECAR is applicable for higher arsenic concentrations, for which the MIT Kanchan or the solar oxidation are not suitable.

Case/substitution evaluation

The substitution addresses fundamental everyday needs in regions that cannot afford sophisticated technologies. It can be an alternative to activated alumina that needs caustic soda solution to regenerate periodically. Activated alumina may contain crystalline silica, an IARC carcinogen to humans. Alumina installations need more experienced operators for proper functioning and maintenance. Their efficiency is dependent on the flow and pH. At pH 8.5 (not unusual in natural water) efficiency can drop to about 2-3% of its optimum. Regenerating alumina with sodium hydroxide (4% solution) generates liquid wastes that are highly concentrated in arsenic and alkaline and therefore not easy to manage. Besides, solid sodium hydroxide or concentrated solutions are corrosive and hard to handle. ECAR also generates wastes (sludge) that passes the standard US EPA Toxicity Characteristic Leaching Procedure (TCLP) tests for landfill disposal, according to authors. The sludge may be also incorporated in construction materials, like concrete or bricks but exposure to arsenic may occur during the manufacturing process or during use needs to be considered and controlled.

State of implementation

Pilot study

Availability ofAlternative

The pilot was planned for market adoption after 2011.

Type of information supplier

Research

Contact

Prof Ashok Gadgil, Dr. Susan Addy-Civil and Environmental Engineering, University of California-Berkeley and the Lawrence Berkeley National Laboratory, http://phys4.harvard.edu/

Further information

US EPA TCLP

Type of publication and availability

internet document, freely available

Publication source: author, company, institute, year

The information is based on the presentation ‘Technology for arsenic-free drinking water: Electrochemical Arsenic Remediation (ECAR)’ made by Prof Ashok Gadgil, Dr. Susan Addy Civil and Environmental Engineering, University of California-Berkeley and the Lawrence Berkeley National Laboratory, in June 2009.The source document was retrieved from the website of the University of Harvard-DEpt. of Physics.

Date, reviewed

November 26, 2021