Arsenic toxicity, health hazards and removal techniques from water: an overview

Abstract

Arsenic contamination in water, especially groundwater, has been recognized as a major problem of catastrophic proportions. The toxicology and health hazard also has been reported for many years. Because of the recognition that arsenic at low concentrations in drinking water causes severe health effects, the technologies of arsenic removal that have become increasing important. The current regulation of drinking water standard is become more stringent and requires arsenic content to be reduced to a few parts per billion. There are several treatment methods capable of this level of performancemembranes, coagulation, anion exchange, disposable iron media, softening etc. Treatment cost, operational complexity of the technology, skill required to operate the technology and disposal of arsenic bearing treatment residual are factors should be considered before treatment method selection. This paper aims to review briefly arsenic toxicology and hazards and also the previous and current available technologies that have been reported in arsenic removal. Residual generation and disposal after treatment will also be discussed.

Contamination of groundwater by arsenic: a review of occurrence, causes, impacts, remedies and membrane-based purification

“…Thus, the prescribed maximum contaminant level (MCL) of arsenic in drinking water (Table 1) is found to vary from country to country (Choong et al 2007). While the value is 50 mg/l in the developing countries like Bangladesh, India, China, Taiwan, it is 10 mg/l in the developed countries like the USA, Germany, and Japan, 25 mg/l in Canada and, 7 mg/l in Australia.…”

“…This means that As(III) remains as a neutral molecule in natural water. Arsenates are stable under aerobic or oxidizing conditions, while arsenites are stable under anaerobic or mildly reducing conditions (Choong et al 2007). In reducing waters, arsenic is found primarily in the trivalent oxidation state in the form of arsenious acid that ionizes according to the following equations:…”

“…The contaminants like iron, calcium, magnesium, bicarbonate, chloride and sulphate are found to be associated with arsenic in the groundwater of these countries. Inorganic arsenic, As(V) and As(III) in the form of Na 2 HAsO 4 and NaAsO 2 , respectively, are toxic to man and plants (Choong et al 2007). Inorganic arsenic is always considered a potent human carcinogen, not only associated with the cancer of the urinary bladder, lungs, skin, kidney, nasal passages, liver and prostrate owing to long term exposure to arsenic in drinking water, but also non-cancerous effects including cardio-vascular, pulmonary, immunological, neurological and endocrine (e.g.…”

“…Therefore, in the last few decades, increasing attention has been focussed on the possible long-term health risks associated with ingestion of low levels of arsenic in drinking water. To prevent arsenic-related diseases, the maximum contaminant level (MCL) in drinking water has been set by different countries as in Table 1 (Choong et al 2007).…”

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“…It is known to be the 20 th most abundant element in the earth [13]. Arsenic abundance in water is due to biological activity, combustion of fossil fuels, geochemical reactions, gold mining, natural weathering process, volcanic eruptions, leaching of man-made arsenic compounds, smelting of metal sores, desiccants, wood preservatives, agricultural pesticides and many other anthropogenic activities [14,15]. Arsenic is broadly present as both arsenic (V) and (III), depending on pH and redox conditions [16,17].…”