Technology for remediation and disposal of arsenic

Groundwater contaminated with arsenic must be treated to meet stringent drinking water standards or guideline values. In recent years, several reliable, cost-effective, and sustainable treatment technologies have been developed, although improvements will continue to emerge as work continues. All treatment technologies work by concentrating arsenic at some stage of treatment. Large-scale use of arsenic removal systems generates arsenic-rich treatment wastes, and indiscriminate disposal of these sizable wastes may lead to environmental pollution. Safe disposal of arsenic-rich media is a growing environmental concern that needs to be addressed. For the developing world, arsenic-contaminated water requires some form of treatment to be sufficiently safe for consumption by local populations. Such treatment is particularly important where arsenic [particularly as As(III)] levels in raw water exceed 200 microg/L. At this level and above, >95% removal efficiency is required to produce water that meets international standards, an unlikely result in many locations. Alternative sources for securing safe water may also include rainwater harvesting, use of uncontaminated (filtered) surface waters, and water extraction from new deep tube wells and dug wells. There are disadvantages attendant to using these alternative water sources. For example, rainwater has few mineral salts and is subject to contamination from air pollution or by microbes, including pathogens. Similarly, surface waters, e.g., pond waters, or water from dug wells may require purification before use. Excessive pumping from deep tube wells may lower the water table sufficiently to allow entry of arsenic-contaminated waters from shallower horizons. Bioremediation and phytoremediation are more suitable to developing countries where sunlight is plentiful. In such countries, plant biodiversity is also great and may allow identification of plants suitable for bioremediation. In addition to removing arsenic from water, phytoremediation can also provide economic benefit to the people who apply the methods.