Energy-efficient small-scale reverse osmosis units: a promising approach for arsenic removal from drinking water

More than 100 million people world-wide are exposed to high arsenic levels through the water in underground wells. Arsenic (As) is one of the most toxic elements that exist. Its adverse effects depend strongly on the dose and duration of exposure. With regard to the toxic effects of As on humans and other living organisms, it is necessary to take into account the permissible levels of As in drinking water and its chemical speciation when establishing the regulatory standards. The WHO guideline value adopted for As in drinking water is 10 ug/L (WH0, 2008). A variety of membrane techniques among them nanofiltration (NF) and reverse osmosis (RO), may be used for As removal (for overview see Shih, 2005 & Uddin et al., 2007). NF and RO have the advantage using very 'dense' membranes in such a way that other dissolved contaminants can be retained along with As, resulting in a very high water quality. Some time ago several companies brought small-scale marine RO units (known as watermakers) to the market. They are applied to produce drinking water from seawater on boats and it is a well-proven technology, which works reliably at remote locations under difficult conditions (e.g high salt concentration). Some of them can be powered by sustainable energy sources, such as PV or wind wheels, or can be operated manually