Sustainable small-scale, membrane based arsenic remediation for developing countries

Membrane technologies for small-scale arsenic removal are currently mainly involving nanofiltration, reverse osmosis, membrane distillation and electrodialysis. Their advantages are the simplicity of the technology and the scalability down to very small modules. Forward osmosis is a relatively new technology for arsenic removal which was mainly applied so far on laboratory scale. Basically, all membrane technologies, with the exception of membrane distillation, show significantly lower rejection for As(III) than for As(V). In order to treat anoxic groundwater with high As(III), which is usually associated with high Fe, a pre-oxidation step and the removal of Fe(oxy)hydroxide is mandatory to avoid membrane clogging. Generally, safe disposal of the occurring arsenic rich sludges and liquid waste streams pose a difficult issue.