AS-sure: A New Technology for Delivering Safe Drinking Water

Lead Research Organisation: Imperial College London
Department Name: Earth Science and Engineering

Abstract

The pollution of groundwater with arsenic through natural or anthropogenic processes, and the subsequent long-term exposure through drinking water, threatens human health on a global scale. Though serious risks are known to occur in developing countries such as Bangladesh, China and India, high blood concentrations have been found in the UK with the residents of Devon and Cornwall. Due to the severe health effects of arsenic (the most toxic element known to humans), most governments worldwide including the US and UK have recently lowered the admissible arsenic concentration in drinking water to 10 ng/ml. Achieving these new stringent threshold values poses real challenges to the water industry and current treatment devices struggle to meet these criteria. One of the foremost reasons for these failures is that the processes currently employed (namely adsorption on iron and activated aluminium oxide substrates) are adversely affected by the presence of small concentrations of phosphorous and silica in the waters, which in turn significantly diminish the performance and life span of the treatment plants. Here we suggest a novel approach based on a combination of two different sorbents, with different treatment tasks. The first stage is composed of a bi-composite synthesised of TiO2 and Fe2O3. This device has been designed to remove phosphorus and silica from the waters and to oxidise any arsenic(III) that might be present to arsenic(V) (i.e. arsenate). This pre-treated water then passes through a second stage, which is composed of an arsenic specific chemical receptor. This second treatment step will be based on metallo-receptors with high affinity for oxoanions such as arsenate. The ultimate outcome of the project is a novel low cost water treatment device using the technologies described above with a long live span that will remove arsenic from water below the levels currently considered to be unacceptable. In order to understand the mechanisms of the arsenic interaction with the bi-composite and the metallo-receptor, we will conduct extensive chemisorptive studies of the functionalised materials and determine the key factors that need optimising for efficient binding. This work will include spectroscopic investigation using various techniques such as synchrotron radiation and nuclear magnetic resonance. Our findings will also have fundamental implications on our understanding of the environmental chemistry of arsenic and oxyanions in groundwater.

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