Desalination of poor quality brackish groundwater for non-potable use

Abstract

Increases in population and water use are increasing pressures on conventional water sources. The use of alternative sources for non-potable applications can relieve some of this demand. Poor quality ground water, combined with quantities of grey water and rain water, was identified as potential alternative to potable water for toilet flushing at the Millennium Dome, a large entertainment complex in London, UK. An 87m deep borehole was sunk on the Millennium Dome site. On abstraction, the ground water was found to be brackish, with further contamination in the form of hydrogen sulphide, ferrous iron, and aromatic hydrocarbons. The chosen treatment process utilises oxidation of the sulphide and ferrous iron with hydrogen peroxide, adsorption of the organics and filtration of the precipitated ferric hydroxide on granular activated carbon, further pre-treatment by hollow fibre ultrafiltration (UF) membranes prior to desalination on Reverse Osmosis (RO) membranes. The final RO product water undergoes re-hardening and residual disinfection prior for use in flushing toilets inside the Millennium Dome. Results for the pre-treatment and membrane processes over a 6 month operational period are discussed. A saving of approximately 50% of the drinking water supply has been demonstrated