Abstract
Human activities unintentionally add pollutants to water bodies. This research has focused on the removal of trace elements from sources of water pollution (point and non-point), using a mineral based by-product (Blueguard® solids). The materials were characterised to identify the mineralogy, structure, porosity, and composition using different techniques including X-ray Fluorescence Spectrometry, X-ray Powder Diffraction and Brunauer–Emmett–Teller gas sorption methods. The results showed that the main compounds of the Blueguard® materials are alteration products of Mg-rich silicates. Three different types of contaminated water originating from different sources were prepared and analysed. These samples included (a) a multi-element solution prepared from trace element stock solutions; (b) rain water contaminated with motorway dust, and (c) contaminated water taken from an industrially polluted site (Cranleigh Brickworks, Surrey). Trace element analysis was undertaken by inductively coupled plasma mass spectrometry. Using a batch equilibrium procedure with optimised conditions of 0.25 g material in 50 ml solution for 5 min contact time, the mixing of the Blueguard® materials with a multi-element solution showed an effective removal of various trace elements under pH 4 to 9 conditions. These materials were then used to treat contaminated rainwater mixed with digested motorway dust. Trace element removal occurred from 80% for manganese up to 100% for lead. Analysis of surface water samples collected from the Cranleigh Brickworks showed that the levels of zinc and manganese were above the World Health Organisation (WHO) guidelines for drinking water. The most contaminated lagoon (25950 µg l-1 Zn and 2843 µg l-1 Mn) on the site was selected for laboratory and on-site testing of the Blueguard® materials. The best removal efficiency for these types of materials took place under a static design system where more than 95% of zinc and up to 97% of manganese was removed. Further investigation of the Blueguard® materials suggested the mechanism by which these materials reduce the level of trace elements in a solution was by precipitation, as a result of pH increase (through release of OH-(aq)). The results obtained for metal removal at Cranleigh has resulted in the application of these materials to remediate the site.