An Investigation of Historical Chemical Industry Ash and Lime Waste, and Local Catchment Chemistry, From Near Northwich in Cheshire, United Kingdom.

Abstract

This project was conducted to characterise the legacy industrial solid waste derived from salt-based chemical industry in Northwich, England. Large amounts of industrial waste were disposed in the nearby area which has a long history of salt mining and subsidence on a large scale. The site is of significant importance due the long history of waste disposal which gradually changed its landscape. The sources of waste stream were studied and the waste materials of lime and coal ash were identified. Approximate disposal dates were determined in aiding of detailed land use study using historical maps. The geochemical, mineralogical and morphological changes, under the environmental conditions, of the legacy wastes of different ages were determined. These were characterised using a wide range of laboratory techniques including TLM, SEM, XRD and XRF. For potential impact on the hydrochemistry of the catchment, surface water samples were collected from the study area and analysed by IC and ICP. The findings showed insignificant chemical changes over time in lime waste samples while morphological textures and mineralogy appeared to undergo bigger alterations. In addition to calcite in all samples, portlandite and bassanite minerals were observed in the younger lime waste. Dissolution and precipitation, and recrystallisation processes were revealed by higher resolution micrographs, suggesting some portlandite reactivity. Coal ash waste appeared to have an enrichment pattern of most trace elements with age, and an increasing pattern of major elements (Al, Si and Fe). Higher content of aluminosilicate glasses and rounded vesicles were observed in young coal ash along with increasing proportions of mullite, anorthite, and albite. The oldest coal ash waste contained higher proportions of residual and vesicular rock fragments and partially unburnt inclusions, and lower volume of high temperature crystals. It was observed by the aid of SEM micrographs, SEM-EDS and SEM x-ray mapping that some Fe-metal and Fe oxide and Ti oxide were retained in the aluminosilicate glass suggesting lower immobility of such elements. The hydrochemistry of the catchment was found to have the background water type that is largely affected by the fingerprint of halite brine solution. However, nearby industrial discharge is still significantly affecting the water chemistry. Concentrations of trace elements detected in the solid waste were compared with chemical standards published by Environment Agency. Similar comparison was done for some water species. In general the studied legacy solid waste was found to have no significant environmental impact.

Date of Award	1 Aug 2016
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Colin Hughes (Supervisor)