Development of a methodology for the physicochemical characterisation of a cutting fluid based sludge

This thesis presents a physicochemical analysis of a cutting fluid based floating sludge that arose in the wastewater storage tanks at a metal machining factory in South Wales, UK. The sludge is causing a range of issues from damaging aspects of the wastewater treatment system to potentially stopping the wastewater treatment plant from operating, which in turn would cause the temporary closure of the metal machining factory. As this type of cutting fluid based sludge has never before been experienced or studied, a structured order of analyses and calculations were developed by reviewing existing analytical methods and formulating new analyses where the existing methods were inapplicable or nonexistent. The chemical components that make up 70% of the sludge are water, oleic acid and palmitic acid. The ratio between these three chemicals is believed to directly influence the physical properties of the sludge. An assessment was undertaken to determine if the sludge could be described as ‘grease’ (formed by the interaction of calcium and sodium with palmitic acid and oleic acid). It was found that only up to 3.6% of the sludge could be grease. This has implications for preventative measures employed to stop the sludge from forming. The routes of formation of the sludge from virgin products is thought to be via biological degradation of the cutting fluids into free fatty acids. Alongside the formation the design of the wastewater treatment facility is reviewed to understand why the sludge has accumulated in such large quantities