The optimisation of legacy water treatment works to produce a more consistent final water quality

Abstract

The project was carried out as part of a Teaching Company Scheme between Wrexham Water and the University of Aston. The initial remit was to identify and remove bottlenecks in a recently constructed potable water treatment plant known as Legacy Water Treatment Works and to design and install an effective process control system. This remit soon changed and the project then concentrated on:-understanding and then optimising the chemical dosing throughout the plant to improve product quality and consistency; initiating and implementing a change in operating philosophy among Wrexham Water staff; and introducing new techniques and technologies to the treatment process. The treatment process at several treatment works was observed and after preliminary trials a change was made to an alternative coagulant which resulted in coagulation costs being reduced by 15%. At one treatment works the investigation into the process revealed an overdosing of both coagulant and lime, the correction of which has resulted in a saving of £44,950 per annum. A significant improvement in the performance of the instrumentation was achieved. The need for improvement and the areas to target were highlighted by a series of instrument audits. An 87% improvement has been realised. Assessment of the performance of Legacy treatment works showed a bottleneck in the existing filter plant. Due to other operational considerations a new filter plant was procured; installation will be completed by August 1995. Quantifiable cost savings from work undertaken as part of this research project amount to £109,450 per annum and one-off savings of £302,000. Many of the benefits of the work carried out are intangible and a monetary value is hard to place on them. Introduction of the changes to the treatment plant has been accompanied by a significant and definite change in attitude of the Wrexham Water personnel to many of the work practices.