Optimised Maintenance Scheduling for Wastewater Systems.

Abstract

Effective functioning of sewer systems is critical for everyday life of people in the urban environment. This is achieved, among other things, by the means of regular, planned maintenance of these systems. Operational maintenance of the sewerage system involves various activities such as visual inspection, flushing, root cutting, CCTV inspections, desilting and jetting. Large district areas require significant budgets and resources to perform these necessary maintenance tasks at various locations around the region at regular intervals. Planning and scheduling these tasks can be challenging due to the ranging priorities, for example travel. Inefficient travel between different locations can result in a large amount of unproductive time, resulting in the delay of the completion of tasks. Review of the literature and of current industry practice revealed that the existing methodologies do not specifically address these issues. Therefore, the overall aim of this research is to develop a novel methodology for effective maintenance of sewerage systems. The maintenance scheduling issue was formulated and solved as an optimisation problem. To help solve this problem the following objectives were created: to reduce the crew travel time, to reduce the total cost of a crew member’s day, and to increase the priority score of the maintenance jobs that were completed. At present water utilities do not always complete all their assigned maintenance jobs planned for the month. The configuration of the algorithm will mean that the most critical jobs are completed at the start of the month. The developed maintenance scheduling methodology is general, allowing it to be applied to any wastewater or clean water maintenance proactive or planned problem. This method has been developed and tested with maintenance managers using historical data provided by Dŵr Cymru Welsh Water (DCWW). The new methodology was tested on one case study. The results obtained from the case study demonstrate that the new methodology is capable of determining optimal, low cost maintenance schedules in a time efficient manner when compared to the corresponding existing company schedules. Daily productivity improves by 26% when the model is applied to scheduling in the case study. Given this, the method has the potential to be applied within water utilities, and DCWW are currently implementing it into their systems.