Cutting the risk from bacteria in water filtration

The bacteria Cryptosporidium in water supplies poses a risk to health and is being kept in check at a Yorkshire Water facility by an intelligent software model.

The bacteria Cryptosporidium in water supplies poses a risk to health and is being kept in check at a Yorkshire Water facility by an intelligent software model

Yorkshire Water has chosen European Simulation Language (ESL) to model the characteristics of a rapid gravity water filter bed as part of a programme to keep Cryptosporidium bacteria levels within safe limits.

The application at Yorkshire Water was in response to danger from the bacteria which is an organism that can lead to a serious illness called Cryptosporidiosis. This is a world wide problem and there is no known chemical process that can safely eliminate the risk. The bacteria come from farm animals and contamination of the water supply in rural areas is possible at any time.

‘The first outbreaks of Cryptosporidium contamination, identified in the early 1990s, led Yorkshire Water to examine closely the maintenance and operation of gravity filter systems,’ explained Tony Appleton, Business Analyst at Yorkshire Water. ‘We know that if the filter beds are working correctly the three main processes: coagulation, clarification and filtration are able to successfully remove the bacteria.’

Yorkshire Water operates and maintains the gravity filters according to standard manuals. However, a partial failure in any one of the three key processes can lead to bacteria entering the water supply. The company had already used computer simulation extensively in its waste water operation and decided to model filtration using Cogsys ESL.

Modelling the filtration process was the best way to reduce risk of contamination. By simulating the operation of the filter beds it is possible to accurately compare the actual conditions with the ideal safe model.

The process removes small sized impurity particles during the final stages of water supply processing. The model comprises sets of highly non-linear partial differential equations representing the interactions between the impurity particles and layers of media in the bed. The simulation models both the normal filter operation and also the backwash process, which cleans the filter.

Yorkshire Water was seeking efficient operation of the filters and optimum timing of the backwash operation, which is critical in to the continuing supply of pure water. The model also allows long-term simulations to be undertaken to investigate ageing effects in the filter beds.

The ability to integrate ESL with other software is demonstrated by the provision of a graphical user interface to the filter simulation written in Visual Basic. In a later stage of the project, the hydraulics of a complete Water Treatment Works has been modelled. This makes use of ESL’s parallel segments and comprises a number of connected filter beds and associated control systems. Consequently, the impact on water turbidity of taking individual filters into and out of service can be predicted.

The model now fits the data and Yorkshire Water is evaluating filters in a water supply works to refine the system’s alarm levels.

Cogsys ESL is a standard continuous system simulation language, which originally evolved from a series of contracts with the European Space Agency over a period of 20 years. ESL Version 7.0 was launched in January this year has a new graphical interface, from which all stages of the simulation activity can be managed.

According to Cogsys, it has a robust simulation engine proven over the years of work in advanced space and engineering projects. It is a cost-effective solution to a water pollution problem that affects people throughout the world.

ESL was used to simulate the control system responsible for the de-spin of the antenna system on Giotto – Halley’s Comet Probe. The probe rotated during flight for even distribution of solar exposure. The communication antenna required rotation in the opposite direction to maintain a fixed orientation around earth.

An ESL study was carried out to simulate the effect on the orientation of the Hubble Space Telescope (HST) as it makes the transition between sunlight and eclipse. The dynamic effect of thermally induced vibrations in the solar panel arrays was investigated.

The package was also responsible for the simulation of the on-board batteries and power supply system for Earth Resource Satellite ERS1. Simulation reduced expensive ground-based testing procedures and provided a model which could be used to plan energy usage within the battery charge and discharge cycle.

Cogsys Tel: 0161 745 7604

http://www.cogsys.com