Modelling the diffusion of lead into drinking water

The use of lead in pipe networks, and the subsequent lead emissions into drinking water, is now a major concern to the European Union Member States. Computer simulation offers the possibility for achieving a greater understanding of the issues that relate to plumbosolvency control. An analytical and a numerical scheme for the diffusion of lead into drinking water within a pipe during a stagnation period are described. These have been validated by experimental work. Three models have been investigated to simulate the flow of water through a pipe. These flow models have been used in conjunction with the equation of mass transfer to simulate the concentration of lead at the tap. This has been used within a Monte Carlo framework in order to simulate a zone of properties. The zonal output data obtained consists of failure rates at specified lead standards. This data can be utilised to investigate and prioritise plumbosolvency control options, and substantially overcomes the severe limitations of sampling. Preliminary results from the zonal model compare well with published DWI data.