1. Pennine Water Group, Univ. of Bradford, West Yorkshire BD71DP, U.K.
2. WRc plc, Frankland Road, Swindon SN5 8YF, UK.
3. Ewan Associates Limited, 12 The Beta Centre, Stirling Univ. Innovation Park, Stirling FK9 4NF, U.K.
4. Dept. of Environmental Engineering, Aalborg Univ., Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark.