1. School of Water Sciences, Cranfield Univ., Cranfield, Bedfordshire MK43 OAL, UK.
2. Yorkshire Water, Research and Process Development, Western Way, Halifax Rd., Bradford BD6 2LZ, UK.
3. United Utilities Service Delivery, Asset Creation-Task Team, Thirlmere House, Lingley Mere, Lingley Green Av., Warrington WA5 3LP, UK.
4. School of Water Sciences, Cranfield Univ., Cranfield, Bedfordshire MK43 OAL, UK. (corresponding author)