1. Dep. of Soil Science; Stellenbosch Univ.; Stellenbosch South Africa
2. Water Institute, Stellenbosch Univ.; Stellenbosch South Africa
3. Dep. of Microbiology; Stellenbosch Univ.; Stellenbosch South Africa
4. Lancaster Environment Centre; Lancaster Univ.; Lancaster LA1 4YQ UK
5. Dep. of Engineering; Durham Univ.; Durham DH1 3LE UK