Although, generally, Sewage Treatment Plants are downstream of local Water Treatment Plants, there are some exceptions. In SEQ, where catchments are unprotected from human activity, there are several instances of Sewage Treatment Plants discharging into creeks that feed into drinking water storages. The relatively small volumes of effluent and long retention times make this an accepted practice. However, in some instances, particularly overseas, effluent forms a significant proportion of the raw water supply so advanced treatments are required at the Water Treatment Plants. Some examples...