This is a reprint of Ministry of Technology Notes on Water Pollution, No. 48, March,
1970. Each of this series of leaflets contains brief notes on some aspect of the control
of pollution or on what is known of the effects of pollution on streams, and includes
a few references to publications on the subject which may be found useful. Further
information, if available, may be obtained by writing to the Director, Water Pollution
Research Laboratory, Elder Way, Stevenage, Herts. It is published by kind permission
of the Director.