Welsh Journals

WATER POLLUTION AND ITS CONTROL W. ROSCOE HOWELLS, B.SC., PH.D. INTRODUCTION This paper will cover certain aspects of water pollution control with the main emphasis being placed on fresh water. Clearly, in a paper of this sort, it will not be possible to deal with any particular aspect in depth. THE NEED FOR POLLUTION CONTROL Although there is a great deal of water on the earth, most of it is salt water, and of the remainder over 75 per cent. is locked in glaciers and in polar ice. The available fresh water in lakes and rivers and in underground sources is a mere 0.7 per cent. of the whole. In spite of this apparent vast reserve it is increasingly clear that water is becoming a scarce commodity. In England and Wales the volume of water used daily, other than for cooling purposes, amounts to about 95 gallons per head per day, of which domestic use accounts for approximately one third. It is obvious that water must be available in the right place and at the right time, and of the correct quality for the very wide range of uses to which water is put, which include: 1. Domestic use. 2. Agricultural use (including irrigation). 3. Industrial use (including process water and cooling water). 4. Fisheries. 5. Recreation, such as swimming, boating, etc. 6. Drainage. 7. Power and navigation. DEFINITION OF POLLUTION Water pollution may be loosely defined as anything which adversely affects the use or uses to which water may be put, or may subsequently be put. Pollution may be solid or liquid and may contain solid matter in solution or suspension, or contain dissolved gasses. It is clear that the pollution of water if not properly controlled may affect some or all of the uses to which reference has been made. Water may be so polluted as to be untreatable for water consumption. It may be tainted by minute quantities of pollutants making it undrink- able. It may be so polluted as to be unusuable by many industries some of which require water of a very high standard indeed. As far as agricultural use is concerned, polluted water may be unpalatable to cattle or directly toxic. The presence of very small quantities of toxic metals can make spray irrigation impossible.