DISCUSSION

Mr H. 5. TRICKER

I have attempted briefly to identify the main features of sewage treatment in the past 100 years or so, to point out particular circumstances existing at present, and to look into future trends.

Everyone is accustomed to concrete, brickwork, iron and steel as the normal construction materials but they are comparatively recent introductions. Not long ago land treatment was relied on but such simple methods were unsatisfactory for bigger conurbations.

The theme of development has been a typical civil engineering exercise, i.e. to assess the problem and utilize the forces of nature to solve it. This has been done successfully. However, it is necessary to take a new look at the situation, to improve what is existing and to provide new methods for emerging problems. There is greater public awareness of pollution and the value of amenities, as opposed to public health considerations, and consequently a greater willingness to pay the cost. First principles should be studied to see what can be learnt from them so that present methods can be improved and adapted to the changing needs.