Near the beginning of his paper, the Author makes a significant statement, viz. 'the day is overdue when public health engineering should be recognized as a separate profession.' The writer should like to add that the day is long overdue for South African universities to make provision for a specialized degree course in public health engineering. Quite a large proportion of graduates in civil engineering enter municipal service where sooner or later they become vitally concerned with the purification of water or sewage, or both.
In die referaat wat die Outeur vanmiddag aan ons voorgedra het, word 'n saak behandel wat vir almal van die grootste belang is, nl. die probleem van ons land se watervooruitsiening. Dit is onnodig om daarop te wys hoe lewensbelangrik ons watervoorrade vir die ontwikkeling van die land is. Wat weI baie nodig is, is dat almal moet meehelp om bestaande voorrade nie in 'n enkele opsig te verkwis nie, maar om hulle ten beste te benuttig. Om dit te kan doen, moet ons die regte wetenskaplike benadering tot die saak h, en moet ons 'n duidelike beeld kan vorm van wat daar vir ons te doen staan.
A pleasing feature of the Author's paper is that his enthusiasm for high-rate digestion is tempered with due caution. It must be remembered that sludge-digestion is not a simple engineering process but a biological one. Although termed anaerobic the process is fundamentally a method of oxidation of the carbonaceous matter by bacteria which do not use atmospheric oxygen but take their oxygen from decomposition of the water.
Mechanical means of screening and degrittor tanks are advocated for the preliminary processes of solids removal. These views are strongly endorsed, especially in the case of larger works. Insofar as settling tank design is concerned it is felt that, to ensure efficient operation, tanks should be designed to satisfy both criteria, viz. detention period and overflow rate. Research is required on plant scale tanks to determine the importance of each design criterion and possibly suggest more rational methods of design. The findings would certainly be most useful.
Some ten years ago, at the instance of the late Mr. James Gray, then chairman of the Health Committee of the Johannesburg City Council, an advisory committee of experts was convened to study the position in regard to atmospheric pollution in the city. As a result of their deliberations, the Council put forward suggestions for strengthening the legal powers to deal with air pollution, and officials of the City Health Department intensified their efforts to improve matters within the scope of the existing legislation. Discussions with industrialists and others whose chimneys belched forth copious volumes of black smoke, and persuasive methods generally, resulted in some improvement and these efforts continue to meet with moderate success.