Valuation of characteristics of water purity. IV. Classification of pollution of waters based on norms of microbiological, hydrobiological and chemical characteristics determined by numerical methods.

Norms of microbiological (coliform titre, nitrification titre, urea hydrolysis titre, number of bacteria, BOD2 and BOD5), hydrobiological (intensity of photosynthesis, saprobic index, number of algae) and chemical (oxidability, DMDT content) characteristics, determining the ecological quality of water, are suggested. Their taxonomic value has been appraised with the use of numerical methods: centrifugal correlation and principle components, used for the classification of a collection of sites with respect to pollution.