SECTION 6 



MICROBIOLOGICAL INDICES OF THE QUALITY OF WATER AND METHODS 



OF THEIR DETERMINATION 



V.I. Romanenko 



In the majority of cases, microbiological indices may be the best way 

 to characterize the quality of water used for both drinking and industrial 

 purposes. Microorganisms are excellent indicators which often exceed the 

 sensitivity of chemical and physical methods. The cells of microorganisms 

 react to minute changes in external medium. Under favorable conditions 

 they start to multiply more rapidly and their metabolism accelerates. 

 Some species of bacteria can exist only in the presence of a definite 

 class of chemical substances. Exhaustive knowledge is not available on 

 the life of millions of microorganisms, however, in the future, the 

 expanded use of microbiological indicators will undoubtedly develop. 



It should be recognized that some of the major questions can be cor- 

 rectly answered only by microbiological specialists who are well versed 

 in the details of microbiological technique. In some cases it may be 

 necessary for the knowledgeable scientist to intentionally depart from 

 established methodology, while a similar departure in the hands of a 

 neophyte may lead to false results. When working with pathogenic micro- 

 organisms is considered, this may lead to serious consequences. 



The present communication deals primarily with bacteria. Algae and 

 small invertebrates, including abundance, or activity, intensity of photo- 

 synthesis, while important as excellent indices of the condition of a 

 water-body, are not included in this consideration. 



Microbiological indices may be divided into two categories as: (1) 

 the presence of bacteria, and (2) the intensity of one or another bacte- 

 rial process (Figure 1). 



DETERMINATION OF THE QUALITY OF WATER BY THE NUMBER OF BACTERIA OR PRE- 

 SENCE OF PARTICULAR SPECIES 



Quantity of Microorganisms 



The quantity of microorganisms may be judged by their total content, 

 or by the content of separate physiological groups. Total numbers of 

 bacteria may characterize the condition of the water-body in general, 



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