[The ATP concentration of drinking water compared to the colony count]

During a four months' period we have monitored the drinking water of the city of Berlin for its ATP-content and for its Total Colony Count. After concentrating the drinking water by a factor of 1000 by filtration, we obtained ATP-values which were always significantly above the blanks. The profile of the ATP-values roughly paralleled that of the Colony Counts; however, as we never observed Colony Counts nearly approaching 100 colonies/ml (which is the value not to be exceeded according to current German Law), we are unable to positively assess how the ATP-value would have behaved in samples with Colony Counts above 100 ml. Analysis of increasing dilutions of sewage tested for both Colony Counts and ATP indicate that values above 100 colonies/ml would have yielded ATP-values well above those normally seen in drinking water. Therefore, ATP could probably be taken as a measure for the Total Colony Count.