Wastewater and sludge: The rapid determination of microbial content by ATP bioluminescence.

A study to optimize a rapid method for the determination of microbial content of wastewater and sludges by means of the ATP bioluminescent assay has been performed. Sampling, ATP extraction and testing of these complex specimens have been considered. A mayor problem was to obtain an homogeneous sampling. Diluition was also a very important step. Several diluitions were tested and the chosen one was 1:100. Different chemical and physical method of extraction have been compared: cationic detergents, ultrasounds and microwaves have been tested, alone or in combination. Obtained data have shown that to combine the physical treatments with detergents is the more effective way to achieve a satisfactory yield of extraction. In particular the use of ultrasounds on samples diluted in detergents solution allows a rapid, simple and effective ATP extraction. The bacterial content determined by the bioluminescent assay was finally compared to results obtained using the plate count method. ATP bioluminescence seems to allow a greater number of bacteria to be detected than with classical determinaton.