STUDY OF THE DEVELOPMENT OF THE MUSTY TAS TE IN WATER ACCORDING TO ITS AGING PROCESS IN PILOT-PLANT

The aim of this study is to determine the influence of the residence t ime and the concentration of microorganisms (in water and biofilm) upo n the appearance and/or the intensification of the musty taste of wate r. According to the literature, the origin of this musty taste is main ly biological, the saporigeneous microorganisms being actinomycetes, a lgae or fungi. This study has been carried out in pilot networks which allow the fixation of residence time and the study of biofilm. The re sults obtained in this study show that : (i) musty taste intensity inc reases up to 72 hours of residence time then stabilizes between 72 hou rs and 120 hours the treated water entering in the pilot networks has an average threshold value of musty taste of 4 and comes close to 50 u p to 72 hours residence time, (ii) concentrations of microorganisms in water and biofilm increase as the residence time increases. Microorga nisms detected in water are fungi (from 5.10(2) to 10(4) l(-1)) and re vivifiable aerobic bacteria (from 10(2) to 2.10(3) ml(-1)) while in th e biofilm are detected not only fungi (from 10 to 3.10(2) cm(-2)) and revivifiable aerobic bacteria (from 10(5) to 5.10(5) cm(-2)) but also actinomycetes (from 0 to 50 cm(-2)). However, no quantitative relation ship between cm this musty taste and the different kind of microorgani sms detected in water or in biofilm could be established. Nevertheless , the biological origin of musty taste remains the most probable but t his taste should be related to the metabolic activity of microorganism s rather than to their concentration.