RESIDENCE TIME DISTRIBUTION MEASUREMENT FOR ACTIVATED-SLUDGE USING PYRENE AS A TRACER ELEMENT

The retention time distribution of activated sludge in a lab scale sec ondary clarifier has been studied by using pyrene as a selective trace r for activated sludge. Pyrene is useful to monitor the bio-solids in activated sludge systems, since it adsorbs preferentially to the sludg e flocs, and, because of its recalcitrance, it is not modified by the micro-organisms. Due to its potential toxicity, the use of pyrene is r estricted to controlled environments. Notwithstanding this disadvantag e, the tracer proposed can be of use in water science technology becau se no other hydrophobic test chemical has thus far been described for activated sludge monitoring.