CONCENTRATIONS OF EARTHY AND MUSTY ODOR COMPOUNDS IN TREATED WASTEWATER FROM DIFFERENT TREATMENT PLANTS

The concentrations of earthy and musty odor compounds were measured for 123 samples of treated wastewater taken from 25 treatment plants. 2, 4, 6-trichloroanisole was detected from 22 treatment plants with the average concentration of 8.4 ng/L out of the 25 target plants with the detection limit of 1 ng/L. Geosmin was detected from 24 treatment plants with the average concentration of 8.4 ng/L. The concentrations of 2, 4, 6-TCA and geosmin in the treated wastewater was usually higher than their odor thresholds, while the contribution of 2-MIB to the odor of treated wastewater was considered not to be significant. Higher cooncentrations of the target odorous compounds were detected for large-scale wastewater treatment plants compared with those for small-scale plants with the oxidation ditch process. 2, 4, 6-TCA was produced in the aeration tanks in the activated sludge process whereas the chlorination process (disinfection) did not affect the concentration of odorous compounds in the treated wastewater.