ODORS AND VOC EMISSION DURING SEWAGE SLUDGE DRYING PROCESS: CHARACTERISTICS, TRANSFER AND TRANSFORMATION

摘要

The drying of sludge is a necessary step for most sludge disposal. In the present study, sludge was collected from two wastewater treatment plants, and then dried at different temperatures in the laboratory. The emission levels of odor and total volatile organic compounds (TVOCs) during the sludge drying process were determined by online odor monitoring system, and the volatile organic compounds (VOC) in the off-gas were analyzed by GC-MS. Results showed that sludge with 30% moisture content could be obtained in 51 min under drying temperature of 100 °C but only within 27 min under 150 °C. Odor intensity, concentration of TVOCs, sulfur-containing compounds (SCCs), and amines were changed with the drying temperature and the sludge sources. At 100 °C of drying temperature, the maximum values of odor intensity, TVOCs, SCCs, and amines were 503.13, 3.01 ppm, 8.15 ppm, and 11.27 ppm, respectively. These values reached 1250.79, 8.10 ppm, 53.51 ppm, and 37.80 ppm when the temperature increased to 150 °C. Odor intensity had close relationship with the emission level of SCCs, amines, and TVOCs. The main VOC released were benzene series and organic acid. The fate and potential migration of substances in sludge were examined via analysis of the off-gas and condensate formed during the sludge drying process, aiming to provide scientific data for effective sludge treatment and off-gas emission control.