Ali Atamaleki - Department of Environmental Health Engineering, School of Public Health, Kashan University of Medical Sciences, Kashan, Iran
Mohammad Bagher Miranzadeh - Department of Environmental Health Engineering, School of Public Health, Kashan University of Medical Sciences, Kashan, Iran
Gholam Reza Mostafaii - Corresponding author:Department of Environmental Health Engineering, School of Public Health, Kashan University of Medical Sciences, Kashan, Iran
Hosein Akbari - Biostatistics and Public Health Department, Faculty of Health, Kashan University of Medical Sciences, Kashan, Iran
Leila Iranshahi - Department of Environmental Health Engineering, School of Public Health, Kashan University of Medical Sciences, Kashan, Iran
Farshid Ghanbari - Abadan Faculty of Medical Sciences, Abadan, Iran
Atieh Salem - Department of Environmental Health Engineering, School of Public Health, Kashan University of Medical Sciences, Kashan, Iran

Background: Dissolved air floatation (DAF) is one of the methods has been used for the sludge thickening in wastewater treatment plants. This study aimed to investigate the effects of coagulation and sonication processes as additional configurations on the efficiency of a lab-scale DAF process for thickening of the biological sludge of an industrial wastewater treatment plant in Kashan, Iran. Methods: The required amounts of sludge samples were collected from a wastewater treatment plant and kept at temperature of 4°C. Variables, such as pressure (3, 5, and 7 atm), flotation time (5 and 10 minutes), ultrasonic irradiation power (0, 75, and 150 W), and presence/absence of Fe-based coagulant were considered on a sequencing batch reactor (SBR) included coagulation, flotation, and sonication processes, respectively. Results: The use of ultrasonic waves led to an insignificant increase in the DAF efficiency (P > 0.05), however, the application of coagulant significantly increased the thickening efficiency (P < 0.05). The maximum efficiency of the process was achieved at flotation time of 5 min, pressure of 3 atm, and sonication power of 75 W. Conclusion: According to the results, DAF has a proper efficiency for thickening of biological sludge. Coagulation compared to sonication has a greater effect on the efficiency of the process.

Ultrasonic waves, Industrial effluent, Dissolved air flotation, Sonication