Abstract
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.
Highlights
Sludge is a biomass produced in large quantities during the primary, secondary, and advanced municipal wastewater treatment [1]
This study proved the advantage of compounds, such as chitosan and bentonite as coagulant agents in Dissolved air floatation (DAF) systems for water treatment [20]
Based on the recycling rates, the volume of air-saturated water and sludge sample was estimated using Eq 2, and the results are shown in Figure 2 and Table 1
Summary
Sludge is a biomass produced in large quantities during the primary, secondary, and advanced municipal wastewater treatment [1]. Given the importance of disposal and processing of sludge [7], as well as economic benefits and high efficiency of DAF systems [6], in this study, the simultaneous and individual effects of sonication and coagulation processes on the efficiency of a lab-scale DAF unit for thickening of the return activated sludge (RAS) of Amir Kabir industrial zone’s treatment plant, were investigated. 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. Effect of coagulation and sonication on the dissolved air flotation (DAF) process for thickening of biological sludge in wastewater treatment.
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