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http://dx.doi.org/10.11001/jksww.2018.32.6.479

Pre-treatment of oily wastewater using a coagulation-DAF process with slit-nozzle  

Choi, Sangki (School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology)
Kim, Youngmo (School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology)
Publication Information
Journal of Korean Society of Water and Wastewater / v.32, no.6, 2018 , pp. 479-485 More about this Journal
Abstract
Large amounts of oily wastewater discharged from various industrial operations (petroleum refining, machinery industries and chemical industries) cause serious pollution in the aquatic environment. Although dissolved air flotation (DAF) separating oil pollutants using microbubbles represents current practice, bubble size cannot be selectively controlled, and lots of power is required to generate microbubbles. Therefore, to investigate performance of the DAF process, this study examined the distribution of different sizes of microbubbles resulting from changes in physical shear force via modifying shapes of a slit-nozzle without an additional power supply. Three types of slit-nozzles (different angle, shape and length of the slit-nozzle) were used to analyze the distribution of bubble size. At a slit angle of $60^{\circ}$, shear force was 4.29 times higher than a conventional slit, and particle size distribution (PSD) in the range between 2 and $20{\mu}m$ more than doubled. Treatment efficiency of synthetic oily wastewater through the coagulation-DAF process achieved 90% removal of COD by injecting $FeCl_3$ and PACl of 250 mg/L and 100 mg/L, respectively, and the same performance resulted using $FeCl_3$ of 200 mg/L and PACl of 80 mg/L employing a slit-nozzle angle of $60^{\circ}$. This study shows that a coagulation-DAF process using a modified slit-nozzle can improve the pre-treatment of oily wastewater.
Keywords
Oily wastewater; Dissolved air flotation; Coagulation; Slit-nozzle; Microbubble;
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