Effect of Geometrical dimensions and wastewater Temperature on the performance of an Induced Air Flotation unit for the treatment of industrial waste water

Abstract

Induced Air Flotation (IAF) systems had found great deal of interest for their high performance in oil/water separation for the treatment of municipal and industrial waste water that can be achieved with simple and cheap operation compared with other systems such as the diffused air flotation. This paper is dedicated to the study of effects of geometrical dimensions, and water temperature on the separation efficiency of IAF process that handles effluent of dairy industry. Operation of IAF was based on the best factors gained by Al-Maliky, Al-Ajawi, Al-Bayati (2009) for the treatment of effluent of dairy industry. Results have shown that ratios higher than 1:1 (width: height) of flotation tank tend to increase the separation efficiency under the same detention time; 1.25:1, 1.5:1, 1.75:1 and 2:1 had made an addition of 4.5, 5.2, 8.3 and 10.12% to the efficiency gain made by 1:1. Far from 2:1 was appeared to have a reverse effect in reducing the separation efficiency. The raise in waste water temperature had shown a significant role in enhancing the water/oil separation efficiency, until it reaches about 80-84 ο C, beyond which that efficiency tends to decrease as oil flocs tend to scrap and layer disturbances take place. An enhancement of 10-17% occurs when operating the system with waste water temperature of 80-84 ο C, and air flow rates of 3-5 l/min, respectively compared with that of 22 ο C and the same air flow rates. This paper was accomplished and edited with the use of logistic and technical resources of the Institute of International Education IIE, Scholars Rescue Fund SRF and College of Engineering/ Ohio University. In Induced Air Flotation process (IAF), a proportion of micro bubbles in the flotation tank form bubble-floc agglomerates, which, when sufficiently buoyant, rise to the top of the flotation tank. At a top of the tank, a sludge-layer is formed, which can be removed by either draining liquid from the top of the tank by means of a weir, or by means of a scraper or skimmer. An exit flow of lower particle content liquid is removed from a lower part of the flotation tank. Recent applied and theoretical analyses have explored the various hydrodynamic and physicochemical parameters that determine the performance of flotation process, for the water/oil separation for both industrial and municipal waste water as an active area of research (Rosa and Rubio, 2005; Al-Shamrani et al., 2002). Al-Maliky et al. (2009) had tested the effect of air flow rate and coagulation agents on the performance of IAF unit. Separation efficiencies were in the range of 66%-70% with an IAF unit that operates with 3-5 l/min. air flow rates treating effluents of dairy industry, and with the addition of 0.5 g/l Alum, efficiencies of 96%-99% were achieved. This paper is dedicated to determine the extent to which the dimensions of IAF unit and water temperature (especially high temperature ranges), may affect the performance of water/oil separation as they will affect gravity/buoyancy and turbulence factors mentioned above.