Flotation-filtration unit operation

The flotation-filtration unit can be either manually operated or completely automated with a level control [17] that operates the inlet flow valve [18]. Filter backwashing can also be automated by a timer or head loss control [19]. 

Part II covers the unit operations of flow measurements and flow and quality equalizations pumping screening, sedimentation, and flotation mixing and flocculation filtration aeration and stripping and membrane processes and carbon adsorption. These unit operations are an integral part in the physical treatment of water and wastewater. 

Physical unit operations Screening Comminution Flow equalisation Sedimentation Flotation Granular-medium filtration... 

The second advantage is the use of positive feedbacks that are arisen in the system at the recirculation mode of action due to saturation of filtered water with oxygen of air and effective removal of products of microbial metabolism, as described in Sections 8.5 and 8.6. The scheme of combined filtration-flotation device that operates continuously, under recirculating conditions (rotating wheel), is shown in Figure 8.14. In this device, the processes of filtration, bioflltration, bubble aeration (exchange absorption), and bubble-film extraction are realized in a common reaction space, separated by the unit case 1. The centrifugal pump 2 is used to ensure the circulation of treated... 

The flotation unit maximum loading is 2.1 L/s/m2 (3.1 gal/min/ft2). The maximum filtration rate is 1.7 L/s/m2 (2.5 gal/min/ft2). Each filter compartment is backwashed at or more than 10.2 L/s/m2 (15 gal/min/ft2) during the backwash operation. The single-medium backwash filter consists of 28 mm (11 in.) high-grade silica sand. The effective size and uniformity coefficient for the sand are 0.35 mm and 1.55, respectively. 

Ovhemical DOSING for improvement of liquid-solid separation is traditionally designed and operated more or less independently of the geometry and hydraulic performance of the actual separation reactor. The widespread use of jar tests in the day-to-day operation of filtration and flotation plants illustrates this fact. Yet it is not difficult to visualize situations in which aggregation processes would furnish floes unsuitable for the subsequent separation unit, such as voluminous floes that do not settle out readily. 

In the case of combined device (i.e., filtration-flotation water treatment under recirculation conditions), it is important to know the values of integrated constants of the filtration process, bioflltration process, bubble-flhn extraction process, gas exchange absorption process, and ion separation process in the functional units of combined device, that is, in the filter and in the bubble-film extractor, operating separately. The initial parameters for the device analysis are the required purification degree and treating time. And the calculated parameters are the integrated rate constants of such processes as filtration, biofiltration, flotation, bubble absorption, and dimensions of reaction spaces. 

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