Filtration compared with coagulation

Filtration is analogous to coagulation in many respects. This is illustrated by juxtaposing the basic kinetic equations on particle removal  

Coagulation a Collision efficiency volumetric concentration of suspended particles G Velocity gradient t time i 

Filtration a W volumetric concentration of filter medium d single- number of collector collectors efficiency (v,d) V contact opportunities  

Design and operational variables Chemicals Coagulation aids, media size, sludge recirculation Energy input, mass transport Residence time filter length and media diameter 

Theoretical dependence of filter efficiency of a single collector (proportional to the rate at which particle contacts occur between particles and the filter grain by mass transport) on particle diameter. For particles of small diameters transport by diffusion increases with decreasing size. Contact opportunities of the larger particles with the filter grain are due to interception and sedimentation they increase with increasing size. 

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UV can also be used in water reclamation and reuse. An example is the reclamation of swimming pool water. Usually, the swimming pool water reuse process includes coagulation, filtration, clarifier, disinfection, and pH adjustment. The conventional swimming pool disinfection chemical is chlorine however, high concentrations of residual chlorine can be harmful to human health. The UV technology can be placed between the filters and chlorine disinfection unit as a pre-disinfection unit and remove pathogens. Hence, much less amount of chlorine (compared with the process without UV unit) is needed for residue disinfectant level. 

ELISA (Dako antibodies). Antithrombin level in the rhAT concentrate was assayed against the 8th British Blood Coagulation Factors Standard to compare the stated dose with the assayed dose per vial. Heparin binding was also assessed by two-dimensional electrophoresis with or without heparin in the first dimension, and by heparin-Sepharose gel filtration. The concentration of rhAT in the vial was 89% of the stated value by this thrombin-based assay, 85% by Xa-based assay, and 119% by the antigen assay. 

As shown in section 0, MF only removes a very small amount of dissolved organics. To increase the organics rejection with MF, the organics need to be transformed into particulates. This can be done by coagulation, which, combined with conventional filtration, is currently the most abundant water treatment process. The interest in this investigation was to be able to compare the flux and rejection achieved with MF and pretreatment to other membrane processes (see following chapters). 

Frenkel [5] classifies raw water supplies into several types with different characteristics (Table 12.1). Other authors propose similar classifications and often add hardness to the list of characteristics. Arden and Forrest [6] take a modular proach to treatment. Silted river water, for example, considered suitable only for irrigation, is improved by sedimentation to a quality comparable to that of most other surface waters. The clarified water then becomes suitable for crude industrial applications. Coagulation and filtration then virtually eliminate suspended solids and make the water suitable for general purposes. These include plant utility use without necessarily qualifying the water for process application. Beyond this point, the intended application determines the extent of treatment required. 

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