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High purity water, free of microorganisms, can be used for various purposes in medical treatments, semiconductor industry for the manufacture of chips and electronic devices etc. The main aim of the present work was to modify positively the surface of filtermedia for capturing negatively charged contaminants mainly bacteria and virus from water. Scanning electron microscope (SEM) and atomic force microscopy (AFM) are employed to characterize the modified surface. Also, the characteristics of charge modification are quantified in terms of surface zeta potential of filter media and filtration efficiency.The most widely used mechanism of filtration is the mechanical sieving process, but this process usually has the characteristics of the high pressure drop and low filtration efficiency. Whereas in the case of the electrokinetic capturing mechanism, contaminants are retained on the surface by attractive short range Van der Waal's forces as shown in Fig.1. It is not necessary that the pore size is smaller than the particle size. Therefore, the filter media modified with electropositive charge modifier is developed and evaluated in order to increase the filtration efficiency. The modified filter media, which has an average pore size of 0.7 ㎛, was made of cellulose (15 ㎛), glass fiber (800 ㎚) and charge modifier [1]. There are two types of resin deposition onto the filter surface such as coverage and surface coating, which are given in Fig.2. Fig. 3 shows the topography images of the modified filtermedia (sample #4). The surface of fibers modified by resins is irregularly rough and the average diameter of fibers is increased by the surface coating. High performance XE-100 AFM (PSIA Corp.) was used as a tool to scan a sample by 10 ㎛ｘ10 ㎛ [2]. A non-contact ultrasharp silicon cantilever (NSC15 series) with Al coating on the laser-reflection side was used. As shown in Table 1, the zetapotential values and separation efficiencies of the non-modified/modified filtermedia are -32/+45 mV at pH 7 and 3%/91% for PSL particles of 0.11 ㎛, respectively.In this study, the investigation of the microstructures of filtermedia surface on a nano-scale was carried out to understand resin features and amount of coverage by utilizing SEM and AFM. The filtermedia samples were proven to be charged positively according to the measurement of the zetapotential and filtration efficiency. This filtermedia shows the potential to be an effective method for removing fine particles (virus, bacteria etc) from the contaminated water for liquid filtration.