Using activated carbon to improve natural water treatment by porous membranes

Environmental transformations caused by the economic human activity generate rapid changes in surface water quality. The application of activated carbon in conjunction with microfiltration/ultrafiltration processes is an emergency technology for the removal of organic compounds from water for consumption purposes. This hybrid process (AC–MF/UF) utilizes the capabilities of activated carbon to adsorption of impurities and the microorganisms and particles removal ability of membranes. Ceramic membranes were applied and granulated and powdered activated carbon was used. Changes of volumetric permeate flux in time were estimated and the efficiency of the unit process was compared with the hybrid one, analyzing the physicochemical indexes of raw water and permeate. Two different methods have been proposed for the mathematical description of hybrid process of natural waters, that is: the model describing the changes of permeate flux in time, the “relaxation” model, and the model of filtration resistance.

Fig. 3. Dependence of experimental and theoretical volumetric flux on time for 19-channel and 7 channel ceramic membranes in the MF and MF+PAC processes: (a) relaxation model, (b) reversible resistance model. model Eq. (5). The dependencies obtained from model calculations as well as the measurement points are presented in Fig. 3.They confirm good correlation of the proposed model with the obtained experimental results. The resistance model connected with reversible fouling is true, but it necessitates a larger number of experiments to be carried out. It is necessary to characterize The hybrid process turned out to be more efficient and effective. Higher retention coefficients of the majority of the determined physicochemical indicators were obtained. The drop of volumetric permeate flux in the hybrid process was lower as compared with the unit process. It was reported that the addition of AC, which supports membrane filtration, was a good solution and it can be successfully applied in the hybrid process of water treatment for drinking purposes since the obtained waters had high physicochemical and organoleptic parameters meeting the requirements specified in the Regulation of the Ministry of Health and Social Care dated 4.09.2000 [14]. The presented models have so far not been used for the description of MF processes as combined with adsorption on AC, and the obtained high correlation coefficients of experimental results with the proposed mathematical description mean that the matching is good (Table 2 and Fig. 3). Having compared practical application of the proposed models describing the velocity at which volumetric permeate flux is decreasing in the filtration process of natural waters (unit process and hybrid process), priority is given to the relaxation model. When we know three quantities (J0, J4, t0) characterizing the MF– PAC process, we can predict the yield of the process. The resistance model connected with the fouling reversible is correct but it requires a larger number of experiments.