Removal of sub-micron size and dilute turbidity from service water by application of an electrochemical carbon filter

A semi industrial scale graphite felt electrochemical filter (ECF) assembly has been used to remove iron and silica turbidity from domestic service water of Kalpakkam. Two test runs are performed. In the first run 17.21 m of water is processed and 2.15 × 10 NTU-liter turbidity is removed [inlet turbidity 1.67 NTU (nephelometric turbidity units), outlet turbidity 0.42 NTU, and efficiency 75%]. In the second run 6.67 m of water is processed and 3.87 × 10 NTU-liter turbidity is removed (inlet turbidity 0.85 NTU, outlet turbidity 0.27 NTU, and efficiency 68%). In this process non-reactive silica removal efficiency of 50% is observed. Nearly complete removal of E.coli is also shown by ECF. It is observed that 600-1200 l/h flow rate and 5.0-8.0 V applied potential with 1 ampere current are the optimized parameters for ECF operation. Teflon is identified as non swelling material in water for the carbon felt electrode isolation spacers and support plates. As ECF is exclusively used for submicron filtration, a macro filter prior to it is must. The ECF has the advantages of treating turbidity irrespective of the sign and magnitude of charge on the turbidity particles as the applied potential can be maneuvered accordingly.