Design of novel ultrafiltration systems based on robust polyphenylsulfone hollow fiber membranes for treatment of contaminated surface water

This work focuses on development of robust but economical hollow fiber ultrafiltration systems that could be operated with or without electric power to treat polluted surface water. A diverse experimental study was carried out to synthesize novel hollow fiber membranes based on polyphenylsulfone (PPSu) and polyvinylidenefluoride (PVDF) fibers for surface water treatment. A manual hollow fiber spinning machine incorporated with an inexpensive spinneret was designed to fabricate hollow fibers from dope compositions of 20wt% PVDF in DMAc and 20wt% PPSu in NMP by phase inversion technique. Isothermal ternary phase diagrams of PVDF or PPSu/solvent/non-solvent systems were established using three different solvents such as N,N-dimethylacetamide (DMAc), 1-methyl-2-pyrrolidinone (NMP) and N,N-dimethylformamide (DMF) with water being the non-solvent. The indigenous fibers had an approximate outer diameter of 1.5mm and the wall thickness of 0.25mm and were housed in inexpensive PVC and UPVC tubes using epoxy resin and nylon end connectors. PVDF hollow fibers (HF) exhibited 94.8% turbidity rejection, whereas PPSu fibers exhibited 91% rejection with 5 log E-Coliform reduction from surface water at a low hydraulic pressure of 1bar with high flux values of 125Lm-2h-1 and 73Lm-2h-1, respectively at a substantial water recovery of 80%. A water purification device capable of generating 25Lh-1 purified water flow at an overhead tank pressure of 0.5bar was designed and fabricated for households along with a hand pump operated submerged ultrafiltration (UF) system for treatment of surface water in flood prone regions. Detailed economic estimation of the indigenously designed water purification device for household purpose is presented which shows a low operating cost of 0.02 US $ per liter of purified water obtained