Synthesis and characterization of novel polymeric membranes for water purification and effluents treatment

摘要

The lack of good quality drinking water in certain regions of the world is a serious issue for the people that live in these regions. The main options for overcoming this are to discover new sources of water or to treat contaminated raw water to produce good quality drinking water. A significant amount of research has focused on the development of suitable methods to obtain fresh water and to enable water reuse. The main focus of this research project was to develop and test hollow fiber membranes for removing pollutants from surface water and ground water (production of potable water), and to develop membranes/membrane based processes for removing pollutants from industrial waste waters. The removal of contaminants from surface water was investigated using six different types of hollow fiber membranes (Polyethersulfone (PES), Polyacrylonitrile (PAN), Polyvinylidenefluoride (PVDF), Polyphenylsulfone (PPSu) and polymeric blend solutions such as PVDF/PAN and PES/Polyetherimide (PEI)). The hollow fiber membranes that were studied were synthesised using a dry-wet spinning method. The best performing hydrophobic membrane (for treatment of surface water) was the PVDF hollow fiber membrane. This membrane achieved 94.8% of turbidity rejection at a low hydraulic pressure of 1 bar with a flux of 125 L/m2h, whereas the PES membrane achieved 95.4% of rejection with a flux of 54.2 L/m2h. The results obtained for the hydrophilic membranes, showed that the PAN membrane had a higher rejection of 99.8% when compared to a PPSu membrane of 91% with a flux of 54.2 L/m2h and 73 L/m2h (at 1 bar) respectively. The PVDF/PAN membrane gave the following performance results: high flux of 120.1 L/m2h and turbidity rejection of 99.5% at 1bar pressure, whereas PES/PEI membrane exhibited 73.8 L/m2h with 99% rejection of turbidity during treatment of surface water. The removal of contaminants from groundwater was investigated using thin film composite (TFC) reverse osmosis (RO) polyamide membranes that were synthesized by an interfacial polymerization method on an ultraporous polyethersulfone (PES) substrate, made by phase inversion technique. Hydrophilized polyamide RO membranes have shown a flux of 51 L/m2h and a fluoride rejection of 93% at a pressure of 15 bar with 60% water recovery. Based on the excellent results obtained a pilot scale RO system was built indigenously to incorporate and test the synthesized membranes. After extensive process standardization studies on a laboratory scale, a commercial defluoridation plant was designed for deployment in different villages across India. The treatment of dairy industrial wastewater and domestic wastewater for water reclamation was investigated using a promising alternative technology, membrane bioreactor technology. A bench-scale aerobic membrane bioreactor of 100 L volume feed capacity was designed in which fabricated shell to tube side feed flow type hollow fiber membrane modules were submerged. The effect of different parameters such as suction pressure, air blowing rate and chemical cleaning on membrane fouling was investigated. A computational fluid dynamics (CFD) based hydrodynamic simulation has been included in order to understand the operational performance of the module under different parametric conditions.