Bısbal ilaveli hollow fiber membran üretimi ve karakterizasyonu: Membran biyoreaktör (MBR) uygulaması

Water scarcity is one of the most important problems of our world. In 21st century, demand of water is getting higher day by day because of increasing population and limited supplies. Treatment and reuse of available water is an important issue for providing water. At the last years, membrane filtration systems have been a popular alternative as advance treatment processes because of their advantages such as low space requirement, easy application and no need for chemical additives when comparing with the conventional systems. With the improvement of advanced treatment technologies, managing and solving emerging water crisis of the world can achieved practically. There are some challenges for the application of membrane filtration systems such as fouling which is the major problem for the operation of membrane processes. Especially, biofouling is the most challenging problem in membrane bioreactors. For solving this problem, some approaches were improved and experienced. The better and more effective way is modification of the membranes before the occurrence of fouling by an enhancement of its structure with antibacterial additives. Improvement of membrane properties at fabrication can be effective and useful for solving the problem. In this study; fabrication and characterization of polyethersulfone (PES) ultrafiltration hollow fiber membranes with an antibacterial additive and investigating its antibiofouling effects with an application of submerged membrane bioreactor were objected. To achieve our aim, BisBAL which is one of the bismuth thioles, known as its antibacterial features, was used as an additive. Ultrafiltration hollow fiber membranes were spun by using phase inversion method. The amount of BisBAL additive was selected as 30µm. according to previous study (Durmaz, 2014). For choosing the optimum dope recipe, many trials were done with pristine and enhanced with BisBAL additive membranes. After choosing the optimum recipe (18 % PES, 7 % PVP K90, 75 % NMP), membranes were fabricated with and without additive (called as enhanced and pristine in order of term) for different spinning parameters. Air gap, take-up speed were changed in these spinning parameters. After spinning, post treatment process applied for all membranes with NaOCl for 2 days. Then, they were prepared as modules. All characterization experiments were done by these modules. Permeability, porosity, contact angle, water flux recovery, total fouling ratio, BSA rejection rate, mechanical stability and surface morphology assessment (by scanning electron microscopy (SEM), optic profilometer and stereo microscopy) of the membranes were measured and calculated. Then, the membranes (pristine and enhanced with BisBAL additive) were fabricated again with the selected spinning condition (air gap: 0 cm, take-up speed: 7.1 m/s, coagulation bath temperature: 35 oC) which had the best results. According to characterization results, membranes were fabricated properly which had circular shapes as expected. Effects of BisBAL observed with images of membranes clearly. It was monitoring that pristine membrane had structure as finger-like that was changed to sponge-like with BisBAL additive. Also enhanced membrane with (30 µm.) BisBAL addition had better permeability, mechanical stability and less fouling properties, contact angle degree (more hydrophilic). Antibacterial properties of the membranes were found using with Escherichia coli which was taken from "Microorganism Culture Collection Research and Application Center (KÜKENS) of Turkey". Pure culture bacteria species were growth on membranes during 6 days at 37 °C in Standard Plate Agar. After incubation, the growth degree of E. coli was observed visually. Less growth found on enhanced (with BisBAL) membranes. According to the results, enhanced with BisBAL additive membranes showed more antibacterial properties than pristine membranes. Hollow fiber (dead end) filtration modules were immersed into an aerated batch bioreactor (6lt.) that fed with synthetic wastewater. To investigate antibiofouling effects of the enhanced membrane with BisBAL additive, system has been operated for 30 days. Throughout the MBR application; flux, COD, VSS and SS were measured and calculated on daily basis. Average suspended solid amounts of mixed liquor was 16000 mg/l. COD removal percentages and flux rates were higher for enhanced membrane than pristine. Because of the parallel correlation between biofouling and EPS-SMP amounts, that was explained at the literature review section, EPS-SMP experiments were done on pristine and enhanced membranes at the end of the MBR operation. EPS-SMP values of enhanced HF membrane were lower than pristine as expected. These results proved the antibiofouling effect of BisBAL. Also, confocal scanning laser microscopy images were taken for observing the deposition of organic matter and fouling rates on the surfaces at 25th, 27th and 29th days of membrane bioreactor operation. Formation of biofilm layer was observed on surfaces of both membranes but biofilm layer thickness of pristine was more than enhanced membrane. All results demonstrated that antibiofouling features of BisBAL.