MBR suppliers are largely recommending NaOCl as the cleaning agent. Despite the popularity of this chemical for membrane cleaning, there is a lack of publications regarding NaOCl optimum cleaning conditions. To properly conduct this optimization study (i.e. obtain the required level of reproducibility and confidence), a rigorous methodology is still required. The potential effect of NaOCl on polymeric materials ageing has drawn attention and recent studies have been dedicated to assess the impact of its exposure on numerous membrane materials (except polyvinylidene fluoride (PVDF)). PVDF and polypropylene (PP) hollow fibers were investigated using unwashed yeast as model fouling solution, while mixture of sodium alginate and bovine serum albumin (BSA) acted as feed solution for PVDF flat sheet. The cleaning efficiency and optimum NaOCl concentration were found to vary between the different membrane materials and between single and cyclical cleanings. During cyclical cleaning, foulant was more difficult to remove. When 2% NaOCl was used, Fourier Transform Infra Red (FTIR) Spectroscopy showed a change in membrane function groups on PVDF flat sheet, indicating ageing occurrence. NaOCl agemg caused changes in membrane properties. PP hollow fibers became more brittle with 60 % elongation decrease after 13 weeks. PVDF flat sheet membrane exhibited two-steps-degradation mechanism; firstly, the removal of its surface modification substance, and secondly, the increase of its hydrophilicity. These results were confirmed by X-ray Photoelectron Spectroscopy (XPS), FTIR Spectroscopy, contact angle and hydraulic measurement. Enzyme is an alternative option for membrane cleaning. However, the enzymatic cleaning study did not present encouraging results. Optimum cleaning efficiency for protease (68%) and amylase (73%) were found to be lower compared to NaOCl cleaning (95%). Lowry and Dubois methods found that residual foulants were present on the membrane after the cleaning process, which caused fouling to occur faster when membrane was re-used.
| Identifer | oai:union.ndltd.org:ADTP/258683 |
| Date | January 2009 |
| Creators | Puspitasari, Vera Liany, Chemical Sciences & Engineering, Faculty of Engineering, UNSW |
| Publisher | Awarded by:University of New South Wales. Chemical Sciences & Engineering |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Puspitasari Vera Liany., http://unsworks.unsw.edu.au/copyright |
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