Membrane fouling of AnMBR in hyper saline condition

Membrane fouling problem is one of the most crucial issues which restricts the development of MBR and is, therefore, the prime research topic for many researchers worldwide. Anaerobic MBRs offer interesting perspectives as a potential solution for the treatment of wastewaters under extreme conditions, e.g. high temperature and/or high salt content, However, the research on membrane fouling of AnMBR system is still limited. Therefore, in this Master Thesis the research is focused on the flux determining conditions of AnMBR systems in hyper saline environment. Hyper saline environment is those containing salt concentration in excess of seawater which is 35g/l. The conditions of AnMBR in hyper saline environment are quite different from aerobic MBR system, so the measures applied in aerobic MBRs to prevent membrane fouling may not be useful in AnMBRs in hyper saline environment. In the first series of experiments of this thesis work, the efficiency of existing measures, which are applied in full-scale aerobic MBRs to prevent membrane fouling, are evaluated for application in AnMBRs under hyper saline conditions. Because the concentration of NaCl in hyper saline wastewater is quite high and NaCl can be used as flocculant (Mietta et al., 2009), one of the experiments was designed to induce proper shear force to the AnMBR reactor to test whether this manner could alleviate membrane fouling. Unfortunately, the result of this experiment was negative and membrane fouling was still serious. Then LCFA was added to the reactor to check its short-term effect on alleviating membrane fouling (Stumm and Morgan, 1995). The result showed that LCFA could not reduce membrane fouling within short time. Because the results of these measures in alleviating membrane fouling in AnMBR in hyper saline environment were not satisfactory, the second series of experiments of this thesis work were designed to analyse the foulant constituents of AnMBRs in hyper saline environment and their characteristics. The results of the second series experiments showed that sodium, calcium, iron and potassium were the main metal ions in cake layer. Likely, ion-exchange activities between calcium ions in the cake layer and sodium ions in the liquid phase were apparent under the hyper saline conditions in lab-scale AnMBR experiment. The functional groups of organic foulants on the fouled membrane were alkanes, carboxylic acid, nitro compounds, alkyl halides and alkenes in this research and chemical cleaning could only remove part of organic foulants. Membrane fouling of AnMBR in hyper saline environment …