Parameshwaran, Kathiravelu creator Visvanathan, C. Chairperson Eckhardt, Ing. Heinz Examination committee Sompol Boonthanon Examination committee Swedish International Development Cooperation Agency (Sida) Scholarship donor text th Bangkok Asian Institute of Technology 1997 monographic eng

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126 leaves The possibility of using microfiltration hollow fiber membrane modules as air diffusers and solid/liquid separator in an alternative cycle for activated sludge process treating domestic wastewater was studied. The activated sludge system consist of anoxic and oxic zone for better nitrogen removal. Two hollow fiber microfiltration modules with the pore size of 0.2 æm were immersed in a 80 L oxic tank (.MBR) to effect the direct solid/liquid separation. Filtration and high pressure air backwashing were employed in an alternative cycle to have improved flux rate. Back washing of membrane with air in turn aerate the activated sludge in the reactor. By doing so, distinct advantages of declogging of membranes as well as aerating reactor contents were achieved simultaneously. In a short term experimental runs, it was found membrane modules are better air diffusers than stone air diffusers. It was also found that the increased back wash air pressure lead to an improved flux rate. In long term experiments, efficiency of membrane coupled bioreactor system at different hydraulic retention times (HRT) of 15, 10, 6 and 3 hours were studied. Wastewater was fed to the anoxic tank which in turn pass into the .MBR. Content of the .MBR was recycled to anoxic tank to effect denitrification. The average IvfLSS concentration in the system was varying between 12,000 to 14,000 mg/Land the sludge age in the .MBR was maintained at 50 days through out the study. Though the desired HRT could be maintained at 15, 10 and 6 h with a moderate transmembrane pressure only ( < 42 kPa) it was not possible in the case of 3 h. After two weeks operation in later case, stable HRT of 8.5 h at 96 kPa transmembrane pressure, could be obtained. Irrespective of the operating conditions, in all experiments COD, BOD, TKN and total nitrogen removal of more than 95, 98, 95 and 80 % respectively were achieved. This study establishes that using hollow fiber membrane capable of air backwashing to solid/liquid separation will lead to a situation of aeration of mixed liquor and declogging of membrane modules simultaneously, so conventional aerators can be eliminated. By using anoxic/oxic system efficient total nitrogen removal also can be achieved. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development Thesis (M.Eng.) - Asian Institute of Technology, 1997 Sewage Purification Reverse osmosis process Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B13926 http://203.159.5.9/ait-thesis/detail.php?q=B13926 20260818154840.0