A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1989

Direct membrane separation using 0.45 micron pore size of microfiltration hol1ow fiber membrane was applied to wastewater treatment in an activated sludge process. This thesis work included two parts of the experiment laboratory-scale experiment and pilot-scale experiment. In the laboratory-scale experiment, each membrane module with a pore size of 0.45 pm and a surface area of 0.3 m2 was immersed in the different reactors which have different depths of the settling zone but the same working volume of 0.02 m3{u2022} The membrane was placed in the aeration zone which had a continuous air flow of about 1.50 L/min. Treated water was permeated through the membrane by gravity. Domestic wastewater collected from AIT sewage pipe was fed to the reactors and operated at hydraulic retention time (HRT) of 1 day and 0.5 day. The COD removal was higher than 93% and faecal coliform was completely removed. Since the sludge was not removed from the reactor except for sampling, a steady state· was attained after the microbial growth balanced with endogenous respiration. The process attained high stability in terms of transmembrane pre~sure and COD removal efficiency because no severe clogging and good treated water quality were observed. In the pilot-scale experiment, 0.45 pm pore size of microfiltration hollow fiber membrane was immersed in a tank with a volume of 1 m3. By using a centrifugal pump suction pressure was applied at a 1 day hydraulic retention time (HRT). AIT sewage was fed to the tank and intermittent suction (10:10) was operated. At 0.111 m3/(m2d) permeate flux, the stable operation in terms of both transmembrane pressure (0.952 m) and COD removal efficiency was achieved. Fecal coliform removal efficiency was 100 %.