A research study 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, 1986

Laboratory scale experiments were conducted to investigate the interactions between the attached and dispersed growth microbial behaviors in activated sludge reactors with sludge recycle. At a 10 d SRT, the performance of the attached growth activated sludge process(AGASP) with various amounts of contact media, such as 5%, 10%, and 20% of reactor volume, was investigated by comparing its effectiveness to the conventional one at various organic loadings of 0.81, 1.44, 2.01, and 3.18 kgCOD/m3. d. AGASP showed more effectiveness than the conventional unit (at 99% of significance level by the t-test). Oxygenation parameters, a & b in AGASP, were also obtained in the range of 0.3-0.5 for a and 0.004-0.054 for b, respectively. The kinetic coefficients k , K., Y, and Kd. for AGASP were found using the LAWRENCE and McCARTY's models and appeared to be in the range of 1-2 d-1, 20-50 mg/l, 0.4-0.8, and 0.14-0.22 d-1, respectively. Computer simulation of the performance of AGASP was also {u2022} conducted using system dynamics simulation model(Attached-Dispersed growth Microbial Interaction Model, ADMIM). Even though this model showed simple results with a little sensitivity, better simulation of the performance of AGASP can be expected by considering other important parameters of the system.