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, 1988

Laboratory experiments were carried out on Attached Growth Activated Sludge Process (AGASP) with volume of attached-growth media in the aeration tank varied at 5%, 10%, and 15% of the aeration tank volume. Different organic loadings (F /M ratio) and different solid retention time(9 ) of the reactors were operated to investigate the c process kinetics and process efficiency. The experiments were carried out in three phases. In the first phase, the 9 were varied from 5 days c to 20 days at a constant organic loading of 0. 3 kg COD/ (kg MLSS. d). In the second phase the optimum 9 was fixed while the organic loadings c were varied from 0. 3 to 1. 0 kg COD/ (kg MLSS. d). Synthetic waste (sodium acetate and ammonium sulfate as main ingredients for carbon and nitrogen sources) was utilized as feed. The hydraulic retention time(9) and influent NH3 -N concentration were maintained at 8 hours and 65 mg/L, respectively, throughout the first two phases of experiments. In the third phase the 9 and the Organic Loading were fixed c at 10 days and 0.3 kg COD/(kg MLSS.d), respectively while the in fluent NH3 -N concentration was increased to 100 mg/L . Experimental results from the first phase revealed that the 9 c of 10 days in all AGASP reactors provided the optimum process efficiency with respect to Carbonaceous and nitrogenous compound removal. At this 9c the carbon (COD) removal was 97% and NH3 -N concentration in the effluent was not detectable. In the second phase, complete NH3 -N removal was observed in the AGASP reactors with 5% and 10% media at organic loadings between 0.3 - 1.0 kg COD/(kg MLSS . d). The COD removal in all four reactors we re between 94% - 98%. In third phase, when the AGASP reactors were fed with a high strength nitrogenous waste (NH3 -N = 100 mg/L). The AGASP reactor with 15% media gave t he optimum NH3 -N removal efficiency of 95%. The experimental results obtained suggested that the installation of 10% media in the aeration tank of an activated sludge reactor will provide a high degree of COD and NH3 -N removal. AGASP with 10% media was found to produce an effluent which should effluent standards when operated at organic 1 . 0 kg COD/(kg MLSS.d) . satisfy most stringent loadings be tween 0.3 - A mathematical model established based on a comination of MONOD expression and diffusion equation could predict the effluent quality of t h e AGASP .