A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1992

An integrated approach of de scribing the s ubstrate removal in a facultative pond by s u s p ende d b i omass in the pond liquid and biomass attached to the inner walls and pond bottom (biof ilm) was attempte d. Mathematical models were developed to combine the effect s of s uspe nded biomass and biof ilm on t h e s ubstr ate remova l kinetics. Monod kinetics a nd first order kine tics were u sed in four different combi nations in developing t he mode l s. Batch experime n ts were conducted to determine the kinetic coefficients for suspended biomass and biofilm separately. It was found from t h e study t h at t h e maximum substrate utilization rates , under the conditions of facultative pond, were approximately 8 times l ower than the typical valu e report ed i n t h e literature for activated s ludge process. The de ve lope d mode l s were tested with the data obtained from a n AIT facultative pond, a nd a facultative pond l ocated i n New Mex i co , USA, moni tored for one year . It was found from the study that, the efflu e n t BOD5 predicted from the mode l u sing f irst order kinetics for both s u spended biomass and biofilm, fits reasonably we ll with the experimental data from a facultative pond of AIT campus and a pond of Ne w Mexico, U.S . A. A design c hart was prepared based on the model using first order kinetics for both s u spended biomass and biofilm. An examp l e was included t o design a f acultative pond based on BOD5 remova l efficiency and incorporating t h e e ffect of biof ilm in the design procedure.