This research focused on use of mathematical models of the activated sludge process to determine the maximum treatment capacity of a full-scale biological nitrogen removal process at the Sai Kung Sewage Treatment Works. ASM No.1, modified ASM No.1 and ASM No.3 models were evaluated for prediction of the performance of this process using data over the past four years. The modified ASM No.1 model gave better prediction than the other two models, and therefore was adopted in this study. _{H H H A} ^{-1 -1 -1}...[ Read more ]

This research focused on use of mathematical models of the activated sludge process to determine the maximum treatment capacity of a full-scale biological nitrogen removal process at the Sai Kung Sewage Treatment Works. ASM No.1, modified ASM No.1 and ASM No.3 models were evaluated for prediction of the performance of this process using data over the past four years. The modified ASM No.1 model gave better prediction than the other two models, and therefore was adopted in this study.

To calibrate the modified ASM No.1 model, four key bio-kinetic constants (Y_H, b_H, μ_H , and μ_A) were determined experimentally, having values of 0.66 mg COD/ mg COD, 0.23 d^-1, 4.66 d^-1 and 0.60 d^-1, respectively in this study. The calibrated model was then validated by the dynamic performance data of the process obtained from the two full-scale stress tests conducted with the addition of urea and sucrose.

The model simulation results demonstrated a good agreement with the measured effluent quality under both steady-state and dynamic operational conditions, confirming the feasibility of using the calibrated activated sludge process model, i.e., the modified ASM No.1 model, to accurately predict the performance of a full-scale biological nitrogen removal process. In order to determine the maximum treatment capacity of this process, various simulations of the adopted model were conducted under different operating conditions. The results confirmed that the process studied can handle a maximum flow of 22,000 m³/d, when the MLSS concentration of the process could be maintained at 2,200 mg/L and the operation of final clarifiers is not affected.