Reaction rate constants and mean population percentage for nitrifiers in an alternating oxidation ditch system

Abstract

This paper presents a methodology for the determination of reaction rate constants for nitrifying bacteria and their mean population percentage in biomass in an alternating oxidation ditch system. The method used is based on the growth rate equations of the ASM1 model (IWA) (Henze et al. in Activated sludge models ASM1, ASM2, ASM2d, and ASM3. IWA Scientific and Technical Report no. 9, IWA Publishing, London, UK, 2000) and the application of mass balance equations for nitrifiers and ammonium nitrogen in an operational cycle of the ditch system. The system consists of two ditches operating in four phases. Data from a large-scale oxidation ditch pilot plant with a total volume of 120 m(3) within an experimental period of 8 months was used. Maximum specific growth rate for autotrophs (μ(A)) and the half-saturation constant for ammonium nitrogen (K(NH)) were found to be 0.36 day(-1) and 0.65 mgNH(4)-N/l, respectively. Additionally, the average population percentage of the nitrifiers in the biomass was estimated to be around 3%.

Effect of operational cycle time length on nitrogen removal in an alternating oxidation ditch system

“…The input data of the model for this example are average experimental values, taken from 1 month of the experimental period, with many measurements and thus better serve this case [14]. This month had an average influent (TKNin) concentration of 56.2 mg/' and the nitrogen used for synthesis was about 10% of TKN in [13]. This leaves a concentration of 50.6 mgN/' for nitrification and denitrification.…”

“…Among them, the simplest is the D-ditch (two ditches without separate settlement tank), which is a very stable system, achieving high effluent quality. Under controlled operation, it can easily perform nitrification and denitrification and thus achieve a high total nitrogen removal [13].…”