Relationship Between Growth Rate and Oxidation Rate

The ammonia oxidation rate can be related to the Nitrosomonas growth rate, as follows:

d dt

or in the differantiated form of Michaelis-Menten:

dSn dt

Table 3.5 Effect of ammonia concentration on nitrification and nitrifying bacteria.

Concentration of Ammonia-nitrogen mg/l


Condition of observation method of study


Ammonia oxidation, a zero order reation

Ammonia oxidation, a zero order reaction. No inhibition.

Film reactor; mixed culture

Activated sludge lab. scale

Huang (1973)

Metcalf and Eddy (1973)

Rate of ammonia oxida- Submerged filter Haug and McCarty (1972)

tlon; a function of receiving pre-oxygenated ammonia concentration feed.

(between first and second orders).

Michaelis constant for Pure culture; Nitrosomonas growth at Warburg respirometer 25 °C.

Painter (1970)

Michaelis constant Dropping-mercury for Nitrosomonas growth electrode; pure culture at 20 °C.

Loveless and Painter (1968)


100- 1000

Michaelis constant for Mixed continuous culture Poduska and Andrews gWi growth of ammonia oxidi- constant obtatined by (1975) zers at 23 °C. computer fit of experi mental data with assumed yield coefficient value.

Oxidation possible

Ammonia oxidation, a zero order reaction

Poultry waste; Repeated nitrification on a batch scale.

Lab. scale batch studies with mixed culture and mineral salt media.

10,1% oxidation possible Bench scale studies, activated sludge, synthetic waste derived from nitrified poultry waste.

Praksam efa/.(1974)

Wong-Chong and Loehr (1975)

Anthonisen (1974)

Table 3.6 Effect of nitrite concentration on nitrification and nitrifying bacteria.

Concentration of Nitrate-nitrogen mg/l


Condition of observation method of study



Activated sludge; lab.scale

Tomlinson, Boon and Trotmann (1966)

140, 160, 280, 700 and 1400

Rate of oxidation may be described by first order rate equations; decrease in rate constant with increasing initial concentration explained by MichaelisMenten kinetics.

Batch studies in a marine nitrifying filter system.

Srna and Baggaley (1975)

Nitrate toxic in the lag phase at all pH values; not so in the lag phase at alkaline pH.

Batch and pure culture of Nitrosomonas

Pokallus (1963)


Ammonia oxidizers not completely Inhibited

Mixed culture from an oxidation ditch; poultry waste: respirometric experiment.

Prakasam et ai (1974)



Causes 40% inhibition of Nitrobacter activity

Complete inhibition of Nitrosomonas.

Measured by decrease in oxygen uptake by bacteria

Boon and Laudelout (1962)

Painter (1970)

Table 3.7 Kinetic constants for nitrifying bacteria.


Max spec, growth rate d

Cellular yield

Ks g/m3

Ko2 g/m3




Marais and Ekema (1976)

Charley et al. (1980)



Painter (1977)

Sharma (1977)


Umax = Peak Nitrosomonas growth rate, day"1, dSn/dt = peak ammonia oxidation rate, mg NH4+ - N

oxidized /mg VSS/ day, Yn = nitrifying yield coefficient, mg Nitrosomonas grown

(VSS) per mg NH4+ -N removed, Sn = The substrate concentration, mg/l, Kg n = Saturation constant, NH4+ -N in mg/l, Xn = nitrifying mass cell concentration in mg/l,

If the substrate concentration S is much higher than Ks then equation (3.13) can be written as:

In equations (3.13) and (3.14) only the effect of ammonia concentration is considered; in later sections, the effect of temperature, pH, organics and dissolved oxygen are also discussed.

If the temperature, pH, organics and dissolved oxygen concentration are unknown, equations (3.13) and (3.14) are proposed. But if the indicated parameters are known, equation (3.37) will be more precise to use.

The growth rate of organisms can be related to the design of activated sludge systems by noting the inverse relationship between solids retention time and growth rate of nitrifiers:

where <|>c = solids retention time, days.

|i = growth rate of nitrifying organisms in day "1.

The solids retention time can be calculated from systems operating data by dividing the inventory of microbial mass in the treatment system by the quantity of biological mass losted daily (EPA 1975).

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