The Influence of Temperature on the Nitrification Rate

The optimum temperature for the growth of nitrifying bacteria, according to the literature, is between 28° C and 36° C, although an optimum temperature of up to 42° C has been reported for Nitrobacter by Painter (1970). Growth constants of nitrifying bacteria are greatly affected by temperature (Table 3.9). Figure 3.2 shows that the nitrification rate is a function of temperatures between 5° and 35° C. The maximum growth rate occurs at approximately 30° C. Curve A, which was produced by Borchardt (1966) indicates that no sharp optimum temperature can be defined and that there is a plateau of maximum activity between 15° C and 35° C. Below 15° C however, the nitrification rate drops sharply, and is reduced by 50 per cent at 12° C. Wild et al. (1971) found (curve B) that an almost straight-line relationship exists between the nitrification rate and temperature. Similar temperature dependencies have been reported in single stage nitrification-denitrification schemes.

Data are also available on the effects of temperature on the oxidation of ammonia to nitrite by Nitrosomonas (curves E, F, G and H), and of nitrite to nitrate by Nitrobacter (curves C and D). Both species seem to be similarly influenced by temperature.

Randall and Buth (1970), however demonstrated that although both nitrite and nitrate formation were strongly inhibited at temperatures of 10° C or less, the inhibitory effect of lowered temperature was greater for Nitrobacter than for Nitrosomonas; this was evident from the nitrite build-up at low temperatures.

Barrit (1933) found that the thermal death point of a pure culture of Nitrosomonas was between 54° and 58° C. Almost no growth of nitrifying bacteria was found below 4° C.

Suspended growth cultures are more sensitive to temperature changes than biofilms (Murphy and Dawson 1972). The dependency on temperature of attached and suspended growths is illustrated below (Fig 3.3).

Downing et al. (1964) presented results for the relationship between temperature and saturation concentration Ks n and temperature and maximum specific growth rate n.. Their results are presented in Fig. 3.4. As can be seen, both the maximum growth rate, n and the saturation constants, Ks for Nitrosomonas and Nitrobacter are markedly affected by temperature. Further, the maximum growth rate for Nitrosomonas in activated sludge was found to be considerably less than for Nitrosomonas in a pure culture.

The literature suggests the following general relationship between the saturation constant Ks n and temperature t in °C.

Reference: EPA 1975; Nitrosomonas in river water and activated sludge.

Reference: EPA 1975; Nitrobacter in river water.

Reference: Watanabe et al. 1980 applied to suspended culture of nitrifier at T °C.

Fig. 3.2 The influence of temperature on the nitrification process, presented in the text as A to H, (Source: EPA 1975).

% of Nitrification Rate

% of Nitrification Rate

Nitrification Temperature

Fig 3.3 Comparison on the effect of the temperature on suspended growth and attached growth nitrification systems. A) to 0) are attached growth systems and E) is a suspended growth system (Source EPA 1975).

Table 3.8 The influence of temperature on the nitrification process.

Temperature

Degree of

Circumstances of

Reference

C

inhibition %

obsevation

15°-35°

0

Nitrification in

Borchardt (1966)

13°

25

activated sludge

12°

50

90

30°

0

Nitrification in

Wild et a/. (1971)

27°

10

activated sludge

17°

50

26°

0

Sutton etal. (1974)

21

53

30°

0

Nitrobacter in

Stratton and

McCarty (1967)

15°

60

river water

75

30°

0

Nitrobacter in

Knowles et al. (1965)

15°

62

estuary water

77

30°

0

Nitrosomonas in

Buswell et a/.(1954)

15°

70

pure culture

83

30°

0

Nitrosomonas in

Stratton and

McCarty (1967)

15°

75

river water

85

30°

0

Nitrosomonas in

Knowles et al.( 1965)

15°

80

estuary water

90

30°

0

Nitrosomonas in

Downing (1968)

15°

85

activated sludge

93

Knowles et al. (1965) proposed the following two relationships between temperature and the saturation constant for Nitrosomonas and Nitrobacter, following the Arrhenius law:

Neufeld et al. (1986) showed that the nitrification rate followed MichaelisMenten Kinetics and proposed the following relationship between KM and the temperature. KM was found to decrease in the temperature range of 22-30 °C in accordance with the equation:

and at temperatures > 30 °C KM was found to follow the expression:

The relationships between the effect of temperature t in °C and the maximum growth rate |imax in d "1 for nitrifying organisms:

Reference: EPA (1975); Nitrosomonas in river water and pure culture.

Reference: EPA (1975); Nitrosomonas in activated sludge.

Reference: Faup, G.M et al. (1982); Nitrosomonas in a UFBR (upflow fluid bed reactor). Temperature, t, between 9 °C and 20 °C.

IVx = 0,79*e0'69it"15) Reference: EPA (1975); Nitrobacter in river water. (3.26)

Table 3.9 Temperature dependence of the maximum growth rates of nitrifiers.

Source Knowles et al. (1965)

The literature shows that the relations obtained between the temperature and Ksn and the temperature and (imax are dependent upon the environment and test circumstances.

Somewhat differing temperature effects have been found for attached growth systems and suspended growth systems.

Comparing the suspended-growth and attached-growth nitrification data, one can conclude that attached-growth systems have an advantage in withstanding low temperatures (below 15°C) without significant reduction in nitrification rates. Measurements of nitrification rates for suspended-growth systems, however, are not normally made on the same basis as those made on attached-growth systems. In suspended-growth systems, rates are expressed on a per-unit-of-biomass basis (MLVSS is used). Precise measurements of biomass are normally not possible in attached-growth systems so other parameters are used, such as reaction rate per unit surface or volume.

Attached-growth systems can also compensate for colder temperature conditions by the biofilm growth growing thicker. If rates could be expressed on a unit biomass basis for both system types, the variation in reaction rates with temperature might thus be more similar.

Shammas (1986) showed that the effect of temperature on nitrogen kinetics fitted the popular modified Arrhenius relationship.

where

Ks n = maximum growth rate at temperature t (d "1).

K20 = maximum rate constant at 20 °C

b = temperature coefficient

8 12 16 20 24 28 32
Figure 3.4 The influence of temperature on a) Ks n and b) |a.max for the nitrification process, (EPA 1975).

Shammas (1986) also showed that b varies with the bacterial concentration calculated as MLVSS. Different values of b is shown in Table 3.10.

where

X = MLVSS concentration in mg/l. and b is constant with respect to pH.

The same authors reported that values of the nitrification rate constant Ks n ranged from 0,0085 d "1 at 4 °C and pH = 7 to 0,175 d "1 at 33 °C.

The temperature relationship to maximum specific growth by an exponential expression has been described by several authors (Zanoni 1969; Andersen and Poulsen (1976); Jenkins (1969) and McHarness et al. (1975)):

where:

Hm and |im ref are the maximum specific constants at temperature t and tref (0°C) respectively, and A is a constant for a specific temperature range referred to as the "temperature coefficient".

All studies mentioned in Table 3.11 were conducted under steady-state conditions, obtained with long-term temperature conditions.

Only very few studies were conducted with rapid temperature changes, and then only under marine conditions.

Table 3.10 Values of b with comparable values from different literature sources. The highest coefficient for b for ammonia oxidation in an activated sludge medium was reported by Downing et ai (1968).

Temperature Condition Reference coefficient b

Activated sludge ammonia to nitrate pH 7,0 to 8,3

0,028 0,059 0,121

MLVSS = 430 mg/l t = 4 MLVSS = 1200 mg/l t = 4 MLVSS = 3200 mg/l t = 4

°C to 33 °C to 25 °C to 25

°C °C °C

Shammas et al. (1986) il il

Ammonia to nitrite

Buswell et al. (1954)

Ammonia to nitrite Nitrite to nitrate

Knowles et al. (1965) il

Ammonia to nitrite Nitrite to nitrate

Stratton et al. (1967) il

0,120 0,075

Activated sludge

Ammonia to nitrite

Single stage activated sludge

Nitrification

Downing et al. (1968) Sutton et al. (1978)

From Shammas (1986).

From Shammas (1986).

Figure 3.5 Variation of maximum nitrification velocity with MLVSS concentration at different temperatures. (From Shammas 1986).

Table 3.11 Temperature coefficient for nitrifying bacteria.

Process

Range

Tnf

A

Vm'ref

Reference

Nitrogenous phase in BOD bottle analysis

10-22° C

20° C

1.097

0,12

Zanoni (1969)

Nitrification in suspended culture

5-20° C

20° C

1.12

-

Andersen and Poulsen (1976)

Nitrifying in treatment process

10-30° C

12° C

1,07

0,5

McCarty (1976)

II M

5-10° C

10° C

1,19

0,25

II II

Nitrosomonas in fill and draw pilot plant activated sludge

8-20° C

-

1,12

1,18

Jenkins (1969)

Nitrosomona in water from Thames estuary

8-30° C

15° C

1,099

0,47

Knowles et.al., from (1965)

Nitrobacter in water from Thames estuary

8-30° C

15° C

1,058

0,79

II II

Nitrosomonas in activated sludge

10-25° C

15° C

1,123

0,18

Downing & Hopwood (1964)

Nitrosomonas in pure culture

10-25° C

15° C

1,103

0,47

»

Attached separate culture

5-25° C

-

1,08

-

McHarness et etal. (1975)

Partly from Ohgaki and Wantawin (1990).

Partly from Ohgaki and Wantawin (1990).

+2 0

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  • Lobelia
    How temperature affects kinetic of nitrification?
    5 months ago

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