Question 2: Impact of temperature on microbial growth

Temperature is one of the key factors that influence microbial growth. Given that the average summer temperature is 20°C and the average winter temperature is 7°C, draw a graph representing the average heterotrophic bacteria growth rate for summer and winter using the information given below.

The Monod equation for bacterial growth is defined as :

\(\dfrac{dX}{dt}=\mu\cdot X\text{ with }\mu = \mu_{max}\dfrac{s}{(K_{s}+s)}\)

With:

• X = Biomass concentration
• S = Substrate concentration
• K_s = Monod coefficient (substrate affinity)
• μ = Growth rate
• μ_max = temperature dependent and the relationship represented in the equation below:
• \(\mu_{max,T}=\mu_{max,20}\theta^{(T-20)}\)

The different parameters are given in the table below. 

	Parameter	Value	Units
	\(K_{s}\)	5	g BOD/m3
At 20 °C:	\(\mu_{max}\)	6	g VSS/g Vss.d
At 20 °C:	\(\theta\) for calculating: \(\mu_{max,T}\)	1.07	-