2.2.2. Kinetics model establishment

Adopted system device is shown in Fig. 32. The relationship among microbial growth, the initial concentration of microbe and that of the substrate is the key factor to establish the degradation kinetics model. The relationship can be reflected by various models and the Monod equation is universally acknowledged as the practical model[61]. For water treatment field, the specific degradation velocity of the substrate is more practical than the specific growth velocity of microbe. Considering the specific degradation velocity of the substrate according to the physical law, the equation below is founded[62]:

_ dC = v XC

dt max Ks + C

Wherein, stands for the degradation velocity of organic substrate; C stands for residual dt

organic substrate concentration in mixed liquor after a reaction time t; Ks stands for saturated constant; vmax stands for the max specific degradation velocity of organic substrate.

In the equation, C is the key factor for calculating kinetic equation. When Ks > C, the equation below is founded:

_ — = k, XC
dt 1

When Ks< C, the equation below is founded:

_ A = k2X

dt 2

Figure 32. Illustration of material balance

Taken X (biomass) as horizontal coordinate and dL as vertical coordinate, if the diagram

obtained is linear, the model belongs to high matrix organic degradation, while if the diagram is in exponential form, the model belongs to low matrix organic degradation.

As both BAC and BCF have a homologous microbial characteristic, by drawing an analogy with the degradation model of BCF, the BAC biodegradation effect can be described. According to the experimental system, material balance can be established which is shown in Fig. 32.

As shown in Fig.32, according to material balance law, along the section, the equation below is founded:

In which AC can be calculated by each C of all the sections, A t can be calculated by the height of filter through each section and the filter velocity; the biomass of each BCF section represented by X can be measured, hence, taking biomass as the horizontal coordinate, ACi/A tof each section as the vertical coordinate to conduct linear regression analysis so as to determine the type of biodegradation model.