10.2.6 Chemical Oxygen Demand (COD) and Biochemical
Oxygen Demand (BOD)
Especially for wastewater treatment and anaerobic digestion processes, different
types of chemical oxygen demand (COD) can be considered, based on its biodegradability, particulate, or soluble state. We distinguish so biodegradable and
nonbiodegradable COD:
– The biodegradable COD can be readily biodegradable and non-readily
biodegradable;
– The nonbiodegradable COD can be soluble nonbiodegradable or particulate
nonbiodegradable.
The chemical oxygen demand indicates the organic matter content of a feedstock
which can be chemically oxidized. The analysis can be performed through the
titration of unreacted potassium dichromate (Standards DIN 38414 (DIN 384148 1985) and APHA 5220 B (5220 CHEMICAL OXYGEN DEMAND (COD) 2017)
apply). Also spectrophotometry can be used or online UV-photocatalytic oxidation
(Dan et al. 2005). The COD is a direct representation of what is the maximum energy
contained in the chemical boundaries of the organic matter in the raw material. This
is in fact the measurement of the presence of potential reacting substances which can
undergo the anaerobic degradation process and produce biogas, at the net of the
energy needed to sustain the microbia converting biomass. Some of the COD is not
biodegradable, for example, the complex organic molecules. Raposo shows an
improved process for determining the COD of substrates with high total solid
content. Some reference data on different matrices are proposed in Table 10.4
(Raposo et al. 2008).
In reality, as above mentioned, COD is constituted by different fractions. As
presented in (Myszograj et al. 2017), the fractions of COD are indicated in the
following equation:
Table 10.4 COD content of different matrices (Kim et al. 2010)
Type of waste
Feedstock
Standard
deviation
Digestate
Standard
deviation
Sludge of municipal wastewater treatment plant
20,400
141
12,800
1992
Sludge of livestock wastewater treatment
plant
25,200
6505
15,833
2650
Sludge of food wastewater treatment
plant
26,300
1273
18,233
961
Organic rumen substance originated from
a slaughter house
26,750
5869
17,000
2600
10 Substrate Characterization in the Anaerobic Digestion Process
315
Oxygen Demand (BOD)
Especially for wastewater treatment and anaerobic digestion processes, different
types of chemical oxygen demand (COD) can be considered, based on its biodegradability, particulate, or soluble state. We distinguish so biodegradable and
nonbiodegradable COD:
– The biodegradable COD can be readily biodegradable and non-readily
biodegradable;
– The nonbiodegradable COD can be soluble nonbiodegradable or particulate
nonbiodegradable.
The chemical oxygen demand indicates the organic matter content of a feedstock
which can be chemically oxidized. The analysis can be performed through the
titration of unreacted potassium dichromate (Standards DIN 38414 (DIN 384148 1985) and APHA 5220 B (5220 CHEMICAL OXYGEN DEMAND (COD) 2017)
apply). Also spectrophotometry can be used or online UV-photocatalytic oxidation
(Dan et al. 2005). The COD is a direct representation of what is the maximum energy
contained in the chemical boundaries of the organic matter in the raw material. This
is in fact the measurement of the presence of potential reacting substances which can
undergo the anaerobic degradation process and produce biogas, at the net of the
energy needed to sustain the microbia converting biomass. Some of the COD is not
biodegradable, for example, the complex organic molecules. Raposo shows an
improved process for determining the COD of substrates with high total solid
content. Some reference data on different matrices are proposed in Table 10.4
(Raposo et al. 2008).
In reality, as above mentioned, COD is constituted by different fractions. As
presented in (Myszograj et al. 2017), the fractions of COD are indicated in the
following equation:
Table 10.4 COD content of different matrices (Kim et al. 2010)
Type of waste
Feedstock
Standard
deviation
Digestate
Standard
deviation
Sludge of municipal wastewater treatment plant
20,400
141
12,800
1992
Sludge of livestock wastewater treatment
plant
25,200
6505
15,833
2650
Sludge of food wastewater treatment
plant
26,300
1273
18,233
961
Organic rumen substance originated from
a slaughter house
26,750
5869
17,000
2600
10 Substrate Characterization in the Anaerobic Digestion Process
315