1. Organic Matter  Energy for Mircoorganisms
Carbonaceous Energy: Carbon as energy source
Heterotrophs
Nitrogenous Energy: Nitrogen as energy source
Chemoautotrophs

2. Energy Measurement (1) Theoretical Oxygen Demand (ThOD)
Chemical Oxygen Demand (COD)
Biochemical (Biological) Oxygen Demand (BOD)
Carbonaceous BOD (C)
Nitrogenous BOD (N)
Total Organic Carbon (TOC)

3. Energy Measurement (2) Theoretical Oxygen Demand (ThOD)
1. Carbonaceous demand: C  CO2; N  NH3
2. Nitrogenous demand: NH3  HNO2; HNO2  HNO3
3. ThOD = O2 req. in steps 1& 2
Ex. Glycine (10 mg/L) [CH2(NH2)COOH] (MW = 75 g/mol)
1. Carbonaceous demand
CH2(NH2)COOH + 1.5O2  2CO2 + H2O + NH3
2. Nitrogenous demand
NH O2  HNO2 + H2O; HNO O2  HNO3
3. ThOD = [1.5 + ( )] mol O2/mol glycine
= 3.5 × 32 g O2/mol = 112 g O2/mol
= 112  75 g/mol = 1.49 g O2/g glycine
Thus, ThOD = 1.49 x 10 mg/L = 14.9 mg/L
Cannot be used if chemical composition is not known.

4. Energy Measurement (3) Chemical Oxygen Demand (COD)
O2 req. for oxidation of organics
Oxidize carbonaceous matter with a strong oxidant (e.g., hot dichromate sol. with sulfuric acid)
Reduction of O2
4e- + 4H+ + O2  2H2O
1 mole of O2 (32 g)  4e- equivalents
1 g COD  1 g O2  1/8 electron equiv.
NH3 not oxidized (carbonaceous energy only)
Aromatic hydrocarbons (benzene and toluene) and pyridines are not oxidized.
H2SO4
Heat
Catalyst
silver sulfate
Dichromate

5. Domestic Wastewater COD Fractionation
Influent COD
(Sti)
Biodegradable
COD (Sbi)
100%
Unbiodegradable
COD (Sui)
Sol. readily
biodegradable
COD (Sbsi)
~80%
Partic. slowly
biodegradable
COD (Sbpi)
Soluble
unbiodeg.
COD (Susii)
~20%
Particulate
unbiodeg.
COD (Supi)
~20%
~60%
~7%
~13%

6. Energy Measurement (4) Biochemical (Biological) Oxygen Demand (BOD)
O2 required for microbial decomposition
Oxygen consumption by microorganisms
BODu
Nitrogenous
energy
DO consumed, mg/L
BOD5
Inadequate to assess the electron donor capacity; after 5 days, still some biodegradable matters exist.
Carbonaceous
energy 5
~30
Time, days

7. Energy Measurement (5) Biochemical (Biological) Oxygen Demand (BOD)
Carbonaceous BOD: aerobic heterotrophs
Decompose organic molecules to minerals (CO2) and residues
Obtain their cell carbon from the organic material
Nitrogenous BOD: obligate aerobic chemoautotrophs
Character of nitrifiers (chemoautotrophs)
DO < 2 mg/L action slow
DO < 0.5 mg/L action ceases
Optimum pH: 8.3
More sensitive than heterotrophs to toxins
Slow growers (longer sludge age required)

8. Inert Organic Matter Measured with COD
Not biodegraded, thus not measured with BOD5
Polymerized waste product
Inert material from lysed cells
Refractory organics: humic acid (M.W ~100,000); fulvic acid (2,000~10,000)
Certain high M.W. carbohydrates alone or in combination with humic material are resistant to microbial attack.
High M.W. carbohydrates are excreted at the end of the logarithmic growth phase and help forming flocs by bridging of bacterial cells.

9. Influence of Acclimated Biomass on COD of Treated Wastewaters
BOD5 equivalents
Total COD – BOD5
COD, mg/L
Not readily
Biodegradable
COD
Non-biodegradable
COD
Untreated
Raw
Treated with
unacclimated
biomass
Treated with
acclimated
biomass
BOD: Not affected by acclimation
COD: Significantly affected by acclimation

10. BOD, CODCr, CODMn, TOC Organic matter TOC CODCr Cl-, H2S CODMn
Biodegradable
Unbiodegradable
TOC
CODCr
Cl-, H2S
CODMn
Cl-, H2S
BOD5
Nitrification

11. Energy Measurement (6) Total Organic Carbon (TOC)
Oxidize in a combustion chamber with O2
Easy to measure
TOC values are very similar for both glucose and glycerol; however, COD values are quite different.
Thus, waste specific; cannot apply the result to other WWTPs.
Good as an operational tool with previous historical data.
Glucose, C6H12O6 (M.W. = 180)
C6H12O O2  6 CO H2O
6 moles O2  6  4 = 24 e-
24/6 = 4 e- available per unit organic C
Ex. 100 mg/L of glucose: TOC and COD = ?
TOC: (6  12)/180  100 = 40 mg/L C
COD: (6  32)/180  100 = 107 mg/L O
Glycerol, C3H8O3 (M.W. = 92)
C3H8O3 + 7/2 O2  3 CO H2O
7/2 moles O2  7/2  4 = 14 e-
14/3 = 4.67 e- available per unit organic C
Ex. 100 mg/L of glycerol: TOC and COD = ?
TOC: (3  12)/92  100 = 39 mg/L C
COD: (3.5  32)/92  100 = 122 mg/L O
Similar
Different

12. Energy Measurement (7)
BOD5/COD ratio: a good indicator for biodegradability of a specific wastewater
Domestic wastewater
BOD5/COD ­ 0.4 ~ 0.8
BOD5/TOC ­ 1.0 ~ 1.6
BOD5/COD  0.6: can be decomposed completely, biological treatment feasible
BOD5/COD  0.2: cannot be decomposed easily, chemical or physical treatment desired
BOD5/COD  0: has toxic materials

13. TOC Analyzer
Measure the amount of total organic carbon present in a liquid sample;
Convert inorganic carbon in the sample to CO2 after adding acid and strip CO2 by a sparge carrier gas;
Oxidize organic carbon by either combustion, UV persulfate oxidation, ozone promoted, or UV fluorescence; and
Measure CO2 stripped using the conductivity or non-dispersive infrared (NDIR) detection system.
On-Line TOC Analyzer: a reagentless analyzer designed for continuous monitoring of organics.

14. Use of BOD5, COD, and TOC COD
Good for regulating organic loading to a receiving water body for DO depletion by heterotrophs
Not good for design since some organics biodegrade slowly or after acclimation
COD
Not good for regulation since it does not reflect true organic loading impact to aqua systems
Good for design if the input and output within a biological system is monitored; true energy count for carbonaceous energy only
TOC
Good for operating a wastewater treatment plant due to real time monitoring capability
Values cannot be transferred to other wastewater due to specificity of carbon in the wastewater in terms of electro donor capability