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

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)

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 NH3 + 1.5O2  HNO2 + H2O; HNO2 + 0.5O2  HNO3 3. ThOD = [1.5 + (1.5+0.5)] 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.

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

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%

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

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)

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. - 5000~100,000); 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.

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

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

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) C6H12O6 + 6 O2  6 CO2 + 6 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 CO2 + 4 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

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

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.

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