2-Contaminants+of+Interest+student+version.pdf

18 1242019 10 lumped measures of organic compounds

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1/24/2019 10 Lumped measures of organic compounds (cont’d) General reaction (organics oxidized to CO 2 ): ܱݎ݃ܽ݊݅ܿݏ ൅ ܱ → ܥܱ ൅ ܪ ܱ ൅ ݋ݐ݄݁ݎ ݌ݎ݋݀ݑܿݐݏ TOC analyzer measures produced in abiotic rxn COD analysis measures consumed in abiotic rxn BOD measures in biological rxn When organics are oxidized, e are released; this is a redox reaction. Where do the electrons go in this reaction? ________________________ 19 ___ ________________ _______________ (If you want to assess organic content of a water, what could you measure in this rxn?) Choosing among TOC, COD, and BOD TOC Sensitive: TOC often used for ________________________________________ . Measure unknown sample with TOC analyzer or calculate TOC of known compound. Results reported as _________________________. COD Use chemical redox rxn to measure oxygen demand. COD often used for ________________________________________ Even biologically recalcitrant compounds can be oxidized. Measure unknown sample with COD kit or calculate COD of known compound. Results reported as __________________________ . BOD Set up biological experiments to measure BOD of unknown sample. BOD often used for ________________________________________ Results reported as __________________________________ . Time for analysis __________________________________________________________ ____________________________ 20
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1/24/2019 11 Example 2 ‐TOC A student adds 100 mg/L acetate (CH 3 COO ) to pure water. What is the TOC of this sample in mg C/L? Atomic weights C=12 mg/mmole, H=1 mg/mmole, O=16 mg/mmole 21 How to write an overall balanced redox reaction 1. Balance stoichiometric coefficients of major species (everything besides O and H). 2. Add H 2 O to balance oxygen. 3. Add H + to balance H. 4. Add e to balance charge. 5. Combine two half reactions (no e in balanced rxn). 22 Review
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1/24/2019 12 Example 3 ‐ COD What is the COD of the solution in Example 1? Write redox reaction: _______________ is oxidized to CO 2 Oxygen is reduced to H 2 O. 23 How to Assess the BOD of a Waste? Procedure for BOD test: 1. Take sample of waste Dilute (if necessary) with dilution water 2. Seed =add microorganisms (if necessary) 3. Measure DO consumption (by microorganisms) over 5 d BOD 5 Experimental parameters: Temperature 20° C Conduct test in dark Final DO concentration must be > 0.5‐2 mg/L Need at least 2 mg/L change in DO over 5 days _________________________________ Review 24
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1/24/2019 13 Sample and Control Bottles (300 mL) Sample bottle Waste sample Dilution water Seed Purpose: to measure DO consumption due to the waste sample Control or blank bottle ______________ ______________ _______________________ _______________________ _______________________ Review 25 BOD t Equation seed volume water dilution volume sample waste volume sample waste volume factor dilution P blank in vol seed sample diluted in vol seed blank in seed to sample diluted in seed of ratio f incubation of days after t
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  • Fall '17
  • CHRISTOPHER NEELY
  • Yorkshire Television, Trademark dilution, treatment plants

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