FE Review for Environmental Engineering Problems, problems, problems Presented by L.R. Chevalier, Ph.D., P.E. Department of Civil and Environmental Engineering Southern Illinois University Carbondale

BIOLOGICAL FOUNDATIONS FE Review for Environmental Engineering

Given the following data, calculate BOD 5 Initial DO of sample: 9.0 mg/L Volume of sample: 10 ml Final DO of bottle after 5 days: 1.8 mg/L Volume of BOD bottle: standard 300 ml

Review and understand the terms of the governing equation

Standard Bottle: 300 ml P = 10/300 =0.033

Time (days) BOD (mg/L) BOD 5 Typical Curve

Further Discussion on BOD Typical values domestic sewage 250 mg/L industrial waste as high as 30,000 mg/L untreated dairy waste 20,000 mg/L After 5 days, BOD curve may turn sharply upward demand of oxygen by microorganisms that decompose nitrogeneous organic compounds into stable nitrate

Time (days) BOD (mg/L) carbonaceous nitrogenous BOD 5 LoLo

If the BOD 3 of a waste is 75 mg/L and k=0.345 day -1, what is the ultimate BOD?

For some of you there may be a confusion as to which equation to use:

Recall the equation for BOD t The amount of DO measured will decrease over time. Does BOD increase or decrease over time?

OXYGEN CONSUMEDOXYGEN DEMAND REMAINING Want to use the equation that shows an increase with time!

Given: DO i = 9.0 mg/L DO = 3.0 mg/L after 5 days Dilution factor P = Reaction rate, k = 0.22 day -1 a) What is the 5-day BOD? b) What is the ultimate BOD? c) What is the remaining oxygen demand after 5 days?

Review and understand the equations needed for the solution

a) What is the 5 day BOD?

b) What is the ultimate BOD?

c) What is the remaining oxygen demand after 5 days? = 100 mg/L

Determine the ThOD of a 400 mg/L solution of glucose C 6 H 12 O 6

Balance the equation Determine the MW of compound and O 2 Calculate ThOD

1. Balance the following equation

2. Determine the MW of glucose and O 2 MW C 6 H 12 O 6 = 12(6) (6) = 180 g/mol MW O 2 = 2(16) = 32 g/mol 3. Calculate the ThOD

Ethanol, or ethyl, alcohol is used in beverages, as a gasoline additive, and in other industrial applications. Because small amounts of ethanol and sugar are used in the biological process to produce methanol, both of these compounds inevitable end up in the waste water of methanol plants. Calculate the ThOD demand for waste water containing 30 mg/L ethanol [CH 3 CH 2 OH] and 40 mg/L sucrose [C 6 H 12 O 6 ]

Balance two equations Determine the MW of both compounds Calculate ThOD for both, then add

1. Write the balanced equation for the oxidation of ethanol (often written EtOH) to the end products of CO 2 and H 2 O. MW EtOH = 46 g/mol

2. ThOD of EtOH is calculated as follows:

3. Calculate the ThOD for wastewater containing 40 mg/L sucrose [C 6 H 12 O 6 ] MW Sucrose = 180 mg/L

4. To calculate ThOD for waste water containing both 30 mg/L ethanol [CH 3 CH 2 OH] and 40 mg/L sucrose [C 6 H 12 O 6 ], you can add the ThOD of the individual compounds. ThOD tot = 62.6 mg/L O mg/L O 2 = mg/L O 2... end of example

A chemical plant produces the amino acid glycine [C 2 H 5 O 2 N]. The wastewater from the facility contains approximately 25 mg/L of this acid. Calculate both the carbonaceous and nitrogenous ThOD for the wastewater.

1. As in the previous example, write the balance equation, but include NH 3 as an end product.

2. Balanced equation: 3. The molecular weight of the acid is 75 g/mol. The amount of oxygen required to oxidize the carbonaceous portion is:

4. One mole of ammonia is produced for each mole of acid oxidized. The equation for oxidation of the ammonia is: ammonia nitrate

5. To determine the nitrogenous oxygen demand:

6. The amount of oxygen required to oxidize the acid is the sum of both the carbonaceous and the nitrogenous oxygen demands. ThOD = = mg/L O end of example