ECP 419 Practicals

8/13/2019 ECP 419 Practicals

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ECP 419 PRACTICALS

1.0 EFFECT OF TEMPERATURE DURING YEAST FERMENTATION

1.1 Introduction

Fermentation is defined as an energy yielding process where yeast converts sugar into

energy, carbon dioxide or/and an alcohol depending on the respiration pathway. Yeast

can respire in anaerobic ally and aerobically. However, yeast gets more energy from

aerobic respiration, but in the absence of oxygen it can continue to respire anaerobic

ally, though it does not get as much energy from the substrate. Yeast produces an

alcohol when it respires anaerobic ally and ultimately the alcohol will kill the yeast.

However the yeast fermentation process is affected by various process conditions and

this determines the amount alcohol produced.

1.2 Purpose

The purpose of this activity is to examine the influence of temperature on yeast

fermentation

1.3 Objective

Determine the influence of temperature on the yeast fermentation

1.4 Materials

Ice water (0.0C)

Bakers yeast

Table sugar (sucrose)

Thermometer

Two 100 mL graduated cylinders

Water (40C)

1.5 Procedure

1. Add 3.0 grams of table sugar to each 100 mL-graduated cylinder.

2. Add 2.0 grams of active dry yeast to each 100 mL-graduated cylinder.


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3. Add 50 mL of ice water to one graduated cylinder. Label the cylinder as ice

temperature.

4. Add 50 mL of 40C water to the other graduated cylinder. Label the cylinder as 40C

temperature.

5. Cap each cylinder with the palm of your hand and shake the cylinder vigorously.

6. Note the time.

7. Make observations for temperature change every five minutes for 20 minutes.

1.6 Questions

1. Calculate the amount of alcohol produced [3 marks]

2. Calculate the moles of CO2produced [3 marks]

3. Explain if different sugars give equivalent number of CO2moles [3 marks]

4. Formulate a conclusion based on your observations. [5 marks]

5. Outline other factors can affect the yeast fermentation process [11 marks]

2.0 DISSOLVED OXYGEN MEASUREMENT

2.1 Introduction

The DO determination measures the amount of dissolved (or free) oxygen present in

wastewater. Aerobic bacteria and aquatic life such as fish must have DO to survive.

Aerobic wastewater treatment processes use aerobic bacteria to break down the

organic compounds found in wastewater into more stable products that will not harm the

receiving waters. Wastewater treatment facilities such as lagoons or ponds, trickling

filters and activated sludge plants depend on these aerobic bacteria to treat sewage.

The same type of aerobic wastewater treatment process occurs naturally in streams

and ponds if organic matter is present, turning these bodies of water into aerobic

wastewater treatment plants. If sufficient oxygen is not naturally supplied through wind

and turbulence to replace the depleted oxygen, the body of water will develop a low DO

and become anaerobic (or septic). The results of septic water bodies include fish killsand anaerobic odors.

If the amount of free or DO present in the wastewater process becomes too low, the

aerobic bacteria that normally treat the sewage will die. The process will not operate

efficiently and septic conditions will occur. The DO test is used to monitor the process to


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ensure that there is enough dissolved oxygen present to keep the process from

becoming septic.

2.2 Purpose

The purpose of this practical is to find out the amount of dissolved oxygen in water.

2.3 Objective

To determine the amount of dissolved oxygen in water.

2.4 Materials

Manganous sulfate solution

Alkaline potassium iodide-sodium azide solution

Sulfuric acid (H2SO4), concentrated

Starch indicator solution

Sodium thiosulfate (Na2S2O35H2O), 0.025 N

Phenylarsine oxide (PAO), 0.025 N

Potassium bi-iodate (KH(IO3)2), 0.025 N

Distilled or deionized water

These reagents are poisonous and should be handled with extreme caution. These reagents

are corrosive and should be handled with extreme caution.

2.5 Equipment

Burette, graduated to 0.1 mL

Burette stand

300 mL glass stoppered BOD bottles

500 mL wide-mouthed Erlenmeyer flasks

Pipettes with elongated tips and minimum volume of 1.0 mL (+/- 0.1 mL)

Pipette bulb

250 mL graduated cylinders

Distilled water rinse bottle


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2.6 Procedure

1. Collect the sample to be tested in a 300 mL BOD bottle taking special care to

avoid adding air to the liquid being collected. Fill bottle completely and add

stopper.

2. Remove bottle stopper and add 1 mL of the manganous sulfate solution at the

surface of the liquid.

3. Add 1 mL of the alkaline-potassium iodide-sodium azide solution at the surface of

the liquid.

4. Replace the stopper, avoid trapping air bubbles and shake well by inverting the

bottle several times. Repeat shaking after floc has settled halfway. Allow floc to

settle a second time.

5. Add 1 mL of concentrated sulfuric acid by allowing the acid to run down the neck

of the bottle above the surface of the liquid.

6. Restopper, rinse the top of the bottle to remove any acid and shake well until theprecipitate has dissolved.

7. Titrate a volume of treated sample which corresponds to 200 mL of the original

sample. This corrects for the loss of some sample during the addition of

reagents. This volume calculated using the formula: mL of sample to titrate = 200

x [300/(300-2)] = 201 mL

8. Pour 201 mL of sample from the BOD bottle into an Erlenmeyer flask.

NOTE: Since variations occur in the actual volume of each BOD bottle, do not pour 99

mL of sample out of the BOD bottle and assume that 201 mL will be left.

If the solution is reddish-brown in colour, titrate with 0.0250N sodium thiosulfate or

0.0250 N PAO until the solution is a pale yellow (straw) colour. Record the amount of

titrant used. Add a small quantity of starch indicator.

If the solution has no reddish-brown colour, or is only slightly coloured, add a small

quantity (approximately 1 mL) of starch indicator. If no blue colour develops, there is

zero dissolved oxygen. If a blue colour develops.

Titrate with 0.0250N sodium thiosulfate or 0.0250N PAO to the first disappearance of

the blue colour. Record the total number of mL of sodium thiosulfate or PAO used.


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2.7 Questions

1. Calculate the amount of dissolved oxygen obtained from the sample [3 marks]

2. Calculate the concentration of the dissolved oxygen in the sample [3 marks]

3. Explain the reaction involved in the determination of DO in water using the Winkler

method [3 marks].

4. Explain how a change in the amount DO affect flora and fauna in the water body

[2 marks]

5. Explain how warming or cooling of the atmosphere affect the amount of dissolved

oxygen in your water [3 marks]

6. Explain how atmospheric pressure affect your DO readings [3 marks]

7. Explain how the amount of dissolved oxygen you measured agree with the amount

you calculated. In addition, explain any deviations [3 marks].

REFERENCES

Dunnivant FM, Hoboken, NJ Environmental Laboratory Exercises for InstrumentalAnalysis and Environmental, 2004.

Common Operations and Wet Chemical Methods in Environmental Laboratories (thisbook). APHA-AWWA-WEF (1998)

Effect of temperature on fermentation,evaluation copy of the vernier student lab,http://www.vernier.com/cmat/bwv.html .

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ECP 419 Practicals