Lab 4 - Cod Test 3y5l2g

UNIVERSITI TEKNOLOGI MARA KAMPUS SAMARAHAN 2 DIPLOMA IN CIVIL ENGINEERING (EC110) WASTE & WASTE WATER ENGINEERING (ECW 351) EC1105C

TITLE: LAB 5 – CHEMICAL OXYGEN DEMAND TEST PREPARED BY: 1) 2) 3) 4)

NORHAZERAH BINTI YUSSOP (2013251252)- LEADER MOHAMMAD SYAFIQ AKMAL BIN ABDULLAH (2013431936) NUR HAFIZAN BINTI ASMAIL (2013617608) NUR AMYRA HIDAYAH BINTI AMIRUL (2013224456)

PREPARED FOR : MISS BEATRICE BIDAUN DATE OF SUBMISSION: 4 AUGUST 2015

TABLE OF CONTENTS ELEMENTS

PAGE

Experiment title

1

Objective

1

Introduction

1-2

Apparatus

3

Procedure

3

Data Acquisition& Calculation

4

Analysis of data

4

Discussion

4

Conclusion

5

Reference

5

EXPERIMENT TITLE Chemical Oxygen Demand OBJECTIVE To obtain the value of COD of water sample using open reflux method. INTRODUCTION Chemical Oxygen Demand (COD) is defined as the amount of a specified oxidant that reacts with sample under controlled conditions. It is

commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD is to determine the amount of organic pollutants found in surface water. It is measured expressed in milligrams per litre (mg/L), which indicates the mass of oxygen consumed per litre of solution. The advantages of the COD test as compared to the BOD test are: 1. COD results are available much sooner. 2. The COD test requires fewer manipulations of the sample. 3. The COD test oxidizes a wider range of chemical compounds.

4. It can be standardized more easily. However, the disadvantage of the COD test is that the results are not directly applicable to the 5-day BOD results without correlation studies over a long period of time. The samples used for the COD analysis may be grab or composite. Preservation of the sample can be accomplished by adding sulphuric acid to depress the pH to 2 and the holding time with preservation is 7 days. On the other hand, the value of COD should always higher than BOD. This is because COD or Chemical Oxygen Demand is the total measurement of all chemicals in the water that can be oxidized. BOD or Biochemical Oxygen Demand is supposed to measure the amount of food (or organic carbons) that bacteria can oxidize (in 5 days). A COD test result (that can be performed in about 2 hours) can be correlated to an expected BOD result (which takes 5 days). It is also because of the chromate refluxing procedure used to measure COD, almost all organic compounds will be oxidized. Hence, the value of COD is higher than BOD. In this experiment, the value of Molarity is already given which is 0.1 M. However, the value of molarity also can be calculated by using this formula: Molarity of FAS, M =

K × 0.25 F

Where, K = volume of 0.04167 M K2Cr2O7 solution titrated (ml) F = volume of FAS used in titration (ml)

APPARATUS  Reflux apparatus  Beaker  Conical flasks

           

Burette Graduated cylinder Pipette Distilled water Analytical balance Glass rod Mercuric sulphate crystals/powder Glass beads Ferroin indicator solution Concentrate sulphuric acid containing argentum sulphate Standard potassium dichromate solution , 0.04167M Standard ferrous ammonium sulphate titrant

PROCEDURES Reflux of water samples 1. 50 ml of distilled water is poured into refluxing flask A and 50 ml sample into refluxing flask B. 2. 1 g of mercuric sulphate (HgSO4), 3-4 glass beads is added into each flask. 3. 5 ml of sulphuric acid (H2SO4) reagent containing argentum sulphate (Ag2SO4) was slowly added to each flask and HgSO 4 is dissolved by mixing it well. 4. 25 ml 0.04167 M potassium dichromate (K2Cr2O7) solution is added to each flask and mixed well. 5. The remaining 70 ml H 2SO4 is slowly added and swirling and mixing is continued while adding the acid. Caution: to prevent local heating of flask bottom and a possible blowout of flask contents, the reflux mixture must be mixed thoroughly before applying the heat 6. Both flasks is attached to condenser and been reflux for 2 hours. 7. The switch if off after 2 hours and let the flasks cool down. 8. The flasks is disconnected from the condenser and let the cool down in the sink. 9. The flask is poured into 500 ml of conical flask and distilled water is added until 350 ml. 10. The solution was titrated with ferrous ammonium sulphate (Fe (NH4)2(SO4)2) titrant using 2 – 3 drops ferroin indicator (the colour changes from yellow to blue- green to reddish brown). Molarity of Fe (NH4)2(SO4)2, FAS titrant 1. 25 ml of 0.04167 M K2Cr2O7 solution is poured 250 ml conical flask. 2. Distilled water is added to 100 ml. 3. 30 ml concentrated H2SO4 is added and let it cooled. 4. Using 2- 3 drops of ferroin indicator, the solution is titrated with Fe(NH4)2(SO4)2 5. The molarity of FAS solution is calculated:

Molarity of FAS, M =

K × 0.25 F

Where, K = volume of 0.04167 M K2Cr2O7 solution titrated (ml) F = volume of FAS used in titration (ml)