sewage determination by COD method
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This document summarizes a seminar presentation on determining sewage quality using the chemical oxygen demand (COD) method. It defines COD as the total oxygen required to chemically oxidize organic matter in water. The presentation covers the history of COD testing using different oxidizing agents, the dichromate principle method, and calculations to determine COD levels in mg/L. Advantages are that COD results are faster than biochemical oxygen demand testing and more compounds are oxidized, while disadvantages are COD cannot differentiate biologically reactive compounds.
sewage determination by COD method
- 1. SEMINAR ON SEWAGE DETERMINATION BY COD METHOD DEPARTMENT OF RURAL TECHNOLOGY AND SOCIAL DEVELOPMENT G.G.V. BILASPUR (C.G.) SESSION 2018-19 PRESENTING BY :- SHARAD KUMAR CHANDRAKAR M.Sc. (RT) 2nd SEM
- 2. CONTENTS Introduction Definition Sewage Necessity of Sewage Treatment History COD test by dichromate principle Calculations Advantages Disadvantages Conclusions References
- 3. INTRODUCTION OF COD • The organic matter present in sewage can be measured in number of ways. • The oxygen required to oxidize the organic matter present in a given waste water can be theoretically calculated . • If the organic compounds and their concentration are known the oxygen demand of the sample can be accurately computed but it is impossible to know the details of organic compounds present in raw water or waste water. • It is expressed in milligrams per liter (mg/L) also referred to as ppm (parts per million), which indicates the mass of oxygen consumed per liter of solution.
- 4. DEFINITION • COD is the total amount of oxygen required to chemically oxidize the bio degradable and non biodegradable organic matter. • Chemical oxygen demand is the amount of oxygen needed to oxidize the organic matter present in water. • Chemical oxygen demand testing is used to determine the amount of oxidation that will occur and the amount of organic matter in a water sample. • Chemical oxygen demand testing is also used to determine the amount of inorganic chemicals in a sample.
- 5. Sewage • Sewage (domestic wastewater or municipal wastewater) is a type of wastewater that is produced by a community of people. It is characterized by volume or rate of flow, physical condition, chemical and toxic constituents and its bacteriologic status (which organisms it contains and in what quantities). • Waste matter from domestic or industrial establishments that is carried away in sewers or drains for dumping or conversion into a form that is not toxic.
- 6. Necessity of Sewage Treatment • Sewage treatment plant plays an important role for the mankind. • The main function of these plants is to make the water of the sewage clean that comes from home, commercial and industrial sectors. • The treatment of sewage water has become the need of the hour as it stops spreading the diseases and illness caused by the sewage water. • It helps society in making the water as well as environment clean. • The three stages of these plants include the primary stage, the secondary stage and the tertiary stage.
- 7. HISTORY • Earlier potassium permanganate was used as an oxidizing agent • COD values were very much lower than that of 5 th day BOD • It indicated that potassium permanganate was not very effective in oxidizing all the organic matter present • After that other oxidizing agents like ceric sulphate, potassium iodate and potassium di-chromate were also used
- 8. HISTORY • Potassium di chromate was found to be the most effective due to – • Completely oxidize all organic matter • Relatively cheap • Easy to purify
- 9. COD TEST BY DICHROMATE PRINCIPLE • Water sample is refluxed in strong acidic solution with a known excess amount of potassium dichromate. • After digestion, the remaining unreduced K2Cr2O7 is titrated with Ferrous Ammonium Sulfate (FAS)to determine K2Cr2O7 consumed. • This gives us the oxidizable organic matter in terms of oxygen equivalent.
- 11. CALCULATIONS • The COD in mg/l is determined by the formula:- • COD mg/l = (A-B)xNx8000 /ml sample taken
- 12. ADVANTAGES OF COD METHOD • COD result are available much sooner than BOD test results. • The COD test requires fewer manipulations of the sample. • The COD test oxidizes a wide range of chemical compounds. • It can be standardize more easily.
- 13. DISADVANTAGES • The major disadvantage is that the results are not directly applicable to 5-day BOD results without correlation studies over a long period of time. • One more limitation of COD is it’s inability to differentiate between biologically oxidizable and biologically inert organic matter.
- 14. CONCLUSIONS • The main purpose of the COD method to provide systematic approach for water treatment.
- 15. REFERENCES • Journal on industrial waste water treatment by k.l moed • Environmental engineering vol 1&2 by S.K Garg • Industrial waste water treatment by metcalf & eddy