Synthetic Oxygen Demand Presentation By Douglas Rittmann, Ph.D., P.E. Water

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Synthetic Oxygen Demand Presentation By Douglas Rittmann, Ph.D., P.E. Water/Wastewater Consultant To CE 4153 On April 18, 2006

General Considerations * COD test permits estimation of a waste as far as aggregate amount required for oxidation to carbon dioxide and water * The COD tests oxidizes natural mixes by the activity of solid oxidizing operators under corrosive conditions * The amino nitrogen will be changed over to alkali nitrogen and natural nitrogen will be changed over to nitrates. * Organic is changed over to carbon dioxide and water paying little heed to the natural assimilability of the substances. Ex: glucose & lignin are both oxidized totally, consequently, COD is higher than BOD.

Advantages and Disadvantages * One of the impediments of COD is its failure to separate between organically oxidizable and naturally idle natural matter. * It doesn't give any proof of the rate at which the organically dynamic material would be balanced out under conditions in nature. * Major favorable position is the brief timeframe required for assessment in 3 hours versus 5 days for the BOD test. * COD information can be translated as far as BOD values after adequate experience has been gathered to build up dependable relationship elements.

History of COD Test * Chemical oxidizing specialists have for quite some time been utilized to gauge the oxygen request of sewage and contaminated waters. * Potassium permanganate were utilized for a long time, and the outcomes were alluded to as oxygen devoured from Potassium Permanganate. * Oxidation by potassium permanganate was exceedingly factor because of quality of oxidant and with deference excessively different sorts of mixes. * Oxygen expended qualities were constantly not as much as the 5-day BOD on account of the failure of permanganate to convey the oxidation to specific endpoint * Potassium dichromate is the most pragmatic oxidizing operator with a silver particle impetus in a corrosive state and refluxed at high temperatures to totally oxidize organics to carbon dioxide and water.

Chemical Oxygen Demand by Dichromate COD outcomes are accounted for in mg/L of oxygen. A 0.25 N dichromate arrangement is identical to 2 mg of oxygen. An overabundance of oxidizing operator must be available to guarantee that all natural matter is totally oxidized. Ferrous ammonium sulfate titrant is a fantastic diminishing operator to gauge the overabundance dichromate after oxidation. 6Fe++ + Cr2O7 + 14H+ 6Fe3+ + 2Cr3+ + 7H2O Blanks are required on the grounds that superfluous natural matter is difficult to avoid. Pointer – Ferroin is an incredible marker for dichromate lessened by ferrous

Calculations COD (mg/L) = 8000 (clear titr.- test titration) (standard. Fe(NH4)2(SO4)2)/ ml test Alternate Procedures: COD test is exact and precise for tests with A COD of 50 mg/L or more noteworthy. It is vital in any alteration that the Volume of test in addition to dichromate arrangement be kept up at 1:1 proportion. In the event that it is littler, the oxidizing force of the arrangement will diminish, while If it is bigger, the clear utilization of dichromate gets to be distinctly intemperate

Inorganic Interferences Chlorides can bring about high outcomes yet disposed of by the expansion of mercuric sulfate before the expansion of different reagents. Nitrites and nitrates impedance can be dispensed with by sulfamic corrosive. Ferrous and sulfides can meddle yet are low in focus.

New Manganese III COD HACH Method

Manganese III Method for COD Virtually dispenses with perilous metals squander transfer Concerned about mercury, chromium or silver in waste streams? With the new Manganese III COD (compound oxygen request) Method, transfer of these overwhelming metals squanders is for all intents and purposes dispensed with. The licensed Manganese III COD Reagent1 dispenses with utilizing trademark substantial metal oxidizers, impetuses and chloride evacuation specialists utilized as a part of customary COD testing. Hach analysts have connected numerous advancements utilized as a part of the first USEPAapproved2 small scale COD framework to build up another strategy for observing wastewater treatment forms. The Manganese III COD Method can be utilized for: • Municipal and modern wastewater• Municipal and mechanical process waters • Environmental checking • Food and drink industry • Pulp and paper industry • Manufacturing plants

Manganese III Method for COD Simplifies COD investigation In under a hour and a half, up to 25 COD tests can be finished. Like Hach's dependable USEPA-endorsed Dichromate COD Method, the new Manganese III COD Method depends on a shut reflux smaller scale strategy, which is both simpler and less work concentrated than the open reflux full scale technique. Besides, investigators at all ability levels can get precise outcomes with this new technique. The Manganese III COD System utilizes arranged reagents, a rearranged method, and dependable Hach gear, including the COD Reactor and a colorimeter or spectrophotometer. The new strategy additionally incorporates a Vacuum Pretreatment Device (VPD) and patent-pending Chloride Removal Cartridges, which dispose of the utilization of mercury-containing reagents for test chloride expulsion. In the wake of setting up the examples, basically process them in the COD Reactor for 60 minutes.

Manganese III Method for COD The Manganese III COD Reagent contains Manganese 3+, an oxidizer, and concentrated sulfuric corrosive. The reagent does not contain metal impetuses or mercuric sulfate. The Manganese III COD Reagent offers a few favorable circumstances when contrasted with open reflux COD testing: • Provides a particular shading change for simple investigation • Simplifies prepare control testing • Minimizes taking care of and presentation to destructive chemicals • Virtually takes out an unsafe metals squander stream and transfer costs

Application of COD Data * Used broadly in examination of modern examples * Used to decide misfortunes in sewer frameworks * Due to brief time for examination, blunders can be amended that day * BOD test with COD Test can decide poisonous conditions all the more adequately * COD test utilized generally for better operation of wastewater office as a result of its speed in examination.