mozhigopi Posted November 14, 2009 Share Posted November 14, 2009 How to reduce COD (Chemical Oxigen Demond) in STP? Link to comment Share on other sites More sharing options...
insane_alien Posted November 14, 2009 Share Posted November 14, 2009 There are a variety of ways. they all amount to 'oxidise it'. also this smacks of a homework question. which is why i won't go into more detail until you give us what you've done already. 1 Link to comment Share on other sites More sharing options...
mozhigopi Posted November 15, 2009 Author Share Posted November 15, 2009 COD is a very broad parameter. So the first step is to find out what substance is causing the high COD and only then to try a solution. Two questions are crucial: - which COD-rich substances are used in the plant ? - taking samples of different rinsing waters and other waste water substreams : which are high in COD ? Bubbling oxygen works fine if the cause is a large concentration of some inorganic reducing substance (e.g. Fe(II), sulphite, some of the reductors used in a chemical plating solution, ...) Activated sludge (preferably the activated sludge of the local city waste water treatment station ; if not, your own installation which could be a serious investment) will do the job if biodegradable organic substances in solution are the main cause. Think of acetate and similar bath ingredients, most surfactants, ... If most of the COD is coming from a water based degreasing operation, then try to separate the waste water from this operation and treat it physically (oil skimmer etc. or if you are using a degreaser with stable emulsions, ultrafiltration). (Find a lab to check the oil content of the sample with high COD). Only of nothing else helps, switch to the very expensive aggresive chemicals like peroxide ... Even then, it is beter to do this on the right substream which causes most of the COD load, before the final waste water treatment and not on the combined waste water stream. A method for reducing the COD of water containing an emulsion of organic material in water. The emulsion contains insoluble organic material and a surfactant. The COD is reduced by mixing a cationic polymer flocculent with the water and maintaining the temperature at from 37° C. to 95° C. for a sufficient length of time for an organic phase and water with reduced COD to form. Link to comment Share on other sites More sharing options...
insane_alien Posted November 15, 2009 Share Posted November 15, 2009 well, you seem to have answered your own question. Link to comment Share on other sites More sharing options...
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