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Last Login: 11/9/2007 2:41:41 PM
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| | I am wondering whether anyone is aware of tools or methods that would help us quantify in a cost/benefit format the impacts of using higher rate substrates in a denitrification process. We are looking to compare the anoxic tankage volume requirements for methanol, ethanol, acetic acid and MicroC given certain effluent TN requirements. We would like to compare the increase in operational cost of using a substrate with a higher rate of denitrification vs. the potential decrease in capital cost from requiring a potentially smaller overall anoxic reactor. The cost/benefit analysis should be accessible enough such people in the town capital planning department can easily understand the tradeoffs in capex vs. opex. |
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Last Login: 3/17/2008 8:47:55 PM
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| One method could consist of calculating the mass of each carbon substrate (electron donor) required per mass of nitrate-N reduced from stoichiometry.
There are also guidelines available in literature but I have seen discrepancies in reported and calculated values resulting from many factors (i.e., wastewater characteristics, thermodynamic constants). Subsequently, one can obtain price quotes for each substrate on a mass basis ($ per mass of donor) for comparison.
Also note that several factors need to be considered to make a decision on which electron donor to select in this case. These include the following:
·Cost per unit mass of electron donor;
·Amount of biomass produced per mass of nitrate reduced;
·Does the industry plan to recycle biomass into the treatment process or dispose to landfill;
·Must consider any necessary added safety precautions for operations.
Perhaps this will help.
-David
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Forum Member
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Last Login: 6/12/2008 2:25:55 PM
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| I would think the key to analyzing this is to see how the denitrification rate is increased by the carbon source. Since every mixed liquor and anoxic tank influent is different one reasonably accurate way to check this is to run denitification rates with your current anoxic mixed liquor. All you need is a nitrate probe and mag stirrer and you can run this in your own lab similar to running a batch respiration rate on mixed liquor with a DO probe. Then try varying doses of methanol and/or other carbon sources and track the increase in nitrification rate with dose. A doubling of rate would correspond to a halving of required detention time and tankage requirements in simple terms but if one wanted to be more accurate you could work with a local consultant who could run BioWin or another process model to most accurately show impacts. The economics are pretty straightforward after that.
Wiff Peterson |
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