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Junior Member
 
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Last Login: 2/18/2008 11:11:06 AM
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| In a activated sludge process, BOD influent concentration is from 3600-10000 mg/l, average is 6000 mg/l. BOD and COD ratio is 0.43-0.7. F/M in the aeration tank is from 0.5 to 1.3. Average F/M is 0.7. BOD and COD removal percentage in the activated sludge process is very high, over 95%. The performance of aeration tank seems good. Ammonia concentration in the influent is from 0.8-7.9 mg/l, average concentration is 4.6 mg/l. But effluent of clarifier ammonia concentration is much higher than the influent. The range is from 8.6-42.1 mg/l, average is 24.4 mg/l. Why does the ammonia concentration increase? Is the F/M ratio too high? Please help me identify the reasons. Thanks. |
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Last Login: 3/17/2008 8:47:55 PM
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| Please clarify the influent sampling location(s).
How do you manage waste biosolids (anaerobic digestion)?
A possible source of ammonia is anaerobic digester supernatant being redirected to your aeration basin.
-David |
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Supreme Being
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Last Login: Today @ 12:43:37 AM
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| What is about temperature and nitrite level? Determining the cause(s) for effluent is often a difficult and confusing problem. However, high effluent ammonia concentration has several possible causes. Effluent ammonia concentration may be high due to : - Cold temperature,
- Organic overloading
- Low oxygen concentration and low alkalinity
- Short hydraulic detention time
- Release of ammonia from old digesting sludge
Ammonia is primarily removed by microbiological nitrification to nitrate. Nitrification requires 2.0 mg/l or greater dissolved oxygen concentration for optimum performance. Inorganic carbon (Alkalinity) is required by the nitrifying bacteria and nitrification becomes limited at a total carbonate alkalinity of <60-80 mg/L. One sign of an alkalinity limitation for nitrification is the buildup of nitrite about 1-2 mg/L. Nitrification can be increased (resulting the decrease in ammonia) by raising the dissolved oxygen concentration and by adding alkalinity but nothing can be done about low temperature.
sabir |
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Supreme Being
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| | What kind of waste are you treating? It looks extremely high in BOD/COD. Do you have Anaerobic Digesters? |
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Junior Member
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Last Login: 2/18/2008 11:11:06 AM
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| | The retention time of aeration tank is about 2.4 days. also why does the retention time matter? I think the cell retention time should be considered. I don't know the cell retention time yet. F/M in this range is overloading? I think it might be a little bit higher, but not that high. influent sampling location is after EQ tank, which flows into aeration tank. The industry is making shampoo, soap products. |
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Junior Member
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Last Login: 2/18/2008 11:11:06 AM
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| | As far as I know, there is no anarobic digester existed. The sludge from the clarifier is collected in a storage tank, then goes to the vacuum filter. The filtrate is back to the EQ Tanks. Filter cake is for offsite disposal. The sampling event is in the end of August. So I think the water temperature is not low. Thanks very much for your inputs. Please share your more thoughts. |
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| | Rather than run ammonia-N only, I recommended you also analyze total Kjeldahl nitrogen (TKN) in the AS influent. The difference between TKN and ammonia-N will give you the concentration of organic nitrogen. Organic nitrogen can be converted to ammonia-N in the AS process. If you do not have the capacity to fully nitrify the ammonia-N that is being formed, you would potentially experience a higher ammonia-N in the effluent than in the influent. Woodie |
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Supreme Being
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Last Login: 6/26/2008 9:18:16 PM
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| Here is the simplistic view: You have a very high influent BOD. As the BOD (organic matter) breaks down, a large concentration of ammonia is released. The "bugs" reduce the BOD before oxidizing the ammonia to nitrate. With such a high BOD, there may not be sufficient treatment time to eliminate the ammonia. Further, if the influent is deficient in alkalinity, the conversion to nitrate will be suppressed. What you may be seeing is a point where the BOD is reduced, but the ammonia carries through to the clarifier. You will not likely oxidize the ammonia in the clarifier. Your type of influent is probably best handled in a pure oxygen plant. You may need to process the aeration basin flow through another unit (like an ammonia stripping tower) to get rid of the ammonia.
David |
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Supreme Being
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Last Login: Yesterday @ 1:37:32 PM
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| | Do an Ammonia test on your centrate. |
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Junior Member
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Last Login: 6/13/2008 12:00:05 PM
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| The wastewater would require a BOD:N ratio of 5:1 for aerobic heterotrophic growth. There is probably a lot of organic N in the influent which is being converted to ammonia and partially nitrified.
ttfn |
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