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Forum Newbie
Group: Forum Members
Last Login: 6/9/2008 5:55:51 PM
Posts: 7, Visits: 34 |
| | Hi, in the plant we have a poor settling in the clarifier. We are working with not many filamentous m.o. but the settling is very poor. we have a constant RAS flow. Do you think that could be the problem? What parameters should I check? Thank you
Nadia |
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Supreme Being
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Last Login: Today @ 5:03:06 PM
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| | Nadia: You say you have settling problems but do not describe the type of plant, domestic/industrial, flow, nutrient removal, whether you have bulking issues. You can still get bulking problems without filaments such as viscous/zoogleal bulking. Need more information about your plant before any help can be given as well as a microscopic examination of your mixed liquor.
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Supreme Being
Group: Forum Members
Last Login: 6/18/2008 10:17:32 AM
Posts: 98, Visits: 161 |
| | There are lots of things you can check. mixed liquor suspended solids in your aeration basin, pH, Dissolved oxygen and you could be over or under wasting. Look at these and let us know. |
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Forum Newbie
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Last Login: 6/9/2008 5:55:51 PM
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| | Ok, I have done a few numbers... The sludge age is set to 30 days (taking into account the TSS of aireation tank and sedimentation tank), and it's done by wasting an amout of effluent, but the recicle is set at a constant rate (could this be one thing???). I get an F/M of about 0.02/0.03, HRT is 35 hours (only the aireation tank), the MLSS is at about 1600mg/l (which I think is low) and in the recicle line in about 3000mg/l and with that we are getting an Moholman Index of more than 400. We don't have a filamentous problem... What can you say about it? Thank you
Nadia |
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Supreme Being
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Last Login: 6/18/2008 10:17:32 AM
Posts: 98, Visits: 161 |
| | Your F/M is in the range of extended aeration and I guess it safe to say that this is an extended aeration plant you are operating? Your MLSS # is very low specially for extended air typically anyways. Sounds like you may be over wasting and over aerating. Decrease your wasting and let your MLSS build up. You may want to try and reducing the return sludge rate if this is possible. This depends on how much you are returning compared to your influent "raw sewage" flow. If your plant is extended air I would try not wasting for awhile. When observing the settability test how does the MLSS look in the cylinder is it smooth or granny in appearance? And what does Moholman mean ? |
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Forum Newbie
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Last Login: 6/9/2008 5:55:51 PM
Posts: 7, Visits: 34 |
| | Thanks for the answer. The Mholman Index is the SVI index. When you put the sludge in a tube you see like smooth. I am not really sure if it works at extended aireation. The F/M and sludge age goes with it, but not the LVR, which is aproximately around 1.0. The lay out of the aireation tank is six surface aireator Actirotor and it works as a piston flow. The first 3 aireator give more oxignen than the other 3. The OD in the last 3 is about 3ppm. Does it help?
Nadia |
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Forum Newbie
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Last Login: 6/9/2008 5:55:51 PM
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| | Another thing, We are having high levels of Amonia and low of Nitrite and Nitrate at this moment. We can put down the recicle line, in which way would taht help?
Nadia |
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Supreme Being
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Last Login: 6/18/2008 10:17:32 AM
Posts: 98, Visits: 161 |
| | Are you required to nitrify? Is the high ammonia in your effluent? Is there any speed control on the mixers? |
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Forum Newbie
Group: Forum Members
Last Login: 6/9/2008 5:55:51 PM
Posts: 7, Visits: 34 |
| | It would be great if we can get some nitrification going. We can change the velocity of the first and second agitator. What about the recicle line that you told me before?
Nadia |
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Supreme Being
Group: Forum Members
Last Login: 6/18/2008 10:17:32 AM
Posts: 98, Visits: 161 |
| | You need to increase your mlss this will help you achieve some degree of nitrification. With the mlss that low it is likely you over wasted and are now over aerating which would explain the high ammonia. So try building the mlss and increasing the return sludge rate. keep us posted |
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