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| | | Forum Newbie
Group: Forum Members
Last Login: 6/13/2008 11:07:36 AM
Posts: 4, Visits: 16 |
| I'm still fairly new to BODs so I figured I would seek some advice from you folks out there. Recently, my lab has experienced a sudden drop in values of our BOD blanks. We can't figure out what is causing this and would like to fix it as soon as possible. So, here's a brief run-down of our efforts thus far.
At the onset of the decline in our blanks we figured that it could be our BOD water source that was the problem. So, we changed our water source to store bought, steam distilled water. This helped but only a little, our blanks were still way out of control. Then we changed our bottle cleaning process by making it more rigorous, more rinsing and a higher concentration acid. This did little or nothing to help us. We then purchased some disposable BOD bottles to run a side-by-side comparison with our regular bottles. Results were identical, both had over 1.0 depletion in the blanks. This caused us to believe there may be something wrong with our carboys, so we tried several different cleaning methods to clear them up. This did not help either. We bought new carboys, results were a good deal better out of the new carboys but still nowhere near the 0.1-0.2 prescribed depletion. Now the results out of one of the new carboys have started to turn sour as well. All this time we have been using steam distilled water.
This a brief synopsis of our problem and efforts thus far. If anyone has any idea about what could be our problem and a possible solution, please let me know. Thanks.
Phil |
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| | | Supreme Being
Group: Forum Members
Last Login: 11/19/2008 10:23:25 AM
Posts: 148, Visits: 301 |
| | Have a look for algal and bacterial growth on the inside of the carboys and on aeration tubes and aeration stones. Also consider posting this in the lab discussion board -- more traffic there for this type of question. |
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Supreme Being
Group: Forum Members
Last Login: 11/18/2008 2:55:41 PM
Posts: 83, Visits: 542 |
| | Have you verified that the incubator is holding a temperature of 20C - even temperature throughout the incubator, and consistant day and night? We just replaced our BOD incubator because the temperature was varying by more than 5 degrees. It wasn't holding 20 degrees C at all, plus the top shelves were considerably warmer than the lower shelves. This wreaked havoc on our blanks. We also use store bought steam distilled water, but add the chemicals directly to the gallon the water comes in. This makes just enough for one batch, and eliminates the errors you can get from algae and bacteria in the carboy. |
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| | | Junior Member
Group: Forum Members
Last Login: Yesterday @ 12:32:53 PM
Posts: 18, Visits: 553 |
| | I have the best results using 5 gallon glass jugs to store water in and then make up the dilution water immediately before use. All the glassware is washed with detergents and water after use. Plastic will eventually degrade and scratch which leads to nice hiding places for bacteria to grow. Don't use rubber or plastic tubing to dispense dilution water. Use a glass beaker instead. Also try this idea to eliminate the possibility of the DO probe contaminating the blank: Fill four BOD bottles with dilution water, record the DO of two of them and discard; cap the other two (unread) and incubate. After 5 days read these two out and see if there is any DO difference between the first 2 bottles and the last 2. Make sure the DO probe is kept clean. I always swish it in a dishwashing detergent solution and rinse thoroughly with water after each run. Gregg |
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| | | Supreme Being
Group: Forum Members
Last Login: Yesterday @ 8:57:06 AM
Posts: 99, Visits: 104 |
| | What type of set-up do you use to aerate/mix your dilution water after adding nutrients to it? If a pump is used, perhaps contaminants in the ambient air of the lab are being sucked and injected into your dilution water. If you have this type of arrangement perhaps try using filter cartridges on the intake side of pump to clean out contaminants. If you already use filter cartridges perhaps they are maxxed out and need replacement. Good luck! Egadz |
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| | | Forum Member
Group: Forum Members
Last Login: Today @ 8:09:31 AM
Posts: 29, Visits: 216 |
| | Have you had any changes in the lab, including painting or any other fumes? We had painting with epoxy paint outside our lab and all blanks depleted until the odor had left. Even BODs in the incubator. |
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