BOD DILUTION WATER

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BOD DILUTION WATER

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Carola

Posted 7/20/2007 5:37:20 PM

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Last Login: 8/18/2008 3:13:30 PM
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I'm getting back to the wastewater lab after being in a private industry lab for about 6 years. The first problem I'm dealing with is the BOD test. In my old wastewater lab we had a still, we aerated our BOD water the day before setting up BOD's and we made all our own reagents. We never had a problem with blank depletion. Now I'm using the pillow packets that are added to the water which I shake for 5 minutes just prior to setting up BOD's. The dilution water pH is only about 6.40 after adding the buffers and nutrients and before adding sample. The temperature of the water is 20 degrees. My blank depletions have been over 0.2 mg/l several times. I air calibrate the DO meter and adjust for barometric pressure. The water that I use is steam distilled water purchased locally. I'm thinking that I may need to go back to my old way of aerating the water for 1/2 hour the day before and I'm also wondering if the problem could be the water itself. The pH before adding anything is about 5.4.

Any suggestions?

Post #5993