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| | | Forum Newbie
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Last Login: 4/30/2008 1:42:08 PM
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| | What can I use to adjust the pH of the BOD water without adversely effecting the seed microbes and BOD sample results? I have "googled" this question, but only seem to find how to adjust samples...do you use the - 1 N sulfuric acid or 1 N sodium hydroxide to adjust the BOD water also? Thanks! |
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| | | Junior Member
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Last Login: 9/3/2008 1:51:17 PM
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| | Are you checking the pH before adding the nutrients to the water? Your water should start with a pH in the range of 6.5 to 7.5. After adding the phosphate buffer, the water pH should be in the range of 7.2+/-0.2 and you should not have to adjust the pH. I am not aware of a situation where you would have to adjust the pH of the prepared dilution water. Any comments Perry? |
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| | | Supreme Being
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Last Login: 9/4/2008 12:12:08 AM
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| If I read your question correctly, BOD5Tech, by "BOD water" you are referring to dilution water and not to samples. If the buffers have done theirs job, the pH will be in the vicinity of 7.2. I have never seen in an EPA-approved method (such as Standard Methods 5210B) where an acceptable range is given, or what to do if dilution water is not in an acceptance range. Chemistry for Sanitary Engineers, 4th Ed., 1994, McGraw Hill, page 276 says dilution water should be between 6.5 to 8.5 pH units, and if it is not, source water is probably the cause and alternative waters should be investigated. Just as dhmh says, dilution water is usually very close to pH 7.2 and wouldn't need adjustment. I have never run into a lab where it was outside the 6.5 - 8.5 range.
There is one thing about your question that makes me wonder if I have interpreted it correctly, and that is your reference to affecting the seed microbes. There are no seed microbes (to speak of) in dilution water, or at least there shouldn't be. So maybe you are talking about waste samples. If so, the requirement is addressed in Standard Methods, but let us know if you don't understand it.
Perry |
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| | | Supreme Being
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Last Login: 9/5/2008 12:57:51 PM
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| If the pH is still out after you add the phosphate buffer, you need to find a different source of make up water.
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| | | Forum Newbie
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Last Login: 4/30/2008 1:42:08 PM
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| thank you for the responses...I can see where the confusion stems from after I re-read my post....I was in a hurry, and a little overwhelmed -  I did mean the BOD/Dilution water - I wasn't sure if you could adjust the pH on the water if it was out of range.....and if you could, what chemicals to use. I was afraid if you used chemicals to adjust the pH, that they would have a toxic effect on the seed, since the water is used to re-hydrate the seed. I just wanted to double check before I assumed it was the nutrients...on Friday I realized they are clumpy and not dissolving all the way. Now I am positive that is the problem. Thank you both!  |
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| | | Forum Guru
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Last Login: 9/5/2008 2:00:08 PM
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| | Obviously you are using some sort of nutrient pillows since you are having "clumping" issues. As the recipient of almost eight years experience of using Hach nutrient pillows, I will tell you to be sure to thoroughly shake up your dilution water after adding the pillows to it. I prefer to batching up fresh reagents from the recipe given in standard methods. They are much more reliable, no "clumping." Egadz |
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