WEF Discussion Forums
Laboratory Management and Technical Issues
Acid washing BOD bottles
How often is it appropriate to acid wash BOD bottles? Normally I would acid wash every 3 to 4 months with hydrochloric ACS grade. I use liquinox to wash after use. Anyone have a view?
We wash our BOD bottles once a month with NoChromix added to concentrated sulfuric acid.
The frequency of acid washing depends on what your blanks are doing.
If your blanks are normally 0.1 or less (that's not a typo...I didn't mean to say 0.2), I would advise acid washing when, 1) your bottles have a visible scum that can't be removed in normal washing, or, 2) when your blanks start to creep upward.
If your blanks are normally 0.2 and sometimes higher, you can try acid washing, but if that doesn't bring the blank down, your problem is probably something other than dirty bottles.
My experience in assessing literally hundreds of labs doing BOD is that dirty bottles are seldom the cause of high blanks, the reason being that people pay so much attention to it. More often than not, high blanks are caused by the choice of source water (e.g., distilled, DI, RO) used to prepare dilution water.
Back when I was in the lab every day I only acid-washed the bottles when they still had water droplets inside after the distilled water rinse AND the droplets remained after a second Liquinox wash and rinse.
I heard that WEF finally allowed non-members to create an account, so I broke down and came back and registered.
My take on this is that you shouldn't ever have to acid wash the bottles because you should be using the disposable bottles anyway. If you are so worried that your normal hot water/soap cleaning isn't getting everything out, how convinced are you that you are adequately removing all traces of your acid wash? The time and equipment used cleaning and worrying about the cleanliness of the bottles is well worth the approximately $0.70 per bottle. Check out Environmental Express (www.envexp.com) for ordering information. I think they will even send you a free sample pack to try out. No, I have no connection to them and receive no compensation for talking them up. I do believe in promoting products and companies that I am impressed with and these guys definitely fit the bill.
I think that an $8 BOD bottle is a good investment as long as the lab is not having any problems with their blanks. The only time we would use disposable BOD bottles is for special BOD studies where we do not want to purchase a lot of additional glass bottles to store after the study is over.
We have some BOD bottles that are probably 30 years old or more. We have to wash other glassware, beakers and cylinders, so it does not add that much time to the schedule. We use a dishwasher with DI water rinse and do not have any blank problems.
If you were only doing BOD and TSS it might be more cost effective to use disposable BOD bottles. Checking the pH of a few BOD bottles after acid washing does not consume much time as we check the dilution water pH anyway. Glass saves much plastic in the landfill as I would be concerned about recycling without deactivating patogens prior to disposal.
I appreciate your comment that blank problems are probably due to source water. We have a two mixed beds and carbon tank (US Filter)treating the source water which is public water from deep wells. We have persistent blank problems. Disposable bottles helped a little. However, it seems the source water is the problem. In your book you suggest that purchased distilled water may be used. Do you have other comments that might help? Thank you, Carl Addy
Hi, Carl! In the book, I suggest trying "steam distilled" water if
all else fails. Sounds like double talk, doesn't it! All distilled
water goes through a steam phase, but to be advertised as "steam
distilled" it goes through much more than that. It is distilled at
higher than normal atmospheric pressure, goes through RO and
deionization, and filtration at the micron level. As far as I know, it
is the purest water available to the general public...it's used routinely by the medical, dental, photography, and other professions needing extra-pure water. If supermarkets
in town don't sell it, ask if they can order it. They will look at you
like you're crazy at first, but explain what it is and they might be
willing to call their water distributor. Appendix B of the book lists
some suppliers in the northwest where it is available for only a few cents more per gallon than "regular" distilled water.
steam distilled, distilled water works for you, then you have a choice
to make...keep buying it, or upgrade your reagent grade water system in
the lab. The problem is, I don't know what to recommend for a system upgrade. Lot's of things will get through a DI column, but a charcoal filter usually gets what's left as long as you change your beds as recommended.
Here again, it's a crying shame that all the old posts are gone. This subject was vetted thoroughly on the old forum.
We finally switched to disposable bottles, and everyone in the lab is glad we did. They're recyclable and cheap. Our central stores orders them by the pallet load.
BTW: Is anybody else ticked at this annoying text box that's too small and has to have that idiotic scroll bar across the bottom? Grrr.
Oh, spam bombs are making their way into various forum postings. I've alerted the Forum.
I use 300ml BOD bottles. just wondering how much Sulfuric Acid acs grade per bottle?and do you fill the rest of the bottle up with distilled water? Or just rinse a small amount of the acid concentrate around in the bottle until it is completly covered .this(later method) is actually how I used to do it but went to contrex det. just thought i'd acid wash ever so often. thank for the help in advance.
We use contrad 70 (an alkaline cleaner) every few weeks to soak our BOD bottles. It seems to keep the blanks in line.