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Polyseed
Shawn
Posted: Tuesday, January 19, 2010 11:54 AM
Joined: 1/19/2010
Posts: 1


  I know this has been asked before! Should the seed be aerated while making.We use Polyseed brand. Also we incubate our dilution water 24hrs prior to use, when should the nutrient buffers be added?


Anonymous
Posted: Tuesday, January 19, 2010 12:34 PM

Hi,

 

We make up 6 liters of dilution water using one of Hach's buffer pillows (6L size) and ultrapure deionized water.  We aerate the 6 liters of dilution water for approximately 1 hour.  We then place this container in an incubator overnight or longer. 

Each time we set up to run a batch of CBOD's, we make up 500 mLs of Polyseed solution.  One capsule of seed to 500 mLs of dilution water in a beaker.  I pour the seed into the 500 mL of dilution water, not the other way around.  Make sure the beaker is set on a slow speed stirrer.  Aerate for 1 hour with an air stone, plastic tubing, and fish pump.  I usually put a cover glass over the top to prevent loss of solution.  After the hour expires, turn off the fish pump and pull out the air stone and tubing.  Allow the solution to settle for approximately 15 minutes. Pour off the top into a clean beaker.  Stir slowly until needed.  Works for us.

 

 


dsmith
Posted: Tuesday, January 19, 2010 2:09 PM
Joined: 12/31/2009
Posts: 40


You really should avoid having the water sit for too long once the nutrients have been added.  Most labs allow their pure water to sit for a day or so before use.  This allows the water to come to equilibrium with respect to the oxygen content.  It also allows you to get everything to the proper temperature.  Typically, once you do this you won't need to to any aerating or stirring other than the minimal amount to dissolve the nutrient pillow contents.  Allowing the water to sit with the nutrients added only encourages microbial contamination to take hold.  We add our nutrients just prior to seed rehydration.  Yes, you should aerate the seed solution while stirring. 


Perry Brake
Posted: Tuesday, January 19, 2010 10:49 PM
Joined: 12/16/2009
Posts: 69


 David (dsmith) is right about not adding the nutrient/buffers the day before you do the test.  The method specifically tells you not to do that.  However, there is a caveat, and that is if your are doing carbonaceous BOD (CBOD), and it appears that is what Shawn is doing.  When you add the nutrients/buffers the day before the test (or earlier), you encourage the growth of nitirifying bacteria which is bad if you are doing BOD.  But if you are doing CBOD, you inhibit those nitrifiers so it doesn't really matter.

 

Like David does, I recommend aerating the source water (distilled, DI, RO, or whatever) at least the day before the test and allowing it to sit in the incubator with the container top sitting on the container's opening, but not screwed down...this allows transport of air in or out so that the water is just saturated on the day of the test.  Add the buffers/nutrients by gentle swirling so as not to cause air bubbles, and let it sit for an hour or so as David suggests.


Eric Rajaniemi
Posted: Tuesday, January 26, 2010 10:46 AM
Joined: 10/7/2009
Posts: 10


Polyseed always used to advise not aerating their seed, so I do not know what they have recently changed about its mix.  If your BOD water is close to saturation regarding D.O. I can't see the need to aerate it while rehydrating the bugs. 

 

~Eric(Egadz)


Perry Brake
Posted: Tuesday, January 26, 2010 3:44 PM
Joined: 12/16/2009
Posts: 69


As soon as the bacteria are re-hydrated, they begin consuming any organic material in the mixture and depleting oxygen while so doing.  If you follow the manfacturer's prep instructions, you use the seed after only an hour (45 minutes?  I don't have the instructions) and the bacteria will not have depleted much oxygen.  But if you stir the mix overnight or longer, they do have enough time to deplete a significant amount of dissolved oxygen which is why you would want to aerate for that longer period.


Eric Rajaniemi
Posted: Wednesday, January 27, 2010 9:02 AM
Joined: 10/7/2009
Posts: 10


Polyseed states that for "best" results to use seed within six hours of rehydration.  Holding overnight is obviously not recommended.  At one time they discouraged you from aerating it at all for it tended to grow undesireable organisms on the glassware, in the tubing, and in the seed solution.  I am unsure what has changed in their formulation of the seed material since then.  Too fast stirring and especially stirring longer than an hour creates conditions in the flask which induce logarithmic growth of the organisms.  That is straight from the mouth of the owner of Polyseed just a few years ago.  Best results come from adhering closely to their instructions.

 

~Eric


LEANNE
Posted: Wednesday, November 10, 2010 1:28 PM
Joined: 11/10/2010
Posts: 1


Does anyone analyze BOD samples for 7 days? If so, where did you purchase the QC?

 


Perry Brake
Posted: Thursday, November 11, 2010 11:07 AM
Joined: 12/16/2009
Posts: 69


Leanne, to the best of my knowledge, there is no "special" QC sample for a 7-day BOD.  You would just use the normal standard...150 mg/L each of glucose and glutamic acid.  The question then becomes, "What result should I expect from that standard for a 7-day BOD?"  Intuitively, you would expect it to be more than 198 mg/L, but I am not aware that any study has been done to determine just how MUCH more.

 

The depletion of oxygen slows way down as the incubation period approaches 5 days, and slows down even more after that, so I would imagine a reasonable expectation would be that a 7-day BOD would give you 210 mg/L or so (that's assuming that the seed you are using gives you something close to 198 mg/L in a 5-day BOD).

 

If you have GGA data for the 7-day BOD, why don't you post some of it here for the benefit of all!

 


James Royer
Posted: Friday, November 12, 2010 8:08 AM
Joined: 9/21/2009
Posts: 98


Leanne,

I have a Table from the old days where BOD was corerelated to Relative Stability. It assigns a BOD5 as being 68% stable. It then gives factors for different days relative to the 20 degree 5 day BOD as 1.00 units.

 

For 6 days you would multiply by 0.92 and 7 days multiply by 0.86 to compare back to the 5 day BOD.

 

All of this data was done on samples with easy oxidized carbonacous BOD as it was to relate to methylene blue oxidation in the Relative Stability test which did not oxidize ammonia.

 

I can e-mail this chart to you if you contact me.


Maddy
Posted: Monday, December 20, 2010 8:52 AM
Joined: 12/20/2010
Posts: 2


Eric Rajaniemi wrote:

Polyseed states that for "best" results to use seed within six hours of rehydration.  Holding overnight is obviously not recommended.  At one time they discouraged you from aerating it at all for it tended to grow undesireable organisms on the glassware, Delete Duplicates  in the tubing, and in the seed solution.  I am unsure what has changed in their formulation of the seed material since then.  Too fast stirring and especially stirring longer than an hour creates conditions in the flask which induce logarithmic growth of the organisms.  That is straight from the mouth of the owner of Polyseed just a few years ago.  Best results come from adhering closely to their instructions.

 

~Eric

 

Best For ReHydration!Good!

 



Maddy
Posted: Monday, December 20, 2010 8:54 AM
Joined: 12/20/2010
Posts: 2


 


Posts: 69


As soon as the bacteria are re-hydrated, they begin consuming any organic material in the mixture and depleting oxygen while so doing.  If you follow the manfacturer's prep instructions, Delete Duplicates  you use the seed after only an hour


JackDorsey
Posted: Friday, June 28, 2013 5:49 AM
Joined: 6/28/2013
Posts: 1


Eric Rajaniemi wrote:

Polyseed states that for "best" results to use seed within six hours of rehydration.  Holding overnight is obviously not recommended.  At one time they discouraged you from aerating it at all for it tended to grow undesireable organisms on the glassware, Delete Duplicates  in the tubing, and in the seed solution.  I am unsure what has changed in their formulation of the seed material since then.  Too fast stirring and especially stirring longer than an hour creates conditions in the flask which induce logarithmic growth of the organisms.  That is straight from the mouth of the owner of Polyseed just a few years ago.  Best results come from adhering closely to their instructions.

 

~Eric

Thank you...nice info.