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Effluent Sampling
Dennis Hudson
Posted: Tuesday, December 8, 2009 3:06 AM
Joined: 12/8/2009
Posts: 3


We are in the design phase of a plant upgrade to install a disinfection system (UV).

Where is the proper sampling location, before UV or after?

Our permit required testing will include BOD5, TSS, pH, Fecal (which the state is now looking at e-coli).

Our engineer shows a sampling port before UV. When questioned they say this port is for everything but the fecal (or e-coli). For that we will take a grab after the UV.

Thoughts???


Anonymous
Posted: Tuesday, December 8, 2009 6:54 AM

At our plant we collect our efflent sample prior to disinfection. This was originally done so that we did not have to run our CBOD5 as a seeded sample. The lack of chlorination or UV dissinfection allowed a sufficient microbial population in our effluent.


Brent Dickey
Posted: Tuesday, December 8, 2009 9:31 AM
Joined: 9/28/2009
Posts: 18


It's interesting that you're having discussions about where to sample FINAL effluent. We sampled for BOD/ TSS pre-chlorination for over 20 years before our state (and federal) regulators said we had to collect all samples post-disinfection. It's hard to argue the fact that you're not sampling FINAL effluent unless you're sampling post-disinfection. Have your regulators affirmed that it is acceptable to sample pre-chlorination (or UV) for BOD/ TSS?


Robert Smith
Posted: Tuesday, December 8, 2009 11:05 AM
Joined: 10/8/2009
Posts: 5


Technically speaking, CBOD5 before and after UV disinfection should be the same.  This would not be true for an oxidizing disinfectant such as chlorine.  I am not sure about the procedural aspect.


Eric Rajaniemi
Posted: Tuesday, December 8, 2009 12:56 PM
Joined: 10/7/2009
Posts: 10


I would say contact your regulatory agency and make sure that they are okay with that sampling point setup. 

 

~Eric


Anonymous
Posted: Tuesday, December 8, 2009 3:09 PM
Eric Rajaniemi wrote:

I would say contact your regulatory agency and make sure that they are okay with that sampling point setup. 

 

~Eric

 

Differences are interesting indeed! I believe we will ask the engineer to confirm sampling location before finalizing design.

Thanks for everyones input!!!



Anonymous
Posted: Tuesday, December 8, 2009 5:32 PM
Dennis Hudson wrote:

We are in the design phase of a plant upgrade to install a disinfection system (UV).

Where is the proper sampling location, before UV or after?

Our permit required testing will include BOD5, TSS, pH, Fecal (which the state is now looking at e-coli).

Our engineer shows a sampling port before UV. When questioned they say this port is for everything but the fecal (or e-coli). For that we will take a grab after the UV.

Thoughts???


My assumption is always when the regulators state "final effluent" they mean after all forms of treatment.  That is, after the disinfection.  And, that would be for all parameters.  However, for your own internal process control, you would want the ability to sample before disinfection, also.

Jeff Naumann, aka anonymous number__?

James Royer
Posted: Tuesday, December 8, 2009 11:18 PM
Joined: 9/21/2009
Posts: 98


The final effluent, especially with chlorination / dechlorination should be the discharge. Excess sulfite for dechlorination will be oxidized as is accepted as part of the BOD value. Suspended solids could settle out while the flow is in the contact tank and thus you would be reporting values biased high as compared to the final effluent.

 

Disinfection greatly reduces the nitrification process and thus BOD values will be lower without the interference. Just be sure not to use a seed material containing any significant nitrifin bacteria.