Hey everyone, I'm new to the forum so I apologize in advanced if this thread is in the incorrect place!

We're currently looking at the installation of a MBBR system to reduce our BOD usage charge. We have not had a problem with our TSS since installing a DAF 5 years ago. I was wondering if someone could help explain the importance of the DAF Clarifier and whether we could use our existing DAF rather than install an additional unit. We have an initial estimate which is outside our payback period and are looking for alternatives if necessary. Please let me know if more information is needed.

Current System:
Influent -> Prescreening -> Equalization -> DAF -> Effluent

Proposed System:
Influent -> Prescreening -> Equalization -> DAF Pretreatment -> MBBR -> DAF Clarifier -> Effluent

MBBR Influent Design Criteria:
Flow Rate: 330,000 gpd
Influent BOD: 3,755 lb/day
TSS: 104 lb/day
Temperature: 20-35C

MBBR Effluent Design Criteria:
80-85% reduction in BOD

sorry/ misread- primary DAF is in the new plan. What are the oil and grease, TSS and particulate CODs leaving the EQ tank currently?

After speaking with the vendor, I learned that if we did not have the clarifying DAF placed after the MBBR system, the bacteria on the media that dies and falls off will be carried away as TSS/BOD, resulting in a dramatically lower removal efficiency. We will be looking into the possibility of placing our existing DAF at the backend of the MBBR System instead of a new DAF Clarifier. In order to do so, we're looking at whether our influent TSS levels would be too high for the MBBR system. I'm seeing some discrepancies in our TSS data but will report back tomorrow once I get them sorted out.

We will definitely obtain other quotes as well but want to make sure we’re in the ballpark in terms of feasibility before doing so. We have not yet looked into a SBR system. To my knowledge, NH3-N is not a contributable factor to the BOD problem. We’re a candy manufacturer if that provides any insight. Our constraints for the project are cost and space (45'x45' outdoor area available). Is an SBR System something that I should consider researching?

TSS Effluent=

We have not yet looked into a SBR system. To my knowledge, NH3-N is not a contributable factor the the BOD problem. Our constraints for the project are cost and space (45'x45' outdoor area). Is an SBR System something that I should consider researching?

Your equalization tank may be used as a primary settlement zone, followed by the biological reactor (MBBR) to remove the BOD, which will be then followed by your DAF which will act as a final clarifier to stop the Suspended solids.  Usually, MBBR reactor effluent prior to clarification, shouldn't exceed 300mg/l SS.  

For your required BOD removal efficiency, MBBRs can be operated at high organic loading rates, which ensure a small reactor.

grrun, thanks for the tip to look into an SBR system. I've reached out to a few companies to explore their thoughts. I'll let you know when I hear back. Everyone else, thanks so much for the information! Below is additional relevant information that I was able to dig up.

We currently don't track our TSS levels because we're well below permissible levels. Using the testing performed for our annual BOD/TSS usage charge statement, I can provide an estimate of our TSS before DAF treatment and after DAF treatment (90% removal efficiency).

Influent TSS (After equalization, before DAF)
1560 mg/L

Effluent TSS (After DAF)
173 mg/L

Our COD levels, however, are tracked daily and are as follows. We don't take measurements immediately before our DAF, just as it comes into the WWTP and as it leaves. I hope this could provide some level of usefulness.

Influent COD
5200 mg/L

Effluent COD
4103 mg/L

I've been told that for our wastewater, an approximate conversion from BOD to COD is (COD*0.65=BOD)

Thanks for everyone’s help and suggestions! We're currently looking into a SBR (aerobic), SBR (anaerobic followed by aerobic), and MBBR. They all have their individual pros and cons but it seems like the limiting factor for our purposes is the cost to remove the sludge from the system! Am I calculating this correctly or am I completely off base? The cost to haul off our sludge will be about $0.125/gal.

Aerobic System (MBBR & SBR Aerobic):
Aerobic
Sludge Yield/Lb BOD      0.5
Sludge Conc. (% solids)      2%
BOD Processed (lbs)      4524
Solids Produced (lbs)      2262
Sludge Produced (lbs)      113100
Sludge Produced (gal)      13561
Cost/Day      $1,695
Cost/Year      $618,728

Anaerobic (SBBR Anaerobic followed by Aerobic)
Anaerobic
Sludge Yield/Lb BOD      0.1
Sludge Conc. (% solids)      4%
BOD Processed (lbs)      4524
Solids Produced (lbs)      452.4
Sludge Produced (lbs)      11310
Sludge Produced (gal)      1356
Cost/Day      $170
Cost/Year      $61,873

The aerobic systems are considerably less expensive to install but if the operating cost prove to be this high ($600,000+/year) it would negate the usage charge decrease we are hoping for. The anaerobic system is much more expensive and would provide a longer payback than we are looking for (even when factoring in the methane that it would produce). We do have a dewatering press but the cost to operate it (energy, filter powder, waste disposal) was greater than the liquid disposal and its disposal method (landfill) did not match our environmental initiatives. We currently decant off about 1,000 gallons of water from 3,500 gallons of sludge from the operation of our DAF before having the liquid sludge hauled off (2,500 gal about once a week).

Basically, is the sludge production as significant as we project it to be? I need a sanity check  

It seems to me that you should not be making such a decision without more "actual" TSS, BOD, COD, and oil and grease data on both influent and effluent.  From the posts it would seem that lots of "assumptions" are being used to predict operational success, such as a BOD/COD ratio.

The idea of using your equalization tank as a primary clarifier would not seem doable to me, as I expect the tank is actually needed for equalization.  In addition, how would the sludge be removed from the tank?  What about floatables?  Can we assume the DAF was originally chosen since the solids tend to float rather than settle?

Regarding the present means of sludge disposal.  Can you be assured that it will be viable for the near and distant future?

All in all, I would recommend that you get better influent and effluent data before deciding on any modifications.

One thing (unless this has changed), " Our constraints for the project are cost and space (45'x45' outdoor area)." that has been forgotten as this discussion has progressed. I thought that the SBR would be more space efficient because it would not need a DAF or clarifier downstream. An MBR might also fit the space restraints. I'm ignorant when it comes to sizing aneraboic systems. However if there is the ability to concentrate sludge and it is unused because of expense; then you should also enter this into your requirements.

grrun