We have a food processing plant in the state that makes vinegar, mustard and apple juice.  They currently pretreat their wastewater in aerated lagoons and then send it to a POTW.  The aerated lagoons need to be abandoned so the processing plant is looking for alternative methods to pretreat their wastewater.  Biological methods such as activated sludge would not be considered.  Are there other physical/chemical methods that might work?

Here are some details:
Wastewater flow = 5,000 - 7,000 GPD
Influent BOD 10,000 mg/l
Effluent BOD needs to be 300 mg/l

The mustard production produces a lot of solids so there will be a filtration step involved prior to BOD treatment.

Thanks for any help you can provide.

If the bulk of the BOD is soluble in nature they will have to work at implementing stringent Best Management Practices in all production areas and prevent it from entering into the water to begin with.

Floor drain sieves, dry clean up, and emphasis upon less water used during cleaning are a help.  They could install very fine roto screens to remove solids more efficiently.  They could insall a DAF unit, run it with coagulants and flocculants, and remove all oil and grease along with TSS and any associated BOD.  pH adjustment may aid in the precipitation of dissolved metals but that will require multiple tanks.  

They must also recognize that their discharge to the POTW will likely be nutrient deficient, it will not have the proper balance of nutrients that aerobic organisms require in order to reproduce at the POTW.  

They might be able to install a large equalization basin equipped with diffused air.  This could enable them to oxidize the long chain molecules of sugar and others down to much smaller chains.  The longer the molecule chain the longer it takes organisms in the process to consume them.

~Eric

The lagoons need to be abandoned for a lot of reasons.  High levels of arsenic have been found in the surrounding groundwater, suspected from leaching of the lagoon contents (clay lined), high sludge levels in the lagoons, serious odor problems, poor BOD removal in the winter, flow limitation by the Town of 20,000 GPD max.  During periods of snowmelt or rainstorms, the discharge needs to go higher than that.  So all parties agree that the lagoons need to go.

I don't think he is saying that it is the source of arsenic contamination - just that it might be. Not unusual for juices and such to contain arsenic - even Baking Soda has arsenic in it.

I will add that arsenic levels in the lagoon sludge are not a problem.

Dear Ripple,

seems to me that with this high BOD load you should consider anaerobic treatment with biogas production. Even if you would be able to remove it purely by physical means, you would to have to do something with the removed organic stuff.

Kind regards
T. Sobisch

Nice sharing.
I think this treatment is so good than other treatments and i hope this
method would be very useful for water purification.

How about a septic tank? You might need a tiny package plant after it or an SBR.

Would take some bench testing - but seems this can be a simple plug/play skidded unit to handle this.

Sludgefather,

All of the options that you have presented have been investigated.  It has been a tense relationship between the industry and the town, making negotiations of any kind difficult.  As long as the industry abides by their permit, everything is fine.  But when the industry needs to discharge more flow than is allowed by the permit, the town balks.  The town has hit the industry with huge monetary fines several times in the last few years for too much flow, BOD, TSS, etc. , hence the main reason to get rid of the lagoons.  Trucking all of the wastes to another plant has been investigated but would be very costly.

I have been pushing the idea of using the wastewater for supplemental carbon and I think there is a market for that.  We are seeing total nitrogen limits here of 3 mg/l and phosphorus to less than 0.2 mg/l.    

Are there small package anaerobic treatment units that can be used? I think the Biothane process was investigated but deemed too large for their small flows.

Hi Tom,

I agree with you 100%, but it is easier said than done.  Our state environmental department has tried to negotiate agreements in the past and have been accused of taking the industry's side.  It is often left up to the lawyers.

Good luck with the supplemental carbon idea. Depending on how desperate people are you may be able to get rid of it for free and maybe even charge the recieving plant for the trucking. In some cases one man's waste is another man's treasure, especially with some of these new super low total nitrogen limits.

best regards,

Ryan