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  • Waste water BOD

    We have put a new permit through the city recently and now the waste water guys are breathing down my neck to get samples, probably to charge me more. The last sample came back good (7.5 pH, low DO, low suspended solids, high phosphorus, low alkalinity, and high BOD). The BOD was so high it maxed out their meter. The dump in question was from keg washing on one fermenter. Below is some background information.

    Keg Washing: We wash under CO2 pressure with Five Stars Acid #6 and sani-clean. The rinses get sent to the "dump tank" and then the chemicals will be sent there as well.

    Fermenter: The first rinse of the fermenter with Hot Liquor goes into the "dump tank" and then each sequential one goes down the drain until it contains chemicals or a first rinse after chemicals. The second rinse(s) / cool down goes down the drain. We use Acid #5 from Five star for our acid cycle, followed by liquid circulation cleaner (caustic) from Five star, and then sani-clean from five star.

    All these chemicals get sent to the "dump tank" and neutralize themselves out for the most part, I rarely need to make additions to the tank to further neutralize it. From the dump tank we attach a sock to help catch any large particulate before it goes down the drain but this obviously won't catch BOD, which is where my problem is. Does anyone out there know how I could further drop my BOD to appease the waste water guys or am I stuck with high BOD?

    Thanks

  • #2
    waste water

    Are we to assume you are on city sewer? Or septic. Who exactly are the "waste water guys" and what are they instructing you to do?

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    • #3
      City sewer

      Yes sorry, I guess that would be important information as well. We are on city sewer and the waste water guys are with the city. We just applied for a new building permit and that's why they are here at my door. They are not telling me to do anything right now they are assessing my waste water against what I had projected it would be prior to opening. If I underestimated they are going to charge me more $$$, which I have already paid them $14K. If I overestimated I probably won't hear anything else from them ever but the guy said the other day that the BOD was maxing out their meter (he said somewhere between 500 and 2000 PPM, which seems like a large range to me) but it could have been a problem with their dilution rate...

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      • #4
        they are going to want to charge a ton for that high BOD, a good way to reduce your BOD in the "dump tank", would be to have a controlled wetland of your own that you send your dump tank water through slowly that will take up all of those nutrients, because thats essentially what the wastewater dept is charging you for. Obviously that isn't really a viable solution for most breweries though.

        I saw a cool design for a house in a hot climate once that has essentially a wetland on the roof and alot of the wastewater gets pumped to the top of the house. This allowed for the house to be cooled by the waste water, and also removed much of the BOD.... i know theres lots of forward thinking breweries out there, theres probably some with cool solutions for issues like the one your experiencing, and pretty much every other brewery for that matter. good way to save some cash..


        An easier solution-- Im assuming they will take one of those samples and figure out a rate to charge, and then assume all the water that comes out of your faucets is going to be going down the drains in your building and charge you that rate. A good way to get the rate to be cheaper is figure out how much water is going into packaging and leaving through the distributor and how much water leaves in your spent barley for cattle feed/compost ... then they can only charge you for the water thats actually going down the drains instead of assuming.

        Dan

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        • #5
          Aeration?

          I also seem to remember reading somewhere that aerating the discharge water in the dump tank may also drop BOD. Is there anyone out there doing this? Whats the science behind this before I go and buy a fish stone to go on the end of my compressed air hose?

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          • #6
            a tree rots much much faster above water than a tree underwater.. this is because: exposure to oxygen.

            I suspect it would probably help to some degree. It can only speed up the process of breaking the BOD down.
            Last edited by Junkyard; 04-06-2014, 01:55 PM.

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            • #7
              Trickster -

              By aerating the dump tank, you are talking about basically making your own "suspended growth" wastewater treatment system. What will happen is that you will convert the dissolved BOD into (solid) bacteria - these are the guys that break down the BOD. A typical wastewater treatment system would have a aeration basin (as you suggest creating) followed by a clarifier to remove the settled solids (bacteria). Some of the bacteria are "wasted" (disposed) and some are "returned" to keep the aeration basin populated.

              So, I think your problems would be: 1) how can you separate the solids from the water (what we'd call "effluent") and 2) how do you keep a consistent population of bacteria for treatment in the dump tank. You'll also need a sufficient amount of time in the aeration tank to build up the population of bacteria and then to let the bacteria do their thing and remove BOD.

              I should also add that if you discharge the bacteria to the sewer, you'll still have a pretty high BOD (the bacteria themselves add to BOD, as they die and are consumed by other bacteria). However, some of your BOD would have been totally degraded to CO2, so you should have a net reduction in BOD, but my guess is that it won't be a whole lot. The longer the treatment time in the aeration basin, the better, in terms of net BOD reduction.

              But, really, this is all to say that I think you should first look at your in-house processes and see what opportunities you might have for avoiding, concentrating and/or diverting the highest-strength waste streams. Then you might consider, as Junkyard suggests, some type of onsite treatment system to cut your BOD down before the sewer. Most sewer utilities are going to surcharge BOD. BOD (which is essentially a surrogate measure for organic carbon) requires aeration to break down (actually it can be done anaerobically also, but it is a much longer process), aeration at wastewater treatment plants mean blowers, blowers mean motors, motors mean energy, and energy means money.
              Victor D'Amato, PE

              Water, wastewater and energy management
              Sustainability consulting

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