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Breaking Down COD

By Heather Jennings, PE 

When I first came into the water field in the 2000s, the general rule of Chemical Oxygen Demand to Biochemical Oxygen Demand (or COD to BOD5) was 2:1. That was pretty much all you needed to know in order to understand whether something could be treated chemically, physically, or biologically. Now, the wastewater industry has moved toward COD instead of BOD5. The reason that COD is sometimes preferred is that BOD5 doesn’t take into account the organics that become biomass nor the non-biodegradable carbonaceous matter. COD can also be evaluated in the field with simple test kits, whereas most operators must send their BOD5 tests to third-party labs and wait weeks for results.   [Read more…]

Love Me Some Lagoons!

By Heather Jennings, PE

Of all the wastewater lagoon systems I have been to, I’ve never met the same lagoon twice! Many consider lagoons old tech, but they can be very reliable and more stable treatment systems than many of the more sophisticated systems out there. Lagoons, like any wastewater system, should not be left unattended for long periods of time! I recommend daily visits rather than once a week or once a month. One of the common issues lagoons have, barring equipment issues, is biochemical oxygen demand (BOD5) issues.

BOD5 effluent issues have several different causes. One of the biggest reasons is short circuiting of the lagoon, either by poor design or due to solids build up. Basically, the treatment process can be cut sometimes to over half of the original intended hydraulic detention in the extreme cases by either issue. Poor design can be overcome by adding baffles and strategically placed mixers or aerators. Solids build up can be handled by dredging, but this usually requires extended closure and, at the least, plastic liner replacements. If you are looking at 30%–50% or more organic solids in your sludge, give me a call as we can break them down with Bio Energizer® without taking your system offline! [Read more…]

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