Q: I have a question for your blog about predicting dissolved oxygen levels. I am looking for an equation that will predict with reasonable accuracy the dissolved oxygen levels of wort using an inline aeration assembly with a lpm regulator on the oxygen tank. I have heard that anywhere from 4 to 6 lpm for 30 to 45 minutes with a 10bbl system with give about 8ppm dissolved oxygen, but this range is far to large. Lets assume that my oxygen stone is clean, I run at 4lpm for 30 minutes into 10bbls of wort at 11 degrees celsius. Is there an equation out there that will take into account these components and provides with a somewhat accurate prediction for DO levels? Any help would be greatly appreciated!
A: Correct wort aeration is critical for yeast health and performance. A fairly easy way to gauge O2 absorption to your flow meter is to simply put the O2 tank onto a scale and observe the net weight used for a typical wort run off. Assuming the O2 is completely absorbed you can take the weight in milligrams and divide it by the total liters of wort run. Compare this figure to the flow rate in liters per minute on your flowmeter and make the necessary adjustments to your aeration flow. The target should be about 8-10 ppm (mg/L) dissolved oxygen. For 10 bbls of wort (1,172 liters) you should be adding 9.4to 12 grams of oxygen to achieve 8- 10 mg/L. Make sure your aeration stone is kept clean, clean it regularly with a causitc-oxidizer solution and soak it in acid every once in a while to dissolve mineral deposits.