FE Civil/FE Environmental - Activated Sludge - Volume of Aeration Tank

[@dand7056]

I wanted to thank you for your videos. After 27 years of being out school I decided to take the FE and finally after many attempts I passed it. I will say your videos helped me get some of the topics I had trouble with. And I enjoyed your motivational intros as well. Time management is key in passing this test and one tip is if you struggle with the problem outside of a test put in the time and learn it but on the test let it go. Don't be stubborn. It's OK to not know every problem. Just do well on the majority. Thanks again. If you have an environmental PE review courses let me know. Or if you can suggest any resources. All the best to you.

[@directhubfeexam]

Hey Dan!! This is wonderful news my friend. Thank you so much for updating me after successfully getting that passing result. It seems like you worked really hard, overcame many obstacles, stumbled a few times, yet you kept going. I'm inspired by your story. This just proves age and time out of school is no excuse to passing this exam. I'm very happy to know the videos helped. I love teaching environmental topics more than others so it always brings me joy to know you were tuned in the whole time. I could tell by your engaging comments. Thanks for that! These are some great tips for any newcomer watching these videos. I'll make sure to pin your comment to help others out. Life is getting a little too busy for me at this time. I haven't started creating content for the PE Course. It's something on my mind though. It will certainly come in the near future.... I suggest checking out the PE reddit forums for PE prep recommendations. I mainly focus on the Water Resources and Environmental PE, so if you need help with that, just email me at [e-mail] Here's another Congratulations 🥳

[@christophermakransky1184]

Great video! Very in depth. Small correction: the process area noted as “Activated Sludge” is actually the secondary treatment. The disinfection process is known as Tertiary treatment, or the polishing/finishing treatment following secondary. Examples include chlorination, fluorination, and Ultraviolet disinfection.

[@js7184]

Why wouldn't you use the Tank Volume equation provided in the FE Manual under the Aerobic Digestion Section?

[@directhubfeexam]

Hi, that equation is not applicable to the volume of aeration tank under the activated sludge process. Aerobic digestion is conducted on the wasted sludge. The primary reason we do it is to kill bacteria, reduce sludge mass, odors and other harmful pathogens. So the wasted sludge is disgusted in this aerobic tank then it is de watered , and disposed of. In summary, aeration tank is different than the digestion tank.

[@js7184]

@@directhubfeexam thank you!

[@amelialevesque2356]

What is the difference between X and S? I don't understand the difference between BOD concentration and suspended solids concentration. You mentioned that the primary treatment handles sediment while the secondary treatment handles microorganisms, is S "BOD concentration" a measure of microorganisms and X "suspended solids concentration" is only non-organic sediment? It's confusing also because X is "suspended solids concentration" but XA is biomass concentration in aeration tank. (I'm using the reference handbook 10.0.1) My exam is tomorrow, and the environmental questions have been the most difficult to re-learn. I knew it well once upon a time!

[@directhubfeexam]

Hello Amelia, sorry for the late reply. As presented in FE Handbook 10.1 X = MLSS or MLVSS. This will be very clear in the problem statement on the FE. MLSS indicates suspended solids which can be done by evaporating a filtered residue which is retained in filter paper at 110-120 deg c. MLVSS is volatile suspended solids which can be found by volatilizing the retained solids in muffle furnace at 600 deg c. S = BOD - Biochemical oxygen Demand. This is the rate of oxygen consumed by microorganisms and bacteria to breakdown organic matter is referred to as the biochemical oxygen demand (BOD). Strong sewage - High BOD Weak sewage - Low BOD

[@Pubefloss]

@@directhubfeexam Thank you! I really appreciate the fast reply.

[@directhubfeexam]

@@Pubefloss Thank you!

[@ln2617]

why did you not consider Qr in the equation for the volume. shouldn't it be (Qo/2 + Qr)*residence time = volume ?

[@directhubfeexam]

Hi Lindsay, good question that I never thought about. So following the equations in the FE Handbook, Organic loading rate (volumetric), Organic loading rate (F:M), Organic loading rate (surface area) all depend on the influent flowrate Q_o. All these calculations are for the aeration basin. So I am assuming these equations were derived always using the influent flow as the basis for the flow coming into the aeration basin. So let's just always stick with that. Why, I have no idea, it's something I need to research but I am thinking Qr would not cause a significant load on the aeration basin because we would technically only recycle the flow to introduce some more of that dirty pollutant in the stream. I hope this makes sense.

[@caseyarbuthnot7316]

You stated the effluent is 138 mg/L, then plugged it in for the "So", isn't "So" influent? Confusion.

[@directhubfeexam]

Yes sorry Casey, that is definitely a mistake on my part. So is influent and Se in effluent.

[@priyabhowmik6227]

@@directhubfeexam I thought it would be effluent due to the problem statement saying "in the primary effluent" so it could be the influent concentration for the secondary portion.

[@directhubfeexam]

@@priyabhowmik6227 Exactly, the effluent out of primary treatment is the influent into secondary treatment.

[@rodbarron]

Dude, please spell check and/or double check for errors if you decide to make future videos. One tiny discrepancy can be the deciding factor in solving problems correctly and can also lead to recalling information incorrectly on the exam. Thanks!

[@directhubfeexam]

Got it 👍🏼