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Extended aeration
« on: Feb 22nd, 2007, 12:23am » Quote Modify
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Dear experts,
I would like to consult you about extended aeration tank design, the wastewater characteristics are as follow:
Q 700 m3/d
CODin 1400 ppm
CODeff 20 ppm
TKNin 85 ppm
TKNeff 20 ppm
I tried using the below design criteria:
SRT 20 Days
Y 0.5 Kg/kg
kd 0.05 1/d
MLVSS 4000 ppm
MLSS 5000 ppm
I got a big tank from calculation and hydraulic detention time is very high (>48 hr). Even though, the organic loading rate and F/M are still high.
Would anyone please advise me regading this matter?
Is it possible to use such high detention time? If I use the maximum organic loading rate of 0.4 kgBOD/m3/d (From metcalf) to design, the required volume is 2450 m3 consequently the hydraulic detention time will be as high as 3.5 d that exceeds the hydraualic detention time indicated in Metcalf (18-36 hr).
Thanks anyone who reply in advance.
BGDS,
Nj

Neerajee,
You have quoted influent COD and yet you have done a calculation using BOD/m3/d.
Most extended aeration plants are 18 to 36 hours hydraulic detention time at design load.
Can you confirm whether it is BOD or COD you are basing your design on.
Cheers
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Sorry for typo.
Actually I use BOD.
BOD inf is 1400 mg/L
BOD eff is 20 mg/L

Thanks in advance for any help.
Neerajee
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