Aeration System - Oxygen Requirement 1


    Oxygen Requirement

     a). Theoretical Oxygen Requirement

(So-S)/BODu » 0.68

O2 (mg)/MLVSS (mg) = 1.42

QAd (gal/day) S0 (mg/l) S (mg/l)
yPX (lb/day)  (S0-S)/BODu

(lb O2/day)

     b). Standard Oxygen Requirement (SOR) under Field Conditions

     C ¾ minimum dissolved oxygen (DO) concentration required in aeration tank

     a ¾ coefficient to account for effect of mixing intensity and tank geometry

     b ¾ coefficient of effect of salinity and solid in waste water on DO concentration

     CS,20 ¾ saturation of oxygen in tape water at 20°C

     C = 3 mg/l

     a = 0.9

     b = 0.85

     CS,20 = 9.1 mg/l

     Pb, pressure at depth of disc diffuser (15.0 ft)

     Generally, oxygen transfer efficiency with diffuser system is about 10%, which can be used to approximately atmosphere pressure to 0.9 atm. More information will be available from a table at the bottom of this page.

     Pb = 1 + 15/33.9 = 1.44 atm

     CSa  = CST[Pb + (1 - 0.1)]/2 (mg/l)

     CS25 = 8.34 (mg/l), oxygen solubility at field condition of 25oC

     CSa  = 8.34[1.44 + (1 - 0.1)]/2 = 9.75 (mg/l)

     Normally average temperature in aeration tank = 25°C

O2T (lb O2/day) a bC (mg/l)
CS20 (mg/l)  Depth of disc diffuser (ft)  CST (mg/l) Feild T (°C)

Pb(atm) CSa (mg/l) SOR (lb O2/day)

     c). Standard Oxygen Transfer Rate of Aeration System



System
Oxygen Transfer Efficiency (%)
Fine bubble diffusers, total floor coverage
20 ~ 32
Fine bubble diffusers, side-wall installation
11 ~ 15
Jet aerators (fine bubble)
22 ~ 27
Static aerators (medium-size bubble)
12 ~ 14
Coarse bubble diffusers, wide band pattern
6 ~ 8
Coarse bubble diffusers, narrow band pattern
4 ~ 6

Table: Standard Oxygen Transfer Efficiency (SOTE) for Air Areation Systems in Clean Water at 15' Submergence

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