Two activated sludge aeration tanks at Turkey Run, Indiana, are operated in series. Each tank has the following dimensions: 7.0 m wide by 30.0 m long by 4.3 m effective liquid depth. The plant operating parameters are as follows:
Flow = 0.0796 m3/s
Soluble BOD5 after primary settling = 130mg/L
MLVSS = 1.500 mg/L
MLSS = 1.40 (MLVSS)
Settled sludge volume after 30 min = 230.0 mL/L
Determine the following: aeration period, F/M ratio, SVI

MLSS stands for (Mixed liquor suspended solids ) which defines the level concentration of suspended solids in an aeration tank when it is actively slugged

MLVSS stands for (Mixed liquor volatile suspended solids) which is the amount of microbiological suspension in an that is found in an aeration tank that is been actively slugged

The General Equation for [tex]\frac{F}{M}[/tex] ration is

[tex]\frac{F}{M} = \frac{(flow)(Time)(Density)}{(Total \ Volume \ of \ the \ tank )(MLVSS)}[/tex]

[tex]= \frac{(0.0796m^3/s)(86400s/day)(130g/m^3)}{(1806m^3)(1500g/m^3)}[/tex]

[tex]=0.33d^{-1}[/tex]

The General Equation for SVI is

[tex]SVI = \frac{(Settled \ sludge \ volume \ after\ 30\ min)}{(MLSS)(MLVSS)} \frac{1000mg}{g}[/tex]

[tex]=\frac{230.0mL/L}{(1.40)(1500mg/L)} (1000 \ mg/g) = 109.52mL/g[/tex]

The Equation for solid concentration in the return sludge is

[tex]X_r = \frac{10^6}{(SVI)}[/tex]

[tex]=\frac{10^6}{109.52} = 9130 mg/L[/tex]

The Equation for the Aeration period is

[tex]\theta = \frac{Total \ volume}{flow}= \frac{1806}{0.0796 m^3/s} = 22688sec[/tex]