Viscosity of domestic sewage?
Viscosity of domestic sewage?
(OP)
Does anyone know where I could find "typical" values for viscosity of domestic sewage. I imagine that the viscosity would vary greatly, but I'm wondering how much different it is than for drinking water. When calculating headloss in a force main, I've always used Hazen-Williams or Darcy-Weisbach, but for D-W the friction factor, f, is dependent on the Reynolds # (at least for lower Re). Re is inversely proportional to the dynamic viscosity, thus f varies with the viscosity. So, I'm wondering how much of a difference this makes, if any. Anyone ever looked at this or have any ideas?





RE: Viscosity of domestic sewage?
"Wastewater Engineering" handbook by Metcalf and Eddy doesn't even mention sewage viscosities. It does mention
typical total solids content 350-1200 ppm, and that of septage (eg: septic tank sludge) as 5-10%, averaging 4%.
Possibly, effect of temperature on viscosity far outweighs effect of dissolved and suspended solids in typical domestic sewage. 1200 ppm is only 0.1%, afterall.
In the Moody diagram, curve of f vs Re, the curve flattens out at high Re. Even if viscosity is significantly different from pure water, the effect of this difference on f, the forcemain pressure drop and design economics, may be small (depending on your system).
Perhaps this is why sewage viscosities were not, and pure water viscosities (as a function of temeprature) were, mentioned in my handbooks.
Hopefully, short of actually measuring your stream's viscosity, one more experienced can comment further.
RE: Viscosity of domestic sewage?
RE: Viscosity of domestic sewage?
I do know that sludge between 10-12% TS is roughly 2500 cp (2500 times that of fresh water) and is non-linear as you reduce the solids content.
Maybe a little late, but hope it helps
RE: Viscosity of domestic sewage?
Sludges are non-newtonian fluids and follow a completely different set of rules
RE: Viscosity of domestic sewage?
RE: Viscosity of domestic sewage?
Good luck:-)
RE: Viscosity of domestic sewage?
RE: Viscosity of domestic sewage?
I usually take 'v' = 1.3*10^-6 [m^2/s], that is the kinematic viscosity (dynamic is [N*s/m^2] - do not take that!). For WWTP in moderate climate that number covers most sewage (and low solid content sludge) applications.