S/T metric conversion error for settling velocities

You have found another latent metric conversion error. When settling velocities are entered directly in the Storage/Treatment Block line E3 there is no conversion applied. Internally, the program uses ft/sec units for settling velocities in Subroutine UNIT, so the program should convert from cm/sec to ft/sec. (The rest of the S/T computations are done internally in metric units, when used.) I will make this correction (Subr. STRT.FOR) in my next release. In the meantime, if you enter settling velocities directly, use units of ft/sec for the E3 data, regardless of whether or not the rest of the simulation is in metric units.

Wayne H.

Dear Sir:

I am using SWMM for my research here at the University of Toronto, Toronto, Canada. When running the Storage/Treatment Block using metric units, according to the program documentation, the settling velocity of particles should be specified in the units of cm/sec. However, if I do that, the final TSS removal rates do not make sense. If I specify settling velocity in m/sec, instead of cm/sec, the results seem to make sense.

Please verify and confirm the above findings and let me know if the program documentation is wrong with respect to the units of settling velocities.

Thank you!
Yiping Guo