Solids Mass Balance

At steady state the mass of dissolved solids entering with makeup equals the mass leaving with blowdown. Evaporation removes pure water, so solids stay behind and concentrate.

$$M\times C_{\text{makeup}}=B\times C_{\text{tower}}$$

Variables

Symbol	Meaning	Unit
M	Makeup rate	gpm
$C_{m}akeup$	Concentration of dissolved solids in makeup water	varies (e.g. ppm or microsiemens/cm)
B	Blowdown rate	gpm
$C_{t}ower$	Concentration of dissolved solids in tower (equal to blowdown concentration)	varies (e.g. ppm or microsiemens/cm)

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Part of The Blueprint of Water