Total Dissolved Solids

Overview

Engineering reference data for Total Dissolved Solids in miscellaneous.

Key Formulas

Unit Conversion

$y = x \cdot k$

Multiply by conversion factor.

Linear Interpolation

$y = y_1 + \frac{(x - x_1)(y_2 - y_1)}{x_2 - x_1}$

Estimate between two known points.

Percentage

$p = \frac{\text{part}}{\text{whole}} \times 100\%$

Part as fraction of whole.

Variables

Measurement Methods

Density Method

$TDS = 1.1 \times 10^6 (\rho - 1)$ where $\rho$ is the relative density of the boiler water at $15.5\ \text{°C}$. This manual method requires measuring a cooled sample with a sensitive hydrometer.

Conductivity Method

$TDS = 0.7 \sigma$ where $\sigma$ is the conductivity of neutralised water in $\mu\text{S/cm}$. This method can be automated to control blow down cycles. Note that electrolytic polarisation may require an AC resistance meter, and conductivity increases with temperature.

Blow Down Rate Factors

The boiler blow down rate depends on:

• Steam consumption (steam used in the process and not returned as condensate to the boiler)
• Concentration of impurities in the feed water
• Maximum allowable TDS in the boiler (typically operated in the 2000 – 3500 ppm range)

Interactive Charts

References

• Original Source