Waterguide - Temperature
What is temperature?
Temperature is a state variable with the symbol T. Germany uses the well-known degrees unit Celsius (°C), invented by the Swedish astronomer, mathematician and physicist Anders Celsius. Another well-known degrees unit is Fahrenheit (°F), invented by the German physicist Daniel Gabriel Fahrenheit. But it is the unit Kelvin (K), invented by the British physicist William Thomson Kelvin, that is relevant for calculations in technology.
What are the differences between the units?
Compared to Kelvin, there are the following differences in terms of the scales:
- O °C = 273,15 K
- 32 °F = 273,15 K
This is because 0 K is the absolute zero point (-273.15 °C).
However, when it comes to waste water and water, degrees Celsius is used to measure temperature.
Temperatures in waters
Raw water from reservoirs has a temperature of 4 °C (extracted from a great depth).
Groundwater extracted from a medium depth in Central Europe has a temperature of 10 °C.
Deep wells have a fluctuating, higher temperature than groundwater.
The temperature in flowing water depends on the time of year, being lower in the winter and higher in the summer. The temperature also depends on the inflow of cool water or heated waste water.
Significance of temperature in water treatment
Increasing the temperature generally accelerates the speed of chemical or physical reactions. The general rule of thumb is that an increase of 10 °C doubles the reaction speed.
In reverse osmosis in particular, a change in temperature has two important effects. Firstly, the increase in temperature causes the flux through the membrane to increase (or the required pump pressure reduces, if the flux is maintained). Secondly, the salt rejection declines (typically by approx. 3 % per °C). This means the design of the reverse osmosis unit is heavily dependent on the temperature.
Herco RO units are configured to a default temperature of 15 °C, which is a typical average value for drinking water applications over the course of a year.
If the temperature of feedwater deviates even by just 5 °C (so a feedwater temperature of 20 °C instead of 15 °C), this can result in a > 20 % reduction in the required pump pressure of the RO unit. Adjusting the high-pressure pump to different operating pressures can help to dramatically reduce energy consumption, and thus operating costs.
The reverse osmosis units from Herco are available with frequency-controlled pumps that adjust automatically. This ensures the energy consumption is always minimal.
You can find out more about our RO units in our product overview.