Hi Tom,
We're trying to get to the bottom of the issue of whether a higher CO2 bubble rate is required in higher Carbonate alkalinity water to achieve the same levels of dissolved CO2 compared to waters having lower carbonate alkalinity.
Most trusted sites seem to agree that solubility depends on the following factors:
1. Pressure
2. Temperature
3. pH
4. Presence of other substances
The pressure and temperature factors seem intuitive so no problem there. Page 11 of this online book mentions the effect of pH: Fundamentals of aquatic toxicology ... - Google Book Search
The second paragraph implies that CO2 solubility is directly related to pH so that at higher pH the Carbonic acid equilibrium equation is driven to the right.
The figure 13 chart shown on this page gives a similar explanation: http://openlearn.open.ac.uk/mod/resource/view.php?id=185884
Since higher carbonate/bicarbonate levels favor higher pH does it follow that higher KH waters, with higher alkalinity would have less dissolved CO2 and additional higher levels of carbonate/bicarbonate even if the injection rate is kept the same?
I think you've explained before that higher kH water has higher carbon content naturally but it's unclear whether factor number 4. presence of other solutes (carbonates/bicarbonates) act in concert with factor 3. pH to lower the dissolved CO2 content.
The implication would be that tanks running at higher kH would need higher injection rates to achieve the same CO2 concentration.
Could you clarify?
Cheers,
We're trying to get to the bottom of the issue of whether a higher CO2 bubble rate is required in higher Carbonate alkalinity water to achieve the same levels of dissolved CO2 compared to waters having lower carbonate alkalinity.
Most trusted sites seem to agree that solubility depends on the following factors:
1. Pressure
2. Temperature
3. pH
4. Presence of other substances
The pressure and temperature factors seem intuitive so no problem there. Page 11 of this online book mentions the effect of pH: Fundamentals of aquatic toxicology ... - Google Book Search
The second paragraph implies that CO2 solubility is directly related to pH so that at higher pH the Carbonic acid equilibrium equation is driven to the right.
The figure 13 chart shown on this page gives a similar explanation: http://openlearn.open.ac.uk/mod/resource/view.php?id=185884
Since higher carbonate/bicarbonate levels favor higher pH does it follow that higher KH waters, with higher alkalinity would have less dissolved CO2 and additional higher levels of carbonate/bicarbonate even if the injection rate is kept the same?
I think you've explained before that higher kH water has higher carbon content naturally but it's unclear whether factor number 4. presence of other solutes (carbonates/bicarbonates) act in concert with factor 3. pH to lower the dissolved CO2 content.
The implication would be that tanks running at higher kH would need higher injection rates to achieve the same CO2 concentration.
Could you clarify?
Cheers,