Alkalinity and Acetate Dosing

[Dan_P]

The chart below represents almost a year’s worth of dosing calcium acetate (calcium hydoxide added to vinegar to ~pH 10) to a fish only system. Currently, the daily dose is about 0.5 mL per gallon.

Calcium acetate adds alkalinity which can be seen during the first two dosing periods. By the second period, acetate addition almost equals the alkalinity consumption before dosing begins, and alkalinity consumption is almost zero. Where the situation becomes a head scratcher is with further increases in acetate dosing. Alkalinity consumption levels off, when it was expected to become positive. Not until the fifth dose increase does alkalinity begin to increase. Is this an indication of a change to the bio filter? Is acetate accumulating during the fifth dosing period where 0.5 mL per gallon is being added each day? Thoughts anyone?

 

[DFR]

Following

 

[Randy Holmes-Farley Verified Community Expert]

Organic carbon dosing has many effects: pH, nitrate and maybe ammonia, phosphate, etc. the numbers you are graphing for consumption are very small (0.04 meq/l) and may relate to a variety of different things changing. Switching from nitrate to ammonia consumption, or aerobic growth vs denitrification will impact alk changes.

 

[Dan_P]

Organic carbon dosing has many effects: pH, nitrate and maybe ammonia, phosphate, etc. the numbers you are graphing for consumption are very small (0.04 meq/l) and may relate to a variety of different things changing. Switching from nitrate to ammonia consumption, or aerobic growth vs denitrification will impact alk changes.

Thank you for the ideas. The data surprised me because so little acetate had a detectable impact (whatever it is) and acetate was not being converted to alkalinity until much higher dosages. On a small scale with a single large dose of acetate, acetate is converted to alkalinity. The two observations aren’t directly comparable, just interesting at this point.

Dan