Kalk slurry aeration

Randy Holmes-Farley · Jul 31, 2023

Here's a nice table of some indicator dyes:

pH Indicator Chart - Colors and Ranges

Get a handy pH indicator chart. See the colors and pH ranges and learn how to choose an acid-base indicator.

sciencenotes.org

piranhaman00 · Dec 31, 2023

I came across this thread from @Lasse thread and decided to try it out for fun.

pH is typically 7.9 -8.1, skimmer pulling air from outside. 420 gallon system in basement with suspected high CO2.

Set up “bubble tower” with 48” of 2” PVC, any wider and it’s too expensive for a trial run. Drilled hole in top to run the pvc pipe in that is being pulled on by a RO skimmer pump that is just turning in sump ( loud bubble sounds). Air is being pumped in by air pump.

I originally put 50g Kalk and 10g NaOH into 1 gallon of water and mixed thoroughly and put in reactor. When I turned bubbles on the tower overflowed significantly. I had to lower the water level to only about 24”, the bubbles rise another 12”.

I put my pH probe right on the pump so I can measure the ph of the water there and stop the pump if I draw in the basic solution.

@Randy Holmes-Farley what ratio of kalk to NaOH would work?

Did @Garf bubbles rise so far? Your picture has the water level very close to the top.

Randy Holmes-Farley · Dec 31, 2023

The problem with mixing NaOH and Ca(OH)2 in water is the common ion effect. The hydroxide from the NaOH reduces the solubility of the calcium hydroxide. Thus hydroxide does not go up as much as hoped and calcium declines. It may still work, but perhaps not noticeably better than calcium hydroxide alone.

Garf · Dec 31, 2023

piranhaman00 said:
Did @Garf bubbles rise so far? Your picture has the water level very close to the top.

Water level used to rise a couple of inches, but the pipe diameter was 4 inches, that's quite a difference volume wise. I don't think there's any other way round either going bigger diameter, or pumping in less air, maybe even finer bubbles if they are so large they combine to form a big bubble that forces it to act like a pump, making a mess. Smaller bubble makers clog quicker.

piranhaman00 · Jan 3, 2024

fryman said:
Possibly you are limited by the skimmer's capacity for gas exchange? Most skimmers happen to do a reasonable job at aeration, but this is not the intended use case and ime they are not the most effective tool for aeration.

Instead my suggestion is to use an air pump and airstone(s). An air pump will have much more airflow than a skimmer and therefore far more effective aeration. The air pump outlet would simply bubble through your cylinder filled w/kalk slurry (need a check valve or place pump above water line so slurry won't backfill into pump when powered off), and at the cylinder outlet plumb to an airstone submerged in the sump or wherever.

I use pentaire fine pore diffusers, which are significantly better than airstones but also cost more (~$30 for a 9in diffuser):

Pentair Aquatic Eco-Systems Sweetwater Fine-Pore Diffusers for Ozone and Pure Oxygen

Sweetwater fine-pore diffusers are the same high quality as our regular Sweetwater diffusers.

pentairaes.com

For an air pump, the more airflow the better. I have an "Active Aqua" Air Pump Model AAPA110L. It's old and loud but puts out over 100l/min.

Question regarding using an air pump. 100l/min is nearly 4cfm. Those diffusers max at 1cfm, do you use more than one diffuser?

Lasse · Jan 3, 2024

I have one idea in my mind - without any diffuser - just a tube down into the media

I visit my local IKEA shop and my cabinet for good to have things. - Testrun with calcium hydroxide in order to see if it mix or not

So far - works as designed. Mix very well - its a slurry and water, air and Ca(OH)2 mix well. Now will nest test phase start - connecting to the skimmer. Whats worrying me is if the contact time is long enough, i.e. is the CO2 in the incoming air transferred to CO3 in the solution and finally bound as CaCO3 fast enough. I`ll be back - I miss some tubes for the moment.

Sincerely Lasse