Need a chemist: filtering of latex paint wastewater?
 

So…I’ve been building some affordable homes in an area of town that needs some significant redevelopment…doing my part for the community so to speak. As I have navigated the construction process, I have found that there is significant waste of materials and potential for pollution runoff from multiple waste streams. The recent spike in lumber prices has me revaluating each phase of construction and seeing what can be recycled, reused, or repurposed to eliminate waste. Just on these smaller homes, 1200-1300sf, I have spent upwards of $3k per and 4 - 40 yard waste bins per house just for waste disposal.

In my quest, I have identified the waste streams and have ideas on their reduction. One item that stands out is the washing and resultant runoff of paint equipment, and the probable pollution this causes. I have witnessed my painter simply washing tools in the yard with no regard for capturing the wastewater.

I’d like to create a filter using a plastic bin and 5g buckets in order to capture the disolved solids. I’ve done some internet research on using sand and activated charcoal, and intend to develop a prototype as an experiment to see if it works.

To my point, does anyone know if such a diy filter would remove the dissolved titanium dioxide, which is the major component of latex paint?

Any other considerations for filtering the braintrust can offer? I’ll post the results of my experiment.

TIA

Around here it's illegal to wash a car and have the water go down the street, so the mobile detailers often use a catch system to recycle the water. Kind of like driving the car onto a plastic swimming pool and blowing up the 'rings' to keep the water captive.
You might look into something like that for rinsing the paint tools off. Not sure what type of filter those systems use but it might be modifiable to capture the titanium dioxide.

I'm not a chemist; just a mechanical engineer that's been around too many chemists...

I don't think the titanium dioxide goes into solution; I think latex paint is a big colloid. I think you would need to collect the waste water with the paint runoff in it, add a flocculant to the waste water, mix it to get the paint solids to come out of colloidal suspension, and then filter the solids.

+1 ^^^^^^^

That ti 2 oxide is water soluble
I would filter the solid with a coffee filter in a oil funnel.


You can always just let the water evaporate (heat or in the sun)and have your solids that way.

Ah, ok i get it. I suspect the amount of runoff would be too much to capture and add a flocculant, but it’s worth a try. Was hoping to have a system that could filter, but it appears colloids can’t be filtered. Shucks.

I would call your water treatment facility. TiO2 is used in water purification by many cities. May be a okay to drain it down the sewer.

There maybe a better mousetrap but there are existing solutions to this problem, both passive and active approaches.

https://outpak.com/paint-washout/

https://www.dromont.com/retail-tinting-machines/envirowash-paint-unit

I wash paint brushes and rollers in a large barrel of water. The paint solids sink to the bottom and pretty (clean enough) clean water is at the top. I do dozens and dozens of washes in the same barrel of water. If I particularly care about the brush I can rinse it in cleaner water afterwards. After the paint job is over I tip out the clean top water and the sludge down the bottom is put into an old paint container and that goes to the dump.

Latex will coagulate when acid (such as acetic / vinegar) is added. IDK if that would work in paint or if it would capture the TiO2 as well. Interesting experiment.

You MIGHT get some help from the local water/air quality weenies.

We don’t clean daily. Wrap the wet brushes and rollers tight in plastic. Remove and reuse tomorrow.

I leave roller covers in the 5 gallon bucket. They last for YEARS.

And yes, plastic wrap a brush and freeze / refrigerate it.

Minimal effort.

Also, I standardize my colors. Less is better!

I've used aluminum foil and fridge. Reusable.
Maybe both is better.