Single-Step Flocculation for reclaiming Parts Washer wastewater?

[kunalvanjare]

Hello,

I am interested in knowing if a single-step wastewater clarifier/reclaimer can be made for used Parts Washer effluent. References can be found here :-

1. https://www.stingraypartswasher.com/stingray-mart-eq-1-wastewater-processing-system.html
2. https://www.hpipro.com/productdetail/roc-2/

Both these products use a Clay based Flocculant/Coagulant. Now I have done some research here in India and spoke to a bunch of manufacturers who have no experience with such Flocculants. I then spoke to a company in the US who have sent me some samples as per their experience of similar applications.
Link - https://www.environmental-expert.co...2305-g-clay-and-flocculant-formulation-601623

The equipment we would like to design will include a Treatment tank with a Mechanical stirrer. The effluent will be fed into the tank where the flocculant is added and then stirred. After flocculation is complete, the liquid is passed through a Filter Paper Bed and collected in a collection tank underneath.

This water can then be sent through some post-filtration to remove odor/color (would like your suggestion for this) and then re-used in the same machine / different process / gardening etc.

The industry standard procedure right now is to drain the effluents from each machine into a reservoir which later goes through an Effluent Treatment Plant (ETP) and then drained/re-used. An ETP is a huge capital expenditure, and that is where we're hopeful of providing a low-cost alternative provided this can actually replace an ETP.

I have not done any Lab Tests of the effluents as the effluents will keep varying with every machine/customer.

Any guidance / help would be appreciated. Thanks.

 

[chemisttree]

Your title suggests you want to reuse the parts cleaning solution but the method you mention will likely only reclaim the water itself. Clays are quite good at sequestering surfactants and if those surfactants are the only thing holding a hydrophobic contaminant in suspension, removing it naturally removes the contaminant as well. Especially if it is filtered through a 5 micron filter! Of course most surfactant packages are mixtures of different surfactants and sometimes water conditioners or corrosion controllers (borates, phosphates, carbonates, amine alcohols, etc) and each component of that package will have its own adsorption isotherm. These will likely be removed to different degrees. So it is likely that you will have a different solution after clay treatment than you had before or you will just have water with some water conditioners if you use enough of the flocculant.

Not likely anyone who hasn’t used your particular product can give you any specific answers. Time for you to do some testing!

 

[Baluncore]

Any guidance / help would be appreciated. Thanks.

I would be concerned that some species in solution would remain and be recirculated in the water. That would progressively contaminate following articles. The presence of a dissolved acid might prevent the flocculant functioning as expected. I would expect a pH buffer and a charcoal filter in the system.

You need a better idea of the chemistry involved and the various flocculant/filters that might be selected for use by different user/customers.

 

[kunalvanjare]

Your title suggests you want to reuse the parts cleaning solution but the method you mention will likely only reclaim the water itself. Clays are quite good at sequestering surfactants and if those surfactants are the only thing holding a hydrophobic contaminant in suspension, removing it naturally removes the contaminant as well. Especially if it is filtered through a 5 micron filter! Of course most surfactant packages are mixtures of different surfactants and sometimes water conditioners or corrosion controllers (borates, phosphates, carbonates, amine alcohols, etc) and each component of that package will have its own adsorption isotherm. These will likely be removed to different degrees. So it is likely that you will have a different solution after clay treatment than you had before or you will just have water with some water conditioners if you use enough of the flocculant.

Not likely anyone who hasn’t used your particular product can give you any specific answers. Time for you to do some testing!

I guess I didn't make it clear in the title, but I am actually looking to reclaim just the water from the spent liquid.

The wastewater since extracted from Parts Cleaning Machines will have quite a bit of oil as well. Will that require any additional (prior) treatment?

 

[kunalvanjare]

I would be concerned that some species in solution would remain and be recirculated in the water. That would progressively contaminate following articles. The presence of a dissolved acid might prevent the flocculant functioning as expected. I would expect a pH buffer and a charcoal filter in the system.

You need a better idea of the chemistry involved and the various flocculant/filters that might be selected for use by different user/customers.

Presence of an acid is unlikely although not impossible. Most applications do not use any acidic chemicals in the machine owing to risk of corrosion. All cleaners/coolants are alkaline. But I cannot rule out the occasional proces ssuch as any pre-treatment process.

Why do you suggest a pH buffer and a charcoal filter? I was under the assumption that charcoal filters only help in removing odor from a stream.

And yes, our idea is to take Lab tests of certain effluents and try the different Floc formulations we have and then try to arrive at a conclusion. But if there are any pre-treatments or adjustments to the process required, i'd like to know :)

 

[chemisttree]

I guess I didn't make it clear in the title, but I am actually looking to reclaim just the water from the spent liquid.

The wastewater since extracted from Parts Cleaning Machines will have quite a bit of oil as well. Will that require any additional (prior) treatment?

Probably not. Clay adsorbs oils.

 

[kunalvanjare]

Hello guys, I'm back after kind of a hiatus. Hope you'll are doing well

So i have tried a pre-pre-preliminary trial with a sample of wastewater i had collected during a visit to a client. The wastewater was basically effluent from an Ultrasonic Part Washer. Effluent consisted of an alkaline cleaner in 3-5% concentration with water used for over 2 weeks. There is a thick layer of oil and the liquid has quite a fair bit of suspended particles from the washer.
Here's a pic of the effluent - https://ibb.co/K02SCGW

So i have treated 100ml samples of this liquid at a time with 0.5-2% of the Cleartreat flocculant (link posted in one of the previous posts). Four different Flocculants were tried with varying degree of results. For agitation, I stirred using a spoon

I observed that most Flocculant powders worked upto a certain extent at the first dosage of 0.5%, in that they helped form Flocs that floated on the surface of the liquid (https://ibb.co/zQf9NMB) but could not clarify the water as it remained turbid. Further additions upto 2% did not really help.

The size of Flocs formed were different for each Cleartreat sample.

I then went ahead and filtered a particular treated liquid sample and what I observed was that most suspended impurity was filtered out, but the filtered liquid was yellow in color. Pic - https://ibb.co/99rdLz9

The pH of the effluent checked before treatment was approx. 9.5. I did not do any pH adjustment nor did I check the pH of the sample post treatment.

Views and opinions please?

 

[chemisttree]

You filtered after flocculation. How long did it take for the ~100 mL?

I would try heating to nearly boiling after treating with flocculant. Fine oil-in-water dispersions sometimes coalesce when the emulsifying agents are heated with gentle to no stirring. Heat after floc treatment.

Don’t know what could be yellow. These parts have cutting oils on them? Could be an additive or base soluble dye used in greases or lubricants. Take out a portion and acidify with strong acid like sulfuric until just acidic (pH=2-3). See if anything separates after acid treatment.

 

[kunalvanjare]

You filtered after flocculation. How long did it take for the ~100 mL?

I would try heating to nearly boiling after treating with flocculant. Fine oil-in-water dispersions sometimes coalesce when the emulsifying agents are heated with gentle to no stirring. Heat after floc treatment.

Don’t know what could be yellow. These parts have cutting oils on them? Could be an additive or base soluble dye used in greases or lubricants. Take out a portion and acidify with strong acid like sulfuric until just acidic (pH=2-3). See if anything separates after acid treatment.

Filtration of 100ml took about 10-12 seconds. I used a cutout of the paper bed filter from my CNC for this. A lot of the flocculated gunk would settle on the paper, but the liquid did filter through slowly.

Yes parts have cutting oils on them for sure. I was thinking of bringing the pH down by adding sulfuric acid before treatment. Would that help? Shouldn't the oil coalesce due to the clays present in the flocculant?

Will adding sulfuric acid to the effluent not disturb any other properties of the liquid?

I could try boiling, but if that even works out, it would be difficult to implement on a larger scale owing to large electrical loads and the necessity of cooling the liquid post treatment.

 

[chemisttree]

1. Would acidifying before flocculation help? I don’t know but perhaps. There are emulsifiers likely present to suspend the oils. If they are anionics, acidifying will cause them to become insoluble in water and they will cease being emulsifiers. If they are non-ionics, little would change.
2. Wouldn’t the clays in the flocculant cause the oils to coalesce?
Mostly, yes but the smallest droplets have much to overcome to reach each other or a clay particle. At high pH the clay particle is negatively charged and could be repelled by the small oil droplets covered by an emulsifier with its (potentially) negatively-charged end groups pointing outward into the aqueous environment. Like charges repel. Any information from the floc mfgr about optimum pH for use?
3. Would adding sulfuric acid disturb any other property of the fluid? It will likely disturb every property of the fluid. Can you live with that?

Adding acid was only suggested after floc treatment to diagnose the yellow color, actually. If a yellow oil separates upon acidification, you can remove it and identify it to decide how to proceed. Adjusting pH before floc treatment might be something to try if you can live with the new pH. If you adjust pH, perform a more efficient cleanup/flocculation and then return the pH to alkaline, you would need to live with the higher salinity (sulfate salts) in use. That’s why I wouldn’t use HCl to adjust pH. Cl^- attacks ferrous and aluminum alloys under sonicating conditions.

 

[kunalvanjare]

If you adjust pH, perform a more efficient cleanup/flocculation and then return the pH to alkaline

Why do I need to return the pH to alkaline?

I will try to change the pH in both cases.. pre & post treatment. The manufacturer has mentioned optimal pH in the neutral to slightly acidic range.

 

[chemisttree]

Why do I need to return the pH to alkaline?

I thought you were trying to reuse the reclaimed water and I thought this was an alkaline solution.

 

[kunalvanjare]

I thought you were trying to reuse the reclaimed water and I thought this was an alkaline solution.

Well, I'd like to reclaim water. It doesn't really need to be alkaline. I have conducted some more tests as per your instructions. I will write a report by tomorrow.

 

[kunalvanjare]

Well, I'd like to reclaim water. It doesn't really need to be alkaline. I have conducted some more tests as per your instructions. I will write a report by tomorrow.

Here is the report.

After 3 separate trials on a Floc powder that gave good results, the resultant liquid is still yellow in color.

Not sure why. Can I use some post-filtration to remove color and odor?