ZLD Scaling Problem
Published on by Tamer ramzy Abd-Elsadek, Employee at Oregon Environmental Engineering, LLC in Academic
I have a scaling problem in my Zero Liquid Discharge (ZLD) Plant and this problem happened when two feeds met at the interstage tank.
We tried several antiscalants and problem still remains.
How can I achieve zero scaling?
I can provide feed streams analysis and any required information if needed.
Media
Taxonomy
- Treatment
- Scale & Corrosion
- Wastewater Treatment
- Zero Discharge
- Zero Liquid Discharge
27 Answers
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Since the alkalinity in your water is at lower range, I recommend you to reduce the pH level between 5.8 to 6.2 , thereby eliminating 90% chances of scale formation. The remaining 10% can be controlled using strong terpolymer with high thermal and pressure stability produced by Dow, Biolabs etc. Sometimes little surfactant may also helps.
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Hi Tamer,
The descaler my company has developed and manufactured removes all types of scales. I have experience in its implementation in Australia to remove even tough silica scales.
If you would like to trial the product, please email me at andrew@waterandoilsolutions.com.au and I am confident I can provide a solution for you.
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Exept of high alkalinity (carbonate scaling) there is too high sulfate concentration......
you need an antiscaling agent for sulfate salts in very high dosage... without concerning the rest of impurities maybe included, because analysis is not complete.
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You can contact me at at adrian@hydropath.com I would be more than happy to assist you.
1 Comment
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(Y)
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You can contact me at at adrian@hydropath.com I would be more than happy to assist you.
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If you want to contact me at Hydropath Technology UK I can then assist you adrian@hydropath.com
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Matthew Brannock Thanks Very much for your interest ,
you accurately what's happening in my process and our process is seeded slurry technology, but the issue that the mixing of feed streams occur in separate tank not containing seeds (interstage tank) . and scale mainly occur in this tank.
Can you advice if adding acid on this mixed streams will help or not.Or
preparing seeds in this tank and then restart feed streams again, and transfer to FFE while the re-circulation line of this tank opened to be sure that there will be minimum Seeds available there.
1 Comment
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Hi Tamer,
If the scale formed is in fact calcium carbonate, then destruction of alkalinity using acid would certainly be an option (we're currently working on a project where this is undertaken). Understanding the implications of adding acid is also necessary though.
For example you also have to be careful that if you dose sulphuric acid it doesn't take you over the CaSO4 precipitation point too early in the process in locations where it would be inconvenient. HCl may be an option but is much more expensive. Modelling can help with this along with an ion balance composition from both streams.
Without knowing the process in detail, I can't say whether preparing the seed in that particular tank is going to create an issue for you.
Cheers,
Matt.
matthew@saltwatersolutions.com.au
www.saltwatersolutions.com.au
www.aqmb.net
1 Comment reply
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It's Ok i agree with you,
But what about Citric Acid Dosing for the HERO Reject stream to get ph down to 6, is it will be helpful option. knowing that HCL will increase the Chlorides Concentration in the fluid leading to more tendency to corrosion.
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Ian Pearson this option not possible as we already removed calcium and Magnesium ions in previous softening process and the feed stream used is the reject of Softening process carrying .this cations
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Tamer,
Like Anro, I also initially thought that the scale in the feed could be calcium sulphate due to the high levels of each in the feed. However, after looking more closely at the feed analysis and confirming via speciation/AqMB modelling (admittedly using a range of assumptions to complete the feed composition), calcium carbonate seems to form preferentially. Although CaSO4 only needs to be above 0.15-0.20wt% at 100C to form, if alkalinity is also present, CaCO3 will form preferentially and consume a lot of the calcium before CaSO4 gets a chance to take hold. A sample of the scale and XRD or FTIR analysis will confirm for sure.
In the down stream process though, calcium sulphate will likely form due to the concentrating up of these two species... and this is what occurs in a seeded process. Calcium sulphate is purposely precipitated in the thermal concentration unit (usually an FFE) to produce sites where other scale inducing species will preferentially form (instead of on heat exchange surfaces). There is a set level (i.e. TSS) of calcium sulphate solids that you want to be at though; this is dependent on the concentration factor and there still may not be enough in Tamer's process to run in full seeding mode.
A seeded CaSO4 process won't help the scaling problem in the feed though. On previous projects, where there is calcium and alkalinity in the feed, we have either dosed acid to prevent hardness formation or removed the hardness. It becomes very much an economic question (CAPEX vs OPEX) which is very much scenario specific.
For your scenario, you need to check that once you dose acid, that you don't inadvertently form CaSO4. If you are below ~0.15% CaSO4 in the mixed stream, you should be okay. Modelling will help confirm.
Cheers,
Matt.
matthew@saltwatersolutions.com.au
www.saltwatersolutions.com.au
www.aqmb.net
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If you do find that the scale is calcium sulphate, you can either try to precipitate out calcium as CaCO3 in the pre-treatment as suggested by Anro, or alternatively precipitate out the sulphate using barium (e.g. barium carbonate) as BaSO4. This is more expensive than adding lime to precipitate the calcium, but may be more suitable for your situation. This is also if the anti-scalents being offered still do not work.
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Tamer,
You may want to look into Electronic Water Conditioning to prevent scale without chemicals. See Hydropath.com for additional information and the distributor in your area.
2 Comments
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Bill Carroll
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Is it will be good choice and applicable in Large pipelines,
can you send me link or website explaining the technique and its application if possible.!!
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Hi,
Try and get a sample of the scale to determine the exact composition thereof. Your feed composition is high in calcium and sulphates and therefore I would think that it is calcium sulphate scaling that occurs. I worked on a falling film evaporator (FFE) where we had similar feed and issues which required regular shutdown for ultra high pressure cleaning. Luckily there was more than one FFE and the cleaning could be staggered. At that stage no one could provide us with a working cleaning in place program to prevent the scaling, only dosing programs to increase the runtime of the plant before mechanical cleaning was necessary. The most common suggestion was to remove the calcium from the feed through pretreatment in order to prevent the scaling from happening. We once introduced a softened feed to the FFE and could increase the cycles of concentration tremendously without any scaling taking place.
Good luck with finding a workable solution.
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Tamer Kindly send the details at rksikri@gmail.com
We are expert in solving this issues thru Galvanic Principal that too without using chemicals. We successfully developed and tried in Power Station. 9899097225 India
1 Comment
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It's already shared here rabinder,
kindly check and advice please according your experience
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Dear Tamer,
Scale buildup can also cause corrosion and the loss of heat transfer, so again, much of the contamination that can cause corrosion in the thermal parts of the ZLD process need to be addressed based on the individual system. The chemical balance, concentrations, level of heat, and pressure can all contribute to this complex calculation. What type of scaling ?
General Problem of Scale
- High PH, Alkalinity
- High Temerature
- High TDS/TSS
- Corrosion.
- Sedimentation
Solution
- To inject Acid or other chemical to down the PH.
- To inject anti scaling reagent easily available in market.
- To increase the fluid velocity to avoid sedimentation.
1 Comment
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Thanks very much Prem for detailed answer, but for your information scale occur mainly after both feed streams mixing, am i have to inject acid before mixing or after mixing??
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i need your feed quality information
you send to this id: abdulgaffar557.ag@gmail.com
i need you membrane details and plant details like permeate flow reject flow feed flow and TDS SILICA HARDNESS COD, and i need which membrane you are using in your plant model no and membrane make.
REGARDS
ABDUL GAFFAR - SENIOR CHEMIST
1 Comment
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Thanks Gaffar for your interest, i already uploaded the feed streams analysis available and ratios. can you check here please
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Hi Tamer,
Thanks for the feed stream compositions. It does make it easier to understand but it is still lacking some important information.
However, I did undertake a speciation simulation while making a few assumptions. It appears that the high hardness in the softener waste stream and the alkalinity in your HERO reject stream may be leading to an amount of CaCO3 scale formation (potentially at difficult levels for anitscalant). You may need to add some sulphuric acid to destroy the alkalinity in the HERO reject stream or even consider running the ZLD system (depending on how it is set up) in seeded mode.
The above statement needs to be confirmed pending an ion balanced analysis. I would also like to run it through our process simulation software AqMB which has the ability to take into account antiscalants performance within thermal processes. It would also assist in investigating potential process related solutions (including running your ZLD system in seeded mode... the high calcium in one stream and high sulphate in the other may enable you to do this after some alkalinity destruction).
Please get in contact if you have any more detailed information about these streams.
Cheers,
Matt.
matthew@saltwatersolutions.com.au
1 Comment
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Thanks Matthew very much for your detailed reply,
,for your information scale mainly occur when two feeds mixed
is it will be better to add acid on the mixed sterams!!
Also, i use hydrex Veolia but i inject before mixing
1 Comment reply
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Hi Tamer,
Assuming the scale is in fact CaCO3 (there is still a little uncertainty on this due to some missing analysis parameters), then you'd add it to the stream containing alkalinity (HERO Reject) before mixing. You can either destroy all the alkalinity using acid (easily calculated - just use the M-alkalinity to work out how much is required) or destroy just enough to avoid scaling (process modelling would be required to do this).
Cheers,
Matt.
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here is attached the feed streams with ratio and before mixing temperature reach about 100 degree .
1 Comment
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@rabinder
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Hi Tami!
Please provide more information about the process and the feed stream analysis. I agree with Nir it is useful to know if there is a rise on temperature or a pH variation at the mixing point. Thank you for shareing your case.
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Analysis may help of course. Meanwhile i wounder if you have pH difference between the streams? or temperature rise in the mixing point, possibly because of exposure to warmer environment?
1 Comment
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analysis attached above Nir but the temperature at mixing point above 100 degree
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Must share the process flow diagram and also analysis of the scales...which salts...Also the material of the inter-stage tank..Have you tried any electronic protection or any inert coating of inside of the tank..?
1 Comment
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can you explain more about electronic protection or any inert coating of inside of the tank
!!!!!!
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Contact us on +2711 974 8161
1 Comment
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we already using this antiscalant Amos
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We are waiting for the feed streams analysis.
Anyway, as you can make trials, you can find the best available prduct this way.
I can propose you an excellent antiscaling product which is produced under my recipe in Greece, but I could not know the final cost to you if I send it from Greece (shipping cost + customs cost). Anyway, I could send you a sample for trials for free, if you could pay the shipping cost.
2 Comments
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Hello Apostolos Kavadias !! looking for your reply
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can you give me more details about this antiscalant and data sheet
1 Comment reply
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I have not tested it in such conditions, but I would propose it anyway.
It consists of phosphonates (organic phosphates, DTPMPA-Na(4-5)) and low/medium Molecular Weight polyacrylate.
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They are right: A profound answer needs data on chemistry and design. Please provide. Did you analyse the scaling products already?
Regards,
Gernot
1 Comment
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feed streams analysis shared already, and scale is white to slightly brown
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Please provide feed streams analysis
Regards
Vijay
1 Comment
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Thanks dr vijay, feed streams already shared,, kindly check
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Try talking to http://www.slipstechnologies.com
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*program - software
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Feed chemistry and equipment configuration are key aspects. Have you run any scale inhibition program using plant data? Please talk to your OEM. Of course we can discuss further if you share the data. Zero scaling in operating plant with its dynamics, you think it's possible?