Home /
Search 🔍
the Site

Free personalized metal finishing help!

High TDS and NaCl problem in effluent treatment


An ongoing discussion beginning back in 2006 ...


Q. I am facing problem of high TDS in effluent due to the water used in regeneration of DM plant?
Can you suggest the way out?

Gaurav Jain
- Chandigarh, India


A. Hi Gaurav,
The high TDS is due to usage of hydrochloric acid. It produces sodium chloride which is highly soluble in water.

If you use dilute sulphuric acid in its place and neutralise the combined effluent with calcium hydroxide ( (not carbonate), it will precipitate calcium sulphate. Its solubility in water is only 2000 ppm, i.e. 2 grams per litre.

Of course it is a lot of work to prepare and stock dilute( 5%) sulphuric acid on the previous day for use to allow time to cool it as it produces tremendous heat during preparation.

The trouble is worth taking for achieving a low TDS in the effluent and also added bonuses of avoiding chloride slip in the DM water produced and also doubling the capacity between two regenerations.
Best of luck,

Parameswaran Iyer
- Mumbai, Maharashtra, India


Q. Hi I am a ETP in charge of Electroplating plant having two different streams in waste water treatment plant separately we treat it by two different methods 1.Biological for sewage and 2.Chemical precipitation for electroplating.

My question is can we reduce the high TDS by using constructed wetland as a biofilters?
As mentioned by Dr.Hammer

Constructed wet lands:-
Constructed wet land is a artificial mangrove like situation having water weeds in it,and it will absorb the salts from the waste water.
Can we do it like this?

Kiran Gangadhar Malbhage
- Aaaurangabad, Maharashtra, India


A. Artificial wetland works fine for:
- extra treatment after biological treatment (to remove some of the dissolved salts e.g. nitrate, ammonia, ...)
- removing the last fraction of the suspended solids (e.g. reducing the suspended solids from 50-100 mg/l after biological treatment down to ~10 mg/l after artificial wetland. In that case you must design the artificial wetland in such a way that the water stream percolates through a sand bed (either vertical percolation : distribution of the water streams on the surface, drainage pipes some 1 - 1,5 m below the surface) of horizontal (infiltration on one side of a strictly rectangular wetland, drainage pipes on the opposite side).

Artificial wetland does NOT remove chloride, sulphate, ... and similar inorganic salts from a waste water stream.

The only reasonable way to reduce the salt load in the waste water is to make changes in the production plant itself (less drag out, reuse of static rinse water, increase life time of plating baths, electrowinning of spent etching fluid instead of chemical treatment, etc.)

Artificial wetlands can support quite some suspended solids from the biological treatment. Artificial wetlands will fail quickly (by plugging, by intoxication of the water plants) if waste water from the chemical precipitation step containing more than say 20 mg/l suspended solids is fed to it.

- Gent, Belgium

February 13, 2012

A. Hello Gangadhar,
I agree with Mr. Bert on the ways to reduce the TDS. The method of measuring TDS is a point to be considered. If it is by Conductivity Meter, what is the factor you have used to convert conductivity to TDS? This factor also affects TDS measurements.

Subramanian Ramajayam
Subramanian Ramajayam
consultant - Bangalore, India

June 24, 2008

Q. Sir, I ask you one question is how to reduce the TDS of effluent in galvanised industry. TDS is 50,000 ppm so which treatment to give for the reduction of TDS and also COD, BOD,chloride, sulphate, metals. Please guide me which treatment useful for reduction of these parameters.

Dharmadhikari Santosh
- PUNE, India

April 11, 2012

Q. Hello, I am a student of Chemical Engineering, and I'm doing an internship on the biological treatment of waste-water by activated sludge (anaerobic, aerobic, aeration and clarifier). We worked with a "problem" in the clarifier. When it reaches a very large load of sulfate (more than 4 g/L), the mud does not seem to settle and the clarifier overflows, compromising the quality of treated water. Does anyone have any ideas on what can influence the sulfate? Or any bibliography?
Thank you.

Ana Kaucz
- France

April 24, 2012

A. Where does all the sulfate come from? Are you adding aluminum sulfate as a coagulant? If so, reduce the dosage. Add a polymeric coagulant if necessary.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina

April 18, 2012

Q. We have difficulty to maintain the TDS below 1500 ppm. Because treated water ppm is 8000-9000 ppm. We add more raw water for reducing the ppm. How to solve the TDS problem? We can maintain easily 2200-2600 ppm.

Anil Kumar singh
- Gurgaon, India

July 26, 2012

Q. Sir,
We treat effluent water that has 300 ppm of chloride content, while we add poly aluminum chloride for a coagulate agent. We want to reduce chloride content to less then 50 ppm, kindly tell me the method.
Thank you

- chennai,tamil nadu,India

July 26, 2012

A. Hi Raja. The first thing to do may be to switch to poly aluminum sulphate, and not use chloride because there is no answer except to reduce the use of chloride at the source.

Were you to invest a fortune in RO or DI equipment, and waste incalculable energy and chemicals doing this, you will still have the salt on your hands, to be disposed of in a landfill ... until such time as the liner leaks or wears out and the salt poisons the earth and kills the aquifer.

Salting the Earth

opinion! The traditional & proper thing to do with saltwater, of course, was to discharge it to the sea. But as you probably realize, in the world's effort to stop irresponsible ocean dumping, we've collectively decided to salt the earth :-(

If I'm wrong, I welcome enlightenment.


Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

July 3, 2013

Q. Sir,
I am working in distillery condensate policing unit, there is very high TDS and high conductivity in the final water. My aim is to reduce the TDS and conductivity of the water, so that we can reuse the water to distillery process.

The responsible thing for TDS is the aerobic culture carry over as per my observation.

Please give me the suggestion to solve it

Mantesh Magadum
- Manoli, Belgaum, Karnataka, India

November 4, 2013

A. Dir Sirs,

Good afternoon. Great day!

Perhaps a technology to view concerning your questions:


- Floating artificial wetlands. Look for the article and paper on landfill leachate treatment with floating wetlands.

The technology was sufficient to render landfill leachate from BLACK/high TDS/inorganics/organics/color to almost clear effluent. Using plants.

See also research with German University: Max Plank Institute - formative basis for wetlands and use of plants for Plant Phytokinetics/phytoremediation.

The complexity of the natural world is designed to handle most anything we can generate and break it down when properly understood and applied (most of these systems requre more room). However, a biological process then must be operated as such -- either aerobic/anaerobic/anoxic -- but again, may have the capacity to handle your questions.

See formative work with plant systems to clean up almost anything in wastewater:

Ocean Arks International is another web site.

Stewardship is a basic understanding that we should employ in all of our endeavors including each other.

Thank you kindly. Have a great day!

Steve Zeller
engineering - Harrisburg, Pennsylvania, USA

Effluent treatment for biscuit plant

August 25, 2015

Q. I am working on an ETP in a biscuit manufacturing unit. The electrical conductivity, residual sodium carbonate, and percent sodium is more than the standard values.

Please suggest methods to reduce them separately. The chemicals we are using in ETP are: Lime, caustic soda, alum & polymer.

Himanshu Jadon
biscuit manufacturing unit - bangaluru,karnataka,india

September 3, 2015

Q. Can anyone give me solution for removal of high TDS from effluent? Which treatment technology is suitable to reduce high TDS from effluent?
Parameters are as follows:
TDS = 83819 PPM
Sulphate = 70324 ppm
Phosphate = 8223 ppm
Chloride = 2184 ppm
pH = 1.25
BOD= <10 mg/lit
COD= 16 mg/lit
sulphuric acid = 7%

type of industry - pharma.
Please reply.

Ganesh patil
- Pune, Maharashtra, and India

September 26, 2015

A. You could try adding calcium hydroxide to about a neutral pH. That will precipitate almost all of the P and most of the S. Then, filter. The solid, I would guess, would be nonhazardous. Might even make a decent fertilizer.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

September 28, 2015

A. I suggest that you try lime precipitation to precipitate calcium phosphate and calcium sulfate. The quantity of sludge will be very large.

Lyle Kirman
consultant - Cleveland Heights, Ohio

October 2, 2015

A. Mr. Kirman is entirely right. Also, I know from experience that such sludges don't dewater well. You might expect 150 - 200 gallons of solids after filter pressing from a 1000 gallon batch.

What I once did to evaluate dewatered solids volume I called "bench scale pressing." Put a wad of cotton, then a little bed of sand in the bottom of a 5 cc syringe. Cover this with a little circle of filter paper. Now, fill the syringe with wet sludge. Now, insert the plunger and start pushing it down. Gradual pressure is best. Press it out until you can't get anymore fluid out. Since the cross sectional area of the syringe is about 0.2 - 0.25 sq. in., it's not hard to exert 80 - 100 psi with your thumb.

Now, evaluate. It may be that you would be better off neutralizing with NaOH, evaporating, then disposing of the residue as a solid waste.

dave wichern
Dave Wichern
Consultant - The Bronx, New York

(You're on the 1st page of this topic)       Next page >

finishing.com is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
Consult'g, Train'g
& Software

About/Contact    -    Privacy Policy    -    ©1995-2022 finishing.com, Pine Beach, New Jersey, USA