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Aluminium Anodizing Plant:Troubleshooting TDS levels from ETP

Our's is an Aluminium Anodizing plant. We are using caustic for etching & sulphuric acid for anodizing. We treat the waste water generated from both.  But in effluent from ETP plant we are getting total dissolved solids very high >50000 therefore how we can reduce TDS?

Our ETP design is as below. We have two holding tanks: 
1. Caustic holding tank
2. Acid holding tank (mainly H2SO4)

What we are doing is we take caustic to neutralization tank, neutralized with acid (from holding tank) pH-around 7.5-8.0.

To this neutralised water we add coagulant, we will mix thoroughly then passed through press filter and the water was collected as final water. Suggestions are welcome.

Harish.M, Chemist.                      




Dear Harish,

TDS removal by ETP is not feasible. You may have to go for membrane process for the same. Besides, just neutralization and adding coagulant may not work for you. The pH must be alkaline for the coagulant to take effect. You may try adding coagulant at a pH of 8.5 and check the result.

Taral Kumar


Dear Sir,

This is the problem for almost all industries TDS, inorganic TDS will be removed either by Reverse Osmosis or recovery, second one can be established only after through treatability study, if you are interested in giving the work we will do with a cost we will quote after getting some details from you.

After getting willingness we will send our offer to you.

IF RO is used back wash will come that you have to evaporate and send to TSDF (Hazrdous waste mgt)

with regards


Dear Mr.Harish,
Your question has been passed on to me for a reply by indiawaterportal/wesnetindia.I am a Bangalore based water management consultant with 40 years experience in the field.

Your problem of very high TDS levels in your ETP where you neutralise NaOH and H2SO4 before disposal is not surprising.My guess is that you use 2 or 3% solutions of these two chemicals.

This means that each solution is of a TDS level of between 20,000 to 30,000ppm.Combining two such solutions for neutralisation will naturally result in such high TDS levels.There are two ways to tackle this problem.
1.Look abroad for cleaner processes in anodising which use far less polluting methods and buy out know how for such a process and replace your existing process.
2.Install a thermal evaporation unit to handle this ultra high TDS effluent.It is likely to be expensive and will result in very high corrosion levels inside the evaporator.

In the long run, alternative 1 is likely to be the more sustainable alternative.

If you need any further information,please ask me.

Water Management Consultant


Dear harish

First question in our mind that what is the waste water? ....The water which has contained low oxygen,... high suspended solids ....and pathogenic organism called waste water.....
removing TDS from ETP is nat very good idea....and co-agulent and Pressure filter dosent help in removing the TDS..they only remove TSS from water..

5. ETP waste

Dear Sir,

How much quantity of waste do we get with a 15 ton anodizing plant?

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