QUESTION
Aluminium anodizing plant : Need suggestions to reduce 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.
harish.muddarangappa@bhorukaaluminium.com                      
by
2 April 2008