Dear Mahmud, Recently we performed test on spent caustic solutions with our electro-coagulation reactor and achieved good removal rates (99%) and the production of sulphur.
We (JIPL) have developed a process to clean the caustic effluent from aluminium extrusion production. It recovers the caustic and sodium aluminate as a 'clean' product which has a resale value.
The process/technology known as Bioremediation has a 40 year history of biodegrading the worst of the worst caustic compounds known to man. It is non pathogenic, non mutational, works in a 5.5 to 10.0 ph. range, and a temp range from 35 F to 427 F. Found in nature. When process is complete only elements remain. No residual of any kind. A side benefit is the organic compounds being degraded release O2 into the solution/water. For a listing of these caustic materials cleaned by this process see U.N.E.P. " The Dirty Dozen". Also an A - Z list is available. When we are connected I can send you the appropriate files. Pics also.
There certainly are processes, all depends on what you want to achieve and what costs. Our process train includes >99,5% organic destruction and then recovery of caustic and production of sulphur. Depending on level of organics, energy recovery is possible that could enable the plant to operate off grid.