Hello Ghazali, There are ...

Hello Ghazali,

There are many factors that determine what the most appropriate and cost effective solution to your particular RO concentrate handling problem. 

First off is how much brine waste are you talking about?

What is the regulatory environment?

And what are your realistic disposal avenues?

What are your available sources of energy and their respective costs? If you have low-grade waste heat you could look to a Humidification-Dehumidification process.

What are the reliability and availability requirements of the process? A tightly integrated process with no buffer storage can quickly run into problems if shutdown of the downstream processes causes/requires shutdown of the upstream process ('the tail is wagging the dog').

Do you have to get to a "Zero Liquid Discharge"? (If doing anything other than simple solar evap, this can become a complex and very expensive process).

Is land cheaply available for evaporation ponds and is the climate conducive to evaporation. This is a low tech solution, though it is not without limitations and drawbacks.

What is the subsurface geology like - deep well injection can also be effective, though you need to be confident that the target strata can both accept the flow (and is chemically compatible) and is also isolated from other geological sequences to prevent migration/cross contamination. This can also be quite expensive if the target strata is very deep and if there is significant probability of drilling dud wells.

Otherwise - there are numerous methods for further concentrating RO brine, most of which are some variant of (energy intensive) thermal desalinatio processes - these are often quite complex and expensive systems to build and to operate, typically requiring pre-treatment steps to reduce or remove alkali earth metals (Ca, Mg, Ba, Sr) and Silica to prevent scaling of great transfer surfaces. They also require operators with the right skills and experience to run them, which can be a considerable expense in order to get them to come/stay at remote locations.

I'm afraid there's no single simple solution - there's an entire industry around trying to tackle the very problem you describe!

Happy to answer more questions. Good luck!