RO REFUSE REUSE

Question

I want to understand an industrial process that will be good to reuse the waste water high in salt contents to be used elsewhere.
The amount may be a few thousand liters of waste water.
What are the best options ?

Xuewen Jiang · Answer

Recover Mg from the waste water.

James Stewart · Answer

Rather than join in with the "sky is falling" crowd, I will suggest you start a small patch of salt tolerant vegetation, irrigate it with the RO waste water, and feed goats with the growth, thereby enabling a harvest of goat milk, or meat.

Maher Louis, PE, PEng. · Answer

Dear Mrs. Bhatnagar,    The solution for this situation is to separate completely salt from water, a process usually named as Zero Liquid Discharge (ZLD), and it simply consists out of 2 steps: 1- Evaporation (separation) of water , 2- Crystallization of salt. We are presenting this ZLD while referring to Room Temperature Evaporation rather than Reverse Osmosis (naturalseawaterdesalination.com).
    Despite you are speaking about a small limited situation, however your problem is now a global emergency.
    Reverse Osmosis is an inappropriate process, unhappily it is baked by an industry which is persisting for survival, dragging the worldwide community into a dramatic environmental problem. You are speaking about "few cubic meters", however now the Mediterranean sea, Red sea, and Arabian (Persian) Gulf salinity is increasing to the level that all reverse osmosis plants in this region will face the results of total inability to generate potable water any more.

David Sherzer · Answer

RO reject was and remains a huge problem, unless it is discharged into the ocean.  We in UET developed a process to take the RO reject and reuse it in another RO systems after special treatment.  This reduces the RO reject to less than 10%, which saves a lot of water.  In our practice, we also use the RO reject as make-up water for cooling towers, as we use our UET water treatment technology, which is a set of reactors that remove scale out of the water into the UET reactors, while the rest of the systems remain free of scale.  David

Obet Acot · Answer

Recovering RO Reject is not practical. The concentration factor for this type of waste is around 3-4x.  Imagine if the feed TDS is around 500 ppm, reject TDS will be around 1500-2000 ppm. Reducing it back to its feed water quality involves a technology that has high cost with high opex. Work instead in increasing permeate yield say about 75-80% range

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