Typical recycling, reuse and process water systems use Reverse Osmosis (RO) technology as the method of decreasing the level of ions in process water. RO recovery rates normally range from 50-75%, therefore 25-50% of the RO feed water is discharged as wastewater. With the increasing cost of water and waste discharge, more companies are looking to recover and reuse RO reject water.

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While it is possible to reuse the reject water from an RO system by feeding it directly into a 2nd RO unit, the likelihood of scaling or fouling the 2nd RO without pretreatment is rather high.