Industrial RO reject is the concentrated stream left behind after a reverse osmosis system has done its job. Depending on your recovery rate, it can represent 15% to 50% of the feed volume, and it carries nearly all the salts, silica, hardness, and organics that the membranes rejected. In most plants I’ve worked on, this stream is the single biggest obstacle to hitting discharge limits or reaching zero liquid discharge. The good news is that you have eight practical routes to choose from, and the right one depends on your water chemistry, your discharge permit, and your operating budget. This article walks through each option from simplest to most complex, with the design trade-offs I’ve seen matter most in real projects.<\/p>\n