What is secondary reverse osmosis water treatment equipment? When do you need to use this equipment? I want to buy one. Give me some advice! thank you

Secondary reverse osmosis means that the effluent from primary reverse osmosis is treated by a set of reverse osmosis equipment. In any case, it depends on your requirements for effluent quality. In industry, if the subsequent equipment is an ion exchanger, it is generally not needed. If it is EDI, it has higher requirements for water inflow, and generally adopts two-stage reverse osmosis treatment.