An Innovative RO Design to Concentrate SALTS at Lower Pressure THAN Osmotic Pressure of the BRINE

This paper introduced ROTOWER, an innovative patent pending RO system design, which can be used to achieve extremely high TDS in the concentrate with obvious lower maximum operation pressure than the osmotic pressure of the concentrate and qualified reuse water in the permeate side. ROTWER based on a new way of understanding the basic RO equations. Compared with a lower B value membrane, a membrane has higher B value means lower differences of concentration and lower osmotic pressure difference across the membrane, consequently lower operation pressure is needed for same feed TDS at same permeate flux, or higher permeate flux is achieved at same feed TDS with same operation pressure, and then we can use the higher B value membrane to further concentrate a solution as the TDS is too high for a lower B value membrane. ROTOWER is a concentrate staged array design with two or three kinds of high pressure RO elements characterized by A/ B value, while the element with lower A/B value was installed in the upstream stages, and the element with higher A/B value was installed in the downstream stages, normally the A and B value of the downstream element is about 2-4 and 2-20 times of the upstream element. Commercial high pressure RO elements, Industrial RO series and Industrial RO HP series with maximum 80 bar and 120 bar respectively, were developed and tested with 5%-15% of NaCl at 60 – 100 bar. This paper also shown the field test result from a pilot plant with 10 pieces of 4040 elements for concentrating a treated brine with about 60g/l of TDS to 140g/l and more of TDS in the concentrate.