RO membrane elements can be coupled together in series in the pressure vessel, typically 1-8 elements per one pressure vessel. In deciding the number of RO elements per pressure vessel, plant size is usually considered first. In a large-scale plant (> 40 m3/h), 6-8 elements per pressure vessel are usually adopted, and in a smaller plant, 3- 5 elements per pressure vessel. In all cases, the space required to install or remove the RO elements should be considered in the plant design.
