MOLSEP^®
Spiral type membrane module

A spiral type membrane module is divided into an “element,” which is packed with the separation membranes and a “vessel,” which is connected to and houses the element. Only the element can be replaced. (Figure 1)

Inside the element, flat membranes and spacers are densely packed and wrapped around the water collecting pipe. The spacers prevent the membranes from sticking together and blocking the flow paths. (Figure 2)

Compared with the hollow fiber and the tubular type modules, a spiral type membrane module has high pressure resistance because its separation membranes are densely integrated. It allows for NF/RO membrane treatment that requires higher pressure than osmotic pressure.

On the other hand, there are disadvantages that its flow paths are narrow, and its treatment target is limited to clear liquid whose FI* value is 4 or less. In the case of turbid liquid containing solids, the solids are removed in pretreatment by a hollow fiber membrane module, etc., before the liquid is supplied to the spiral membranes.

*FI value = Fouling Index: quantitative indicator of how suspended solids in feed water affect fouling (contamination) of RO membranes, also known as the membrane fouling index. It is calculated from the filtration rate measured by filtering the test liquid through a membrane with a pore size of 0.45 μm for 15 minutes at a pressure of 2.1 kg/cm2.