What is the difference between Thin Film & CTA Membranes?
CTA (Cellulose Triacetate) membrane is a paper by-product membrane bonded to a synthetic layer. CTA membranes are made to allow contact with chlorine in the water. These require a small amount of chlorine in the water source to prevent bacteria from forming on it. CTA membranes have a rejection rate of 85-95%.
TFC (Thin Film Composite) membrane is made of a a synthetic material, and requires chlorine to be removed before the water enters the membrane. Chlorine will cause irreversible damage to a thin film membrane element - for this reason, carbon filters are used as pre-treatment in all residential reverse osmosis systems using TFC membranes. A Thin film membrane has a higher rejection (95-98%) and longer life than the CTA membrane.
What is the difference between tap & brackish water membranes?
There is no difference in the membrane material. Brackish water membranes have an outer shell of fiberglass whereas Tap water have a tape wrap. The construction allows Brackish water membranes to be operated at higher pressures required to treat brackish water.
What are the differences of different brands of membranes?
What are the differences of different types of membranes? Are all membranes of the same type (e.g. TFC) from different manufacturers the same? (example: an oil filter by Toyota is different from that of Mitsubishi).
You are right. These are very similar in construction and performance. Like other products, the main difference is in the reputation and reliability of the manufacturer. However, because there are different manufacturers, membranes do come in several end type configurations depending on the manufacturer. When ordering vessels, you will need to specify what brand of membrane you plan on using so the appropriate end adapters can be built in. When replacing membranes with a different brand, you should check the membrane specifications to make sure the end configuration is compatible for direct replacement.
What is the difference between dry and wet membranes?
When the thin-film membranes are manufactured they are dry. These dry membranes have an indefinite shelf life, when stored properly. Membranes become wet when they are flushed or tested with water. Once wet, the membranes can not be dried. The wet membranes must be preserved to prevent the growth of micro-organisms on them. This is done usually by using a 1-2% solution of sodium metabisulfite. For more details look for information on storing membranes.