Reverse Osmosis Membranes
To view the range of reverse osmosis membranes, please select an element size below.
Derwent Water Services Limited provides many different types of membranes for a variety of applications and duties. Membranes to satisfy the following processes are available:
- Reverse Osmosis water passing through the membrane with all the dissolved solids discarded as a reject stream.
- Nano-filtration ions such as sulphate or phosphate with more than one negative charge are rejected, and also uncharged ions and positively-charged ions are similarly rejected. The ions which are passed through the membrane are single-charged ions.
- Ultra-filtration is selective in its choice for certain molecular weights. High molecular-weight compounds, such as proteins, are rejected and the low molecular-weight compounds pass through the membrane.
- Micro-filtration is where suspended solids (e.g. particles of clay, bacteria) are rejected and other soluble substances pass through the membrane.
Within the four membrane processes are different membrane materials, e.g. cellulose acetate, polysulphone (PSO) and polyvinyldifluoride (PVDF) membranes. Also, composite membranes (referred to as TFM or TFC membranes) have been introduced to provide advantages of high salt rejection and high flux over the cellulose acetate membranes. These composite membranes have good temperature and pH resistance but are disadvantaged in an oxidising environment. The composite membranes are available in two- or three-layers designs.
Selection of the correct membrane depends on its overall chemical resistance which includes its resistance to temperature, pH and oxidising environment.
The membranes are supplied in various configurations: spirally-wound elements, tubular membranes, fibre systems and ceramic systems.