DESIGN AND INNOVATION AT YOUR REACH
As an Industrial Technical Engineer, specialized in desalination of brackish and sea water via the reverse osmosis system, with energy recovery, I can affirm that this is the most reliable, cost-effective and environmentally friendly system that we have in order to obtain fresh water.
What is Reverse Osmosis?
Reverse osmosis is a process by which the chemical, bacteriological and physical desalination treatment of water is guaranteed. It works by using semi-permeable polyamide membranes that act as a filter, trapping and eliminating most of the dissolved salts while preventing the passage of bacteria and viruses. Obtaining pure and sterilized water.
Water with a high content of salts such as sodium, calcium, born, iron …, chlorides, sulfates, nitrates, and bicarbonates etc., can be treated via reverse osmosis in order to reach the limits considered water as acceptable for use.
The filtering membranes are the key and responsible for separating salts in the water. These membranes can be considered as molecular filters. The size of the pores of these filter membranes are extremely small, requiring considerable pressure in order to move water through them. The appropriate choice of membrane model is based on the water to be treated and its subsequent us, thus determining the most suitable installation type.
Semi-permeable membrane is one that contains pores or holes, the same to that of any filter, of molecular size. The size of the pores is miniscule passing only small molecules, not the larger ones, typically the size of microns.
The end result is that, although water passes from the low concentration to the high concentration area and vice versa, there is a greater net flow of molecules of water that pass from the area of low concentration to that of the high area.
Mediante este procedimiento es posible obtener agua desalinizada (menos de 500 micro siemens/cm de conductividad eléctrica) partiendo de una fuente de agua salobre, agua de mar, que en condiciones normales puede tener entre 20.000 y 55.000 micro siemens/cm de conductividad.
Through this procedure desalinated water is obtained (less than 5,000 micro Siemens/cm of electrical conductivity) from a source of brackish or sea water, which in normal conditions can have between 20,000) and 55,000 micro Siemens/cm of conductivity.
The water conductivity measure, gives an indication of the quantity of diluted salts contained, due to the fact that pure water is not a good electrical conductor (its dissociation potential is less than 0.00001).
Reverse or inverse osmosis (RO) has today become one the most efficient systems for desalination and purification of water, used in ships, airplanes, industries, hospitals and homes.
Through reverse osmosis raw water that reaches the desalination plant is converted both into side water product and brackish water.
The key is in the configuration of the stack membranes that, interlace the circulation network channels between layers converging in the center of the system. There is an input stream and two output streams, one is known as rejection and the other as water product, values for each will depend on the inlet pressure applied to the system. Specific membranes exist for different types of water, whether it is brackish to sea water.
Reverse osmosis industrial equipment mount several trains or cars of interconnected membranes connected to a high pressure pump, PH and flow meters.
For the optimal functioning of these systems anti-encrusted silica treatment is required.
The comercial and large-scale use of this technique for the separation of various components and for that of obtaining fresh water is relatively recent. The first synthetic membrane was obtained in the 60s by Loeb and Sourirajan, using cellulose acetate. It was the first membrane that in addition to rejecting the salts eased the passage of water that made it usable in practice, hence emerging as the first system…
At present, semi permeable membranes are made out of different materials typically from acetate or triacetate cellulose, as mentioned prior. Modern membranes are made from more stable materials such as that of aromatic polyamides.
These membranes have small pores on their surface that allow the passage of water or “permeated”, rejecting the salts or solutes in a liquid stream called “rejection” or “brine”.