RESERVE OSMOSIS
REVERSE OSMOSIS
If water of high salinity is separated from water of low salinity via a semipermeable membrane, a natural process of transfer of water will occur from the low-salinity side to the high-salinity side of the membrane until the salinity on both sides are equal. This natural process is known as osmosis. In order to remove low-salinity water from a high-salinity source, i.e. seawater or waste-water using membrane separation, the natural osmosis-driven process must be revered. The high-salinity source water must be pressurised at a level higher than the osmotic pressure and the pressure losses for water transfer thorough the membrane. The reverse pressurised process is known as reverse osmosis (RO) and will result in a process of salt rejection and accumulation on one side of the membrane and freshwater production on the other. Such process are widely used in seawater desalination (SWRO) as well as brackish water (BWRO). High pressure feed pumps are used to deliver source water to the RO membranes at pressure required from membrane separation of the fresh water from the salts. The actual required feed pressure is determined by the salinity, temperature, target water quality, ad the configuration of the RO system.
TECHNOLOGY SPECIFIC
Materials
All wet end of the pump as well as system parts should be of adequate-quality stainless steel. Typically low-salinity BWRO application require the use of 361 L or greater quality stainless steel. For SWRO and high salinity BWRO, duplex and super-duplex stainless steel is recommended.
Variable Frequency Drive
VFD are sometimes installed on the high-pressure pump motors to adjust motor speed in order o maintain optimum pump efficiency with changing feed pressure requirements driven by natural fluctuations in source water salinity and temperature. VFD also allows for the pumps to maintain optimum performance when membranes foul or scale and loose permeability overtime.
Centrifugal vs Reciprocating Pumps
Reciprocating pumps are typically used for small size plants of capacity of 4000m3/day (1.1 mgd), or less. This is due to a limitation of high power pump as well as cost. The two main advantages of positive displacement pump as compared with centrifugal pumps are the higher efficiency (95%+ vs 80% of CF pump) and with a very flat pump curve. RO is a energy intensive process and energy saving will of 24/7 running requirement will make a huge impact on production cost. Pulsating flow issues can be solved by using more pistons pump, with the flow pulsation can be down from from 46% (2 pistons) to only 2% (9 pistons). A typical RO membrane can accept 20% or less.
Centrifugal high-pressure pump on the other hand, are used for all size of desalination plants. The pump curve however is not flat, i.e. the pressure deliver change with flow. CF typically can deliver a higher flow and require less numbers of flow for a given flow compare to PD pump.
System Size
System size can be varies and we supply small SWRO system to ship and island, as well as system to small-mid size SWRO plants.
ENERGY SAVING SOLUTION
Variable Frequency Drive (VFD)
VFD drive is also widely used to save energy and such technology is particularly important in RO energy intensive process.
OUR ENGINEERING SOLUTION
Hydrofinio provides clients with an expert engineering team equipped with diverse skills to meet various challenges across industries. We leverage our knowledge to reduce risk. We’re constantly looking for new advancements and technologies to find the smartest and most optimal solutions. Contact us now with your requirement and we will come back with solutions to suit your need.