What is an Industrial Seawater Reverse Osmosis (SWRO) System?
An industrial seawater (salt water) reverse osmosis (SWRO) water system is a highly effective water treatment process for reducing up to 97% of total dissolved solids (TDS) in water in a single pass and over 99% with a second pass. RO Applications include drinking water, waste water, cooling tower, hotels, oil and gas, potable water, high purity, domestic water, boiler feed, and many industries. SWRO systems have improved in performance and economic viability of using membrane technology for seawater TDS reduction. As industries strive to reduce energy consumption, control pollution and reclaim waste streams, SWRO is a leading option.
Industrial Seawater Reverse Osmosis Water (SWRO) Systems from 5,000-400,000 GPD
NECO offers industrial seawater (salt water) reverse osmosis water systems from 1,500-400,000 GPD (1 – 277 GPM) in a single skid and specially engineered systems that may be outside of the performance factors below. SWRO is a highly effective water treatment process. And with two passes can reduce over 99% of dissolved mineral salts, organics, and other dissolved particles by forcing water under high pressure through a semi-permeable membrane. The process for SWRO systems is named “reverse osmosis” because it is the opposite of the natural osmotic process. In the seawater RO process which mirrors the standard industrial fresh water RO process, water from a solution with a low concentration of dissolved solids (TDS) travels through a membrane seeking to dilute a higher concentration solution. A seawater reverse osmosis system is induced by applying pressure with a pump to a solution with a high concentration of dissolved solids, causing water from the concentrated solution to pass through the membrane, which is called product or permeate water. Dissolved solids do not easily pass through the membrane and are continually flushed to drain as waste. Fouling and scaling is eliminated or reduced by this flushing action across the SWRO membrane.
Industrial Seawater Reverse Osmosis Water System (SWRO) Performance Factors
- Pressure: 750 -1,000 psi is the feed pressure needed. A minimum amount of pressure must initially be reached to overcome the natural osmotic pressure of the seawater (SWRO) membrane. Flux (product water production rate) will increase as pressure is increased. Salt rejection does not continually improve as pressure increases as there is a practical limit to the SWRO membrane. The result of too much pressure or flux is usually scaling or fouling.
- Recovery: 25 – 40% recovery rates for SWRO are typical as a percent of feed water converted to the product or permeate water. A practical limit exists for the recovery rate – too high of a rate requires a more concentrated waste stream, which increases the likelihood of membrane fouling as salt precipitates and forms scale on the membrane surface.
- Temperature: 45°F-85°F is the operating temperature range of a SWRO. Membrane flux is highly dependent on temperature. If temperature increases and pressure remains constant, water production increases. Higher temperatures also result in a drop-off in salt rejection/water quality due to an increase in diffusion rate for salt ions through the membrane.
- Pretreatment/Posttreatment: additional water treatment steps before or after the SWRO process varies, depending on water conditions and water quality requirements. If raw water contains hardness, iron, turbidity, and high total dissolved solids, then pretreatment equipment and or pretreatment chemicals should be used to extend membrane life and improve system performance. If water quality requirements require ultra-pure or sterilized water, then a second RO pass and posttreatment steps should be considered.
Typical Applications of an Industrial Seawater Reverse Osmosis (SWRO) Water System
Seawater reverse osmosis is typically used for potable water, oil and gas production, domestic water, cooling water, manufacturing process water, boiler feed/makeup water, chemical process water, drinking water, beverage processing, hotels and humidification. Seawater typically has a salinity around 3.5% or 35,000 ppm (mg/L), which is mostly sodium chloride.