RO plant

BWRO & SWRO Turn key plant from pre-treatment to post treatment

Desalination has become a very affordable solution to cope with fresh water shortage specially in tropical as well as of off-shore areas. Reverse osmosis (RO) is the leading pressure driven membrane processes which can be used for seawater or brackish water desalination. Every SWRO or BWRO unit shall be safeguarded with proper pretreatment. Desalinated water would be re mineralized in post treatment unit for potable purposes.

The pretreatment includes the entire necessary treatment step ahead of the reverse osmosis plant. It is determining for plant life time and to minimize chemical cleaning and membrane replacement. It has a direct impact on the plant performance.

The reverse osmosis process can also be built with one or two passes, depending on the product water requirements and the seawater salinity and temperature. In most cases, 1 pass is sufficient to reach the EU drinking water standards, specially regarding the boron content (1 mg/L). To reach WHO boron guideline (0.5mg/L), a second pass might be necessary (Boron removal process)

The energy recovery device is the key factor that determines the plant electrical costs. It must be chosen carefully based on the local energy costs and environment policies.

Post-treatment and/or polishing steps are required to condition the water after the reverse osmosis membrane process to make it suitable to your application.

Brine disposal can be an environmental and economical issue in some areas where the fauna and flora are sensitive to local seawater salinity increase. Brine disposal should be studied and engineered case by case.

The art of desalination is to determine and combine available technologies to optimize water production costs and quality.

Faran Company offers optimum process solutions for SWRO and BWRO plant from seawater intake to storage tank as turnkey project to produce high quality drinking or process water.

 

Pretreatment System

The efficiency of pretreatment for RO feed water depends on the source and quality of the seawater feed. A correct design of the system is the key for a successful operation of the SWRO plant.

Pretreatment is essential for the proper operation of the SWRO equipment and can add substantially to the project's CAPEX and OPEX since higher load of suspended solids, colloids and/or biological growth can cause unwanted fouling on the RO membrane if not treated properly.

Inadequate or inappropriate pretreatment may result both in a decline of water production and in the deterioration in product quality. The main result of a failed pretreatment is the RO membrane fouling with consequently increases in membrane replacement and chemical treatment. As a consequence of high fouling conditions, an increase in salt passage is registered while a higher feed pressure is required to maintain the design flow.

All the above effects due to failed control of the pretreatment system result in a direct influence on operational cost.

The aim of the sea water pretreatment system is to reduce the fouling constituents in the feed; a proper pretreatment system should remove colloidal and particulate matter and control the formation of chemical and biological deposits in order to reach a value able to provide stable and long term performance of the RO membranes.

Generally the pre-treatment system performances are compared using two parameters: SDI and turbidity

SDI is a measure of membrane fouling potential that is frequently utilized as a warranty condition by RO membrane manufacturers. The required maximum SDI value is usually < 3.0 for 95% of the time and 4 for 100% time, based on 15-minute measurements. A low SDI value in the feed water should result in lower power consumption, RO cleaning Requirements, and membrane replacement interval.

Turbidity is a measure of the degree to which light is scattered by suspended solids, and absorbed by soluble colored compounds in water. Due to its ease of measurement, turbidity is frequently utilized to characterize the level of particulate removal.

 

 

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