It is a water purification technology in which a semi-permeable membrane is used. In which, the flow of pretreated water passes tangentially with respect to the surface of the membrane; while the permeate is extracted perpendicularly the water is separated from its almost total dissolved mineral content, which is continuously swept from the surface and goes to waste or is recirculated with the help of a high pressure pump .

It is based on applying pressure to overcome osmotic pressure, a colligative property driven by the chemical potential (thermodynamic characteristic of the water source). Typically, a high-pressure pumping system is applied in the process to force the flow across the membrane surface. The characteristics of water according to its function are regulated by different standards that establish references according to their applications, among these are the American Society for Testing and Materials (ASTM), British Standards Institution (BSI) and the International Organization for Standardization (ISO).

The use of reverse osmosis by different sectors for water treatment has been very successful. For example, it is often used in the pretreatment system of wastewater reused for industrial purposes (oil, food, pharmaceuticals, etc.). The importance of implementing this methodology lies in the fact that the treated wastewater meets the quality standards to be reused for purposes such as boiler feed, heat exchangers, chiller, etc. This technology offers advantages such as low energy consumption and high rate of pollutant removal, provides a perfect rejection of all impurities and for different pollutants.

Method for efficient pretreatment of wastewater

In the production of quality water for technical applications, reverse osmosis is implemented as post-treatment water. To use this technology, microbiological pretreatment is necessary as a precautionary measure, especially when working with muddy streams. Since the disinfection system depends on the type of material of which the membrane is made, the deposition of suspended solids increases the risk of their colonization by microorganisms. In addition, the pretreatment system should include devices for sediment control, which depends on the mineral composition of the wastewater source; an activated carbon filter to reduce the loads of substances (organic and inorganic solvents) that may be dissolved in the flow; and softeners to reduce the hardness of the water.

Reverse osmosis membranes have a narrow pore structure (less than 0.0001 micron) that effectively removes up to 99% of all contaminants and impurities. This technology is capable of removing up to 99% of dissolved particles, colloids, organic matter, bacteria, viruses, pyrogens/pathogens from feed water. However, it is necessary to find an optimal configuration of the physical-chemical treatment unit used for the operation of each type of effluent, ideally the membranes should only receive water with dissolved matter.

Characteristics to consider for process design

For the design of a reverse osmosis wastewater pretreatment system, certain process characteristics must be considered:

• The type of membrane to choose: they are generally made of cellulose acetate and an aromatic polyamide.
• The configuration of the membrane assembly: the one- or two-pass membrane scheme is usually used,
• Pumping: the use of booster pumps between stages depends on the flow rates.
• Recoveries: the recirculated flow and the disposal of remaining sediments must be taken into account.
• Chemicals for scale control: a solvent injection system can be used to dissolve organic matter.
• Membrane cleaning strategies and biological control methods: this is of great importance because control of membrane fouling extends membrane life.
• Energy consumption: the variability of wastewater can greatly affect the expected energy consumption for treatment.

In KALSTEIN we have different purification systems that fit the user’s requirements. Our equipment has an integrated control system that allows monitoring the conductivity of the water, has a temperature compensation system and a leak sensor. If you require information for PURCHASE or SALE contact us. You can find more information about the different types of systems that Kalstein has to offer. Visit our catalog HERE