MEMBRANE FILTRATION

The tangential filtration process is an innovative process that allows longer operation time minimizing the need for cleaning stops, thus gives the filtration system greater productivity and reliability.

Due to these characteristics, this process is widely used in several processes in the most diverse industries, such as foods, juices, beverages, textiles, water, chemicals, biotechnology, among others. It is also a great alternative for effluent treatment and water reuse, contributing to environmental preservation.

Membranes are barriers made with high technology materials, which allow a selective passage of materials according to their size, shape and characteristics. The membranes have various configurations and are selected according to the specific needs of each application.



The cross-flow separation system consists of a feed stream under pressure on a membrane placed in parallel with the flowing stream. A portion of the feed passes through the membrane with the applied pressure, since that its components are smaller than the pores of the membrane. This portion that crosses the membrane is called the permeate.

The flow that does not pass through the membrane drags from its surface the materials that do not permeate. This stream is called concentrate.

The feed rate should be much higher (typical 10 times more) than the filtration rate to reduce membrane fouling.



Tangential Separation Types

There are 4 main membrane separation processes currently applied for liquid / liquid and liquid / solid separations:

Microfiltration (MF); Ultrafiltration (UF); Nanofiltration (NF); Reverse Osmosis (RO).

The application is determined by the characteristics of the product to be filtered. For each process, there are various degrees of separation and various membranes configuration, including: spiral; hollow fiber flat sheet and tubular.

Microfiltration

Microfiltration is a process with low applied pressures (5-100 psig), it is used for the separation of suspended materials, colloids, viruses, bacteria from an aqueous stream.

Microfiltration retains suspended solids with large particles, letting pass very small particles and dissolved material. Range of pore opening: 0.1 micron to 3 microns.



Microfiltration Applications

Juice Clarification

Wine Clarification

Clarification of Fermentation Broths

Industrial Effluent Treatment

Recovery of caustic soda solution (CIP solution)

Water purification

Others

Ultrafiltration

Ultrafiltration is a process with medium applied pressures (30-150 psig) a little higher than the microfiltration pressures.

Ultrafiltration is used for the separation of large molecular weight solutes from aqueous solutions and is considered a semipermeable membrane. We thus obtain a clear permeate, free of suspended solids.

Ultrafiltration retains proteins, polysaccharides, emulsified oils, particulate matter, viruses, bacteria, colloids and suspended solids, allowing most of the surfactants, water, minerals, acids and alkalis to pass through. Pore range: 0.005 - 0.1 micron; 1K - 500K MWCO.



Ultrafiltration Applications

Gelatin (concentration)

Plasma (concentration)

Milk and Whey (protein concentration)

Endotoxin removal from solutions

Solutions and extracts purification

Concentration of Heparin and Chondroitin

Potable water

Clarification of Juices and Syrups

Oily Effluent

Electrocoat paint

Treatment of industrial and municipal effluents

Others

Nanofiltration

Nanofiltration is a process where pressures range from medium to moderately high (50-450 psig).

In this process the monovalent ions pass freely through the membrane and the multivalent ions and low molecular weight organic matter are retained.

Usually the applications of Nanofiltration include low molecular weight concentration (e.g. lactose and sugars), water softening, desalination of dyes, recovery of acid and caustic solutions and removal of color.

Nanofiltration retains divalent salts and organic matter, leaving monovalent salts, water, acid and alkaline solutions pass. Range of pores between UF and OR.



Nanofiltration Applications

Recovery of lactose and sugars

Concentration of Whey with partial reduction of the salt content

Desalination of Paints (Textile Industry)

Recycling of Caustic and Acid Cleaning Solutions (CIP)

Water Softening

Concentration and Desalination of Antibiotics

Others

Reverse Osmosis

Reverse Osmosis is used for separating dissolved mineral salts from a water stream, including monovalent salts, producing that way pure water.

The pressures applied in these systems are moderate to high (80-1200 psig). The OR membranes are manufactured with different rejection indices, which allows to select the most appropriate membrane for the required application.

Reverse Osmosis retains organic salts, allowing molecules to pass in a range of 5 Angstroms (0.0005 micron) or 100 MWCO.



Reverse Osmosis Applications

Water Potabilization and Demineralization

Whey Concentration

Evaporate Condensate Polishing

Salts Concentration

Others

Hybrid Filtration

For liquid streams with low suspended solids when the filtration is used for a polishing, this process can be used which is the result of the combined use of the Tangential Filtration with Dead End technique.

Hybrid filtration occurs in two phases: filtration is initiated as in the conventional process, all the stream to be filtered passes through the membrane, the suspended material is retained on the surface of the membrane and the filtrate (Permeate) free of impurities.

When the suspended material accumulated on the membrane´s surface reaches a certain value the second stage of the process starts: the backwash, which a small fraction of the cleaned permeate is pumped back to the membrane surface cleaning, at the same time the raw water is pumped parallel to the surface of the membrane by dragging all the dirt accumulated therein.

The advantage of this technique is to be able to reduce energy consumption compared to the Tangential Filtration process, as it does not require the constant circulation of the liquid on the surface of the membrane.