Principle, Construction, Working, Uses, Merits and Demerits of Membrane Filter and Seitz Filter

Membrane Filter

Principle

Membrane filters are thin layers of semi-permeable materials that separate chemicals when they are subjected to a driving force. The membrane works by separating substances physically. Biological filters are used to remove bacteria, microorganisms, particulates, and organic material from water, producing by-products of disinfection that impart color, odor, taste, and smell to the water. In order to reduce capital and operating costs, advances are made in membrane production and module design. Here are some examples:

• Ultrafiltration
• Nanofiltration
• Reverse osmosis
• Microfiltration

Construction

Filter membranes are plastic membranes with pores that are typically smaller than or equal to microns or submicrons. Approximately 120 mm thick, they must be handled with care. By trapping particulates on their surfaces, they act like sieves. Filters with pore sizes ranging from 0.010 ± 0.002 to 5.0 ± 1.2µ are available in several grades. These two extreme ranges are coded VF and SM by Millipore Filter Corp.

From air or water, pore sizes as small as 0.010 to 0.10 are effective for removing virus particles. The removal of bacteria is done with filters with pores between 0.30 and 0.65. Larger pore sizes are used in applications such as aerosol, radioactivity, and particle sizing, for example. There are several types of membrane filter modules made from flat sheets of stock or hollow fibers. During module construction, the membrane material is inserted or sealed into an assembly, such as with a hollow-fiber module. Over a number of years, these types of modules can be used over and over. Also manufactured for long-term use are spiral-wound modules, as shown in Figure.

Working

A semi-permeable membrane is the basis for membrane separation. Membrane filters out suspended solids and other substances while letting water pass through. Membrane filters are maintained in operation on rigid supports such as perforated metal, plastic, or coarse sintered glass, as with fibrous pad filters. The membrane filter is less likely to clog if a depth filter is used during sterile filtration if the solution contains considerable suspended matter. When dry, they are brittle and can be stored for indefinite periods of time, but are tough when wet.

Microfiltration

The term "microfiltration" is defined as the separation of fluids by using membranes with pore sizes between 0.03 and 10, molecular weight cutoffs (MWCOs) greater than 10,00,000 Daltons, and low feedwater pressures between 100 and 400 kPa (15 to 60 psi). The operation removes sand, silt, clay, cysts from Giardia lamblia and Crypotosporium, algae, and some bacterial species. However, when combined with disinfectants, this filter appears to control viruses. The number and concentration of chemicals used in water treatment are increasingly being limited. With membrane filtration, pathogens can be physically removed, reducing the need to add chemicals such as chlorine. Natural-synthetic organic matter can also be removed to reduce fouling potential. By pretreatment, organic matter is removed more effectively. It can also be used to reduce bad odors and to remove hardness from groundwater prior to reverse osmosis (RO) and nanofiltration (NF).

Ultrafiltration

These ultrafilters have a pore size of approximately 0.002 to 0.1, have a MWCO of around 10,000 to 100,000 Daltons, and operate between 200 and 700 kPa (30 and 100 psi). In addition to removing all microbiological species, humic materials and some viruses are also removed, but isn't a total barrier. This second barrier to contamination can be achieved through disinfection. Here are some of the main benefits of low-pressure UF membrane processing:

• Coagulation, flocculation, disinfection, pH adjustments are not required.
• Filtration by size only.
• Particles and microorganisms are consistently removed from the treated water.
• Plants and processes are compact.
• Water treatment with membrane technology can be simple and automatic, but fouling can cause difficulties.

Reverse Osmosis

Almost all inorganic contaminants can be removed from water by reverse osmosis. Using this machine, radium, natural organic substances, pesticides, cysts, bacteria, and viruses can be effectively removed. The best results are achieved when multiple units are used together. Water should also be disinfected before use. This filter removes nearly all contaminants and most non-ions dissolved in the water. Flow rate and total dissolved solids are relatively insensitive to it. The system operates immediately after installation. Concentrated effluents with low solids can be processed. Bacteria and particles can be removed. Automation makes it easier for operators to operate.

Uses

• Isolating and categorizing microorganisms is possible with it.
• Ammonium ions are removed from potable water with this device.
• Dairy industry - MF is a significant component of dairy ingredient manufacturing. Among its uses are milk, whey, and clarified cheese brines.
• Starch and sweetener industry - Dextrose and fructose syrups can be clarified, rinse water distilled from starch can be concentrated, dextrose can be enriched, depyrogenated dextrose syrup can be concentrated, and maceration water can be divided or concentrated.
• Sugar industry - Unprocessed juice can be clarified using MF without using a primary clarifier. Throughout the production process, sugar solutions can be clarified, divided, and concentrated.
• Chemical industry - MF can be used in numerous chemical processes such as desalinating dial filters and purifying dyes, pigments, and optical brighteners, cleaning wastewater and rinsing water currents, to concentrate and dehydrate minerals, such as calcium carbonate, titanium dioxide, and kaolin clay, or to clarify caustic agents or to produce polymers or recover metals.
• Pharmaceutical industry - The harvesting of cells or the recovery of biomass is used in the fermentation process during the manufacture of antibiotics. Microfiltration reduces labor costs and increases productivity. It is used to concentrate enzymes before other processes in the industrial production lines.

Merits

• The rate of filtration is rapid.
• Due to their disposable nature, they do not cross-contaminate.
• During prolonged filtration, bacteria cannot grow on the filter.
• The filtrate is free of fibers and alkali due to negligible adsorption.

Demerits

• Solvents like chloroform pose a greater risk to ordinary types.
• It is possible for them to clog, but it is rare.

Seitz Filter

Principle

Using asbestos pad filters and sieve-like mechanisms

Construction

• The filtering medium consists of a pad of compressed asbestos.
• To fill the slurry with one upper part.
• A curved section at the bottom receives the filtrate.
• Seitz filters have a typical thickness of about 2mm.

Working

• Fill the upper part of the container with slurry.
• The asbestos pad is deposited with slurry and the filtrate is passed through it.
• Filtering and retaining small viruses are almost perfect with the finest pore sizes.

Uses

• Filtration of sterile solutions.
• This purpose is also served by air filters.

Merits

• It is extremely easy to use.
• Viscose solutions are useful.

Demerits

• It is fragile or delicate.
• It is imperative to use a new pad for every filtration to prevent residue from previous filtrations.

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