Membrane filtration is a technique used to separate particles from a liquid in order to purify it.In membrane filtration, a solvent is passed through a semi-permeable membrane. The membrane's permeability is determined by the size of the pores in the membrane, and acts as a barrier to particles which are larger than the pores, while the rest of the solvent can pass freely through the membrane. The result is a cleaned and filtered fluid on one side of the membrane, with the removed solute on the other.There are three membrane filtration processes:Microfiltration [MF] - MF is a low pressure [up to 100 psi (7 bar)] process for separating larger size solutes from aqueous solutions by means of a semi-permeable membrane. This process is carried out byhaving a process solution flow along a membrane surface under pressure. Retained solutes (such as particulate matter) leave with the flowing process stream and do not accumulate on the membrane surface.Pore ranges from 0.1 - 3 µm (micron meter).Applications:Clarification of dark juices for example, in the clarification of wine and dark juices, MF is to separate the suspended solids from the juice to produce a low turbidity juice while allowing the passage of color and flavor.Wastewater treatmentUltrafiltration [UF] - UF is a low pressure [up to 150 psi (10 bar)] process for separating solutes from aqueous solutions by means of a semi-permeable membrane. UF provides an essentially complete barrier against particles larger than the pore size, bacteria and the much smaller viruses usually found in the feed water.UF operates by a surface removal mechanism resembling a fine sieve with a highly uniform pore size. Any particles greater than the pore size are rejected. This characteristic makes UF membranes ideal for meeting absolute filtration quality requirements.In addition to high removal efficiency and an absolute removal rating, UF membranes tend to be more compact, allow higher automation with unattended operation and have lower chemical usage.The pore size is approx. 0.02 µm (micron meter).Applications:Microbiological contaminants rejection [Rejection of Cryptosporidium]Reverse osmosis pre treatment [Reduction of SDI and TOC (Total Organic Carbon)]Reduction of Turbidity [colloids, proteins, large organic molecule]Wastewater treatmentNanofiltration [NF] – NF is a low to moderately high pressure [up to 450 psi (31 bar)] process. Pore sizes range between UF and RO. Pores have not been observed in NF membranes under any microscope, however, water can still pass through the membrane and multivalent salts and low molecular weight organics are rejected. It is difficult to predict the performance of NF membranes since membrane rejection is influenced by the size, structure and charge of the components in solution. As a result, piloting is highly recommended for NF applications, even if a detailed feed water analysis is available.Applications:Water softeningOverall reduction of TDS (Total Dissolved Solids)Color and TOC ( Total Organic Carbon).Separation of organic from inorganic matter (in special food and wastewater applications) 

Technology DescriptionReverse Osmosis (RO) is a modern process technology used to purify water for a wide range of applications, including:SemiconductorsFood processingPower plantMunicipal drinking waterEtc.BiotechnologyPharmaceuticalsSeawater desaltingMobile water purificationThe Reverse Osmosis system includes:Pre TreatmentR.O. unitPost TreatmentThe quality of the feed water is defined in terms of concentration of suspended and dissolve particles and saturation levels of the soluble salts. The common indicators of those particles used in the RO industry are Turbidity, Silt Density Index (SDI) and Total Dissolve Solids (TDS).The feed water, depending on its source, may contain various concentrations of suspended and dissolved solids. The objective of the feed water pretreatment process is to improve the quality of the feed water to the level which would result in reliable operation of the RO membranes.In RO, the water passes through the membrane at a much faster rate than the dissolved solids (salts).The driving force of the reverse osmosis process is applied pressure. The amount of energy required for osmotic separation is directly related to the salinity of the solution. Thus, more energy is required to produce the same amount of water from solutions with higher concentrations of salt.The RO system produces purified water (permeate) from the feed water via rejection of organic and inorganic constituents by a semi permeable membranes.It separates the incoming feed stream into two effluent streams:The permeate passes through reverse osmosis membranes and as a result,contains contains much lower quantities of salts and organics.The concentrate is the stream which passes tangentially across the membrane surface and thus contains the impurities separated from the permeate.Post treatment depends on the required water quality defined by the customer.