30-03-2017, 09:58 AM
Generally, there are four types of membrane processes. They are microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Microfilter (MF) - Operating pressure (psi) is less than 30. Types of materials removed are clay, bacteria, large viruses, suspended solids. Ultrafilter (UF) - Operating pressure (psi) is between 20 and 100. Types of materials removed are viruses, proteins, starches, colloids, silica, organic, dye and grease. Nanofilter (NF) - Operating pressure (psi) is between 50 and 300. The types of materials removed are sugar, pesticides, herbicides, divalent anions. Reverse osmosis (RO) - Operating pressure (psi) is between 225 and 1000. Types of materials removed are monovalent salts. The applications of Micro and Ultrafiltration are conventional water treatment (replace all processes except disinfection), water pretreatment for R.O and nanofiltration, iron / manganese removal (after oxidation) and elimination of precursors of DBP. Apps by R.O. And nanofiltration are R.O. Application are mainly used for desalination. Nanofiltration was first developed to eliminate hardness. The nanofiltration can be used to eliminate the precursors of DBP.
During the 1970s, RO membranes with higher operating pressures were developed. This resulted in a considerable increase in the cost of energy. Thus, low pressure RO membranes developed and came to be known as NF membranes. In the second half of the 1980s, NF was established. From the early 1990s, it had become common and several applications were discovered. Nanofiltration due to the increase in demand for good quality water due to population growth, Reduction of waste and water reuse, Improved reliability and durability of filter membranes and to reduce total cost of operation. Different polymers used for nanofiltration are: polyethersulfone, polysulfone, polyphenylsulfone, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitriles, nylon, polypropylene, cellulose acetate (CA), regenerated cellulose and compounds, ceramics and barbed metals and carbon nanotubes. Two types of membranes. Spiral Membranes - Cheaper, more sensitive to contamination. Tubular Membranes - Most used, not easily contaminated. But the surface area of the spiral membranes is larger than that of the tubular membranes and therefore a greater capacity.
Benefits of Nanofiltration:-
1) Low operating cost.
2) Low energy cost.
3) Lower the discharge and less waste water than the typical system of reverse
osmosis.
4) Reduction of heavy metals (eliminates 95%).
5) Reduction of water hardness.
6) Reduction / Elimination of viruses, bacteria, VOCs and Pesticides.
7) Reduction of Nitrates and Sulphides.
8) Reduction of the salt content (brackish water).
9) Filtration without chemicals (without salt use).
10) The pH of the water can be altered for better health.
11) Ideal for municipal water supply, well water, river and rainwater.
12) Removes iron, lime and other chemicals that cause problems, often neglected
by water softeners.
During the 1970s, RO membranes with higher operating pressures were developed. This resulted in a considerable increase in the cost of energy. Thus, low pressure RO membranes developed and came to be known as NF membranes. In the second half of the 1980s, NF was established. From the early 1990s, it had become common and several applications were discovered. Nanofiltration due to the increase in demand for good quality water due to population growth, Reduction of waste and water reuse, Improved reliability and durability of filter membranes and to reduce total cost of operation. Different polymers used for nanofiltration are: polyethersulfone, polysulfone, polyphenylsulfone, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitriles, nylon, polypropylene, cellulose acetate (CA), regenerated cellulose and compounds, ceramics and barbed metals and carbon nanotubes. Two types of membranes. Spiral Membranes - Cheaper, more sensitive to contamination. Tubular Membranes - Most used, not easily contaminated. But the surface area of the spiral membranes is larger than that of the tubular membranes and therefore a greater capacity.
Benefits of Nanofiltration:-
1) Low operating cost.
2) Low energy cost.
3) Lower the discharge and less waste water than the typical system of reverse
osmosis.
4) Reduction of heavy metals (eliminates 95%).
5) Reduction of water hardness.
6) Reduction / Elimination of viruses, bacteria, VOCs and Pesticides.
7) Reduction of Nitrates and Sulphides.
8) Reduction of the salt content (brackish water).
9) Filtration without chemicals (without salt use).
10) The pH of the water can be altered for better health.
11) Ideal for municipal water supply, well water, river and rainwater.
12) Removes iron, lime and other chemicals that cause problems, often neglected
by water softeners.