Reverse OsmosisReverse osmosis is a high-efficient technique fordewatering process streams,concentrating/separating low-molecular-weightsubstances in solution, or cleaning wastewater.It has the ability to concentrate all dissolved andsuspended solids. The permeate contains a very lowconcentration of dissolved solids. Reverse Osmosisis typically used for the desalination of seawater
Nanofiltration Nano-filtration is selected when Reverse Osmosisand Ultrafiltration are not the correct choice forseparation.Nanofiltration can perform separation applicationssuch as demineralization, color removal, anddesalination.In concentration of dissolved organic solutes,colloidal solids, and polyvalent ions, the permeatecontains monovalent ions and low-molecular-weight organic solutes like alcohol.
UltrafiltrationUltrafiltration is a selective fractionation processusing pressures up to 145 psi (10 bar). Ultrafiltrationis widely used in the fractionation of milk and whey,and in protein fractionation. It concentratessuspended solids and solutes of molecular weightgreater than 1,000. The permeate has low-molecular-weight organic solutes and salts
MicrofiltrationMicrofiltration is a low-pressure cross-flowmembrane process for separating colloidal andsuspended particles in the range of 0.05-10microns. Microfiltration is used for fermentation,broth clarification and biomass clarification andrecovery.
Reverse Osmosis• In order to describe Reverse Osmosis, it is first necessary to explain the phenomenon of osmosis. Osmosis may be described as the physical movement of a solvent through a semi-permeable membrane based on a difference in chemical potential between two solutions separated by that semi- permeable membrane.• The following example serves to demonstrate and clarify this point. A beaker of water as shown in figure 1 is divided through the center by a semi-permeable membrane. The black dotted line represents the semi-permeable membrane. We will define this semi-permeable membrane as lacking the capacity to diffuse anything other than the solvent, in this case water molecules.
Now we will add a little common table salt (NaCl) to thesolution on one side of the membrane (see figure 2). Thesalt water solution has a lower chemical potential than thewater solution on the other side of the membrane.In an effort to equilibrate the difference in chemicalpotential, water begins to diffuse through the membranefrom the water side to the salt water side. This movementis osmosis.The pressure exerted by this mass transfer is known asosmotic pressure.
• The diffusion of water will continue until one of two constraints is met. One constraint would be that the solutions essentially equilibrate, at least to the extent that the remaining difference in chemical potential is offset by the resistance or pressure loss of diffusion through the membrane. The other constraint is that the rising column of salt water exerts sufficient hydrostatic pressure to limit further diffusion. By observation then, we can measure the osmotic pressure of a solution by noting the point at which the head pressure impedes further diffusion.• By exerting a hydraulic pressure greater than the sum of the osmotic pressure difference and the pressure loss of diffusion through the membrane, we can cause water to diffuse in the opposite direction (Figure 3), into the less concentrated solution. This is reverse osmosis. The greater the pressure applied, the more rapid the diffusion. Using reverse osmosis we are able to concentrate various solutes, either dissolved or dispersed, in a solution.
Figure 1. Reverse Osmosis DiagramFigure 2. The osmosis process Figure 3. Hydraulic Pressure at work Causing Reverse Osmosis
Ultraviolet Water Purification - UV - Ultraviolet water purification lamps produce UV-C or "germicidal UV," radiation of much greater intensity than sunlight. Almost all of a UV lamps output is concentrated in the 254 nanometers (nm) region in order to take full advantage of the germicidal properties of this wavelength.- Most ultraviolet purification systems are combined with various forms of filtration, as UV light is only capable of killing microorganisms such as bacteria, viruses, molds, algae, yeast, and oocysts like cryptosporidium and giardia.- UV light generally has no impact on chlorine, VOCs, heavy metals, and other chemical contaminants. Nevertheless, it is probably the most cost effective and efficient technology available to homeowners to eliminate a wide range of biological contaminants from their water supply. - Recent testing has also shown that UV can be effective at destroying certain VOCs, although we would not specifically recommend the technology for VOC reduction.
• UV water treatment offers many advantages over other forms of water treatment for micobiological contaminants. Most importantly, it does not introduce any chemicals to the water, it produces no bi-products, and it does not alter the taste, pH, or other properties of the water. Accordingly, in addition to producing safe drinking water, it is not harmful to your plumbing and septic system. Further, it is easy and cost- effective to install and maintain without any special training.• Trojan Technologies, manufacturer of the Trojan UVMax line of household ultraviolet sterilizers, and R-can which makes the popular Sterilight brand of UV sterilizers, are pioneers and world leaders in the field of UV water treatment. These companies even manufacturers large UV sterilization systems that can be used by municipalities and regional water districts for large-scale water disinfection.
How it WorksUltraviolet purification uses a UV light source (lamp) which is enclosed in aprotective transparent sleeve (usually quartz). The lamp is mounted suchthat water passing through a flow chamber is exposed to the UV-C lightrays. When harmful microbes are exposed to the UV rays, their nucleic acidabsorbs the UV energy, which then scrambles the DNA structure of theorganism. The cell is rendered sterile and can no longer reproduce. The cellis now considered dead and is no longer a threat.ApplicationsUV treatment is an excellent choice to eliminate biological contaminationfrom most home drinking water, whether your home is on a municipalwater system or untreated private system (well, lake water, etc.). Its solepurpose is to kill harmful biological contaminants, and therefore shouldalways be combined with other forms of filtration (GAC / carbon block, KDF,or reverse osmosis) for reduction of heavy metals, chlorine, VOCs, andother chemical contaminants.
What Contaminants Does Ultraviolet Remove?- There are no micro-organisms known to be resistant to UV,unlike chlorination. UV is known to be highly effective againstbacteria, viruses, algae, molds and yeasts, and diseasecausing oocysts like cryptosporidium and giardia.- In practice, bacteria and viruses are the cause of most majorwaterborne pathogenic diseases. Of these enteric viruses,hepatitis virus and Legionella pneumophila have been shownto survive for considerable periods in the presence ofchlorine, but are readily eliminated by UV treatment.- For most microorganisms, the removal efficiency of UV formicrobiological contaminants such as bacteria and virusgenerally exceeds 99.99%. Specifically, the following aremoved to an efficiency of greater than 99.99%:
- E-coli, Salmonella typhl (Typhoid fever), Salmonella enteritidis (Gastroenteritis), Vibrio cholerae (Cholera), Mycobacetrium Tuberculosis (Tuberculosis), Legionella pneumophila (Legionnaires Disease), Influenza Virus, Polio virus, and Hepatitus A Virus (better than 90%).- Countertop UV systems are generally not recommended for removing oocysts such as giardia and cryptosporidium unless equipped with a 0.5 micron carbon block pre-filter since the exposure time the contaminant has to the UV ray is not always long enough to provide an adequate UV dose for disinfection of these more complex organisms.- Whole house UV systems like the Trojan UV Max on the other hand, are capable or killing waterborne oocysts at household flow rates when a properly sized model is selected for the application.
Advantages• one of the few affordable technologies for the home that effectively kills the majority of bacteria, viruses, and other harmful microorganisms.• energy efficient (requires about the same amount of energy as a 60 watt light bulb Disadvantages• requires electrical connection (usually a standard plug-in)• requires pre-filtration to maintain effectiveness - sediment and other contaminants can create a "Shadow" which prevents the UV rays from reaching the harmful microorganisms Typical Maintenance Requirements• UV lamps (bulbs) require annual replacement to ensure optimal performance. UV lamp performance, just like any other light source, will slowly diminish over time. Beyond one year, there is no assurance that the UV light emitted from the bulb will provide sufficient disinfection. Remember, UV light cannot be seen. The bulb may still produce light, but not necessarily UV rays. The quartz sleeve does not need replacement unless it gets broken, however, it should be cleaned several times per year (outside only).
• 1. What is UV? Ultraviolet (UV) light is at the invisible, violet end of the light spectrum. Even though we cant see UV light, we are exposed to UV rays from all light sources, including the sun.• 2. How does ultraviolet light purify water? UV-C rays penetrate the cells of harmful bacteria and viruses in our drinking water, destroying their ability to reproduce. Without this ability, these organisms die and no longer pose a health threat. It is a simple but very effective process, with the system destroying 99.99% of harmful microorganisms.• 3. Why not use chlorine instead? Chlorine changes the tastes and odor of water. Chlorinating also produces harmful by-products called Trihalomethanes (THMs) which are linked to incidence of cancer.• 4. Does a UV system use a lot of energy? No, the UV unit will use about the same amount of energy as a 60 watt light bulb. It is a cost effective, natural way to increase water quality.
• 5. Why do UV purifiers require sediment pre-filtration? UV systems require pre-filtration to maintain effectiveness as sediment and other contaminants in the water can create a "shadow" which prevents the UV rays from reaching and disinfecting the harmful microorganisms.• 6. How often does the UV light bulb (lamp) need to be replaced? It is essential that you change your UV lamp annually. The ability of the lamp to emit UV light decreases over one year in operation. Remember - UV light is invisible! Even though the lamp is still glowing after one year, there might not be enough UV light reaching your water to be effective.• 7. How often do your need to replace the sleeve? The sleeve doesnt need to be replaced unless it is broken, but it will need to be cleaned several times a year in order to keep the bulb effective in delivering high water quality.
What is Ozone in Relation to Water Purification?• Ozone - or O3 - is Mother Natures purifier and disinfectant. The 3 stands for the three oxygen atoms that compose Ozone. The normal Oxygen we breathe is called O2, and is made up of only two chemically linked Oxygen atoms.You may have noticed that a sudden summer storm leaves behind a very distinct smell, sort of a "fresh scent" which lasts for about an hour. In this case, you smell Ozone, which has been creating from lighting bolts during the electrical storm. Ozone is also created by the Suns ultra violet rays.• How Does Ozone Kill Germs and Bacteria to Purify Water? As mentioned above, Ozone is made up of three Oxygen atoms. Once of these has a weak hold on the others, and is more than willing to transfer electrons with other organic substances, such as bacteria, and viruses. This single Oxygen atoms binds with the other substance, causing it to oxidize (turn into something else. Rust is an example of Iron oxidizing into Iron Oxide). The byproduct of Oxidation in this case is simply O - a single Oxygen atom.
How Do Ozonation Water Purifiers Make Ozone? Ozonation water purification systems create Ozone with something called an Ozone Generator, which creates O3 in much the same way as the sun does. Inside ozone generators chamber is a high intensity Ultraviolet (UV) light. Compressed air is forced into the generators chamber, which then converts some of the oxygen in the air into Ozone. This process is part of the reason why the layer of Ozone in the Earths upper atmosphere protects us from most of the harmful UV rays emanating from our Sun.• The Ozone that has now been created inside the Ozone generator is then sent through a line into a diffuser, which creates ozone-saturated bubbles. Water is drawn in to mix with the bubbles, and then fed into the water purification tank. The weak Oxygen molecule in the Ozone attaches to other organic molecules in the water and oxidizing them. In effect - the Ozone "eats em up" and Viola! Clean, fresh, purified drinking water.• This, of course, was the laymens version of Ozone Water Purification. To learn more about Ozonation, you might try doing a search on Google, checking out How Stuff Works, or reading this article about Ozone Drinking Water Treatment.