Blogged in Uncategorized Sunday December 19, 2010 at about 3:27 pm

CHOOSING WATER FILTERS

Water Filtration is one of several methods of purifying water. The other methods are: Boiling, Distillation, Aeration, Chemical Treatment, and Radiation Treatment. These processes can be applied singly or in combination with each other, depending upon the nature of the contaminants and the extent of purity required of the processed water. For example, Boiling as a method of water purification, kills some pathogenic microorganisms such as bacteria and viruses, but is not effective in removing other contaminants like organic and inorganic chemicals, hardness, solids, etc. Water Distillation can be effective in eliminating inorganic chemicals, microorganisms, and solid contaminants, but may not be able to remove organic chemicals that boil off with water. Water Aeration involves getting the water into contact with the oxygen in the air to eliminate undesirable dissolved gases, some chemicals, and some microorganisms. In Water Chemical Treatment, water is doped with certain chemicals such as Chlorine (for Chlorination) and Iodine (for Iodination), to eliminate certain harmful microorganisms. Radiation Treatment is essentially Ultraviolet (UV) Water Sterilization employed to kill air-borne type microorganisms that contaminate water.

Choosing water filters is a rational process and it involves essentially determining the right filter, or combination of filters, for a specific purpose. It requires knowing 1) the various types of filters and how they work 2) the type and extent of the contaminants or impurities present in the input raw water, and 3) the type and extent of the impurities that is acceptable in the finished “purified” water. For example, water intended for drinking must be free from harmful microorganisms and harmful chemicals, and therefore the filter or filter combination to use should be able to eliminate these undesirable contaminants so that the trace amount left in the final product is within accepted levels.

Water filters are devices employing “strainer action” for the purpose of eliminating undesirable (harmful) substances and materials called contaminants from impure water. The contaminants are commonly inorganic and organic in nature such as chemicals, microorganisms, viruses, metals, rusts, and minerals. Filters are intended to remove most of these contaminants to the extent that the remaining levels of impurities in the water have become acceptable. To accomplish this, filtering devices are either in the form of mechanical filters whereby the contaminants are “screened out”, or the filters are in the form of a physical barrier whereby the contaminants are selectively “adsorbed”, thus purifying the water. In principle, the pores of the filter of mechanical filters are designed to be smaller in size relative to the contaminants to be eliminated, but big enough to allow the water molecules and other desirable substances to pass through. As the contaminated water is introduced, the impurities are retained but the water is allowed to pass through. On the other hand, the “adsorption” action of the physical type filters is based on their ability to chemically attract and hold certain contaminants while the water molecules which are unaffected are allowed to pass through. “Adsorption” described here is different from “absorption” in terms of their actions relative to the contaminants. (Adsorption and Absorption).

In choosing water filters it is important also to establish the criteria to be used in the selection process. Essentially, the criteria are: effectiveness, price, availability, and filter life. Ideally, the best choice will be the filter or combination of filters which is not only the most effective, but is also the cheapest, the most easily available and with the longest filter life. However, since it is not always possible to have everything ideal, the ultimate decision on which type of water filters to use has to involve optimizing or balancing of these criteria. Effectiveness refers to the ability to eliminate the undesirable contaminants taking into account the 1) expected use and desired quality of the filtered water, and 2) the type and nature of the contaminants in the water to be filtered. Price and availability depends on the locality and location relative to the suppliers. The source could be specialty high street outlets for water accessories and supplies, or hardware stores, home builders’ supply stores, home accessory shops, etc. Long life will depend on the nature and quality of the materials used in the manufacture of the filter, on the design and workmanship in the manufacture of the filter, on the degree of contamination of the raw water to be filtered, and on whether the filter can be back-washed or on whether it can be regenerated.

Blogged in Uncategorized Sunday December 19, 2010 at about 3:20 pm

KINDS OF WATER BASED ON USAGE

In general, water usage can be classified into Utility Water, Washing/Bathing Water, Drinking/Cooking Water, and Commercial/Industrial Water.

1.    Utility Water – Home and community water for plants, garden, lawn, yard and driveway cleaning, toilet flushing, fire fighting, irrigation, road and street cleaning, etc. It may not be of the highest quality and may not even be free from microorganism. It should perhaps only be color free and odor free.

2.    Washing/Bathing Water – Water for these purposes, i.e., bathing, shampooing, personal grooming, laundering and dishwashing, need to be “soft” or free from Calcium and Magnesium salts to minimize soap and detergent usage, and minimize occurrence of scales on the surface when dried. Presence of “hardness” (or Calcium and Magnesium salts) makes it difficult to produce suds when using soap to wash. Car washing can also be included in this category because of the need for the car finish to be free from scales or mineral deposits when dried.

3.    Drinking/Cooking Water – Water to be used for drinking and cooking must be of the highest quality. It must be relatively free from harmful contaminants like microorganisms, viruses, organic chemicals, heavy metals, pesticides, disinfectants, odor, taste, and coloration. Since it is not possible to produce pure H2O (except probably in the laboratory) that is completely free of these contaminants, the allowable levels are established by standards set by location-specific regulating government agencies, i.e., EPA of the USA, etc.

4.    Commercial/Industrial/Institutional Water – In general, the quality of water required by this user classification range from high quality to extremely high quality. For example, commercial establishments like laundries, beauty salons and car washers will need soft water that is free from color, odor, and micro-organisms. Industries need the water for rinsing, steam power generation, chemical processes, unit operations, etc. In these cases, the water requirements need to be high quality and should be free from hardness, chemicals, metals, colors, odors, micro-organisms, and are de-ionized. In specialized institutions like hospitals and laboratories, the requirement is for an extremely high quality water, specific to the application at the point of use.

The type of water filters to use depends on the type of contaminants that have to be eliminated. To identify the contaminants, a sample of the raw water supply is sent to a water testing laboratory for analysis. The result of the laboratory analysis will then become the basis of determining the specific filter or the combination of water filters to use. In some instances, some other purification processes may need to be included to make the overall filtration effective and economical.

Blogged in Uncategorized Sunday December 19, 2010 at about 3:15 pm

THREE MAIN SOURCES OF RAW WATER

There are basically three main sources of raw water: rain water, surface water and ground water. In some areas, facilities are designed to catch rainwater. Roofs for example drain into containers to gather water for use by households. Others design their roof drainage system such that the rainwater is directed into underground or basement cisterns, where they are stored and withdrawn for household use as needed. Surface Water is found in lakes, rivers, and reservoirs while Ground water lies under the earth’s crust where it moves and seeks openings and settles in reservoirs called aquifers. Ground water in aquifers must be pumped out to the earth’s surface for use.

Consumers and end-users receive their water from two basic delivery systems: a private well or private reservoir, or a community water system. A household well pumps groundwater for own household use. The community water system may be supplied from either surface water or groundwater.

Private well or reservoir owners are solely responsible for the safety of their water supply. However, there are steps that can be taken to ensure that the well water is made safe and acceptable before use. As a first step, well owners should contact their local public health agencies for guidelines on the steps needed to be done.

Contamination can come from the water containment and surrounding human activities. As the rainwater flows into the surface reservoirs or seeps into the underground aquifers, it comes in contact with variety of matters. Water, being a very good solvent, tends to absorb things along its path, including harmful microorganisms, heavy metals, viruses, organic and inorganic chemicals, gases, etc. In the reservoir, where it comes in contact with various forms of rocks, it tends to absorb naturally occurring minerals and a variety of other substances. Some of these harmful contaminants are uranium, radium, nitrates, arsenic, chromium and fluoride.

Chemical and microbiological contamination resulting from human activities such as manufacturing, refining, agriculture, or individual misuse, almost always pose serious health risks if they find their way into drinking water. Specifically, contamination is  brought about by: 1) leakages from indiscriminate handling of waste disposal, waste treatment, and waste storage sites; 2) improper handling of discharges from factories, industrial sites, or sewage treatment facilities; 3) accidental chemical and oil spills; 4) leakages from underground storage tanks; 5) improper disposal of household  and shop wastes such as cleaning fluids, paint, petroleum fuels, brake fluids,  motor coolants, and motor oils; 6) improper disposal of hospital wastes such as medicines, fluids, containers, surgical materials, medical packaging, etc.; 7) improper disposal of washings from non-biodegradable detergents and soaps.

The water impurities or contaminants can be summarized into the following:

Hardness, abrasiveness, odor, coloration, taste, turbidity, microorganisms, viruses, heavy metals, organic compounds, inorganic chemicals, minerals, pesticides, herbicides, biocides, fungicides, fertilizers, and disinfectants.

Blogged in Uncategorized Sunday December 19, 2010 at about 3:07 pm

TYPES OF WATER FILTERS

There are several types of water filters in the market today. According to filtering action, filters can be classified into mechanical filters, adsorption filters, and chemical filters.

Mechanical Filters

The “screening action” of mechanical filters is based on the size differential between the contaminants and the pores of the filter. Pores of the filter must be smaller than the contaminants to be eliminated, and the rest are allowed to pass through. Filter pores can range from 0.0001 microns to 100 microns. (1 micron = 0.001 millimeter). On the basis of pore size, mechanical filters can be further classified into Particulate Filters (1 to 100 microns), Micro Filters (0.1 to 3.5 microns), Ultra Filters (0.006 to 0.25 microns), Nano Filters (0.0008 to 0.01 microns) and Reverse Osmosis (0.0001 to 0.002 microns).

Particulate Filters screen out relatively larger particulate contaminants such as suspended fine sands, dusts, rusts, organic matters, decaying materials, etc. They allow all other contaminants to pass through. An example of Particulate Filter is the multi-media sand filter consisting of layers of sand of sizes varying from coarse, to medium, to fine, and extra fine. These are contained in a cylindrical tank where the feed water is introduced to the coarse sand first and then passed on to the next finer size sand, until finally to the extra fine sand.

Particulate Filters are cheap and easy to maintain. They can be regenerated by way of backwashing

Micro Filters are designed to remove all particles and microorganisms greater than their pore size. They are generally used as pre filters to remove almost all suspended solids, and protect other more expensive filter elements downstream from clogging and fouling. However, they do not remove dissolved inorganic and organic chemicals, bacteria, viruses and colloids. Though cheap and they require minimal maintenance, they can not be regenerated and are therefore relatively more expensive over the long term.
Ultra Filters use tough, thin selectively permeable membrane with infinitesimally fine pores that act as a molecular sieve. They retain most, but not necessarily all, large molecules above their rated size including colloids, microorganisms, and viruses, but not smaller molecules like water and ionized contaminants. Ultra filters are available in several ranges and they produce very high quality water for least amount of energy. Since they can be regenerated, Ultra Filters are therefore more economical over the long term.
Reverse osmosis (RO) uses a semi-permeable membrane that has a pore structure much tighter than Ultra Filters. RO membranes are capable of rejecting practically all particles, bacteria, viruses, heavy metals, ions (like salts, whether strongly ionized or weakly ionized), colloids, and dissolved molecules (like sugars). The water produced has very low Total Dissolved Solids (TDS).
In normal osmosis, when two water solutions of different concentrations are separated by a semi-permeable membrane, the natural tendency is for the solvent to migrate through the semi-permeable membrane from the less concentrated solution to the more concentrated one, until the degree of concentration on both sides equalize thus equilibrium is achieved. It is believed that a pressure called Osmotic Pressure drives the water through the membrane until the concentrations equalize.
In the reverse osmosis (RO), as employed in water purification, hydraulic pressure is applied to the concentrated solution to overcome the osmotic pressure. Pure water is forced from the concentrated solution through the membrane and collected downstream of the membrane.
Because RO membranes are very restrictive, the rate of production is very slow, thus requiring storage tanks for the accumulation of purified water in volumes.
Overall, reverse osmosis as a mode of purifying water is very effective against practically all kinds of contaminants, requiring minimal maintenance. Relatively high upfront cost, but very economical over the long term. (As a note, combination RO and Activated Carbon Filters presents the most effective filtration process against the broadest range of water impurities and contaminants.

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Blogged in Uncategorized Sunday December 19, 2010 at about 2:47 pm

OTHER TYPES OF WATER FILTERS

Adsorption Filters (also called Activated Carbon Filters) use materials that have the ability to attract and hold on to the contaminants. The attraction is due the opposite electrical charges of the contaminant and the filter material. The filter material must present a huge surface area relative to its weight. This design is exemplified by activated carbon water filter systems in the form of granular activated carbon (GAC) or solid block carbon.

Activated carbon is made from carbon-based materials, the most common of which is coconut shell. The raw material is subjected to a high temperature process under carefully controlled conditions in order to create a matrix of billions of microscopic pores, and a huge amount of activated surface area. The pores trap microscopic particles and large organic molecules, while the activated surface areas attract and hold (adsorb) organic and inorganic molecules, including chlorine which is a common chemical resulting from the chlorination of municipal or city water supplies.

Activated carbon filters are widely used in home water treatment because of their ability to improve water by removing disagreeable tastes and odors, including objectionable chlorine. Activated carbon effectively removes many chemicals (especially pesticides)   and gases, including microorganisms in some cases. Generally however, activated carbon filters do not affect total dissolved solids, hardness, or heavy metals.

Carbon Filters, with their long life and high capacity, are usually used in combination with other treatment processes. The placement of carbon in relation to other components is an important consideration in the design of a water purification system.

Chemical Filters use chemicals to react and retain the contaminants in water. The water softener is a very good example of a chemical filter. It is packed with a solid resin matrix with an open fishnet-like structure called the ion exchanger. It removes the Calcium and Magnesium ions in the hard water by exchanging them with Sodium ions in the resin. In effect, the hardness is captured and attached into the resin bed while the sodium from resin is released into the water during the exchange process. When the exchange resin becomes almost all changed to Calcium and Magnesium compounds and its ability to produce softened water is exhausted, it is backwashed to cleanse and regrade the bed and regenerated with solution of common salt to restore to its sodium state. Regeneration removes the Calcium and Magnesium in the form of soluble chlorides.

Water softeners remove the “hardness” but not other contaminants and microorganisms. They are an important component of a total water purification system when used in combination with Reverse Osmosis, mechanical filters and activated carbon filters.

It has a high upfront cost, and although it can be regenerated, it is expensive over the long term.

Ultraviolet (UV) Radiation is an effective sterilizer. It is used as a component in a water conditioning system to kill bacteria and other microorganisms. It is usually placed in the final stage where it maximizes its contribution to the elimination of harmful microbiological contaminants.

Ultra Violet sterilizer is not however effective against particles, colloids, ions, organics and inorganics.
Types of Water Filters By Location of Application

Whole House Filters are placed in the main water line entering the house. Usually, WHF are particulate type of filters that are designed to eliminate sediments and rust particles. They can serve as pre-filters for other downstream filters if needed.

Under Sink Filters are installed usually as multiple cartridges under the sink. They may be plumbed in such a way as to enable selection of water lines to be filtered with the desired type of water filters and to which faucet for particular usage. They are out-of view but relatively more expensive. For example, bath water may need to be clear and free from odor, taste, hardness, and bacteria.

Faucet-mounted Filters attach directly to the faucet, thus are basically a point-of-use type, requiring no complicated plumbing.  They may be types specific to the kind of contaminants intended to be removed. They are small and easy to install, but highly visible.

Countertop or Canister Filters are essentially countertop units with combination of filters to remove certain contaminants. They however require provision for connection to water outlets.

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Blogged in Uncategorized Sunday December 19, 2010 at about 2:32 pm

THE NATURE OF WATER

Water is nature’s universal solvent. It dissolves more things than any other liquid or gas. It may not dissolve some substances like fats, oils, sand, sulfur, but it dissolves almost all other substances if given enough time at the right temperature.

Water goes through a cycle in nature. From clouds as vapor, it condenses and drops as rainwater, flows over land surface to streams and rivers, and ultimately finds its way into the oceans and seas. During its voyage over land, streams, rivers, on oceans and seas, it is heated and evaporated into the atmosphere where it forms clouds and again ready to repeat the cycle. Some of it seeps through the various layers of the earth’s crust and find their way into the water table. From here, it is once more pumped out to the surface. Given the journey that it takes, it is no wonder then that practically all water found in nature are contaminated with dissolved minerals, chemicals and microorganisms.

Water is nature’s most abundant resource. It covers nearly three fourths of the earth’s surface in the form of oceans, seas, icebergs, and ice caps. It is carried in the air as vapor and lies beneath the surface of the earth. It is found in all living things where it accounts for about two thirds by weight.

Water with high mineral content is a problem. When it contains calcium and magnesium compounds it is called “hard water”. Also dissolved are irons, limestones, and other minerals. Hardness vary from place to place.

Hard water has its disadvantages. It contains objectionable amounts of dissolved salts of Calcium and Magnesium. These are present as bicarbonates, chlorides, or sulfates. When used as laundry water, it forms no suds, and consumes and wastes a lot of soap. Minerals in hard water form scales. In coffee kettles, minerals are seen as scales at the bottom, and in engines of cars, trucks, tractors, and generators, the scales form in the cooling systems and radiators thus causing overheating.

Pure water is a chemical compound made up of atoms which have united to form a molecule. A molecule of water is made up of 2 atoms of hydrogen and one atom of oxygen. Pure H2O tastes differently from what we know. Pure H2O is tasteless – no taste at all. It is almost impossible to produce it outside the laboratory. Ordinary distilled water usually contains traces of other chemicals, gases, minerals, and other chemicals which give them a typical flavor.

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Blogged in Uncategorized Sunday December 19, 2010 at about 6:02 am

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