Iron is known to leach into water supplies throughout the United States from rock and soil formations. It has been said, probably an exaggeration, that there is hardly a square foot of soil that does not have some iron content. Iron is at least 5% of the earth’s crust.
A yellow to reddish discoloration can appear in water in concentrations as low as 0.3 ppm (parts per million) and begin the staining and scale process, depending on the pH, as well as taste and odor problems.
Five types of iron that can be found in potable water
- Sequestered Iron
- Heme iron – Iron Found in organics
- Iron Bacteria
- Ferric Iron – Red water iron
- Ferrous Iron – Clear water Iron
Sequestering agents are used by municipalities & industry for treatment of large quantities of water. It is not important to farming where private wells are the principal source of water.
Heme iron– Iron Found in organics
This type of iron can not be removed by softening resins. Heme iron is most common in surface water and shallow wells. It is usually a yellow / brown color. Heme iron is a breakdown product of dead vegetation.
The iron and organics (tannins) require one ppm of sodium hypochlorite and a retention time of 20 to 25 minutes in a pH range of 6.5 – 7.5. Following the oxidation, a filtration media must be used to remove the oxidized iron and the residual of chlorine.
Favorable conditions for the growth of Crenothrix, Gallionella, and Clonothrix (or “iron bacteria”) can exist at very low levels of iron. Oxygen creates an oxidizing energy to precipitate ferrous iron into bicarbonate that is necessary for iron bacteria to exist. This bacterium can now live in a very wide range of conditions.
Iron bacteria water will have a reddish color and an objectionable odor. These organisms’s growths cause a jelly-like bio-mass. This mass can render media and resin filtration ineffective, reduce the effectiveness of any oxidizing agent, and plumbing fixtures. Iron bacteria is, because of its organic nature, the most difficult to remove and control.
Ozonation is the recommended solution to this problem.
Ferric Iron– Red water iron
In nature, iron is usually found in its oxidized insoluble form. Clear water iron, or soluble iron, once exposed to an oxidant or to oxygen will precipitate into an insoluble hydroxide form usually yellowish or reddish in color. This iron, while in the clear water state, could be removed by softening resins or by activated multi-media filtration. If one uses a 5-25 micron filter it may pack out in a short time and reduce flow and pressure. Changing these filters then become expensive and time consuming. Multi-media filters are more expensive to purchase upfront but the cost per gallon of water filtered is much less and requires little or no time.
Filtration is the recommended solution.
Ferrous Iron– Clear water iron
Sometimes this iron is called ferrous bicarbonate iron. This iron may be removed by a softening resin with a positive charge; however, it must be in the invisible soluble form until it is filtered. To prevent the iron from precipitating to its insoluble form frequent regenerations are necessary. If the iron does precipitate, fouling on the resin surface will occur, as well as within the matrix of the bead. This fouling can be minimized by pre-treating the incoming water with an activated carbon filter or by adding chemical cleaners to the brine or potassium regenerate. There are a number of chemical cleaners that will reduce red water iron to clear water iron. These cleaners are necessary when iron levels are high and normally they do not harm the resins. Many filter medias available today oxidize ferrous iron into ferric iron which can then be removed physically.
Softening is the recommended solution.
Hydrogen sulfide gas produces an offensive “rotten egg” or “sulfur water” odor and taste in the water. In some cases, the odor may be noticeable only when the water is initially turned on or when hot water is used. Heat forces the gas into the air which may cause the odor to be especially offensive in a shower.
One of the many troubles with hydrogen sulfide is its strong corrosiveness to metals such as iron, steel, copper and brass. It can tarnish silverware and discolor copper and brass utensils. Hydrogen sulfide also can cause yellow or black stains on kitchen and bathroom fixtures. Coffee, tea and other beverages made with water containing hydrogen sulfide may be discolored and the appearance and taste of cooked foods can be affected.
High concentrations of dissolved hydrogen sulfide also can foul the resin bed of an ion exchange water softener. When a hydrogen sulfide odor occurs in treated water (softened or filtered) and no hydrogen sulfide is detected in the non-treated water, it usually indicates the presence of some form of sulfate-reducing bacteria in the system. Water softeners provide a convenient environment for these bacteria to grow. A “salt-loving” bacteria that uses sulfates as an energy source may produce a black slime inside water softeners.
Sulfur-reducing bacteria, which use sulfur as an energy source, are the primary producers of large quantities of hydrogen sulfide. These bacteria chemically change natural sulfates in water to hydrogen sulfide. Sulfur-reducing bacteria live in oxygen-deficient environments such as deep wells, plumbing systems, water softeners and water heaters. These bacteria usually flourish on the hot water side of a water distribution system.
Hydrogen sulfide gas also occurs naturally in some groundwater. It is formed from decomposing underground deposits of organic matter such as decaying plant material. It is found in deep or shallow wells and also can enter surface water through springs, although it quickly escapes to the atmosphere. Hydrogen sulfide often is present in wells drilled in shale or sandstone, or near coal or peat deposits or oil fields.
Occasionally, a hot water heater is a source of hydrogen sulfide odor. The magnesium corrosion control rod present in many hot water heaters can chemically reduce naturally occurring sulfates to hydrogen sulfide.
Hydrogen sulfide is effectively removed utilizing an oxidizing media filter or chemical feed pump with an oxidant and retention tank.
I’m sure you’ve heard the terms ‘hard water’ and ‘soft water’, but do you know what they mean? Is one type of water somehow better than the other? What type of water do you have? Let’s take a look at the definitions of these terms and how they relate to water in everyday life.
What is Hard Water?
Hard water is any water containing an appreciable quantity of dissolved minerals.
What is Soft Water?
Soft water is treated water in which the only cation (positively charged ion) is sodium.
The minerals in water give it a characteristic taste. Some natural mineral waters are highly sought for their flavor and the health benefits they may confer. Soft water, on the other hand, may taste salty and may not be suitable for drinking.
If soft water tastes bad, then why might you use a water softener? The answer is that extremely hard water may shorten the life of plumbing and lessen the effectiveness of certain cleaning agents.
When hard water is heated, the carbonates precipitate out of solution, forming scale in pipes and tea kettles. In addition to narrowing and potentially clogging the pipes, scale prevents efficient heat transfer, so a water heater with scale will have to use a lot of energy to give you hot water. Soap is less effective in hard water because its reacts to form the calcium or magnesium salt of the organic acid of the soap. These salts are insoluble and form grayish soap scum, but no cleansing lather. Detergents, on the other hand, lather in both hard and soft water. Calcium and magnesium salts of the detergent’s organic acids form, but these salts are soluble in water.
Hard water can be softened (have its minerals removed) by treating it with lime or by passing it over an ion exchange resin. The ion exchange resins are complex sodium salts. Water flows over the resin surface, dissolving the sodium. The calcium, magnesium, and other cations precipitate onto the resin surface. Sodium goes into the water, but the other cations stay with the resin. Very hard water will end up tasting saltier than water that had fewer dissolved minerals.
Most of the ions have been removed in soft water, but sodium and various anions (negatively charged ions) still remain. Water can be de-ionized by using a resin that replaces cations with hydrogen and anions with hydroxide. With this type of resin, the cations stick to the resin and the hydrogen and hydroxide that are released combine to form pure water.
Hard Water Problems
Laundering in Hard Water
Clothes washed in hard water often look dingy and feel harsh and scratchy. The hardness minerals combine with some soils to form insoluble salts, making them difficult to remove. Soil on clothes can introduce even more hardness minerals into the wash water. Continuous laundering in hard water can damage fibers and shorten the life of clothes by up to 40 percent.
Bathing in Hard Water
Bathing with soap in hard water leaves a film of sticky soap curd on the skin. The film may prevent removal of soil and bacteria. Soap curd interferes with the return of skin to its normal, slightly acid condition, and may lead to irritation. Soap curd on hair may make it dull, lifeless and difficult to manage.
Problems with Hard Water in Water Boiler Systems and Pipework
Hard water also contributes to inefficient and costly operation of water-using appliances. Heated hard water forms a scale of calcium and magnesium minerals (limescale deposits) that can contribute to the inefficient operation or failure of water-using appliances. Pipes can become clogged with scale that reduces water flow and ultimately requires pipe replacement. Limescale has been known to increase energy bills by up to 25%.
Limescale in Solar Heating Systems
Solar heating, often used for heating swimming pools is prone to limescale buildup, which can reduce the efficiency of the electronic pump. This, in turn can cause the overall system performance to deteriorate.
How Does Your Water Measure Up?
|0.3 grains||4-7 grains||8-10||10 grains plus|
|17.1-51.3 ppm or mg/L||68.4-119.7 ppm or mg/L||136.8-171 ppm or mg/L||188.1 ppm or mg/L plus|
Do I have Hard Water?
For municipal water, call your water provider. They can tell you the average hardness and iron levels. If you have a private well, you can send us a water sample and we will test it FREE and review your options. Use this chart to estimate water softener size. To calculate total hardness, multiply total dissolved iron x 3, then add to total hardness.
Picking the right water softener is an important step in the purification of your water. A water softener trades “hard” minerals in water for “soft” minerals. The typical trade is as calcium (hard mineral) enter a water softener it is traded for sodium (soft mineral). Inside a water softener are a bunch of chemical magnets called “ion exchange resin”. These little chemical magnets do the trading. The more chemical magnets you have in a softener, the higher the capacity is. Capacity is the amount of gallons a softener will purify before you need to recharge (regenerate) it.
Capacity of water softeners are measured in “grains” or “grain removal”. This is a chemical measurement that has been used for a long time. One “grain per gallon” is equal to 17.1 parts per million. The average water in the United States has 10 grains of hardness per gallon. You can calculate the exact amount of hardness you have in your water using a water softener test kit. To calculate how much water you need to purify, multiply the number of people in your house by 80 (the average person uses 80 gallons of water per day). Then multiply that number by 1.5 for a safety factor. For an average family of 4 the calculation would look like this:
|Gallons per person||80|
|Gallons used per day||4 x 80 = 320|
|Safety factor||(x 1.5) = 480|
|Grains of hardness||10|
|Total grains used per day||4800|
Most homes use a one cubic foot water softener (1 ft3). Each cubic foot of resin will remove 30,000 to 36,000 grains of hardness. Each cubic foot will also flow 5 gallons per minute (g.p.m.). In selecting the right softener using the example above you would pick either a 30,000 grain softener and regenerate it about once a week, or pick a 60,000 grain softener and regenerate it about every 2 weeks.
Regeneration is done using a timer (regenerates after a given time has passed) or by a meter valve (regenerates after a given amount of water is purified). A meter softener is the most efficient because if you use less water, it will regenerate less. A timer based softener is cleaner because the regeneration process cleans the resin and if you do not use a lot of water bacteria can accumulate inside the softener. Regenerating the softener at least once a week will help keep bacteria in control. `
|Grains of hardness||Number of persons using water in household|
Please visit our section on water softening products.
What is Nitrate and what does it do?
Nitrate (NO3) can exist as an organic or inorganic compound, it can be natural or man made, and it is often found in drinking water supplies. Nitrates come in different forms such as ammonium nitrates (NH4NO), potassium nitrates (KNO3), and sodium nitrates (NaNO3). Nitrates can be expressed as nitrate as nitrogen (NO3-N), or nitrate as nitrate (NO3-NO3) on the water analysis. It is very important that the form of nitrate tested be identified on a water analysis test.
While nitrate itself is nontoxic, it is reduced to nitrite (NO2) by bacteria in the well or stomach. Nitrite passing into the bloodstream can be taken up by hemoglobin, reducing the blood’s ability to transport oxygen, causing oxygen deficiency anemia. Infants under six months of age are especially susceptible to this effect, causing the so-called “Blue baby” syndrome.
In poults, as with other infant monogastrics (single stomached system), their digestive systems contain nitrate-converting bacteria. Because of this, they are much more susceptible to methemoglobinemia. Fully grown monogastrics are not as susceptible to methemoglobinemia because their digestive system does not contain these bacteria. They are, however, susceptible to thyroid enlargement. Even so, it is believed that nitrate levels over 20 ppm are detrimental to performance. Nitrate levels as low as 3 ppm has been suspect in affecting broiler performance. It is also believed that heat stress and low pH compound the negative effects of nitrites in various breeds of birds.
As nitrates are produced during the final stage of decomposition of organic matter, nitrites are produced during intermediate stages of decomposition. Nitrites are toxic at much lower levels than nitrates as concentrations as low as 1 ppm can be toxic.
Nitrate in ground water has been known to be a potential health problem for more than 50 yrs. Depending on the form of nitrate, the USEPA maximum contaminant level (MCL) for humans in public drinking water varies from 45 ppm (NO3-NO3) down to 1 ppm (NO2-N). Water guidelines for poultry have set 25 ppm (NO3-N) as the maximum acceptable level which is substantially higher than the USEPA standards of drinking water of 10 ppm for the same form of nitrate. It is estimated by EPA’s 1990 National Pesticide Survey that over 5% of private water wells exceed the MCL for nitrates. The size of the animal is the main determinate of MCL in livestock.
Nitrates & Nitrites must be removed from private wells!
We need to be religious about keeping nitrates under control in our private wells (those used for drinking water for our family and our livestock). Just a few years ago, nitrate removal was not a problem for private wells, because there was no way to remove it. You can not oxidize it with chlorine nor filter it with sand or carbons. Using reverse osmosis or distillation would work but only for small volumes of water, but large volumes of water would make them cost prohibitive and labor intensive.
The past solution was to find a more promising location for a new, deeper well away from septic fields, cess-pools, hog wastes sprayed on fields for cultivation, poultry litter spread on fields for cultivation, inorganic fertilizers applied on row crops etc., and go to an aquifer deeper than the one presently used. Once nitrates have percolated into the aquifer, they can spread considerable distances. A deeper well may or may not solve the problem and it is a costly gamble at best. If your well is an old dug or drilled shallow well, the chances are high that a deeper well will be an improvement.
Today, there are nitrate-specific, anion resins manufactured primarily for nitrate removal (Water Softener). This resin does not remove nitrates only, but it does have a higher affinity for the nitrate versus the sulfate, tannins or bicarbonates.
Strong base anion resins will remove nitrates; however, they are actually more selective for sulfates over nitrates. If the sulfate ppm is high, it will preferentially collect sulfates over nitrates on the resin. If the resin is not regenerated and it becomes saturated or over exhausted, then the resin will release collected nitrates in exchange for sulfates causing a sharp rise in nitrate levels (nitrate dumping).
Sulfates must be considered when examining nitrate removal. Sulfates have been known to scar the intestinal tract of animals which effect the feed conversion, reduce body weight, and may cause a laxative affect. When removing nitrates, sulfates must also be removed. Choosing a nitrate-select resin could cause sulfate dumping.
The proper resin in the proper cubic footage and adequate regeneration will produce beneficial results. Other factors such as pH, the ppm of sulfates, and bicarbonates should also be considered in the selection of the resin and its volume.
In this type of treatment, a solution (usually sodium chloride) is introduced into the water to assist in the nitrate removal process. Chlorides are exchanged for nitrates and sulfates. The nitrates and sulfates are then captured in the adsorptive resin. Potassium may be used in place of salt if high sodium levels are a concern. It will require about 1.26 times as much potassium as salt, which makes it more expensive.
Coliform & Bacteria
Currently, 42 million people in the United States obtain their water from private well water or surface water systems. Research is needed to find improved treatment technologies which include point of use/point of entry (POU/POE) treatment devices for individual homes, buildings, and structures and transportable or modular treatment systems. These could be employed for the duration of time when water supplies are contaminated or treatment systems are inoperable.
Intec has the research team and capabilities in place to offer a solution to this problem.
Recently, there have been some advances in alternative disinfection methods and technologies (Ozonation, Chloramines, Ionization and Ultraviolet radiation, etc.). At the same time, there is a growing concern of the potential long term affect of the Disinfectant Byproducts (DBPs). Due to the ability of many forms of disease causing organisms to become resistant to currently utilized disinfection methods, a dual approach method or rotation of disinfection methods have become of more interest.
Chlorine and its various forms (chlorine gas, chloramine, chlorine dioxide, calcium hypochlorite, sodium hypochlorite, etc.) have been utilized as disinfectants in public water supplies for about a century. However, recent studies have shown that chlorine may directly or indirectly be the principal cause of many forms of cancer.
The EPA adopted a trihalomethane regulation in 1979 to limit the allowable level of carcinogenic disinfection byproducts in drinking water. Although chlorine is a good disinfectant, it also can form trace amounts of a DBP called trihalomethane (THM)[i]. THMs are chemicals that are formed when organic materials (e.g., decaying trees and leaves as well as urban farm run-off) combine with free chlorine. This has caused concern about using chlorine, in recent years, and water companies have searched for ways of reducing these byproducts.
Chloramines are actually used as DBP inhibitors in 30% of the nation’s surface water supplies and are expected to grow to 65% within 10 years[ii]. Chloramines are formed by the mixture of chlorine and ammonia in water. However, chloramines have their drawbacks as well. According to the California Professional Association of Specialty Contractors, chloramines contribute to pitting, pinholes, and potential failure of copper pipe[iii]. It is believed that this reaction only occurs when there is aluminum present in the water[iv]. Chlorine dioxide can also be utilized as a DBP inhibitor. When added to chlorine, a reduction in total trihalomethane (TTHM) has been observed[v]. At the same time, chlorine dioxide is known of producing chlorites that are identified as causing hemolytic anemia[vi]. Currently, the maximum contaminant level for total THMs is 0.1mg/L in drinking water.
Ozone has also received a lot of attention recently. It is highly effective for all groups of organisms, particularly viruses and bacteria and it can treat high volumes of water. Ozone may be the strongest and most capable disinfectant against cryptosporidium. However, it does have its disadvantages as well. Ozone can produce excessive bromates (which is a potential carcinogen) if the water contains bromide[vii]. It also possesses a reduced efficacy in cold water. Ozone also does not provide a persistent residual disinfection capability, may require high capital investments, and has relatively high operating and maintenance costs[viii].
In the United States and abroad, ionization is utilized as an alternative for chlorine disinfection in many applications. It has proven to be very effective against Legionella in hot water systems and had great residual disinfection capabilities.
Ultraviolet (UV) disinfection is becoming more popular and economical than ever before. UV light is a point-of-contact disinfection system that is highly effective in the inactivation of protozoa (viruses remain most resistant) and does not require the addition of any chemicals, requires short contact times, and posses no known DBPs. It does this without altering the chemistry, taste, and quality of water. Turbidity, however, does affect the quality of disinfection because of what is known as the shadowing effect. Also, as in the case of ozone, UV has no residual disinfection capacity.
To date, no single disinfection method is capable of producing the results that are necessary in keeping our drinking water safe 100% of the time. Many water treatment facilities are now using multi-barrier approaches to disinfection. Most are still utilizing chlorine as their primary disinfectant and then using additives to reduce DBPs. The industry focus does not need to be on the reduction of DBPs such as TTHM, but on eliminating it altogether.
Common Disinfection By-products
Disinfection byproducts form when disinfectants, added to drinking water to kill germs, react with naturally-occurring organic matter in water. Below is a recap of DBPs and their health affects:
- Total Trihalomethanes – Some people who drink water containing trihalomethanes in excess of EPA’s standard over many years may experience problems with their liver, kidneys, or central nervous systems, and may have an increased risk of getting cancer.
- Haloacetic Acids – Some people who drink water containing haloacetic acids in excess of EPA’s standard over many years may have an increased risk of getting cancer. Caused from chlorination
- Bromate – Some people who drink water containing bromate in excess of EPA’s standard over many years may have an increased risk of getting cancer.
- Chlorite – Some infants and young children who drink water containing chlorite in excess of EPA’s standard could experience nervous system effects. Similar effects may occur in fetuses of pregnant women who drink water containing chlorite in excess of EPA’s standard. Some people may experience anemia.
The Surface Water Treatment Rule (SWTR) was one of the first regulations to set standards for the control of Giardia in water by requiring a 3-log (99.9%) cyst removal or inactivation. The 3-log removal is accomplished by properly operating treatment plants, which achieve 2-log removal by conventional treatment and then requiring the disinfection process to achieve the remaining removal[ix]. These stringent demands are intended to protect our citizens from future outbreaks. Other characteristics need to also be considered when evaluating a system.
Ultraviolet Radiation (UV) disinfection is a process where microorganisms are exposed to UV light at a specified intensity for a specific period of time. This process renders the microorganism to be considered “microbiologically dead” UV light penetrates the cell membrane of the microorganism and fuses the thyamine bonds within the DNA strand, which prevents the DNA strand from replicating. This fusing of the thyamine bond is known as forming a dimerase of the thymine bond. If the microorganism is unable to reproduce/replicate then it is considered “microbiologically dead” While providing 99.99 percent inactivation of bacteria and viruses, UV light will have no effect on water chemistry[x].
Relatively low dosages of UV radiation (1-9mJ/cm2) have shown to inactivate 2-4 log10 (99 – 99.9%) of C. parvum oocysts and G. lamblia cysts[xi], [xii]. Studies have shown that while the C. parvum oocysts have the capability of repairing DNA damaged from the UV radiation process, the oocysts were not capable of recovering their infectious nature after the UV exposure[xiii], [xiv], [xv].
NSF is an independent accreditor of water treatment systems. The protocol for validation of residential UV disinfectant systems is the NSF Standard 55. This standard is broken down onto two parts:
- Class A – Point-of-entry and point-of-use (POU/POE) devices are designed to disinfect and/or remove microorganisms, including bacteria and viruses, from contaminated water to a safe level. They aren’t intended for treatment of water that has an obvious contamination source such as raw sewage; nor are systems intended to convert wastewater to microbiologically safe drinking water. Class A systems are capable of delivering a UV dose, at a wavelength of 254 nanometers (nm), to at least 40 milliJoules per square centimeter (mJ/cm? at the alarm set point the point where a manufacturer will set its UV sensor to activate the system alarm.
- Class B – Point-of-use (POU) systems are designed for supplemental bactericidal treatment of treated and disinfected public drinking water or other drinking water tested and deemed acceptable for human consumption by the state or local health agency having jurisdiction. Class B systems aren’t intended for disinfection of microbiologically unsafe water but are designed to reduce normally occurring nonpathogenic or nuisance microorganisms only. The systems are capable of delivering a UV dose, at 254 nm, to at least 16 mJ/cm2 at 70 percent of the normal UV lamp output or alarm set point.
For drinking water, we are only interested in the Class A certification. Under this certification, there is 99.99 percent inactivation of Rotavirus, Cryptosporidium, and Giardia. A recent study has shown that a UV dose of 20 mJ/cm2 is the equivalent to 2.4 mg/L of chlorine for one minute or 2.4mg/L of chloramines for one hour[xvi]. The same study concluded that a low dose of 1.4 mJ/cm2 would provide a 2 log10 inactivation of Giardia lamblia cysts. Furthermore, Cryptosporidium parvum was damaged to a point where it could not repair itself at dosages of 17 mJ/cm2. While the results of UF disinfection are impressive, UV has absolutely no residual effect, would not prevent recontamination, repair, and is not as effective in turbid solutions.
The Pulsating UV Light is an attractive design because of its ability to penetrate opaque or turbid liquids. This devise pulses at a rate of up to 10,000 times per second. A UV light similar to the one shown in Figure 2 below will be utilized on this research effort.
The initial construction costs for a UV system are higher than those for a chlorine system. However, operation and maintenance costs for the UV system are significantly lower over a 20 year time period. Also, the only chemical that is used in the UV disinfection process is a dilute acid used for cleaning tubes. Table 1 shows the UV dose that is required by UV light to deactivate a wide range of microorganisms.
The environmental impact associated with UV light is the disposal of the light source once it has been utilized. Mercury, a toxin, is utilized in the device and is a hazard if not disposed properly. However, the microwave pulsating UV light shown above does not utilize mercury in its bulb.
Transition Metal Ionization Disinfection
Ionization is becoming more widely accepted as a disinfection method, especially in hospital hot water systems. The biocidal effect of copper and silver stems from a combination of mechanisms. These positively charged metallic ions attach to the negatively charged bacteria cell membrane and cause cell lysis and death[xvii], [xviii], [xix]. The copper ions disrupt the enzyme structures of the cell allowing the silver ions to penetrate inside where they rapidly kill the cell’s life support system. This is because the positively charged silver and copper ions have an affinity for electrons and when introduced into the interior of a bacterial cell, they interfere with electron transport in cellular respiration systems. Metal ions will bind to the sulfhydryl, amino and carboxyl groups of amino acids, thereby denaturing the proteins they compose. This renders enzymes and other proteins ineffective, compromising the biochemical processes they control. Cell surface proteins necessary for transport of materials across cell membranes also are inactivated as they are denatured. When copper binds with the phosphate groups that are part of the structural backbone of DNA molecules, the result is the unraveling of the double helix and consequent destruction of the molecule[xx]. Copper concentrations of 0.2 to 0.4 mg/liter and silver concentrations of 0.02 to 0.04 mg/liter are recommended for sufficient disinfection levels according to in vitro and field studies[xxi], [xxii], [xxiii].
Unlike chlorine, copper-silver ionization does not result in dangerous halogenated organic by-products such as trihalomethanes, chloramines and chloroform. Also these ions are stable, making it easier to maintain an effective residual [xxiv]. Furthermore, the ions will remain active until they are absorbed by a microorganism. However, using soluble metal salts as a source of these ions and monitoring their concentrations to maintain consistent effects is cumbersome at best. Consequently, most modern copper-silver systems use electrolytic ion generators to control the concentrations of the dissolved metals. The electrolytic ion generator is the most cost effective approach.
The efficacy of copper-silver disinfection is dependant upon several variables. The concentration of copper and silver ions in the water has to be of sufficient levels and is determined by the water flow, the volume of water in the system, the conductivity of the water, and the present concentration of microorganisms. This is similar to chlorine in the fact that active disinfection levels are decreasing as it comes into contact with microorganisms.
Electrodes should be in good condition and be comprised of pure metals. When the water is hard or fouling is present, there will be a decrease in electrode release. Examination of the electrodes on occasion can prevent these problems in the future. The more pure the metals utilized on the electrode, the less the electrodes suffer from limestone formation and fouling.
The pH of water needs to be considered when examining the effectiveness of copper-silver ionization. When the pH values are high, copper ions are less effective. When the pH value exceeds 6, insoluble copper complexes will precipitate. When the pH value is 5, copper ions mainly exist as Cu(HCO3)+; when the pH value is 7 as Cu(CO3) and when the pH value is 9 as Cu(CO3)22-. Silver ions are not affected by the pH of the water and neither metal is affected by the temperature.
Copper-silver ionization affectivity is also determined by the presence of chlorine which causes silverchlorine complex formation. When this occurs, silver ions are no longer available for disinfection. However, copper ions are still active and when combined with low levels of free chlorine, prove to be an effective method of killing a wide range of pathogenic bacteria under controlled test conditions [xxv]. To combat the potential of bacteria having the ability to develop a resistance to most treatment of disinfection and even heavy metals, a program of periodic chlorination or ozination can be implemented. As mentioned earlier, it is very effective for pathogen control and will prevent the ability to develop a resistance.
The ionization systems have several advantages that include:
- Installation and maintenance is easy
- Efficacy is not effected by water temperatures
- Very good residual disinfection protection
- Recolonization is delayed because copper-silver ions kill rather than suppress
- Effective on even on Legionella
- Some bacteria are believed to have developed resistance to copper-silver ionization
- High pH levels reduce the disinfection of copper (levels < pH 8.5).
- No oxidation affect
Legionella bacteria are very susceptible to copper-silver ionization and will even take care of the bio film it produces. The copper ions remain within the bio film, causing a residual effect. When copper and silver ions are added to water constantly, the concentration of Legionella bacteria remains low. The deactivation rate of copper-silver ionization is lower than that of ozone or UV. A benefit of copper-silver ionization is that ions remain in the water for a long period of time causing long-term disinfection and protection from recontamination. Copper and silver ions remain in the water until they precipitate are absorbed by bacteria or algae, or removed from water by filtration.
|Coelastrum||0.05 – 0.33||Pandorina||10.00|
|Chlamydomonos||0.50||Nematodes||0.70 – 1.0|
|Cryptomonas||0.50||Peridinium||0.50 – 2.00|
|Dinobryan||0.18||Synura||0.12 – 0.25|
|Euglena||0.50||Uroglena||0.05 – 0.20|
|Asterionella||0.12 – 0.20||Nitzchia||0.50|
|Fragilaria||0.25||Synedra||0.36 – 0.50|
|Navicitia||0.07||Tabellaiia||0.12 – 0.50|
|Chara||0.10 – 0.50||Potamogeton||0.30 – 0.80|
|Nitella, flexilis||0.10 – 0.18|
The health benefits of copper and zinc are well documented. The trace mineral copper helps prevent anemia, bone and skeletal defects, a degeneration of the nervous system, defects in the color and structure of hair, reproductive problems, and abnormal cardiovascular problems[xxvi]. Also, copper is as important as calcium and zinc for bone formation, red blood cell integrity, skin and immune functions, nervous system functions, and the conversion of beta carotene into vitamin C[xxvii].
Currently, Intec utilizes only copper in its disinfection process for drinking water. Other metals are being researched and funding has been applied for through both the EPA for small public drinking water systems and the USDA for poultry water disinfection. The information above is part of one of our research efforts.