Real-Time Field Water Analysis with an Ultrameter III 9P: Myron L Meters

Posted by 30 Apr, 2014

Tweet The Ultrameter III 9P Titration Kit allows for fast, accurate alkalinity, hardness & LSI titrations in the field. The Ultrameter III 9P is based on the tried and tested design of the Ultrameter II 6P and measures conductivity, resistivity, TDS, pH, ORP, free chlorine and temperature quickly and accurately. The 9P also features new […]

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The Ultrameter III 9P Titration Kit allows for fast, accurate alkalinity, hardness & LSI titrations in the field.

The Ultrameter III 9P is based on the tried and tested design of the Ultrameter II 6P and measures conductivity, resistivity, TDS, pH, ORP, free chlorine and temperature quickly and accurately. The 9P also features new parameters that allow the user to perform titrations in the field. The Ultrameter III 9P has a unique method of performing alkalinity, hardness and LSI titrations that makes field monitoring fast and feasible.

How does it work?

The 9P titrations are based on conductometric titration methods that are possible with the 9P’s advanced conductivity cell and microprocessor based design. Titrations are chemically equivalent to standard methods using colorimetric techniques, but replace color change identification of equivalence points with changes in conductivity, thereby replacing a subjective, qualitative assessment with a quantitative one. This means the instrument determines the equivalence point instead of the user and the method of analyzing the equivalence point is objective, rather than subjective.

What is a conductometric titration?

A conductometric titration is performed just like a colorimetric titration, only the equivalence point is determined by a change in conductivity rather than a change in color. This is based on the fact that changes in ionic concentration that occur as constituents react with reagents change the electrical conductivity of the solution.

A simple example can be given of the titration of a strong acid with a strong base. The acid solution, before the addition of the base, has a very high conductance owing to the concentration and mobility of the small hydrogen ions.

With the addition of the base, the hydroxide reacts with the hydrogen to form water, thus reducing the hydrogen ion concentration and effectively lowering the conductivity of the solution. The conductivity continues to decrease until all the hydrogen ions are consumed in the reaction, but then sharply increases with the next addition of base, which contains highly conductive hydroxide ions. The solution conductivity then continues to increase with each base addition. The equivalence point in this example would be a clearly defined minimum point of lowest conductivity (see Figure 2).

Not all solutions will give a plot with an equivalence point that is as easy to distinguish as the sharp upturn found in a strong acid-base titration, however. The 9P plots several reagent additions beyond any changes in conductivity and matches the derived curve to the behavior of solutions of known concentration.

Is a conductometric titration a standard method?

(Standard method comparison to methods listed in the Standard Methods for the Examination of Water and Wastewater published by the American Public Health Assn., the American WaterWorks Assn. and the Water Environment Assn.)

Myron L’s conductometric titration methods are chemically equivalent to standard methods that use the same procedure, but with pH indicators. That means that they use the same reagents in the same sequence with the same theoretical approach. The difference lies in the 9P’s ability to determine the equivalence point based on numerical data, rather than subjective observation of a color change.

The alkalinity titration is modeled after standard method 2320. The sample is titrated with sulfuric acid and conductivity changes are recorded at each titration point.

The hardness titration is modeled after standard method 2340. To reduce the affects of high alkalinity in the form of bicarbonate, acid is first added to the sample. This shifts the bicarbonate toward carbonic acid, then carbon dioxide (reference the carbonic acid equilibrium), which is gassed off the sample. The sample is buffered above pH 10 (effectively pH 12) by the addition of sodium hydroxide. EDTA reagent is then added incrementally, with conductivity measured after each addition.

The LSI titration uses a simplified version of the thermodynamic equations for the determination of the scaling tendency of water developed in 1936 by Dr. Wilfred Langelier. The user simply titrates for alkalinity and hardness, then measures pH and temperature, and the 9P generates the saturation index value automatically.

Conductometric vs. Colorimetric

The benefits of determining the equivalence points by conductometric titrations are that the user does not have to interpret any results. The 9P does it for you using objective measurements. And the 9P is a faster method. For example, a typical colorimetric titration for hardness can take up to 30 drops of reagent, while the 9P method for the same concentration only requires six to eight drops. Colorimetric distinctions are sometimes hard to make, as well, especially when adding reagents drop by drop while trying to carefully observe the precise point at which the color changes—and that can lead to inaccurate data. This is especially true in colored or turbid solutions.

The conductometric method can also be used with very dilute solutions or for solutions for which there is no suitable indicator. The conductometric titration method gives you empirical results that are calculated for you, eliminating potential sources of error. And the measurements can be stored in memory for later data transfer using the optional U2CI software and bluDock Bluetooth hardware installed on the 9P . This makes data analysis and reporting seamless.

What else can the Ultrameter III 9P do?

Alkalinity, hardness, pH and temperature values used to compute the saturation index of a sample can be manipulated in the LSI Calculator function, allowing you to perform on the spot analysis of water balance scenarios. You can use historical or theoretical data to populate the required values in the calculator.

And the 9P titration kit comes with all required accessories, reagents, and calibration solutions (see Figure 6). Streamline your field testing with an Ultrameter III 9P from MyronLMeters, where you can save 10% when you order online.

Myron L Meters is the premier online retailer of accurate, reliable, and easy-to-use Myron L meters like the Ultrameter III 9P.  Save 10% when you order online at MyronLMeters.com. Find out more about the Ultrameter III 9P in our Myron L Meters – Ultrameter III 9P Titration Kit Overview video.

 

Categories : Case Studies & Application Stories, Product Updates

Water Quality Parameters: MyronLMeters.com

Posted by 15 Apr, 2014

TweetWater Quality Parameters Measuring Key Water Quality Parameters The right meter is essential for measuring any of several key water quality parameters: Conductivity is the ability of water to conduct an electrical current and is an indirect measure of the conductive ionic mineral concentration. The more conductive ions that are present, the more electricity can be […]

Water Quality Parameters

Measuring Key Water Quality Parameters

The right meter is essential for measuring any of several key water quality parameters:

Conductivity is the ability of water to conduct an electrical current and is an indirect measure of the conductive ionic mineral concentration. The more conductive ions that are present, the more electricity can be conducted by the water. This measurement is expressed in microsiemens per centimeter (µS/cm) at 25º Celsius. Myron L Meters carries a complete line of conductivity meters, including the Ultrameter II 4P.

Resistivity is the inverse of conductivity. Electrical conductivity is a measure of water’s resistance to an electric current. Water itself has a weak electrical conductivity. Electric current is transported in water by dissolved ions, making conductivity measurement a quick and reliable way to monitor the total amount of ionic contaminants in water. Myron L Meters carries a complete line of resistivity meters, including inline monitor/controllers like the 753II Resistivity Digital Monitor/Controller. Read more about Measuring Key Water Quality Parameters

The Ultrameter III 9P is the most comprehensive water meter on the market, measuring 9 parameters with a single instrument: Conductivity, Resistivity, TDS, Alkalinity, Hardness, Langelier Saturation Index,
ORP/Free Chlorine, pH, Temperature. Three parameters – LSI, hardness, and alkalinity require titration. Find out more about the Ultrameter III 9P

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Water Quality Parameters: MyronLMeters.com was originally published on Myron L Meters Blog

Categories : Uncategorized

Measuring Key Water Quality Parameters: MyronLMeters.com

Posted by 12 Apr, 2014

TweetThe right meter is essential for measuring any of several key water quality parameters:Conductivity is the ability of water to conduct an electrical current and is an indirect measure of the conductive ionic mineral concentration. The more conductive ions that are present, the more electricity can be conducted by the water. This measurement is expressed […]

The right meter is essential for measuring any of several key water quality parameters:

Conductivity is the ability of water to conduct an electrical current and is an indirect measure of the conductive ionic mineral concentration. The more conductive ions that are present, the more electricity can be conducted by the water. This measurement is expressed in microsiemens per centimeter (µS/cm) at 25º Celsius. Myron L Meters carries a complete line of conductivity meters, including the Ultrameter II 4P.

Resistivity is the inverse of conductivity. Electrical conductivity is a measure of water’s resistance to an electric current. Water itself has a weak electrical conductivity. Electric current is transported in water by dissolved ions, making conductivity measurement a quick and reliable way to monitor the total amount of ionic contaminants in water. Myron L Meters carries a complete line of resistivity meters, including inline monitor/controllers like the 753II Resistivity Digital Monitor/Controller.

Total Dissolved Solids (TDS) is also a measurement of the amount of dissolved minerals in the water. In this instance they would be called solids in solution. The quantity of dissolved solids in the solution is directly proportional to the conductivity. In this case, conductivity is the measurement but it is used to estimate TDS. It is measured with a conductivity meter but is reported as TDS in parts per million (ppm), via a complex algorithm. Myron L Meters carries a complete line of TDS meters, including the Ultrapen PT1.

pH is a measure of the concentration of hydrogen ions in the water, indicating the acidity or alkalinity of the water. On the pH scale of 0-14, a reading of 7 is considered to be neutral. Readings below 7 indicate acidic conditions, while readings above 7 indicate the water is alkaline or basic. Naturally occurring fresh waters have a pH range between 6 and 8. Myron L Meters carries a complete line of pH meters, including the Ultrapen PT2

Temperature is expressed in degrees Celsius (C) or Fahrenheit (F). Most digital handheld Myron L Meters include a temperature function.



Oxidation reduction potential (ORP)can correlate millivolt readings to the sanitization strength of the water. Microbes can cause corrosion, fouling, and disease, and oxidizing biocides are usually used to keep microbial levels under control. ORP is expressed in millivolts (mV). Myron L Meters carries a complete line of ORP meters, including the Ultrapen PT3

Free Chlorine refers to both hypochlorous acid (HOCl) and the hypochlorite (OCl–) ion or bleach, and is commonly added to water systems for disinfection. Free chlorine is typically measured in drinking water disinfection systems to find whether the water system contains enough disinfectant.  Myron L Meters Ultrameter II 6PFCe and Ultrapen PT4 can both be used to measure free chlorine.

Salinity is simply a measure of the amount of salts dissolved in water, a measurement useful to pool service technicians and others.  You can measure salinity with a Myron L Pool Pro PS6.

Alkalinity is a measure of the capacity of water or any solution to neutralize or “buffer” acids. This measure of acid-neutralizing capacity is important in figuring out how “buffered” the water is against sudden changes in pH. Alkalinity is a titration function of the Ultrameter III 9PTKA.

Hardness is caused by compounds of calcium and magnesium, and by a variety of other metals.  As water moves through soil and rock, it dissolves very small amounts of minerals and holds them in solution. Calcium and magnesium dissolved in water are the two most common minerals that make water “hard.” Hardness is a titration function of the Ultrameter III 9PTKA.

LSI or Langelier Saturation Index helps you determine the scaling potential of water. LSI is a calculated number used to predict the calcium carbonate stability of water. It indicates whether the water will precipitate, dissolve, or be in equilibrium with calcium carbonate. LSI is a titration function of the Ultrameter III 9PTKA.

MyronLMeters.com is the premier internet retailer of accurate, reliable Myron L meters.  Save 10% when you order Myron L meters online at MyronLMeters.com. You’ll find reliable instruments for every water quality parameter mentioned above.



 

 

 

Categories : Uncategorized

Using LSI to preserve an Arizona treatment plant’s distribution systems

Posted by 16 Aug, 2013

Tweet                    The first thing anyone who manages water and wastewater learns is that water is the universal solvent. Because of the unique properties of that dihydrogen monoxide molecule, owing to the extreme electronegativity of the oxygen atom, water is highly polarized and dissolves almost everything with […]

Myron L Ultrameter II 6P

 

 

 

 

 

 

 

 

 

 

The first thing anyone who manages water and wastewater learns is that water is the universal solvent. Because of the unique properties of that dihydrogen monoxide molecule, owing to the extreme electronegativity of the oxygen atom, water is highly polarized and dissolves almost everything with which it comes into contact. This fact is important when one has to maintain equipment and structures that process and distribute water because what the water has dissolved in it can cause it to be corrosive or scaling. What water generally has dissolved in it is at least some carbon dioxide and some calcium carbonate.

Carbon dioxide is ubiquitous and dissolves at the surface of the water, forming carbonic acid in solution. Calcium carbonate, dissolved by the carbonic acid, is globally present in rock formations (limestone), as well as in the physiological structures of organisms (particularly oceanic organisms) that excrete it. Calcium carbonate in its various forms is also used to buffer pH and stabilize solution in process control. Managing the calcium carbonate equilibrium becomes critical to managing any water and wastewater treatment process.

Too little calcium carbonate yields water that is not saturated and may cause corrosion and deteriorate equipment and structures. A supersaturated solution will likely precipitate calcium carbonate, causing scale, reducing efficiency and eventually leading to system failure.

LSI in AZ

One method for analyzing and managing corrosion and scale deposition of water is to use the Langelier Saturation Index (LSI). In Scottsdale, Ariz., Gary Lyons is managing LSI at his water treatment facility using the Myron L Ultrameter II 6P.

His drinking water treatment plant takes 70 million gal per day (mgd) of water from the Central Arizona Project canal and treats it for residential and commercial use. Within the 143-acre campus, the plant processes 20 mgd to of wastewater from the city of Scottsdale collection system using microfiltration and reverse osmosis (RO). Water coming from the RO treatment process is acidic around pH 5.5. It is then moved to decarbonation towers and lime is added to bring the LSI value close to zero. The water reclamation plant features 8 mgd of storage capacity. Recycled water treated by the plant is used for the irrigation of 20 Scottsdale golf courses.

There is great concern about how the water balance will affect this distribution system over time, especially due to higher total dissolved solids values. Plant technicians compute LSI values in the field with the 6Psi hand-held to determine what adjustments should be made and how in real time. The LSI calculator allows them to perform what-if scenarios on changes in pH, alkalinity, hardness and temperature. They are able to measure the effects of changes immediately as well in the facility and at distribution points.

Hardness and alkalinity are variables in the LSI calculation because they account for the availability of calcium in various forms in the water. Variables such as temperature and pH contribute to the likelihood of the formation of calcium carbonate.

The version of the LSI calculation used by the 6Psi LSI calculator is:

LSI = pH + TF + CF + AF – 12.1

In this calculation, pH = the measured value of pH in pH units; TF = 0.0117 x temperature – 0.4116; CF = 0.4341 x ln(Hrd) – 0.3926; and AF = 0.4341 x ln(AL) – 0.0074.

The first thing anyone who manages water and wastewater learns is that water is the universal solvent. Because of the unique properties of that dihydrogen monoxide molecule, owing to the extreme electronegativity of the oxygen atom, water is highly polarized and dissolves almost everything with which it comes into contact. This fact is important when one has to maintain equipment and structures that process and distribute water because what the water has dissolved in it can cause it to be corrosive or scaling. What water generally has dissolved in it is at least some carbon dioxide and some calcium carbonate.

Carbon dioxide is ubiquitous and dissolves at the surface of the water, forming carbonic acid in solution. Calcium carbonate, dissolved by the carbonic acid, is globally present in rock formations (limestone), as well as in the physiological structures of organisms (particularly oceanic organisms) that excrete it. Calcium carbonate in its various forms is also used to buffer pH and stabilize solution in process control. Managing the calcium carbonate equilibrium becomes critical to managing any water and wastewater treatment process.

Too little calcium carbonate yields water that is not saturated and may cause corrosion and deteriorate equipment and structures. A supersaturated solution will likely precipitate calcium carbonate, causing scale, reducing efficiency and eventually leading to system failure.

Indicator Analysis

LSI has been useful as a scaling/corrosion indicator in municipal water treatment for more than 70 years. The original Langelier Saturation (or Stability) Index calculation was developed by Dr. Wilfred Langelier in 1936 to be used as a tool to develop strategies to counteract corrosion of plumbing in municipal water distribution systems. It is a statement about the change in pH required to bring the calcium carbonate in water to equilibrium. LSI is a measure of the disparity between the pH of the system and the pH at which the system is saturated with calcium carbonate: LSI = pH – pH of saturation.

As such, the LSI indicates the change in pH required to bring water to equilibrium. If the LSI is +1, then the pH needs to be lowered by one unit to bring the water to equilibrium. If the LSI is -1, the pH needs to be raised by one unit to bring the water to equilibrium.

A positive saturation index means that the pH of the water is above equilibrium. The water is scaling because as pH increases, total alkalinity concentration increases. This is due to an increase in the carbonate ion, which bonds with calcium ions present in solution to form calcium carbonate (reference the carbonic acid equilibrium, in which hydrogen ions bond with carbonate ions to form bicarbonate and hydrogen ions bond with bicarbonate to form carbonic acid). Thus, any positive value for LSI is scaling.

If the pH is less than the pH of saturation, the index will be negative, which is corrosive. This means that the water is more acidic than it would be at equilibrium. There are less carbonate ions present, according to the carbonic acid equilibrium. The water will be aggressive because it has room for more ions in solution. Thus, any negative value for LSI indicates that the water may tend to be corrosive.

The use of LSI as an indicator is well documented and time-tested. Managing water balance through LSI analysis will prevent loss of efficiency and failure of equipment and structures, saving time and money.

Myron L Meters is the premier online internet retailer of the Myron L Ultrameter II 6P.  Find out more about the Ultrameter II 6P here:

https://www.myronlmeters.com/Myron-L-6P-Ultrameter-II-Multiparameter-Meter-p/dh-umii-6pii.htm

Categories : Application Advice, Case Studies & Application Stories, Technical Tips

The Ultrameter III 9PTKA: MyronLMeters.com

Posted by 12 Jun, 2013

Tweet Myron l Meters Ultrameter III 9PTKA from Myron L Meters

Myron l Meters Ultrameter III 9PTKA from Myron L Meters
Categories : Product Updates, Uncategorized

Water Hardness and LSI – MyronLMeters.com

Posted by 2 Nov, 2012

Tweet Hard water is water that has high mineral content. Hard drinking water is generally not harmful to one’s health, but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment that handles water. In domestic settings, hard water is often indicated […]

Hard water is water that has high mineral content.

Hard drinking water is generally not harmful to one’s health, but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment that handles water. In domestic settings, hard water is often indicated by a lack of suds formation when soap is agitated in water. Wherever water hardness is a concern, water softening is commonly used to reduce hard water’s adverse effects.

Sources of hardness
Water’s hardness is determined by the concentration of multivalent cations in the water. Multivalent cations are cations (positively charged metal complexes) with a charge greater than 1+. Usually, the cations have the charge of 2+. Common cations found in hard water include Ca2+ and Mg2+. These ions enter a water supply by leaching from minerals within an aquifer. Common calcium-containing minerals are calcite and gypsum. A common magnesium mineral is dolomite (which also contains calcium). Rainwater and distilled water are soft, because they also contain few ions.

The following equilibrium reaction describes the dissolving/formation of calcium carbonate scales:
CaCO3 + CO2 + H2O ⇋ Ca2+ + 2HCO3−
Calcium carbonate scales formed in water-heating systems are called limescale.
Calcium and magnesium ions can sometimes be removed by water softeners.

Temporary hardness
Temporary hardness is a type of water hardness caused by the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate). When dissolved, these minerals yield calcium and magnesium cations (Ca2+, Mg2+) and carbonate and bicarbonate anions (CO32-, HCO3-). The presence of the metal cations makes the water hard. However, unlike the permanent hardness caused by sulfate and chloride compounds, this “temporary” hardness can be reduced either by boiling the water, or by the addition of lime (calcium hydroxide) through the softening process of lime softening. Boiling promotes the formation of carbonate from the bicarbonate and precipitates calcium carbonate out of solution, leaving water that is softer upon cooling.

Permanent hardness
Permanent hardness is hardness (mineral content) that cannot be removed by boiling. When this is the case, it is usually caused by the presence of calcium and magnesium sulfates and/or chlorides in the water, which become more soluble as the temperature increases. Despite the name, the hardness of the water can be easily removed using a water softener, or ion exchange column.
Effects of hard water

With hard water, soap solutions form a white precipitate (soap scum) instead of producing lather. This effect arises because the 2+ ions destroy the surfactant properties of the soap by forming a solid precipitate (the soap scum). A major component of such scum is calcium stearate, which arises from sodium stearate, the main component of soap:
2 C17H35COO- + Ca2+ → (C17H35COO)2Ca

Hardness can thus be defined as the soap-consuming capacity of a water sample, or the capacity of precipitation of soap as a characteristic property of water that prevents the lathering of soap. Synthetic detergents do not form such scums.

Fouling
Hard water also forms deposits that clog plumbing. These deposits, called “scale”, are composed mainly of calcium carbonate (CaCO3), magnesium hydroxide (Mg(OH)2), and calcium sulfate (CaSO4).[1] Calcium and magnesium carbonates tend to be deposited as off-white solids on the surfaces of pipes and the surfaces of heat exchangers. This precipitation (formation of an insoluble solid) is principally caused by thermal decomposition of bi-carbonate ions but also happens to some extent even in the absence of such ions. The resulting build-up of scale restricts the flow of water in pipes. In boilers, the deposits impair the flow of heat into water, reducing the heating efficiency and allowing the metal boiler components to overheat. In a pressurized system, this overheating can lead to failure of the boiler. The damage caused by calcium carbonate deposits varies depending on the crystalline form, for example, calcite or aragonite.
The presence of ions in an electrolyte, in this case, hard water, can also lead to galvanic corrosion, in which one metal will preferentially corrode when in contact with another type of metal, when both are in contact with an electrolyte. The softening of hard water by ion exchange does not increase its corrosivity per se. Similarly, where lead plumbing is in use, softened water does not substantially increase plumbo-solvency.

In swimming pools, hard water is manifested by a turbid, or cloudy (milky), appearance to the water. Calcium and magnesium hydroxides are both soluble in water. The solubility of the hydroxides of the alkaline-earth metals to which calcium and magnesium belong (group 2 of the periodic table) increases moving down the column. Aqueous solutions of these metal hydroxides absorb carbon dioxide from the air, forming the insoluble carbonates, giving rise to the turbidity. This often results from the alkalinity (the hydroxide concentration) being excesively high (pH > 7.6). Hence, a common solution to the problem is to, while maintaining the chlorine concentration at the proper level, raise the acidity (lower the pH) by the addition of hydrochloric acid, the optimum value being in the range of 7.2 to 7.6.

Softening
For the reasons discussed above, it is often desirable to soften hard water. Most detergents contain ingredients that counteract the effects of hard water on the surfactants. For this reason, water softening is often unnecessary. Where softening is practiced, it is often recommended to soften only the water sent to domestic hot water systems so as to prevent or delay inefficiencies and damage due to scale formation in water heaters. A common method for water softening involves the use of ion exchange resins, which replace ions like Ca2+ by twice the number of monocations such as sodium or potassium ions.

Health considerations
The World Health Organization says that “there does not appear to be any convincing evidence that water hardness causes adverse health effects in humans”.
Some studies have shown a weak inverse relationship between water hardness and cardiovascular disease in men, up to a level of 170 mg calcium carbonate per litre of water. The World Health Organization has reviewed the evidence and concluded the data were inadequate to allow for a recommendation for a level of hardness.

Recommendations have been made for the maximum and minimum levels of calcium (40–80 ppm) and magnesium (20–30 ppm) in drinking water, and a total hardness expressed as the sum of the calcium and magnesium concentrations of 2–4 mmol/L.

Other studies have shown weak correlations between cardiovascular health and water hardness.

Some studies correlate domestic hard water usage with increased eczema in children.

The Softened-Water Eczema Trial (SWET), a multicenter randomized controlled trial of ion-exchange softeners for treating childhood eczema, was undertaken in 2008. However, no meaningful difference in symptom relief was found between children with access to a home water softener and those without.

Measurement
Hardness can be quantified by instrumental analysis. The total water hardness is the sum of the molar concentrations of Ca2+ and Mg2+, in mol/L or mmol/L units. Although water hardness usually measures only the total concentrations of calcium and magnesium (the two most prevalent divalent metal ions), iron, aluminium, and manganese can also be present at elevated levels in some locations. The presence of iron characteristically confers a brownish (rust-like) colour to the calcification, instead of white (the color of most of the other compounds).
Water hardness is often not expressed as a molar concentration, but rather in various units, such as degrees of general hardness (dGH), German degrees (°dH), parts per million (ppm, mg/L, or American degrees), grains per gallon (gpg), English degrees (°e, e, or °Clark), or French degrees (°f). The table below shows conversion factors between the various units.

The various alternative units represent an equivalent mass of calcium oxide (CaO) or calcium carbonate (CaCO3) that, when dissolved in a unit volume of pure water, would result in the same total molar concentration of Mg2+ and Ca2+. The different conversion factors arise from the fact that equivalent masses of calcium oxide and calcium carbonates differ, and that different mass and volume units are used. The units are as follows:

Parts per million (ppm) is usually defined as 1 mg/L CaCO3 (the definition used below). It is equivalent to mg/L without chemical compound specified, and to American degree.

Grains per Gallon (gpg) is defined as 1 grain (64.8 mg) of calcium carbonate per U.S. gallon (3.79 litres), or 17.118 ppm.

a mmol/L is equivalent to 100.09 mg/L CaCO3 or 40.08 mg/L Ca2+.

A degree of General Hardness (dGH or ‘German degree (°dH, deutsche Härte)’ is defined as 10 mg/L CaO or 17.848 ppm.

A Clark degree (°Clark) or English degrees (°e or e) is defined as one grain (64.8 mg) of CaCO3 per Imperial gallon (4.55 litres) of water, equivalent to 14.254 ppm.

A French degree (°F or f) is defined as 10 mg/L CaCO3, equivalent to 10 ppm. The lowercase f is often used to prevent confusion with degrees Fahrenheit.

Hard/soft classification
Because it is the precise mixture of minerals dissolved in the water, together with the water’s pH and temperature, that determines the behavior of the hardness, a single-number scale does not adequately describe hardness.

Langelier Saturation Index (LSI)
The Langelier Saturation Index (sometimes Langelier Stability Index) is a calculated number used to predict the calcium carbonate stability of water. It indicates whether the water will precipitate, dissolve, or be in equilibrium with calcium carbonate. In 1936, Wilfred Langelier developed a method for predicting the pH at which water is saturated in calcium carbonate (called pHs). The LSI is expressed as the difference between the actual system pH and the saturation pH:

LSI = pH (measured) — pHs
For LSI > 0, water is super saturated and tends to precipitate a scale layer of CaCO3.
For LSI = 0, water is saturated (in equilibrium) with CaCO3. A scale layer of CaCO3 is neither precipitated nor dissolved.
For LSI < 0, water is under saturated and tends to dissolve solid CaCO3.

If the actual pH of the water is below the calculated saturation pH, the LSI is negative and the water has a very limited scaling potential. If the actual pH exceeds pHs, the LSI is positive, and being supersaturated with CaCO3, the water has a tendency to form scale. At increasing positive index values, the scaling potential increases.
In practice, water with an LSI between -0.5 and +0.5 will not display enhanced mineral dissolving or scale forming properties. Water with an LSI below -0.5 tends to exhibit noticeably increased dissolving abilities while water with an LSI above +0.5 tends to exhibit noticeably increased scale forming properties.
It is also worth noting that the LSI is temperature sensitive. The LSI becomes more positive as the water temperature increases. This has particular implications in situations where well water is used. The temperature of the water when it first exits the well is often significantly lower than the temperature inside the building served by the well or at the laboratory where the LSI measurement is made. This increase in temperature can cause scaling, especially in cases such as hot water heaters. Conversely, systems that reduce water temperature will have less scaling.

Hard water in the United States
More than 85% of American homes have hard water. The softest waters occur in parts of the New England, South Atlantic-Gulf, Pacific Northwest, and Hawaii regions. Moderately hard waters are common in many of the rivers of the Tennessee, Great Lakes, and Alaska regions. Hard and very hard waters are found in some of the streams in most of the regions throughout the country. The hardest waters (greater than 1,000 ppm) are in streams in Texas, New Mexico, Kansas, Arizona, and southern California.

Measuring Hardness and LSI
The Myron L Ultrameter III 9PTK measures water hardness and LSI, as well as 7 other water quality parameters.
Measures 9 Parameters: Conductivity, Resistivity, TDS, Alkalinity, Hardness, LSI, pH, ORP/Free Chlorine, Temperature
LSI Calculator for hypothetical water balance calculations
Wireless data transfer capability with bluDock option
Auto-ranging delivers increased resolution across diverse applications
Adjustable Temperature Compensation and Cond/TDS conversion ratios for user-defined solutions
Nonvolatile memory of up to 100 readings for stored data protection
Date & time stamp makes record-keeping easy
pH calibration prompts alert you when maintenance is required
Auto-off minimizes energy consumption
Low battery indicator
(Includes instrument with case and solutions)

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Categories : Science and Industry Updates

Posted by 23 Jan, 2011

Tweet Basic Tips For Choosing The Proper Instrument For Water Quality Tests

Basic Tips For Choosing The Proper Instrument For Water

Quality Tests

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