مصطلحات وتعاريف علمية وكيميائية خاصة التنظيف الكيميائى الخاص بمعالجة المياه واجهزة معالجة المياه

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5.

GLOSSARY

Acid — A compound, usually having a sour taste, which can neutralize an alkali or base; a substance that dissolves in water with a formation of hydrogen ions.

Aeration — Intimate contact between air and liquid by one of the following methods: spraying the liquid in the air; bubbling air through the liquid; or agitating the liquid to promote surface absorption of air.

Algae — Tiny plant life, usually microscopic, existing in water. They are mostly green, blue-green, or yellow-green, and are the cause of most tastes and odors in water.

They create suspended solids (SS) when they grow in an industrial water system.

Alkalinity — (a) A term used to represent the content of carbonates, bicarbonates, hydroxides, and occasionally borates, silicates, and phosphates in water. (b) The capacity of water to react with hydrogen ions.

Alkalinity, total or mixed indicator (M) — A measure of the total alkalinity of water. Measured by the quantity of 0.02 normality (N) sulfuric acid required to bring water to pH of 4.4, as indicated by the change in color of methyl orange or a mixed indicator.

Results are expressed in parts per million (ppm) as calcium carbonate.
Alkalinity, Phenolphthalein (P) — A measure of hydroxide ions (OH) plus one-half of the normal carbonates in water.

Measured by the quantity of 0.02 normality (N) sulfuric acid required to bring the water to pH 8.2, as indicated by the de-colorization of phenolphthalein indicator.

Results are expressed in parts per million (ppm) as calcium carbonate.

Alkalinity, Hydroxyl — A measure of hydroxyl ion (OH-) contribution to the alkalinity.

This is related to the system pH and also may be referred to as “causticity.”
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Bacteria — Simple single-cell microscopic organisms generally free of pigment. They do not require light for their life processes.

Backwash — The reversal of flow through a filter or an ion exchanger to wash clogging material out of the filtering medium and reduce conditions causing loss of head.

Backflow preventer — A device for a water supply pipe to prevent the backflow of water into the water supply system from the system which it supplies.

Base — An alkali or hydroxide of alkali metals and ammonia. They can neutralize acids to form salts and water.

A base will ionize to form hydroxyl ions (OH-).
Biocides — Material typically used to destroy microorganisms (also called “microbiocides”).

Biological Deposits — Water-formed deposits of organisms or the product of their life processes.

Biological deposits may be composed of microscopic organisms, as in slimes, or of macroscopic organisms such as barnacles or mussels.

Blowdown — Draining a portion of water from a system to reduce the concentration of dissolved solids or to discharge accumulations of materials carried by the water.

British Thermal Unit (BTU) — The amount of heat necessary to raise the temperature of one pound of water one degree Fahrenheit (°F).

Brine — A saturated solution for ion exchange regeneration, refrigeration, or cooling processes.

It is usually a sodium chloride water solution for ion exchange regeneration.

It may be sodium chloride water solution or calcium chloride water solution for refrigeration.

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Causticity — A common term that describes hydroxyl alkalinity or the alkalinity resulting from the presence of the hydroxyl ion (OH).

Concentration — A measure of the amount of dissolved substances contained per unit volume of solution.

This may be expressed as grains per gallon, pounds per million gallons, milligrams per liter, ppm, or percent.

Condensate — The material formed when vapor returns to the liquid state. In steam heating systems, the water condensed from steam.

In air conditioning, water extracted from air by condensation on the cooling coil of a refrigeration machine.

Conductivity, Specific Conductance — The reciprocal of the resistance in ohms measured between opposite faces of a centimeter cube of an aqueous solution at a specified temperature.

Electrical conductivity is expressed in micromhos (μmhos), the reciprocal of megohms. This is used as a measure of total dissolved solids (TDS).

Corrosion — The destruction of a substance, usually a metal, or its properties because of a reaction with its (environmental) surroundings.

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Disinfection — The process of killing most (but not necessarily all) of the harmful and objectionable microorganisms in a fluid by various agents such as chemicals, heat, ultraviolet light, ultrasonic waves, or radiation.

Cycles of Concentration (COC) — In a system in which water lost through evaporation and blowdown is replaced with makeup water, COC is the ratio of the makeup quantity to the blowdown quantity (COC = M/B).

It is the number of times the makeup water is concentrated in the system. The COC can also be calculated by dividing either the conductivity or the chloride content of the blowdown by the conductivity or chloride content of the makeup (COC = Condbd/Condmw).

Deaerator — Device for removing non-condensable gases from the boiler.

It may operate on the principle of either heat or vacuum.

Dealkalization — Exchange of bicarbonate for chlorides in an ion exchange process.

Deionization — Complete removal of ions from water.

Demineralization — Reduction of the mineral content of water by a physical or chemical process; removal of salts.

Dissolved solids — (a) Solids, usually minerals, which are present in solution. (b) The dried residue from evaporation of the filtrate after separation of suspended solids (SS).

Distribution Ratio (D.R.) — This is a measure of the vapor/liquid ratio for a given material. Extremely high and low values are generally unadvisable.

A high D.R. results in either high amine losses at any vents or little availability of amine at points of initial condensation, or both. A low D.R. results in high amine losses in the blowdown.

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Evaporation — The process by which water passes from a liquid state to a vapor. It is the main process by which heat is removed from a cooling tower and steam is produced in a boiler.

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Feedwater — Water being applied to the feedwater heater or to the boiler, consisting of both makeup and condensate return.

Filming Amines — Chemicals that form an impervious barrier between metal and the steam condensate to prevent corrosion.

Foulants — Deposition of materials normally in suspension.

This includes silt, air-scrubbed dust, microbiological residuals, reaction products from treatment, and corrosion products.

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Generic Chemicals — A chemical identified and purchased by the recognized chemical name, such as the International Union of Pure and Applied Chemistry (IUPAC) designation.

These generic chemicals may be blended or used separately.

They are usually much less expensive than special chemical blends developed by manufacturers under a trade name.

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Hardness — (a) A characteristic of water, chiefly due to the existence of carbonate and sulfate (and occasionally the nitrite and chloride) salts of calcium, iron, and magnesium.

(b) Commonly computed from the amount of calcium and magnesium in the water and expressed as equivalent calcium carbonate.

(c) Causes "curding" of water when soap is used, increased consumption of soap, deposition of scale in boilers, injurious effects in some industrial processes, and sometimes objectionable taste in the water.

Hardness, Carbonate — Hardness caused by the presence of carbonates and bicarbonates of calcium and magnesium in water.

Such hardness may be removed to the limit of solubility by boiling the water. This is also called temporary hardness.

Hardness, Non-Carbonate — Hardness caused by calcium and magnesium sulfates and chlorides and compounds other than carbonates which cannot be reduced materially by boiling the water.

(Also called "permanent hardness".)

Hardness, Total — The sum of carbonate and non-carbonate hardness.

Hydrogen Ion Concentration — Commonly expressed as the pH value that represents the logarithm of the reciprocal of the hydrogen ion concentration.

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Inhibitor (applied to corrosion) — A chemical substance or mixture that effectively decreases corrosion when added to a liquid (usually in small concentrations).

Ion — A particle, atom, or group of atoms, carrying either a positive or negative electrical charge, formed when an electrolyte is dissolved in water.

Ion Exchange — A process where water is passed through a granular material wherein ions on the granular material are replaced by ions contained in the water.

For example, in the zeolite softening process, the sodium ions (Na+) of the granular zeolite are replaced by the calcium ions (Ca++) in the water to leave the water free of calcium (the cause of hardness), but with an increased amount of sodium.

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Langelier Index (saturation index) — An index based on the calcium hardness, total alkalinity, total dissolved solids (TDS), temperature, and pH. It is used to classify waters
by their ability to either dissolve or deposit calcium carbonate.

It is the algebraic difference between the actual pH and the calculated pH of saturation.

It was one of the first indices developed for this purpose and was designed specifically for municipal water flowing in distribution lines.

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Makeup Water — Water supplied to replace the loss in a system due to leaks, evaporation, wind drift, bleed-off, blowdown, or withdrawal.

Microbiocide — A material added to cooling tower water and chilled water to control the growth of microorganisms such as algae, bacteria, and fungi.

Micromho — An electrical unit of conductance (one-millionth of a mho), which is the reciprocal of electrical resistance.

Microorganism — A minute plant or animal in water or earth that is visible only through a microscope.

Milligrams Per Liter (mg/l) — A unit of the concentration of water or wastewater constituent.

It is 0.001 gram of the constituent in 1000 milliliters (ml) of water.

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Neutralizing Amines — Chemicals used to neutralize carbon dioxide in steam condensate to prevent corrosion.

Normality (N) — The concentration of a solution in relation to a normal solution.

Normality is a measure of the “strength” of a given solution.

The normal solution contains a specific weight of a substance per liter based on the characteristics of the substance.

Thus, a half-normal solution would be expressed as 0.5N or N/2.

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Oxygen Scavenger — A chemical used to remove final traces (trace amounts) of oxygen from boiler feedwater.

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pH — Logarithmic measure of hydrogen ion concentration indicating degree of acidity or alkalinity of a solution.

The pH range varies from 1 to 14. Values below 7.0 indicate acidity and above 7.0 indicate alkalinity (basicity).

pH eq — The pH of equilibrium. The adjusted pH value of a water-based on the empirical
relationship between total alkalinity and pH developed from studies of hundreds of cooling systems.

Development of an empirical relationship was necessary because pH in cooling waters is often buffered, a factor which affects the relationship between pH and bicarbonate alkalinity.

pHs — The pH of saturation. It is the pH value below which a material will go into solution (dissolve) and above which it will precipitate.

It is applied to calcium carbonate in the Langelier, Ryznar, and Practical Scaling Indices.

It is a function of the calcium hardness, the total alkalinity, the total dissolved solids (TDS) and the temperature.

It is determined with graphs, tables, or special slide rules.

This equation is useful:
pHs = 12.27 - 0.00915T - log CaH - log TA + (log TDS)/10.

Phosphates — Chemicals used for corrosion control in cooling towers and deposit control in boilers.

Commonly, these occur as orthophosphates or polyphosphates.

The level of the active phosphate chemical is reported either as percent P2O5 (phosphorus pentoxide) or as PO4 (phosphate), with these two oxides of phosphate being related by factor as follows: PO4 = 1.34 x P2O5.

ppm — Parts per million; one pound of material dissolved in one million pounds of water.

Precipitate — (a) To separate a dissolved substance in the solid form by its removal from a solution.

(b) The substance in solid form that has been separated from solution.

Practical Scaling Index (PSI) — A modified scaling index developed by P.R. Puckorius and J.M. Brooke to provide a better and more consistent indication of scaling conditions of cooling water.

It is based on using the pH of equilibrium (pHeq) rather than the actual pH, and is calculated as follows:

PSI = 2 pHs - pHeq.

As with the RSI, a value less than 6.0 in natural water indicates a scale-forming tendency.

A value greater than 6.0 in natural water indicates a scale-dissolving tendency.
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Regeneration — That part of the operating cycle of an ion exchange process in which a specific chemical solution is passed through the ion exchange bed to prepare it for a service run (i.e., return the ion exchange bed to its original composition).

Ryznar Index (stability index) — An index classifying water as to its ability to dissolve or deposit calcium carbonate scale.

It is calculated as twice the pH of saturation minus the actual pH (RI = 2 pHs - pH). Although in theory an RI of 7.0 should be neutral, experiments indicate that 6.0 is a better value.

A value less than 6.0 in natural water

indicates a scale-forming tendency.

A value greater than 6.0 in natural water indicates a scale-dissolving tendency.

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Scale — Deposition on a heat transfer surface of normally soluble salts. Scale is usually crystalline and dense, frequently laminated, and occasionally columnar in structure.

Shock Feed — The process of adding one or more water treatment chemicals in one application rather than gradually.

Slime — Biological growths that may accumulate to the extent that they foul equipment.

Sludge — A water-formed deposit that will settle, and may include all suspended solids (SS) carried by water. Sludge is commonly formed in boilers where it may be baked into place and become hard and adherent.

Softening Water — The process of removing from water the mineral substances that produce a condition called hardness.

There are two softening processes in general use: chemical precipitation (lime and lime/soda softening) and the zeolite ion exchange process.

Solids, Suspended (SS) — All matter in water that is not dissolved and can be removed with filtration.

Solids, Dissolved — The total concentration of all substances in a filtered solution which exist as solids after the liquid is completely evaporated from the solution.

Solids, Total — The sum of the suspended and dissolved matter (solids).

Zeolite — Natural minerals as well as synthetic resins used for ion exchange.[/b]

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مصطلحات وتعاريف علمية وكيميائية خاصة التنظيف الكيميائى الخاص بمعالجة المياه واجهزة معالجة المياه Intro113

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