Acid A substance that has a pH of less than 7, which is neutral. Specifically, an acid has more free hydrogen ions (H+) than hydroxyl ions (OH-).

Acidity The quantitative capacity of a water or water solution to neutralize an alkali or base. It is usually measured by titration with a standard solution of sodium hydroxide, and expressed in ppm or mg/L of its calcium carbonate equivalent.

Adsorbate Any substance that is or can be adsorbed. The liquid, gas or solid substance which is adsorbed as molecules, atoms, or ions.

Adsorbent A water treatment medium, usually solid, capable of the adsorption of liquids, gases, and/or suspended matter. Activated alumina and activated carbon are common adsorbents used in water processing.

Adsorption The process occurring when liquids, gases, or suspended matters adhere to the surfaces of, or in the pores of, an adsorbent media such as activated carbon. Adsorption mostly is a physical process which occurs without chemical reaction.

Aeration The process in which air is brought into close contact with water, often by spraying water through air, or by bubbling air through water. Aeration may be used to add oxygen to the water for the oxidation of matter such as iron, or to cause the release of dissolved gases such as carbon dioxide or hydrogen sulfide from the water.

Aggressive Water A term usually applied to waters containing acid or oxygen which hasten corrosion (rusting).

Algae Plant life (green scum) containing chlorophyll is usually found in stagnant surface water. Excessive growths may create taste and odor problems, and consume dissolved oxygen during decay.

Alkalinity The quantitative capacity of water to neutralize an acid; that is, the measure of how much acid can be added to a liquid without causing a significant change in pH. In the water industry, alkalinity is expressed in mg/l of equivalent calcium carbonate. There are three kinds of alkalinity: carbonate, bicarbonate, and hydroxide alkalinity. Total alkalinity is the sum of all three kinds of alkalinity.

Base A substance that has a pH of more than 7, which is neutral. A base has less free hydrogen ions (H+) than hydroxyl ions (OH-).

Brine A strong solution of salt(s), such as the sodium chloride or potassium brine used in the regeneration of ion exchange water softeners, but also applied to the mixed sodium, calcium and magnesium chloride waste solution from regeneration.

Chlorinator A mechanical device specifically designed to feed chlorine gas or pellets, or solutions such as hypochlorides, into a water supply in proportion to the flow of water.

Chlorine Widely used in the disinfection of water and as an oxidizing agent for organic matter, iron, hydrogen sulfide, etc. It is available as a gas, as a liquid in sodium, hypochlorite, or as a solid in calcium hypochlorite. In water chlorine reacts with organics to form trihalomethanes (THM) which
can cause cancer.

Conductivity The quality or power to carry electrical current; in water, the conductivity is related to the concentration of ions capable of carrying electrical current. The unit of measure is the mho or simens, which is the reciprocal of resistivity which is the ohm.

Deionization The removal of the ionized minerals and salts (both organic and inorganic) from a solution by a two-phase ion exchange procedure. First, positively charged ions are removed by a cation exchange resin in exchange for a chemically equivalent amount of hydrogen ions. Second, negatively charged ions are removed by an anion exchange resin for a chemically equivalent amount of hydroxide ions. The hydrogen and hydroxide ions introduced in this process unite to form water molecules.

Desalination The removal of dissolved inorganic solids (salts) from a solution such as water to make it free of dissolved salts. Typically accomplished by reverse osmosis, distillation, or electrodialysis.

Drinking Water Standards National Primary Drinking Water Standards are established by the U.S. Environmental Protection Agency (EPA) are health related and establish the maximum contaminant levels (MCL’s) for regulated substances in drinking water. A MCL is the highest permissible level of a contaminant allowed in water delivered to the consumer’s tap. These standards relate to public water systems. National Secondary Drinking Water Standards are also issued by the EPA and pertain to aesthetic characteristics of water and are recommended only.

Fresh water Water that contains less than 1,000 mg/L of dissolved solids; generally, if the amount of dissolved solid is more than 500 mg/L, it is undesirable for drinking and many industrial uses as well.

Gallon A common unit of liquid volume; the US gallon has a volume of 231 cubic inches or 3.78533 liters; the British (Imperial) gallon has a volume of 277.418 cubic inches or 4.54596 liters.

Grain (gr) A unit of weight equal to 1/7000th of a pound or 0.0648 gram.

Grains Per Gallon (GPG) An expression of concentration of material in solution. One grain per gallon is equivalent to 17.1 parts per million. This is the common reference for hardness of water.

Hardness The presence of dissolved calcium and magnesium in water called hardness. In some references pointed that hardness includes calcium, magnesium iron and manganese (all have 2+ charge). Hardness is responsible for most scale formation in pipes and water heaters and forms insoluble “curd” when it reacts with soaps. In other words, hardness indicates of the existing of alkaline salts in water, mainly calcium and magnesium. If the water you use is “hard” then more soap, detergent or shampoo is necessary to raise a lather. These minerals are scale forming, affect taste and color of certain foods and react with soap to form insoluble soap curds. Hardness is usually reported milligram per liter (mg/L) which is equal to parts per million (PPM) or grains per gallon (gpg), all as calcium carbonate equivalent.

Hard water When the total hardness of water is more than 1.0 gpg (17.1 mg/L) as calcium carbonate equivalent, the water considers as hard water. The following table classified different types of water based on the concentration of total hardness.  

 

Ion An atom, or group of atoms in a solution which function as a unit, and has a positive or negative electrical charge, due to the gain or loss of one or more electrons. It is smaller than a colloid.

Ion Exchange A reversible process in which ions are released from an insoluble permanent material in exchange for other ions in a surrounding solution. The ion exchanger media is an insoluble permanent solid medium.

Lime The common name for calcium oxide (CaO); hydrated lime is calcium hydroxide, Ca(OH)2.

Maximum contaminant level (MCL) The designation given by the U.S. Environmental Protection Agency (EPA) to water-quality standards promulgated under the Safe Drinking Water Act. The MCL is the greatest amount of a contaminant that can be present in drinking water without causing a risk to human health.

Nanofiltration A membrane process that treats water between reverse osmosis and ultrafiltration the filtration/separation spectrum. It can remove particles in the 300 to 1,000 molecular weight range such as humic acid and organic color found in water. Nanofiltration may be used for selective removal of hardness ions.

Neutralizer A common designation for alkaline materials such as calcite (calcium carbonate) or magnesia (magnesium oxide) used in the neutralization of acid waters. Alkaline water can also be neutralized by the addition of an acid. The neutral point of the pH scale is 7.0, indicating the presence of equal numbers of free hydrogen and hydroxide ions.

Osmosis A process of diffusion of a solvent such as water through a semi-permeable membrane which will transmit the solvent but impede most dissolved substances. The normal flow of solvent is from the dilute solution to the concentrated solution. Osmosis causes the stronger solution to become more diluted and tends to equalize the opposing solutions.

pH A measure of the relative acidity or alkalinity of water. Water with a pH of 7 is neutral; lower pH levels indicate increasing acidity, while pH levels higher than 7 indicate increasingly basic solutions.

parts per billion The number of “parts” by weight of a substance per billion parts of water. Used to measure extremely small concentrations.

parts per million The number of “parts” by weight of a substance per million parts of water. This unit is commonly used to represent pollutant concentrations.

pH (potential of Hydrogen) An expression of the acidity of a solution; the negative logarithm of the hydrogen ion concentration. It is the logarithm of the reciprocal of the hydrogen ion concentration of a solution. The neutral point of 7 indicates the presence of equal concentrations of free hydrogen and free hydroxide ions.

Point of Entry (POE) A water treatment device which installs at the main inlet to a building and acts as centralized treatment.

Point-of-Use (POU) A water treatment system designed to connect at the actual point-of-use for water; countertop or under sink treatment systems.

Resin Synthetic organic ion exchange material, such as the high capacity cation exchange resin widely used in water softeners. Technical name- sulfonated co-polymer of styrene and divinyl
benzene.

Reverse osmosis The process of removing salts from water using a membrane. With reverse osmosis, the product water passes through a fine membrane that the salts are unable to pass through, while the salt waste (brine) is removed and disposed.

Saline water It is the water that contains significant amounts of dissolved solids. Here are our parameters for saline water:  

 

Solvent A substance that dissolves other substances, thus forming a solution. Water dissolves more substances than any other, and is known as the “universal solvent”.

Specific conductance A measure of the ability of water to conduct an electrical current as measured using a 1-cm cell and expressed in units of electrical conductance, i.e., Siemens per centimeter at 25 degrees Celsius. Specific conductance can be used for approximating the total dissolved solids content of water by testing its capacity to carry an electrical current

Soft water When the concentration of calcium and magnesium (total hardness of water) is less than 1.0 gpg (17.1 mg/l) expressed as calcium carbonate equivalent, is considered soft water.

Softened water Water that is treated to reduce the total hardness, expressed as calcium carbonate equivalent, is called softened water.

TDS The abbreviation for “total dissolved solids”.

Turbidity The very small particles that are suspended in water and that cause light rays shining through the water to scatter. Thus, turbidity makes the water cloudy or even opaque in extreme cases. Turbidity is measured in nephelometric turbidity units (NTU).

Tannin A naturally occurring substance in wood, grape skins, seeds and stems. Considered a pollutant in water that changes the taste and color of water.

Trihalomethanes (THM’s) A group of organic chemicals to known to be carcinogenic in more than trace amounts which are produced from chlorination. They reduce the germicidal activity of chlorine in alkaline water.

Total Chlorine The total amount of chlorine is a solution, which includes the combined chlorine as well as the free available chlorine.