A
Acid
A substance that when dissolved in water releases hydrogen ions. It has the ability to react with bases to form salt. Acidic water is characterized by a sour taste and turns litmus paper red.
Acidity
A condition of water when the pH level is below 7.0. Too much acidity can be corrosive on equipment, discolor water, and create an off-taste.
Activated Carbon
Very porous structure used as an adsorbent in water conditioning. Commonly used for reducing many types of chemicals, such as chlorine, and removing organic compounds from water.
Adsorption
The process by which a substance in a liquid becomes attached to a solid. Used by carbon to reduce taste and odor in water.
Alkali
Also called a base, this is the opposite of an acid. It is characterized by a bitter taste. Examples include carbonate and bicarbonate salts.
Alkalinity
A condition of water when the pH is above 7.0. It is the capacity of a water to neutralize an acid. This is caused by the water's content of carbonate, bicarbonate, and hydroxide.
Anion
A negatively charged ion in a solution. Examples include chloride, nitrate, and sulfate.
B
Back Washing
The process of reversing the flow of water through the filter media to remove entrapped solids.
Bacteria
Tiny, one-celled organisms found in water that break down organic matter. Not all bacteria is harmful, but some can cause health problems. Chlorine or chloramine are typically added to municipal water supplies to kill bacteria.
Biofilm
Bacteria that has grown and reproduced within a filter canister to form a slime film over the filter media. This film can clog the pores of the carbon and reduce its ability to filter.
Buffer
A solution or liquid whose chemical makeup neutralizes acids or bases without a great change in pH.
C
Calcium
Dissolved calcium compounds are a major factor in making water hard and causing the formation of scale.
Cation
A positively charged ion in solution. Examples include sodium and calcium.Cation Exchange A common process for reducing hardness in water. A synthetic resin is coated with positively charged sodium ions. When water containing dissolved, negatively charged cations meets the resin, the sodium ions are exchanged with the cations.
Chemical Filtration
Any filtering substance that is designed to change the chemical composition of the water, but most often refers to the use of activated carbon. Activated carbon pulls dissolved organics from the water by adsorbing them.
Chloramines
A combination of chlorine and a small amount of ammonia. Used by some water utilities as a disinfectant. The addition of ammonia helps make the solution more stable and longer lasting. Chloramines can have an adverse effect on the taste and odor of water and are more difficult to remove by activated carbon.
Chloride
A salt that is highly soluble in water. It can cause corrosion on plumbing pipes and pitting corrosion on stainless steel. At high levels it imparts a salty taste to food and beverages.
Chlorination
The application of chlorine to water for the purpose of disinfection and controlling tastes and odors.
Chlorine
Chemical used by many water utilities for the disinfection of water and as an oxidizing agent for organic matter, manganese, ironic, and hydrogen sulfide. It imparts a noticeable taste and odor to water and may contribute to form trihalomethanes, a suspected carcinogen. Total chlorine is a total of both combined chlorine and free chlorine.
Chlorine, Combined
The portion of chlorine in the water that bonds with contaminants such as soils and organic matter.
Chlorine, Combined Available
The concentration of residual chlorine which is combined with ammonia and/or organic nitrogen in water as chloramine yet is still available to oxidize organic matter and utilize its bactericidal properties. The combined chlorine compounds are more stable than free chlorine forms, but are somewhat slower in reaction.
Chlorine, Free
The portion of chlorine in the water that does not bond and remains as residual. Carbon should be used to adsorb free chlorine from the water.
Chlorine Requirement
The amount of chlorine needed for a particular purpose, such as reducing the number of bacteria, obtaining a particular chlorine residual, or oxidizing some substance in the water.
Cistern
A tank or storage facility used to store water.
Coliform
A group of bacteria found in the intestines of warm-blooded animals, plants, soil, air, and water. Fecal coliforms are a specific class of bacteria that only inhabit the intestines of warm-blooded animals. The presence of coliform bacteria is an indication that the water is polluted and may contain pathogenic organisms.
Color
A tint that is usually caused by dissolved organic matter (often fulvic and humic acids). It cannot be removed by mechanical filtration.
Continuous Flow
The flow that occurs a majority of the time throughout the day.
Cryptosporidium
A group of common waterborne intestinal parasites usually found in water contaminated by animal waste. It causes illness and can sometimes be fatal to individuals with weakened immune systems. Cryptosporidium is resistant to chlorine disinfection but can be removed from water with fine filtration.
Cyst
A parasite that develops a hard protective shell when it leaves its host. This shell makes them strongly resilient, capable of surviving chlorine disinfection. When a cyst is ingested, it can cause intestinal illness, including diarrhea, abdominal pain, cramps, and nausea. Cysts can be removed from water by fine filtration. Examples of cysts include Cryptosporidia and Giardia.
D
Dechlorination
The deliberate removal of chlorine from water. The partial or complete reduction of residual chlorine by any chemical or physical process. Activated Carbon is typically used for this purpose.
E
Effluent Water
Water that has passed through the filter system or is downstream of the water treatment device.