Residential Water Treatment Glossary

Water Filtration and Contaminants Glossary

The quest for pure, contaminant-free water remains a pressing concern for many people. From understanding the potential contaminants lurking in tap water to navigating water filters and water filtration systems, there’s much to learn. This glossary breaks down the essential terms used in water treatment and filtration. Whether you’re concerned with water quality or the processes that make it safe to drink, this comprehensive guide helps clarify the terminology.

Water Quality and Treatment

Water quality is a cornerstone of public health, with water treatment practices ensuring that our drinking water is safe and free from harmful contaminants. This section defines terms commonly used in water quality and treatment discussions

Backwash: Reversing the flow of water through a filter or ion exchange system to clean out trapped particles or regenerate the medium.

Biocide: A chemical agent that can kill living organisms; often used to disinfect water or other substances.

Brackish water: Water with more salinity than freshwater but less than seawater; typically found in estuaries where freshwater rivers meet the sea.

Brine: A high-concentration solution of salt in water.

Buffer: A substance that minimizes changes in pH when acids or bases are added to a solution; essential in maintaining a stable pH in water systems.

Calcite: A naturally occurring form of calcium carbonate used in water treatment to neutralize acidic waters.

Carbon dioxide: A colorless and odorless gas. In water treatment, it can be used to lower pH or removed if present in excess.

Coagulant: A substance that causes particles in suspension to aggregate and form clumps. In water treatment, coagulants are used to remove suspended solids.

Compensated hardness: A measure of water hardness that considers calcium and magnesium concentrations.

Condensate: The liquid formed when a gas cools and condenses. In water systems, it often refers to the pure water formed from steam.

Deashing: Removing ash or mineral matter from a solution; often used when referring to wastewater treatment.

Dechlorination: Removing chlorine from water; often necessary after disinfection to prevent the taste or odor of chlorine in drinking water.

Degassing: Removing dissolved gasses from liquids, especially in water treatment processes.

Deionization: Removing all ionized minerals and salts from water using ion-exchange processes.

Desalination: Removing salt and other minerals from seawater or brackish water to produce fresh water.

Drinking water standards: Regulations or guidelines set by authorities that specify the maximum levels of contaminants allowed in potable water.

Eutrophication: Enriching water bodies with nutrients, leading to excessive growth of algae and other aquatic plants; can result in a lack of oxygen, harming aquatic life.

Hard water: Water containing high levels of dissolved calcium and magnesium ions; can cause scale buildup in pipes and appliances and reduce the effectiveness of soaps and detergents.

Lime softening: A water treatment process that uses lime to remove hardness (calcium and magnesium ions) from water.

Potable water: Water that is safe and suitable for drinking and cooking.

Pre-chlorination: Adding chlorine to water before it undergoes other treatment processes.

Purification: Making water or another substance pure by removing contaminants or undesired materials.

Remineralization: Adding minerals back into water; often used in reverse osmosis systems to restore minerals removed during filtration.

Softened water: Water with hardness minerals (primarily calcium and magnesium ions) removed or exchanged.

Total dissolved solids (TDS): The total amount of all inorganic and organic substances dissolved in water, usually measured in milligrams per liter or parts per million.

Total hardness: A measure of the concentration of calcium and magnesium ions in water, which contribute to the “hardness” or soap-scum-forming ability of the water.

Total organic carbon: A measure of the total amount of carbon in organic compounds in water.

Total solids: The total concentration of all substances (dissolved and suspended) in water.

Ultrapure water: Water that has been purified to remove all contaminants to extremely low levels, often used in semiconductor manufacturing or pharmaceutical applications.

Water conditioning: Improving water quality by altering its characteristics, often to make it more suitable for a specific use or application.

Water softening: Removing calcium and magnesium ions, the primary causes of water hardness, and replacing them with sodium ions.

Well water: Water drawn from underground sources through a well; varies in quality and might contain minerals, contaminants, or microorganisms, often requiring treatment before consumption or use.

While understanding the broader concepts of water quality is vital, it’s equally important to recognize specific contaminants that might be present in our water sources.

Organic Compounds

Organic compounds are carbon-based molecules, some occurring naturally, while others are synthetic. This section explores these compounds, their sources, and their effects when present in water.

Benzene: A volatile organic compound (VOC) that can contaminate water from industrial discharges or leaching from underground storage tanks; a known carcinogen.

Bicarbonate alkalinity: Represents the concentration of bicarbonate ions in water. Bicarbonates can neutralize acids and play a role in buffering pH.

Biochemical oxygen demand (BOD): A measure of the amount of oxygen required by bacteria to decompose organic materials present in water; an indicator of the organic quality of water.

Chloramines: Compounds formed when chlorine reacts with ammonia; used as disinfectants in some water treatment systems due to their longer-lasting residual effect compared to chlorine alone.

Chlorine demand: The amount of chlorine required to oxidize all organic and inorganic materials in water.

Detergent: A synthetic cleaning agent containing surfactants that break up and remove dirt and grease.

Organics (i.e., organic chemicals): Chemical compounds containing carbon atoms. In the context of water treatment, “organics” usually refer to unwanted organic compounds that can affect taste, odor, color, or health.

PFAS (Per- and polyfluoroalkyl substances): A group of manufactured chemicals known for their resistance to heat, water, and oil. They can contaminate drinking water and are associated with health risks.

Soda ash: The common name for sodium carbonate; used in water treatment to adjust pH or soften water.

Tannin: Organic materials derived from plants that can give water a brownish color and astringent taste; more common in surface waters that pass through peaty soils or decaying vegetation.

Trihalomethanes (THMs): A group of organic chemicals formed when chlorine or bromine reacts with organic matter in water. Some THMs are considered carcinogenic and are regulated in drinking water.

Volatile organic compounds (VOCs): Organic chemicals that have a high vapor pressure at room temperature. Some VOCs in water can be harmful to health and may need to be removed during treatment.

Xylene: An aromatic hydrocarbon used as a solvent and in the production of aviation gasoline and other products; can contaminate water sources and must be removed during treatment.

Alongside organic compounds, water can also be home to various microorganisms.

Organisms and Microbes

Water sources can harbor a multitude of microorganisms, from harmless to potentially pathogenic. This section shines a light on these tiny inhabitants, their behaviors, and their significance in water quality.

Algae: Simple aquatic plants that can perform photosynthesis, ranging from microscopic phytoplankton to larger forms like seaweed. Some can produce toxins harmful to humans or cause taste and odor issues in drinking water.

Amoeba: A type of single-celled organism found in freshwater and marine environments. Some species can cause diseases in humans when ingested with contaminated water.

Anaerobic organism: Organisms that can live and grow in the absence of oxygen. Some anaerobic bacteria in water can produce unpleasant tastes and odors.

Bacteria: Single-celled microorganisms that can be found everywhere. While many bacteria are harmless or beneficial, some can cause diseases, especially when ingested through contaminated water.

Bactericide: An agent that kills bacteria.

Bacteriostatic: An agent that inhibits the growth or reproduction of bacteria without necessarily killing them.

Coliform bacteria: A group of bacteria predominantly inhabiting the intestines of humans and other warm-blooded animals. The presence of coliform bacteria in water is an indication of potential contamination by pathogens.

Cryptosporidium: A microscopic parasite that can cause the disease cryptosporidiosis in humans. It’s resistant to many common disinfectants, making removing it from contaminated water sources challenging.

Giardia: A microscopic parasite that can cause gastrointestinal symptoms when ingested through contaminated water.

Legionella: Bacteria that can cause Legionnaires’ disease, a severe form of pneumonia. It can thrive in warm water environments like hot tubs, cooling towers, and hot water tanks.

Protozoa: Single-celled organisms that can be parasitic. Some protozoa found in water can cause diseases in humans when ingested.

Pyrogens: Substances, often of biological origin, that can cause fever when introduced into the bloodstream. They can be a concern in medical applications where water purity is crucial.

Virus: Microscopic infectious agents that can replicate only inside the living cells of an organism. Some viruses in water can cause diseases in humans when ingested.

Transitioning away from living organisms, let’s now explore the inorganic compounds that can be found in water.

Inorganic Compounds

While they lack the carbon-based structure of organic compounds, inorganic substances play a pivotal role in water chemistry and quality. This section discusses these compounds and their implications for water treatment.

Arsenic: A naturally occurring metalloid that can contaminate groundwater. Long-term exposure to high levels can lead to serious health problems.

Barium: A metal that can be present in water due to industrial discharges or natural deposits. At high levels, it can increase blood pressure.

Chloride: An anion commonly found in water, often due to the dissolution of salt. High levels can affect water taste and corrode pipes.

Chromium-6 (hexavalent chromium): A toxic form of the metal chromium that can enter water supplies from industrial discharges; a known carcinogen.

Cyanide: A compound that can enter water supplies from industrial discharge; toxic to humans, even in small amounts.

Fluoride: A compound often added to public water supplies in small amounts to prevent tooth decay. However, excessive levels can lead to dental or skeletal fluorosis.

Lead: A heavy metal that can leach into water from plumbing materials. Even at low levels, lead exposure can be harmful, especially to children.

Mercury: A heavy metal that can contaminate water from industrial discharges; can be harmful when ingested and can bioaccumulate in fish.

Mineral: Naturally occurring inorganic substances with a defined chemical composition and crystal structure. Some minerals can affect water quality, taste, and appearance.

Modified zeolites: Synthetic or naturally occurring minerals that have been treated to change their ion exchange properties, commonly used in water softening.

Nitrate: A compound often found in fertilizers that can contaminate groundwater. High levels in drinking water can be harmful to infants.

Pesticides and herbicides: Chemicals used to control pests and weeds that can enter water sources through agricultural runoff; often regulated due to potential health risks.

Sulfate: An anion often found in groundwater. High concentrations can give water a bitter taste and act as a laxative.

Zeolite: A group of minerals with a porous structure, often used in water softening to exchange hardness ions for sodium ions.

Beyond compounds, understanding individual elements is crucial for a comprehensive grasp of water composition.

Elemental Properties

Elements, as the fundamental building blocks of matter, influence the properties and behaviors of water. This section delves into specific elements, their roles, and their interactions within aqueous environments.

Calcium (Ca): A soft gray alkaline earth metal. In water, calcium can contribute to hardness when present as calcium bicarbonate or calcium sulfate.

Copper (Cu): A metal essential for health in trace amounts but can leach into water from copper plumbing. High levels cause gastrointestinal distress and more serious health effects over time.

Magnesium (Mg): A shiny gray alkaline earth metal. Magnesium contributes to hardness in water, often in the form of magnesium bicarbonate.

Manganese (Mn): A hard, silvery metal. Manganese can cause black staining in water and be a health concern at high concentrations.

Radon (Rn): A radioactive gas that can enter groundwater from natural deposits. Ingesting or inhaling radon can increase the risk of cancer.

Sulfur (S): A yellow non-metal element. In water, sulfur can be present as hydrogen sulfide gas, which has a rotten egg odor.

Zinc (Zn): A metal that, in trace amounts, is essential for human health but can be harmful in excessive concentrations.

Uranium (U): A heavy radioactive element. While naturally occurring in some water sources, excessive levels can be harmful and must be removed.

Expanding from individual elements, we’ll now examine broader chemical aspects of water.

Chemical Properties and Reactions

Chemistry is a vast field, and as a universal solvent, water exhibits a myriad of chemical behaviors and reactions. This section clarifies the fundamental concepts that form the basis of water science.

Acid: A substance that donates a proton (H+) when dissolved in a solution. Acids have a pH of less than seven and can neutralize bases.

Acidity: The measure of how acidic a substance is, typically determined by the amount of H+ ions present.

Adsorption: The process by which atoms, ions, or molecules from a substance (usually a gas, liquid, or dissolved solid) adhere to the surface of another substance.

Aeration: Adding air to water; used in water treatment to remove dissolved gasses (like radon) or volatile organic compounds.

Alkali: A substance that can neutralize acids, resulting in the formation of salts. Alkalis are bases that are soluble in water.

Alkalinity: The capacity of water to neutralize acids, often due to the presence of bicarbonates, carbonates, and hydroxides.

Anode: An electrode through which electric current flows into a polarized electrical device. In electrochemical reactions, oxidation occurs at the anode.

Cation: A positively charged ion, typically formed when a metal loses one or more electrons.

Chemical stability: The ability of a substance to remain unchanged under specified conditions over time.

Chlorine: A chemical element commonly used as a disinfectant in water treatment to kill harmful bacteria and pathogens.

Corrosion: The gradual destruction or alteration of a material (especially metals) by a chemical or electrochemical reaction with its environment.

Dissociation: The splitting of a molecule into smaller molecules, ions, or atoms.

Electrolyte: A substance that dissociates into ions when dissolved in a solution, making the solution capable of conducting electricity.

Elution: Extracting one material from another by washing with a solvent, as in removing a solute from an adsorbent by running solvent through it.

Neutralizer: A substance used to adjust the pH of a solution to make it neutral (neither acidic nor alkaline).

Osmotic pressure: The pressure required to prevent the flow of solvent into a solution through a semipermeable membrane.

Oxalic acid: A colorless, crystalline, toxic organic compound belonging to the family of carboxylic acids.

Oxidation: A chemical reaction in which a molecule, atom, or ion loses electrons.

Oxidizing agent: A substance that can accept electrons from another substance, thereby causing oxidation of that substance.

Oxidizing filter: A filter that removes certain contaminants from water by using oxidation.

Ozone: A molecule consisting of three oxygen atoms, often used in water and air purification due to its strong oxidizing properties.

Precipitate: A solid substance that forms and settles out of a liquid solution.

Reactivation/Revivification: The process of restoring the adsorptive capacity of a spent adsorbent, such as activated carbon.

Redox: Short for “reduction-oxidation;” refers to all chemical reactions in which atoms have their oxidation states changed.

Regeneration: The process of renewing the ability of an adsorbent or ion-exchange system to remove contaminants by removing the adsorbed material or exchanging ions.

Sodium hydrosulfite: A chemical compound often used as a reducing agent in water treatment to remove contaminants like iron and manganese.

In addition to these chemicals and reactions, water also has distinct physical properties.

Physical Properties

From turbidity to temperature, the physical characteristics of water influence its behavior, treatment, and suitability for various uses. This section defines these tangible aspects in detail.

Air gap: A safety feature designed to prevent contamination of potable water by ensuring a physical separation between the end of a water supply outlet and the flood-level rim of a receiving vessel.

Attrition: The gradual reduction in particle size, typically due to repeated mechanical actions such as in water treatment processes.

Back pressure: The resistance or force opposing the desired flow of fluid in pipes or systems.

Backflow: The reverse flow of water or other substances into the main distribution pipes of a potable water supply.

Bed: A layer of material, typically sand, gravel, or other granular substance, used in water treatment processes.

Bed depth: The height of the filtering material (e.g., sand or activated carbon) in a filter.

Bed expansion: The increase in bed depth that occurs during backwashing due to the lifting and separation of the filter medium.

Breakthrough: The appearance of unremoved or unadsorbed contaminants in the effluent (outflow) of a filter or adsorber, indicating that the filtering capacity is exhausted.

Bulk Density: The weight of a substance per unit volume, including the spaces or voids within the substance; also known as apparent density.

Channeling: The formation of channels in a filter bed, allowing water to bypass the filtering material and reduce treatment efficiency.

Color throw: The release of color from a resin or adsorbent into the treated water.

Cross connection: Any actual or potential connection between a potable water supply and a source of contamination or pollution.

Exchange sites: Specific sites on ion exchange resins where ions are held and can be exchanged with ions in a solution.

Exchange velocity: The rate at which ions are exchanged in ion-exchange processes.

Operating pressure: The pressure at which a system or component operates under normal conditions.

Pores: Small holes or openings in a material, often responsible for the material’s ability to filter or adsorb contaminants.

Pressure drop: The decrease in pressure as water flows through a system or component.

Residual: The concentration of a substance remaining in treated water, especially after a water treatment process.

Sediment: Solid particles, often from soil erosion or organic decay, suspended in or settled at the bottom of water. Its removal is essential for water clarity and equipment protection.

Silt density index (SDI): A measure of the fouling potential of water, indicating the presence of particulate matter.

Swelling: The increase in volume of a material when it absorbs water or another fluid.

Throughput volume: The volume of water that can be treated or processed before a system or component requires regeneration or replacement.

Turbidity: A measure of the cloudiness or haziness in water caused by suspended solids or other particulate matter.

Upflow: The upward flow of water through a system or component, opposite to the force of gravity.

Venturi: A device used to introduce air into water by forcing water through a constricted section of pipe, creating a reduction in pressure.

Void area: The space or gaps between particles in a packed bed, such as in a filter or ion exchange column.

Water hammer: A sudden surge of pressure in a water system caused by the abrupt stoppage or change in direction of water flow.

With a foundation in water’s inherent properties, we move to the tools and devices designed to manage and treat it.

Equipment and Devices

Modern water treatment employs an array of sophisticated equipment to ensure optimal water quality. This section introduces these devices, their functions, and their significance in the treatment process.

Air check: A device or mechanism in a water treatment system that prevents water from entering the air pump or compressor.

Brine line: A pipe or conduit for discharging the concentrated solution (brine) from a water softener or desalination system.

Bypass: A system or pathway that allows water or another fluid to be diverted around a specific component or section of a system.

Chemical feeder: Equipment designed to add a specific amount of chemicals to water to aid in the treatment process.

Chlorinator: A device that introduces chlorine or chlorine compounds into water for disinfection.

Degasifier: Equipment used to remove dissolved gasses from water, commonly used in demineralization processes.

Demineralizer: A system or device that removes minerals (especially salts) from water. This can be achieved through processes like ion exchange, reverse osmosis, or distillation.

Dispenser: A device designed to release a specific amount or flow of water for consumption or use. Dispensers can be standalone units or integrated into larger systems like refrigerators or water coolers.

Downflow: A mode of operation in which water flows downward through a filter or ion exchange column, using the force of gravity.

Flow control: A device or mechanism that regulates the flow of water in a system.

Flow rate: The volume of water that flows through a system or component per unit of time, often measured in gallons per minute (GPM) or liters per minute (LPM).

Injector: A device used to introduce a substance into another substance. In water treatment, it can be used to add chemicals or air into water.

Inline filter: A filter designed to be installed directly in the water supply line, treating all water that passes through it.

Ion exchanger: A substance or device that can interchange ions with a liquid, often used in water treatment to remove unwanted ions.

Manifold: A pipe or chamber with multiple outlets that collect or distribute fluids.

Metered softener: A type of water softener that regenerates based on the volume of water treated, ensuring efficient use of salt and water.

Ozonator: A device that produces and introduces ozone into water for disinfection and oxidation.

Permeate pump: A device used in reverse osmosis systems to increase the system’s efficiency and performance by using the brine water’s energy.

Pressure tank: A tank designed to hold and dispense water under pressure, often used in well systems and other water supply setups.

Replacement filters: Cartridges or components designed to replace spent or clogged filters in a water treatment system. Regular replacement ensures optimal filtration efficiency and water quality.

Resin tank: A tank that contains ion exchange resin used in water softening or demineralization processes.

Reverse osmosis membrane (RO Membrane): A semipermeable membrane used in reverse osmosis systems to separate contaminants from water at the molecular level.

Riser: A vertical pipe that distributes or collects treated water in a system; also known as a distributor tube.

Under sink water filter: A compact water filtration system installed beneath a sink, designed to treat water at the point of use. It directly connects to the sink’s faucet, providing filtered water for drinking and cooking.

Underbed: Material placed below the main bed in a filter or softener, often to support the main bed and prevent it from entering the distribution system.

Ultraviolet lamp (UV lamp): A lamp that emits ultraviolet light, used in water treatment systems to inactivate or kill microorganisms.

Water filter pitcher: A portable container equipped with a built-in filter designed to remove contaminants from tap water. It combines storage and filtration in one convenient unit, ideal for immediate drinking water needs.

Water purifier: A device or system designed to remove contaminants, impurities, or undesired substances from water, ensuring it is safe and suitable for consumption or specific uses.

Whole house water filtration system: A system that is installed where the main water line enters a home. Whole house water filters reduce contaminants and provide clean water to the entire home.

Diving deeper into water treatment, we’ll next explore more of the specific technologies and mechanisms employed.

Filtering Mechanisms and Technologies

A water filter system is a cornerstone of water purification, and the technologies behind it are continually evolving. This section discusses these mechanisms and the science that drives them.

Absolute filter rating: The size of the largest particle that will pass through a filter under specified conditions. This rating indicates that a certain percentage (usually 98-99.9%) of particles larger than a specific size will be trapped on or within the filter.

Activated alumina: A porous form of aluminum oxide used as a filter medium for adsorption and removal of various contaminants from water, such as fluoride, arsenic, and selenium.

Activated carbon: A highly porous material made from organic materials such as wood, peat, or coconut shells. It’s commonly used in water filters to remove organic compounds, chlorine, and other contaminants due to its high adsorption capacity.

Activated silica: A compound used in water treatment as a coagulant aid to remove suspended solids and colloidal particles.

Adsorbate: The substance that is captured on the surface of a solid during the process of adsorption.

Adsorbent: The material (often a solid) that captures another substance on its surface through adsorption.

Automatic water softener: A water treatment system that automatically regenerates, backwashes, and rinses on a preset time or volume; also called an automatic filter.

Carbon block: A type of water filter composed of compressed carbon that offers finer filtration than granulated activated carbon.

Carbonaceous exchangers: Ion-exchange resins made from coal-based activated carbon.

Mechanical filter: A device that removes particles by passing water through porous materials such as sand, fabric, or membranes.

Micron rating: A measure of the size of particles a filter can effectively remove. A 5-micron filter, for example, traps particles larger than 5 microns in size.

Oxidizing filter: A type of filter that uses an oxidizing agent, such as potassium permanganate or chlorine, to treat water containing certain contaminants, such as iron or hydrogen sulfide.

Sand filter: A filter that uses sand as the primary filtering medium to remove suspended particles from water.

Siliceous gel zeolite: A synthetic zeolite used in water softening to exchange hardness ions for sodium ions.

Thin-film composite membrane (TFC): A type of semipermeable membrane used in reverse osmosis systems, known for its high rejection of unwanted molecules and high water production rate.

Ultrafiltration: A membrane filtration process that separates particles based on size, typically used to remove larger molecules and suspended solids from water.

Beyond the devices and technologies, understanding the broader processes and methods in water treatment is crucial.

Processes and Methods

Water treatment is a multifaceted discipline, encompassing a range of methods to achieve desired water quality. This section sheds light on these processes, from coagulation to disinfection.

Alternating system: A system with multiple units, where one unit is in service while the other is in standby or regeneration mode. It ensures continuous operation even during maintenance or regeneration.

Batch operation: A water treatment process where a specific volume of water is treated in a single, discrete unit of time, as opposed to continuous flow systems.

Cathodic protection: A method used to protect metal structures from corrosion by making them the cathode of an electrochemical cell. This can involve attaching a sacrificial anode or using an external direct current source.

Chelation: The process where a large molecule forms multiple bonds with a metal ion, effectively “wrapping” the ion and preventing it from interacting with other substances.

Coagulation: The process of adding chemicals to water to cause the aggregation of suspended particles, making them easier to remove.

Countercurrent regeneration: A process where the regenerant flow is in the opposite direction to the service flow. This method is often more efficient than co-current regeneration.

Dealkalization: The removal or neutralization of alkalinity (or bases) in a solution.

Disinfection: The process of eliminating or reducing harmful microorganisms from water.

Effluent: Treated water or other liquid that flows out of a treatment system or facility.

Exhaustion: The point at which a system or component (like a filter or ion-exchange resin) can no longer perform its intended function and needs regeneration or replacement.

Filtration: The process of removing suspended particles by passing water through a porous material or media.

Flocculation: The process of forming larger aggregates or flocs from coagulated particles, making them easier to settle out or be filtered.

Influent: The incoming water or other liquid flowing into a system or facility for treatment.

Ion exchange: A process where unwanted ions in a solution are replaced with other ions from an ion-exchange resin or medium.

Leach: To dissolve soluble components from a substance, such as ash or rock, by the action of a percolating liquid.

Micron filtration: A type of filtration that removes particles in the size range of about 0.1 to 10 microns.

Osmosis: The movement of solvent molecules through a semipermeable membrane from a lower solute concentration region to a higher solute concentration region.

Overrun: The volume of treated water produced after an ion exchange system has reached its rated capacity, often of lower quality than desired.

Oxidation: A chemical reaction in which a molecule, atom, or ion loses electrons.

Polishing: A final treatment process to further improve water quality, removing any remaining impurities.

Pre-treatment: The initial treatment of water before it undergoes the main treatment process, aimed at removing larger contaminants or conditioning the water for subsequent treatments.

Reverse osmosis (RO): A water purification process that uses a semipermeable membrane to remove ions, molecules, and larger particles from drinking water.

Softening: Removing calcium and magnesium ions (which cause hardness) from water, typically through ion exchange.

Spent: A material or medium that has reached its capacity and can no longer function efficiently.

Sterilization: Killing or inactivating all microorganisms in a sample, rendering it free from live bacteria, viruses, fungi, and their spores.

Zero soft: Water that has been completely softened (i.e., all hardness ions have been removed or exchanged).

With these processes in mind, it’s essential to comprehend the units and measurements that quantify water quality.

Measurements and Units

Quantifying water quality requires precise metrics and units. This section introduces these measurements, offering a standardized lens through which we can assess and compare water characteristics.

Angstrom unit: A unit of length equal to 10-10 meters, often used to express atomic and molecular sizes.

Bar: A unit of pressure equivalent to 100,000 pascals or roughly the atmospheric pressure at sea level.

Calcium carbonate equivalent: A standard measure used to express the lime requirement for soil or the hardness of water, referencing calcium carbonate as the benchmark.

GPD: Acronym for “gallons per day,” it’s a measure of flow rate.

Langelier Saturation Index (LSI): A calculated number used to predict the calcium carbonate stability of water. It indicates whether water will precipitate, dissolve, or be in equilibrium with calcium carbonate.

Micrograms per liter (µg/L): A unit representing the concentration of a substance in water. It indicates the presence of one microgram of the substance in one liter of water.

Microhm: A unit of electrical resistance equal to one-millionth of an ohm.

Micromho: An outdated unit of electrical conductance, which is the inverse of resistance. It’s equivalent to a microsiemens (µS).

Micron: A unit of length equal to one-millionth of a meter; commonly used to describe the size of particles in water filtration.

Milligram per liter (mg/L): A unit representing the concentration of a substance in water. It indicates the presence of one milligram of the substance in one liter of water. Often equivalent to parts per million (ppm) for water solutions.

Nephelometric Turbidity Unit (NTU): A unit used to measure water’s clarity or cloudiness (turbidity) based on how much light is scattered by suspended particles.

Ohm: A unit of electrical resistance; represents the resistance of a circuit in which a potential difference of one volt produces a current of one ampere.

Particulate: Solid particles suspended in a liquid or gas.

Parts per billion (PPB): The concentration of a substance in a solution at a ratio of one part of the substance to one billion parts of the solution.

Parts per million (PPM): The concentration of a substance in a solution at a ratio of one part of the substance to one million parts of the solution.

Service flow: The rate, often in gallons per minute (GPM), at which water is processed during the service cycle.

TDS: Acronym for “Total Dissolved Solids;” refers to the total concentration of all inorganic and organic substances in a liquid in molecular, ionized, or micro-granular suspended form.

Total acidity: The total measure of all acidic substances present in water.

Total alkalinity: The total measure of all alkaline substances present in water.

Total chlorine: The total amount of chlorine present in water, including both free and combined chlorine.

Potential of Hydrogen (pH): A measure of the acidity or alkalinity of a solution, ranging from zero (acidic) to 14 (alkaline), with seven being neutral.

Beyond the science and metrics, a broader landscape of associations and standards guides and governs water treatment practices.

Associations and Standards

Professional bodies, regulatory agencies, and industry associations play a pivotal role in setting standards and best practices for water treatment. This section highlights these entities and the standards they uphold, ensuring the safety and quality of our water.

American National Standards Institute (ANSI): An institution responsible for supervising the development of voluntary agreement-based standards for products, services, processes, systems, and personnel within the United States.

American Society of Mechanical Engineers (ASME): A professional organization that sets codes and standards for engineering practices, especially in the field of mechanical engineering.

American Water Works Association (AWWA): A professional association focused on improving water quality and supply, setting standards for water treatment and distribution systems.

Maximum contaminant level (MCL): The highest level of a contaminant allowed in drinking water by regulations. MCLs are set to ensure that drinking water is safe for human consumption.

Maximum contaminant level goal (MCLG): The concentration level of a contaminant in drinking water at which there is no known or anticipated risk to human health; serve as aspirational targets for public health protection, allowing for a margin of safety despite being unenforceable.

National Sanitation Foundation (NSF): An independent organization that tests, certifies, and develops standards for products, including those used in water treatment, to ensure they meet health and safety requirements.

Water Quality Association (WQA): A trade association that represents the residential, commercial, and industrial water treatment industry. It provides education, certification, and standards for industry professionals and products.

These associations and standards serve as a testament to the collective effort and expertise dedicated to ensuring accessibility to safe and clean water. With this foundation of knowledge, let’s draw our glossary to a close and reflect on the importance of understanding and safeguarding our most vital resource.


As we’ve defined water contaminants and filtration, one thing stands out: Knowledge is our best tool. When we understand the challenges posed by different contaminants and choose the right filtration methods, we can bring back the natural purity of water. Whether you’re deciding on a water filter or just learning more about the water you use every day, you can make it cleaner and safer. Let’s value this vital resource, protect against contaminants, and work together toward clean water for everyone.


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