Garratt-Callahan is an industrial water treatment company with more than a century of expertise in serving businesses. We’re committed to effective, efficient, and safe water treatment. The following glossary is meant to aid in education about commercial water treatment and is not intended for diagnostic purposes.
Table of Contents
— A —
Opening in natural draft tower used for access to the cold water basin.
Is defined as a ‘suspension’ of microorganisms, both living and dead’ in a wastewater. The microorganisms are active by an input of air (oxygen) thus known as activated-sludge. Activate-sludge is that sludge which settle down in a secondary sedimentation tank after the sewage has been freely aerated and agitated for a certain time in an Aeration tank.
Biological wastewater treatment process used as secondary treatment to remove soluble, colloidal, and particulate (suspended) organic substances. It consists of a reactor receiving a mixture of primary treatment effluent and recycled activated sludge, which is aerated and agitated, promoting the formation of microbially-active, flocculent settleable solids. Upon sedimentation, part of this activated sludge is recycled back into the reactor.
Mechanical process, such as mixing or agitation, by which air comes in close contact with a liquid, allowing the removal of dissolved gases, and the diffusion of atmospheric oxygen responsible for the oxidation of dissolved metals and volatile organic compounds (VOCs).
Chamber in which water is mechanically aerated to promote the diffusion of oxygen from the atmosphere.
Bacteria requiring oxygen for growth and energy production, via aerobic respiration..
Total amount of dry air and associated water vapor flowing through the tower.
Opening in cooling tower through which air enters a tower.
A condition that exists when hot humid exhaust vapor finds its way back to the tower air intake. This happens mostly in forced draft towers operating in enclosed areas.
A measure of the buffering capacity of a liquid solution, or the ability to neutralize acids and bases.
A low form of plant life generally requiring sunlight and air for existence.
A material that will retard or prevent the growth of algae.
The atmosphere adjacent to but not affected by the cooling tower.
Refers to an environment partially or completely depleted of any form of oxygen.
Refers to an environment devoid of dissolved oxygen (DO), but in which other forms of oxygen, e.g. nitrates and phosphates may be present.
The difference between the temperature of the cold water leaving the tower and the wet bulb temperature of the air entering the tower. This determines the lowest temperature to which the tower water can be cooled. Do not confuse with chiller approach—the difference between the exiting condenser water temperature and the condensed refrigerant temperature.
- the arrangement of multiple stages within a system
- effluent from the first stage in an array enters the second stage in the array and so on
- the arrays may be “permeate staged” or “concentrated staged” as described below
One in which air movement through the tower is dependent upon atmospheric conditions, rather than induced by mechanical fans.
— B —
Microscopic, unicellular prokaryotic organisms that lack nuclear membrane, divide through binary fission, and exist in different shapes, e.g. spherical, rod-shaped or spiral.
A material that will retard or prevent the growth of bacteria.
Refers to an in-situ bioremediation process through the addition of biomass from activated sludge for the enhanced degradation contaminants or pollutants.
The amount of oxygen consumed by the biomass present in a unit volume of sample over five days, under aerobbic conditions, and expressed in milligrams of oxygen per liter.
General term for algicides, bactericides, and fungicides.
Process by which microbial activity causes the oxidation of chemical compounds, e.g. pollutants.
The tower water sent to waste to control the concentration of dissolved solids in the remaining tower water.
A small side wall drum, either a circular or rectangular cross section, into which tubes are rolled.
By definition, the generation of 34.5 lbs steam/hour from and at 212oF. By common acceptance, 10 square feet of heating surface is one rated boiler horsepower. For developed horsepower, however, use the 34.5 lbs steam/hour figure.
Those deposits precipitated from solution at the boiler tube surface.
Solid matter from boiler water which precipitates throughout the body of water and not at the tube surface. Such deposits may drop down on the surfaces and remain, but they are not formed there.
BTUs are the amount of heat required to raise the temperature of 1 pound of water 1 degree Fahrenheit at or near 39.2oF. Calorie is a similar measure of the heat needed to raise one gram of water one degree centigrade at a pressure of one atmosphere.
The quantity of heat required to raise the temperature of 1 pound of water 1 degree Fahrenheit.
— C —
The amount of water in a cooling tower system at any given time.
Carryover is the process whereby liquid boiler water is physically entrained with the steam and passes off into the steamline. A general term applied to the result of either foaming or priming.
The vertical enclosing sidewall of a tower, excluding the louvers.
Width: dimension perpendicular to tower longitudinal axis and usually at right angles to the louver area; Length: dimension parallel to longitudinal axis and the plane where louvers are usually placed; Height: distance from basin curb to top of fan deck, but not including fan stack. Nominal width and length are measured from and to the column centerlines.
The volume of water that is pumped over a tower measured in gallons per minute. It is the capacity of the
The effective circulation rate based on the heat load when the average ∆T is not 10oF.
The disinfection method consisting of adding chlorine or other chlorinated compounds, e.g. chloramines, to water.
The process by which a positively charged chemical (coagulant) is added to water to destabilize the charge on colloids and suspended solids, thus promoting the clumping of fine flocs into larger flocs, and accelerating the settling process.
A device beneath the tower to receive the cold water from the tower and direct its flow to the suction line or sump.
The lowest portion of the basin that has been deepened to accommodate submerged pumps.
A sample consisting of individual grab samples collected over a specific period of time.
- effluent with dissolved solids
- high in dissolved solids
- sometimes called “reject” water (if it is not the stream of interest)
- may be the stream of interest (process applications, e.g., juice concentration, dairy processes, etc.)
Condensed steam, usually recirculated back to the boiler.
Transfer of heat to boiler tubes by hot gases passing over the tubes.
The ratio of water being pumped over the tower to the amount of air being forced through the tower.
The number of degrees water is cooled while falling through a cooling tower. Also commonly referred to as Delta T (∆T), or change in temperature.
A device for the evaporative cooling of water by contact with the air.
A tower in which air is drawn or forced in through the air intakes by the fan, flows horizontally across the fill section and mixes perpendicularly with the falling hot water.
A tower in which air is drawn in through the louvers (induced draft) or forced in (forced draft) at the base by the fan. It flows upward through the fill material and mixes countercurrently with the falling hot water.
See Cold Water Temperature.
The number of times the tower water has been concentrated. It is measured by the ratio of dissolved solids in the tower water to those in the makeup. Chlorides are measured in preference to other dissolved solids unless chloride containing chemicals are being added to the system.
— D —
See Dry Bulb Temperature.
Deaerating or Closed Heater
Feedwater heater runs above make up temperatures and is vented so that gases can escape.
Water that has gone through a dual unit softener where all cations are exchanged for sodium and all anions exchanged for chloride and hydroxide. The total solids will be the same as before, but they will be virtually all sodium chloride. The silica content will not be greatly affected.
Deionized or demineralized is water from which all mineral content has been removed by ion exchange.
Defined as the combination of hot water temperature (HWT), cold water temperature (CWT), gallons per minute (gpm), and wet bulb temperature (WBT) in mechanical draft towers. In natural draft towers: HWT, CWT, gpm, and WBT, plus either dry bulb temperature (DBT) or relative humidity (RH).
The area in the cold water basin, usually at a low point, where silt can be flushed to a drain.
A device for removing all or part of the superheat from steam by spraying water into it or by use of a heat
- the pressure difference between the initial feed stream and the final reject (concentrate) stream
- ∆P provides the driving force to move water across the membrane surfaces
- if flows are constant ∆P will not change unless scaling, or fouling physically blocks the membrane
- monitoring ∆P across each stage of the system can help pinpoint problems, often isolating them to a single stage, pressure vessel or element
Aeration method consisting of pumping air through a pipe or tubing and releasing it though a diffuser below the water’s surface.
Water treatment process in which air and pressurized water are mixed, leading to the formation of microbubbles that adhere to coagulated flocs of suspended materials, thus increasing their buoyancy. The resulting floating bed of sludge can then be mechanically skimmed at the surface of the water to obtain a cleaner discharge water.
Amount of oxygen dissolved in liquid, and measured in milligrams oer liter.
Dissolved combined content of organic and inorganic substances within a liquid in an ionized, molecular and colloidal or suspended form.
A shallow pan-shaped basin used to distribute hot water over the tower fill.
One used in conjunction with the manifold and valve assembly in a cross flow tower to disperse the hot water uniformly in all directions, thereby increasing the effectiveness of the distribution nozzles.
See Nozzle and next entry.
Those parts of a tower, beginning with the inlet connection, which distribute the hot circulating water within the tower to the points where it contacts the air. In a counterflow tower, this includes the header, laterals, and distribution nozzles. In a crossflow tower, the system includes the header or manifold, valves, distribution box, basin pan, and nozzles.
ALSO: The method of spreading the hot water uniformly over the top of the tower.
Water lost from the tower as liquid droplets entrained in the exhaust air. It is independent of water lost by
A valve on top of the top drum of the boiler, used to vent air from drum on boiler startup, and opened when boiler is
cooling down to prevent a vacuum in the drum.
The temperature of the inlet or ambient air adjacent to the cooling tower, as measured by a dry bulb thermometer.
— E —
A tube bank that is not part of the boiler circulation but is used to heat feedwater before it enters the boiler drum. Cooler gases heat it after these gases have gone through the boiler tube sections.
The outflowing gas or liquid from a natural or man-made reactor.
A unit for production of steam by heating water either with electrical resistance elements or by passing an AC current through the water between electrodes.
See Drift Eliminator.
A term used to express the amount of heat transfer per unit area expected from a heating device using a particular fluid medium.
Average wet bulb temperature of the entering air. Includes any effects of recirculation.
Rod-shaped, Gram-negative bacterium in the family Enterobacteriaceae, which inhabits the lower intestines of warm-blooded animals, and is released into the environment via faeces and/or wastewater effluent.
Water evaporated from the circulating water into the atmosphere by the cooling process.
The volume of water being evaporated to cool the remaining water measured in gallons per minute.
The evaporation of a portion of the cooling tower water in order to lower the temperature of the remaining water.
Average wet bulb temperature of the air discharged from the tower.
Temperature of the circulating water leaving the cold water basin.
Diameter of the shell at the top in the hyperbolic natural draft tower.
— F —
A device for moving air in a mechanical draft tower. The fan can be applied as induced draft or forced draft.
The structure supporting and enclosing the fan in an induced draft tower.
- water entering the membrane
- Contains dissolved solids
- Has (or should have) gone through extensive pretreatment
Somewhat similar in its usage to the term steam header. A feed pump that supplies water to one boiler is usually called a feedwater line, but if the line branches off and supplies several boilers, it is often called a feedwater header.
A trough in the upper drum used to distribute feedwater along the drum. Usually just above normal water level.
The narrow boards or plastic slats placed inside the tower to intercept the falling water. The resultant splashing exposes new water surfaces to the air, and thus increases the efficiency of heat and vapor transfer from water to air. That part of a crossflow, counterflow, or natural draft tower consisting of splash bars, vertical sheets of various configurations, or honeycomb assemblies, tile, or other materials, that are placed within the tower to effect heat and mass transfer between the circulating water and the air flowing through the tower.
The assembly of splash bars comprising the tower filling. Fill bars intercept the downward fall of water at regular intervals, forming splash surfaces that cause water drops to break into smaller droplets, providing wetted surfaces for air-water contact.
A valve actuated by a float, generally used to control makeup water supply.
Mass resulting from the precipitation or aggregation of suspended particles.
- may refer to feed, permeate, or reject
- typical units are gallon per minute (gpm); cubic meter per hour (m3/h)
- MGD (million gallon/day) is also common
A manually controlled valve generally located in the hot water supply line.
- permeate flow/membrane area
- gallons per square foot per day (gfd)
- liters per square meter per hour (1/m2h)
A trough that may be either totally enclosed or open at the top. Flumes are sometimes used in cooling towers to distribute the hot water over the fill.
A type of mechanical draft tower in which one or more fans are located at the air inlet to force air into the tower.
— G —
Tubes that are subject to high convection or radiant heat and in which steam is generated. The water-steam mix rises in these tubes toward the top drums or steam headers.
A solid to semi-solid product of dispersion of a thickening agent in a liquid lubricant, including fats, waxes, and free fatty acids, among others.
Gallons per minute.
Heavy mineral material found in raw, untreated wastewater, and consisting of gravel, sand, broken glass, fragments of metal and inorganic solids.
— H —
In a counterflow tower, the main pipe carrying hot water to a series of laterals for distribution over the fill
The amount of heat dissipated in a cooling tower, measured in BTU per minute.
Temperature of circulating water entering the distribution system.
A cooling tower of hyperbolic shape that depends
— I —
A type of mechanical draft tower in which one or more fans are located in the air outlet to induce airflow throughthe air inlets.
The average of the wet bulb temperature obtained from several stations located on both the windward and leeward sides of the tower.
Chemical compounds with no elemental carbon, and no Carbon-Hydrogen bonds. Inorganic materials are the building blocks of non-living things, e.g. salts and metals, while organic materials are present in all living organisms.
Introduction of harmful microorganisms in drinking water systems.
— L —
An equilibrium index developed to indicate the saturation (i.e., scaling or dissolving) characteristics of calcium carbonate in water.
LSI = pH – pHS
The sloping boards on the outside of the tower that allow air in and prevent spray from escaping.
— M —
Water added to the circulating water system to replace water lost from the system by evaporation, drift,
blowdown, and leakage.
The water required to replace the water lost to evaporation, drift and bleed, usually measured in gallons per minute.
Names for tubes where the circulation is in a downward direction. These tubes are not in the hot gases, and the boiler water goes down through them to supply generating tubes. Steam is not generated in these tubes.
Opening in a drum which permits a person to crawl in for inspection.
A tower through which air movement is effected by one or more fans.
A filtering equipment using three or more different media in series, in contrast to single medium filter, e.g. coal and sand.
The bottom drum of a water tube boiler. A blowdown line is normally taken off this drum for removal of mud and sludge and for emptying the boiler.
These arrange pressure vessels filled with membrane elements in such a way as to maximize the quantity of pure water produced. The concentrated “reject” water from the first stage becomes the feed to the second stage. The first stage usually has twice as many pressure vessels (and membrane elements) as the second stage. These are the most common types of systems and are often seen in power generation and desalination applications.
These arrange pressure vessels filled with membrane elements in
such a way as to maximize the quality of pure water produced. The purified “permeate” water from the first pass becomes the feed to the second pass. The first stage/pass usually has twice as many pressure vessels (and membrane elements) as the second stage/pass. These systems are commonly found in the microelectronics industry where the purity of rinse water is essential to production. Three-pass systems are the most common.
— N —
One in which air movement is dependent upon the difference in density between the entering air and the internal air. As the heat of the water is transferred to the air passing through the tower, the warmed air tends to rise and draw in fresh air at the base of the tower. No fan is needed.
NDP:(Net Driving Pressure)
- pressure that forces water through the membrane
- net driving pressure is the feed pressure, minus the permeate backpressure, minus the osmotic pressure
- NDP = P feed – P perm – π ,where π is the osmotic pressure of the feed solution
- in systems open to the atmosphere, permeate back-pressure is negligible
- for most brackish water systems, osmotic pressure (π) is also negligible
- for seawater systems or other highly concentrated brines, π becomes an important factor
Microbial process by which reduced nitrogen compounds (primarily ammonia) are sequentially oxidized to nitrites and nitrates.
One of the primary nutrients critical for the survival of all living organisms, and present in the environment as ammonia (NH3), nitrates (NO3-) and nitrites (NO2-).
Biogeochemical process through which nitrogen passes from the atmosphere to the soil to organisms and back into the atmosphere. It involves several processes such as nitrogen fixation, nitrification, denitrification, decay and putrefaction.
Width and length measured from and to column centerline or walls; height measured from basin curb to top of fan deck (counterflow design) or to top of distribution basin (crossflow design). Dimensions measured in feet.
- this mathematically corrected version of flow takes into account changes in pressure, temperature and osmotic pressure.
- used to compare sets of data on an equal basis
- comparing data without the normalization step can lead to poor conclusions
- drop in NPF generally indicates membrane fouling or scaling
- increase in NPF generally indicates membrane or system damage
Nutrients are elements that are essential for plant growth. They include nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S) and silicon (Si). N, P and K are considered primary nutrients. N and P are the major limiting nutrients in most aquatic environments.
— O —
A heater where feedwater is heated by steam, but the temperature does not go above the boiling point.
Biodegradable material originally produced by living organisms (plant or animal) that is returned to the soil and goes through the decomposition process.
See Organic Matter.
A negatively charged ion (anion) composed of one phosphorus atom and 4 oxygen atoms (PO43-), which measurement in natural waters is used to evaluate the nutrient load of the system. Also used as corrosion inhibitors in iron, copper, and lead water pipes.
Width: overall dimensions perpendicular to the tower’s longitudinal axis; Length: overall dimensions parallel to the air inlet louvers and the longitudinal axis; Total height: distance from basin curb to top of fan stack. Dimensions measured in feet.
Refers to an environment in which oxygen is present.
A process involving the transfer of electrons from an oxidizing reagent to the chemical species being oxidized. In water and wastewater engineering, chemical oxidation serves the purpose of converting putrescible pollutant substances to innocuous or stabilized products.
Large, shallow ponds designed to treat wastewater through the interaction of sunlight, bacteria, and algae. Algae grow using energy from the sun and carbon dioxide and inorganic compounds released by bacteria in water.
— P —
The percent of time that the cooling equipment is online or the percent of maximum capacity at which the equipment is operated. This can be estimated from hours of operation or average Delta T.
- purified (recovered) effluent stream
- low in dissolved materials
- sometimes called “product” water
Defined as the logarithm of the reciprocal of the hydrogen ion concentration. pH is a measure of the acidity or alkalinity of a water solution, with 7.0 as the neutral point. This is an exponential function, so that a pH of 9.0 represents 10 times as much alkalinity as a pH of 8.0. This is also a measure of the ion concentration, not molecular concentrations.
An equilibrium pH value used in calculating the scaling indexes (LSI, RSI, PSI). It uses the values of TDS (expressed from μmhos – to convert μmhos to a TDS value for cycled cooling water, multiply the μmhos by 0.8); Temperature (the highest temperature that the cooling water is exposed to); Calcium Hardness, and Total Alkalinity. Often the only temperature information available is the bulk water temperature which is not the highest temperature in the system. A skin temperature value should always be used when known. If the skin temperature is not known, we add a “safety factor” of 20° F to the maximum bulk water temperature (up to 115° F). If the bulk water temperature is greater than 115° F, then we use that value to determine the temperature factor. Lookup tables of factors for each of the four parameters are used to obtain the values used in the formula:
pHS = (9.3+A+B) – (C+D)
A measure of the quantity of hydrogen ions in solution that gives an indication of the acidic or alkaline properties of a sample.
An instrument that operates on the principle of differential pressure. Its primary use in cooling towers is the measurement of circulating water rate.
Visible exhaust from a cooling tower.
Water that meets the required (chemical, biological and physical) quality standards at the point of supply to the users, and is considered safe for drinking, food preparation, personal hygiene and washing.
Polymer of electrolytes with several repeating chain units. Polyelectrolytes have properties of both electrolytes and polymers, and have a high molecular weight. Often used as coagulant aid in wastewater treatment or to reduce or prevent corrosion on metallic substrate surfaces.
Pounds per Square Inch
A modification of the Ryznar Stability Index developed in 1983 by Brooke and Puckorius using water analysis data from operating cooling towers (as opposed to municipal waters). While very similar to the RSI as an equilibrium index for calcium carbonate saturation, it uses a new value, pHeq, the equilibrium pH which was developed from these studies.
pHeq = 1.465 x log10 (Total Alkalinity) + 4.54
PSI = 2pHS – pHeq
- the hard sided vessel (usually stainless steel, PVC, or fiberglass) that holds membrane elements
- typical pressure vessels house 3 to 7 membrane elements
— R —
Transfer of heat from flame to boiler tubes by radiation. This does not require any actual contact of gases with tubes, but requires only that the tubes see the hot luminous flame. Furnace tubes are subject to this type of heating.
Difference between the hot water temperature and the cold water temperature, also known as cooling range. Range is the number of degrees water is cooled while falling through a cooling tower. Also commonly referred to as Delta T (∆T), or a change in temperature.
Water as received in the plant before any treatment.
Any untreated water which quality has been adversely affected by humans and comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture.
Delineated space in which chemical, biological and physical processes occur in nature. Lakes, segments of a river, and settling tanks in treatment plants are examples of reactors.
Bodies of water such as an ocean, stream, river, pond, lake into which treated or untreated wastewater is discharged.
- Percent of salts removed by the membrane
- Alternative measure: Salt Passage (SP = 100 – %Rej)
- Maximum rejection of total dissolved solids (TDS) is desired
The time required for the tower water to fall from the top distribution system to the tower basin. (Not to be confused with the time that a slug-fed chemical remains in the system before its level is reduced to a certain point by loss due to bleed.)
See ‘Return Sludge.
Piping that connects the circulating water supply line from the level of the base of the tower to the supply header of the tower inlet connection
An equilibrium index developed to indicate the saturation (i.e. scaling or dissolving) characteristics of calcium carbonate in water. Developed from an empirical study of the Langelier Index.
RSI = 2pH – pHS
— S —
That temperature at which water boils is fixed for each pressure and may be obtained from steam tables.
- a plugging factor used to determine the amount of particulate matter entering your RO
- in an ideally operating system, the 15-minute SDI should be less than 3
- poor technique can cause highly variable readings
Biological treatment aimed at removing fine suspended solids and dissolved biodegradable organic matter that remains in wastewater after primary treatment, and enhanced by addition of external or recycled living biomass.
A vessel where suspended particles settle out of water or wastewater as it flows slowly through the tank; also called settling tank or clarifier.
Adversely impacted water discharge from human activities, most commonly referring to the effluent from human habitations.
Pipe distribution systems used to collect domestic wastewater from habitations, industrial wastewater from industries, and stormwater run-off from the environment, to a point of treatment and disposal.
Solid, semisolid, or slurry residual material that is produced as a by-product of wastewater treatment processes.
Represents how long biomass remains in the system. It is defined as the ratio of mass of biomass in the aeration tank to the mass of biomass leaving the system per day.
Wastewater treatment facilities with a large number of primary clarifiers often employ a concrete tank with chambers and gates known as a splitter box, or distribution box, to split the influent flow into multiple streams that are routed into the bank of clarifiers. A similar device may also be used to split mixed liquor flows between secondary clarifiers.
Horizontal component of a fill deck that constitutes the principle splash surface.
- a group of membrane pressure vessels running in parallel
- most systems contain multiple stages arranged to provide either maximum permeate volume or maximum permeate purity
Any device for production of steam under pressure through firing with some form of fuel (gas, coal, oil, wood, etc.).
Tubes extending between two drums of a boiler, above the water line. These carry steam, not boiler water.
The upper drum of a water tube boiler where final separation of the liquid and vapor states occurs. The steam outlet line almost always takes off from this drum.
This term is often applied to a large steamline which is fed by several boilers or which has several take off lines.
A device or structure at the top inside of the steam drum which is used to prevent water passing over with the steam.
A bank of tubes (not part of the boiler water circuit) used to heat steam above the saturation temperature. These tubes take steam from the boiler drum, heat it with combustion gases, and the superheated steam goes then to the process. Such tube banks are usually just behind the first generating tube bank.
Small solid particles which remain in suspension in water as a colloid or due to the motion of the water.
Portion of the water supply system from which riser or inlet connection receives the circulating water flow.
— T —
Tertiary treatment is designed to filter out nutrients and waste particles which could negatively impact sensitive or protected ecosystems.
Total solids is the term applied to the material residue left in a vessel after evaporation of a sample and its subsequent drying in an oven at a defined temperature (either 103°C or 180°C) Total solids includes total suspended solids, the portion of total solids retained by a filter, and total dissolved solids, the portion that passes through a 2-um filter.
- the stages in a single array are sometimes called a train
- Large installations have multiple, redundant trains to allow for off-line cleaning and/or repairs to one train without losing production
A flat plate in a fire-tube boiler into which tubes are rolled.
Measure of the relative clarity of a liquid. It is a measurement of the amount of light scattered by materials in the water when a light is shined through the water sample. The higher the intensity of scattered light, the higher the turbidity.
A maintenance term for a regularly scheduled shutdown to clean the tower and make any necessary repairs to system equipment.
— U —
That part of the boiler structure where the gases leave the boiler.
— W —
Usually part of the furnace wall. Always a riser.
Water contaminated by various effluents from human origins.
An enclosed, steady flow device for cooling water by evaporation through direct contact with air.
Circulating water flow expressed in gallons per minute (gpm) per square foot of effective horizontal wetted area of the tower. Measured in gpm per square foot.
Release of substances into subsurface groundwater or into lakes, streams, rivers, estuaries, and oceans to the point where these substances interfere with the beneficial use of the water or with the natural functioning of ecosystems.
A wet (evaporative) cooling tower in combination with a dry (nonevaporative) heat exchanger system, used to reduce or abate cooling tower fog during cold weather by modifying the tower exhaust air condition.
Allowable pressure for a given boiler. This is not necessarily the operating pressure. Operating pressure is less than or equal to the working pressure.
— Y —
A type of fungi that can grow on various types of organic matter, including food, plants, and animals. Yeasts are unicellular organisms that typically ferment sugars and produce alcohol and carbon dioxide, while molds are multicellular organisms that grow as a network of thread-like structures called hyphae. Both yeasts and molds can be beneficial or harmful, depending on the context in which they are found.
- Access Tunnel
- Acid Descale
- Activated Sludge
- Activated Sludge Process
- Adiabatic Cooling
- Aeration Tank
- Aerobic Bacteria
- Air Inlet
- Air Recirculation
- Air Separator
- Air Washer
- Ambient Atmosphere
- Ambient Wet Bulb Temperature
- Anaerobic Bacteria
- Anodic Reaction
- Atmospheric Pressure
- Atmospheric Tower
- ATP (total and free)
- Basin Sump
- Bioaugmentation (Secondary Treatment)
- Biochemical Oxygen Demand (BOD)
- Biological Oxidation
- Blowdown or Bleed
- Boiler Header
- Boiler Horsepower
- Boiler Scale
- Boiler Sludge
- British Thermal Unit (BTU)
- Bulking Sludge
- Cathodic Reaction
- Cell Dimensions
- Chemical Oxygen Demand (COD)
- Chiller Tube
- Circulation Rate (CR)
- Circulation Rate, Load Corrected (CRc)
- Closed Loop
- Cold Water Basin
- Cold Water Temperature (CWT)
- Cold Well (or Sump)
- Coliform Organisms
- Combined Sewer
- Composite Sample
- Condensate Tank
- Convection Heat Transfer
- Cooling Factor
- Cooling Range
- Cooling Tower
- COP (Coefficient of Performance)
- Corrosion Cell
- Corrosion Coupon
- Corrosion Inhibitor
- Counterflow Tower
- Crevice Corrosion
- Crossflow Tower
- Crystal Modification
- Cycles of Concentration
- Dealkalized Water
- Deionized or Demineralized Water
- DeltaT (∆T)
- Design Conditions
- Desilting Sump
- Dew Point Temperature
- Differential Pressure (∆P or “delta p”)
- Diffused Air
- Diffusion Deck
- Dissolved Air Flotation
- Dissolved Oxygen (DO)
- Dissolved Solids
- Distribution Basin
- Distribution Box
- Distribution Nozzle
- Distribution System
- Double Flow Water Cooling Tower
- Drift Eliminator
- Drift, Windage Loss, or Carryover
- Drum Vent
- Dry Bulb Temperature
- Electric Boiler
- Eliminator Board
- Entering Wet Bulb Temperature
- Environmental Debris
- Equivalent Direct Radiation (EDR)
- Erosion Corrosion
- Escherichia Coli
- Evaporation Loss
- Evaporation Rate
- Evaporative Condenser
- Evaporative Cooling
- Exhaust Wet Bulb Temperature
- Exit Basin Temperature
- Exit Diameter
- Expansion Tank
- Extended Aeration
- Facultative Bacteria
- Fan Deck
- Feedwater Header
- Feedwater Trough
- Fill Bars
- Fill Deck
- Fill or Packing
- Float Valve
- Flow Control Valve
- Fluid Cooler
- Fluorescent Tracer
- Forced Draft Water Cooling Tower
- Galvanic Corrosion
- Generating Tubes (Risers)
- GPM (gpm)
- Head pressure
- Heat Exchanger
- Heat Load
- Heat Load or Tower Capacity
- Hot Deck
- Hot Water Temperature (HWT)
- HTI (Holding Time Index)
- Hyperbolic Induced Draft Water Cooling Tower
- Induced Draft Water Cooling Tower
- Inlet Wet Bulb Temperature
- Inorganic Material
- Langelier Saturation Index (LSI)
- Larson-Skold Index
- Latent Heat
- Lateral Header
- Legionnaire’s Disease
- Makeup Rate
- Makeup Tube, Downcomer, Supply Tube
- Makeup Water
- Mechanical Draft Water Cooling Tower
- Microbiologically Influenced Corrosion (MIC)
- Mixed Liquor
- Mixed Liquor Suspended Solids (MLSS)
- Mixed Media Gravity Filter
- Mud Drum
- Multiple Pass (or Permeate Staged) Systems
- Multiple Stage (or Concentrate Staged) System
- Natural Draft Water Cooling Tower
- NDP (Net Driving Pressure)
- Net Positive Suction Head (NPSH)
- Nitrogen Cycle
- Nominal Tower Dimensions
- Nonoxidizing Biocide
- NPF (Normalized Permeate Flow)
- Open Feed Water Heater
- Organic Material
- Organic Matter
- ORP (Oxidation-Reduction Potential)
- Overall Tower Dimensions
- Oxidation Ponds or Lagoons
- Percent Load (% Load)
- pH of Saturation (pHS)
- pH Value
- pHeq (pH of Equilibrium)
- Pitot Tube
- Pitting Corrosion
- Plate and Frame Heat Exchanger
- Potable Water
- Practical Scaling Index (PSI) (a.k.a. Puckorius Scaling Index)
- Pressure Vessel
- Primary Waste Treatment
- PSI (psi)
- PSIG (psig)
- Psychrometric Chart
- Radiant Heat Transfer
- Raw Wastewater
- Raw Water
- Receiving Waters
- Redistribution Basin
- Retention Time
- Return Activated Sludge
- Return Sludge
- Reverse Osmosis
- Riser (Generating Tubes)
- Ryznar Stability Index (RSI)
- Sacrificial Anodes
- Saturation Temperature
- Scale Inhibitor
- SDI (Silt Density Index)
- Secondary Waste Treatment
- Secondary Waste Treatment (Bioaugmentation)
- Sedimentation Tanks
- Shell & Tube Heat Exchanger
- Sludge Age
- Sludge Digestion
- Sludge Index
- Sludge Reaeration
- Softened Water
- Specific Conductance
- Specific Heat
- Splash Bar
- Splitter Box
- Stage Heater
- Steam Boiler or Steam Generator
- Steam Circulator Tubes
- Steam Drum
- Steam Header
- Steam Separation or Steam Scrubber
- Steam Trap
- Stress Corrosion
- Supply Header
- Suspended Solids
- Tertiary Waste Treatment
- Thermal Capacity
- Thermal Storage System
- Threshold Inhibition
- Total Dissolved Solids
- Total Solids
- Trickling Filter
- Tube Sheet
- Wall Tube
- Waste Activated Sludge
- Waste Treatment Sludge
- Water Cooling Tower
- Water Loading
- Water Pollution
- Wet Bulb Temperature
- Wet Dry Tower
- White Rust
- Working Pressure
- Yeast & Molds