Terminology

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A

• ADSORPTION:  Adsorption is the binding of a molecule to a surface (solid or liquid) by non-specific physical forces.  For example, the removal of free chlorine and chloramines by activated carbon is through the mechanism of adsorption.
   

• AERATION:  A process in which air is intimately mixed with water to remove undesirable gases, such as carbon dioxide and hydrogen sulfide.  Carbon dioxide can be more economically removed from water by aeration than by chemical precipitation or by the use of ion exchange resins.
   

• ALKALINITY:  Capacity of water to accept acid, ordinarily because of its bicarbonate content.  In some cases a part of the alkalinity in water may be due to carbonate, hydroxide, phosphate, or silicate.  It is expressed in terms of mg/l of calcium carbonate.  Total alkalinity is determined by titration with acid to a pH of 4.3.  Methyl orange indicator is frequently used as the end point, but potentiometric titration is preferable.
  If the pH of the water is greater than 8.3, it is probable that carbonate is present.  Carbonate alkalinity is determined by titration with acid to pH 8.3 (phenolphthalein indicator).
   

• ANION:  A particle of matter dissolved in water that has a negative charge.  In each system of matter the number of anions is equal to the number of cations (positively charged ions).
   

• ASYMMETRIC MEMBRANES:  See Membranes.

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B

• BACTERIA:  Bacteria are single cell microorganisms capable of replicating on their own.  They can be divided into two broad categories:  aerobic (requiring oxygen) and anaerobic (not requiring oxygen).  Bacteria can live in a very broad range of habitats.  Some, for example pseudomonads, can thrive in environments containing very low level of nutrients.  These bacteria are frequently slime producers and are a major problem in water treatment systems.  Other bacteria, which adhere to surfaces, secret gelatinous material which serves to protect the bacteria from chemical disinfectants.  This combination of bacteria and their protective coating is sometimes referred to as biofilm.  The concentration of bacteria in water is commonly given in terms of colony forming units (cfu) per ml.  A colony forming  unit is a viable bacterium able to replicate to form a whole colony when incubated in a given environment.
   

• BICARBONATE:  Bicarbonate is formed in water by the reaction of carbon dioxide with mineral matter, such as limestone or dolomite.  The carbon dioxide is absorbed from air or from decaying organic matter, and the bicarbonate that is formed imparts alkalinity to water.  See Alkalinity.  Calcium and magnesium bicarbonate do not exist in solid form.  When water is removed from solutions of these salts, they lose carbon dioxide and form calcium and magnesium carbonate.
   

• BLOWDOWN:  Discharge of water containing concentrated dissolved solids that is replaced by water containing less concentrated dissolved solids.  It is conventionally used in connection with the operation of boilers and cooling towers.  It is also sometimes used as a term for the concentrate from the reverse osmosis process.
   

• BOD:  Abbreviation for Biochemical Oxygen Demand.  It is an empirical test used on wastewater in which organisms capable of oxidizing organic matter are introduced.  The test is not precise.  See COD.
   

• BOUNDARY LAYER:  A very thin liquid layer immediately adjacent to the rejecting surface of reverse osmosis membranes in which the concentration of dissolved solids is higher than it is in the main body of the water being processed.  The phenomenon is known as concentration polarization.
   

• BRACKISH WATER:  Water containing between 1,000 mg/l and 15,000 mg/l of dissolved solids is generally considered to be brackish.
   

• BRINE:  Another term for concentrate.
   

• BRINE SEAL:  A  U-cup of synthetic rubber attached to the upstream end of a membrane element.  It is activated by water pressure to form a joint with the inner surface of the pressure vessel in which the module is placed to prevent water from bypassing around the module.
   

• BUFFER:  A substance or combination of substances that resist a change in pH when an acid or an alkali is added to water in which they are dissolved.
   

• BUFFER SOLUTION:  A solution of salts that is used to calibrate pH meters.  Different combinations of salts are used to prepare buffer solutions with different pH values.

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C

• CALCIUM BICARBONATE:  A salt that is present in most natural waters.  Water containing calcium bicarbonate loses carbon dioxide when it is evaporated or concentrated by reverse osmosis and calcium carbonate is precipitated.
   

• CALCIUM CARBONATE:  Occurs in nature as limestone.  It dissolves in water containing carbon dioxide by forming calcium  bicarbonate.
   

• CALCIUM SULFATE:  Commonly called gypsum.  It is sparingly soluble and precipitates when water is removed from saturated solutions of the salt.
   

• CARBONATE HARDNESS:  See Hardness.
   

• CATION:  A particle of matter dissolved in water that has a positive charge.  In each system of matter, the number of cations is equal to the number of anions (negatively charged ions).
   

• COAGULATION:  A process in which small particles of suspended matter are combined by chemical means into larger particles to effect more rapid settling or better filtration.  The most widely used coagulant is alum.  Other coagulants that are sometimes used are sodium aluminate, ferric chloride, lime and mangnesium oxide.  Polyectrolytes are frequently used as coagulant aids.
   

• COD:  Abbreviation for Chemical Oxygen Demand.  It is a test used on wastewater in which a strong chemical oxidizing agent react with some of the organic matter in the water.  The test is more precise than the BOD test, but it does not measure all of the organic matter in the water.  See TOC.
   

• COLORIMETRIC TITRATION:  A titration in which a change in color is used to measure the end point.
   

• COMPACTION:  A change in the physical structure of RO membranes caused by exposure to excessive pressure and/or temperatures which result in a decreased ability to produce permeate.
   

• CONCENTRATE:  Water that is rejected in the process of reverse osmosis which contains dissolved solids in the water being processed in more concentrated form.
   

• CONCENTRATION POLARIZATION:  See "Boundary Layer".
   

• CONDUCTIVITY:  The ability of an aqueous solution to carry electric current depends on the presence of ions in the solution.  Conductivity is a quantitative measure which describes this ability.  Solutions of inorganic ions are relatively good conductors (and exhibit high conductivity), whereas solutions of organic molecules are rather poor conductors (and exhibit low conductivity).  Highly purified water is also a poor conductor.  Conductivity is expressed in units of Siemen/cm (previously known as mhos/cm).  Conductivity measurements are typically encountered in monitoring the performance of reverse osmosis equipment.  Conductivity is temperature dependent and should be measured with a temperature-compensated meter.  The usual reference temperature is 25ºC.  Conductivity measurements are sometimes used to estimate total dissolved solids in water.  While convenient, this practice is imprecise.  (See also resistivity.)
   

• CONVERSION:  Another term for "Recovery Rate".

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D

• DEIONIZATION (DI):  Use of ion exchange resins to demineralize water.  See Ion Exchange.
   

• DISINFECTION:  Disinfection is the process of killing micro-organisms, usually by one of a variety of chemical agents, such as formaldehyde and sodium hypochlorite.  Disinfection lowers the number of micro-organisms without necessarily killing all those present.  Although total killing of all organisms is virtually impossible, sterilization will reduce the number of organisms to a safe predetermined level.  Sterilization can generally only  be achieved routinely by heat, gamma irradiation, ethylene oxide, and, in certain cases, special filtration.  Of these methods, only filtration is suitable for mass sterilization of water and none is suitable for sterilization of water treatment equipment used in hemodialysis facilities.  However, a proprietary chemical disinfectant incorporating paracetic acid as the active ingredient has recently qualified as a sterilant and this agent may be suitable for sterilization of certain water system components.
   

• DO:  Abbreviation for Dissolved Oxygen.
   

• DRY RESIDUE:  Amount of dissolved solids in water determined by evaporating a sample to dryness and heating.  The heating is usually done at  220°F (105°C)  and at 355°F (180°C).   Dry residue is almost always not equal to total dissolved solids because bicarbonate loses carbon dioxide in the heating process, and some of the dry salts that are formed retain water of hydration.

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E

• EMPTY BED CONTACT TIME:  The empty bed contact time (EBCT) is used as a measure of how much contact occurs between particles, such as activated carbon, and water as the water flows through a bed of the particles.  As the EBCT increases, the time available for particles to adsorb solutes from the water also increases, as does the amount of solute removed from the water during its transit through the bed.  EBCT is calculated from:
                       EBCT = Vm/Q
  Where:  Vm is the volume of particles in the bed and Q is the volumetric flow rate.  A consistent set of units must be used when calculating EBCT with this equation.  For example, if Vm is given in ft³, then Q must be expressed in ft³/min for the EBCT to have units of minutes.  Values of Q can be converted from other units, such as gpm, to ft³/min using the conversion factors given in the flow rates table on the Conversion Factors Page.

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F

• FLOW VELOCITY:  The flow of fluid at any point in a water treatment system may be expressed quantitatively in two ways, either in terms of the volume of fluid passing the point in a given time (volumetric flow rate) or in terms of the velocity with which fluid passes the point (flow velocity).  The flow velocity (V) depends on the geometry of the conduit through which the fluid flows and is related to the volumetric flow (Q) by:
                       V = Q/A
  Where:  A is the cross-sectional area of the conduit.  As an example, Table F.1 shows the volumetric flow rate as a function of flow velocity in PVC schedule 80 pipes of different diameters.  (The values in Table F.1 are based on actual, rather than nominal, pipe diameters.)  Note that for such calculations, it is essential that consistent units be employed.  Thus, the term Q would be expressed as ft³/sec and A as ft² to yield V as ft/sec.

Table F.1 - Volumetric Flow Rates as a function of velocity for schedule 80 PVC pipe

 

• FLUIDIZATION:  A flowing liquid impinging on a bed of particles imparts some of its momentum to each particle.  The imparted momentum is in the direction of the fluid flow.  The particles are held to the floor of their container by gravity and to each other by adhesive forces.  If the fluid flow is upward through the bed of particles, and if the transfer of momentum from the fluid to the particles is sufficient to overcome both the gravitational and the adhesive forces, the particles become suspended, of fluidized, in the fluid stream.
   

• FLUX:  A term that is commonly used for the flow rate of water through reverse osmosis membranes.
   

• FOULING:  Deposition of solid substances on the surface of the reverse osmosis membrane or in ion exchange resin particles.  Fouling can be due to the presence of suspended solids, sparingly soluble salts, or biological growth.  Fouling reverse osmosis membranes causes a decrease in both the amount of water produced and the quality of the water.  The performance of fouled membranes can usually be restored by appropriate cleaning procedures.  Fouling of Ion Exchange resins causes a loss of efficiency and sometimes necessitates replacement of the resins in the beds.
   

• FRENCH DEGREE:  Sometimes used as a unit of measure for any dissolved subtance, but it is most frequently used as a measure of hardness.  It is usually abbreviated as °F, and it is equivalent to 10 mg/l of calcium carbonate.  See Hardness.

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G

• GERMAN DEGREE:  Sometimes used as a unit of measure for any dissolved substance, but it is most frequently used as a measure of hardness.  It is usually abbreviated as °d, and it is equivalent to 17.9 mg/l of calcium carbonate.  "See Hardness".
   

• GRAINS OF HARDNESS:  Although the theoretical hardness of water is the sum of the concentrations of all metallic ions, other than the alkali metals, it is commonly expressed as the equivalent concentration of calcium carbonate in grains.  Ionic concentrations can be expressed in terms of their combining potential (Eq/L), the number of moles present (mol/L), or their masses in any of several conventions.  In the English system masses are expressed in terms of pounds (avoirdupois) which contains 7000 grains each.  Although considered outdated in most of the world, the U.S. water purification industry continues to express hardness in units of grains/gal expressed as calcium carbonate.  Grains/gal expressed as calcium carbonate can be converted into metric units (mg/L) by multiplying the former by 17.1.  Grains/gal expressed as calcium carbonate can also be converted into mEq/L of a univalent ion, such as sodium (Na⁺) by multiplying by 0.342. 
  Note:  Care must be taken in using these conversion factors to size equipment based on ion exchange principles since the ionic content of the water will depnd on the type of ions present as well as their total mass.
   

• GREENSAND:  See "Manganese Zeolite".

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H

• HARDNESS:  Hardness was originally defined as a measure of the ability of water to precipitate soaps made from fatty carboxylic acids.  These "soaps" precipitated in the presence of calcium and/or magnesium ions.  Today, hardness is used to describe the total concentration of calcium and magnesium, expressed as mg/L of calcium carbonate.  It is generally calculated from measurement of calcium and magnesium in ion concentrations using:

Hardness (mg CaCO₃/L) =
2.497 x Ca (mg/L) + 4.118 x Mg (mg/L)

• HOMOGENEOUS MEMBRANES:  See Membranes.
   

• HYDROGEN SULFIDE:  A gas which is more toxic than hydrogen cyanide.  it has an offensive rotten egg odor, and it is present in some ground waters as a result of microbial action on organic matter under anaerobic conditions.  Its odor can be detected at concentrations of a few tenths in an mg/l in water.
   

• HYDROLYSIS:  Chemical degradation of a substance by water that is usually accelerated by acids or alkalies.

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I

• ION:  A charged particle of matter.  In each system of matter, the number of positive ions (cations, such as sodium) is equal to the number of negative ions (anions, such as chloride).
   

• ION EXCHANGE:  Ion exchange is based on the principle of electroneutrality, that is, charged species are stable only when they exist as balanced pairs of positive and negative charges.  Ion exchange resins, the materials used to carry out the process of ion exchange, are particles which contain fixed charges on their surface.  To maintain electroneutrality, each of these charges has an ion of equal and opposite charge held to it; these ions are called counter ions.  The counter ions are mobile and can leave the fixed charge if some other counter ion is available to replace it.  The replacement ion must be of the same charge as the initial counter ion in order to maintain electroneutrality.  The initial counter ion is established by washing the resin with a concentrated solution of the desired counter ion.  For example, softener resins are cation exchangers containing carboxylic acids on their surfaces.  If these resins are washed with strong NaCl solutions, the predominant cation solution is Na⁺ and it will become the counter ion.  In use, the perfusing water will provide competing counter ions, such as Ca²⁺.  Because of the preference of carboxylic acids for Ca²⁺ over the Na⁺ in dilute solutions, the water will be depleted of the Ca²⁺ in exchange for the Na⁺ initially present.
   

• IONIC STRENGTH:  Some properties of dissolved solids, such as the solubility of calcium sulfate and calcium carbonate, are affected by ionic strength.

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J,K

No Terms Currently Listed in This Section.

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L

• LANGELIER SATURATION INDEX:  The precipitation of calcium and magnesium carbonates in water purification systems is a serious cause of system failure.  The insolubility of these compounds is a complex function of the pH of the water, the dissolved carbon dioxide content, the carbonate content, the presence of other salts, and the temperature.  The Langelier Saturation Index is a method of predicting whether or not carbonate deposits will form under given conditions.  Calculation of the Langelier Saturation Index is complex and will not normally be done by hemodialysis personnel.  Reverse Osmosis vendors may use the index in determining the maximum recovery and rejection rates that can be obtained from a reverse osmosis system before carbonate deposits will seriously reduce water quality and recovery. 
  Note:  It should be noted that the utility of such determinations is limited to those situations in which a softener is not used as part of the pre-treatment scheme for reverse osmosis.

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M

• MANGANESE ZEOLITE:  A bed of greensand granules used for the removal of iron and manganese from water.  The greensand is a naturally occurring mineral that has cation exchange properties.  The bed is first treated with manganous chloride to convert it to the manganese form and then it is activated (and subsequently regenerated in repetitive cycles) with potassium permanganate.  In use, soluble iron and manganese in water precipitate on the granules, and these solids are backwashed out of the bed at the end of each cycle.
   

• MATERIALS BALANCE:  The amount of dissolved substances in the permeate plust the amount in the concentrate must equal the amount of the feedwater.  Since the volume of the permeate is a fraction corresponding to the recovery of the feedwater volume rate and the volume of the concentrate is a fraction corresponding to one minus the recovery rate, materials balance is calculated from the equation:

  Materials Balance =

  RCp + Cc (1-r) _______________ Cf

 

• MEMBRANES:  Membranes are thin films made with structures designed to provide selective transport of solutes.  In general, the selectivity of a membrane is based on its ability to pass or exclude species according to their size.  Membrane structures may be homogeneous or asymmetric.  Homogeneous membranes have structures which are uniform in cross-section, at least to a magnification of 100x (Figure M.1a).  Most homogeneous membranes have been developed for Microfiltration and hemodialysis.
  
  Membranes reduce not only the flow of undesired solutes, but also the flow of solvent.  In order to minimize the reduction in solvent flow, asymmetric membranes have been developed.  These membranes are made with asymmetric cross-sections, that is, they consist of two parallel layers (Figure M.1b).  The resistance to flow of the skin layer, which gives the membrane its filtration selectivity, is minimized by reducing its thickness.  The resistance to flow of the thicker support layer, which provides structural strength, is minimized because of its open pore structure. These different layers may be made from the same material, as in asymmetric cellulose acetate membranes, or from different materials, as in thin-film composite membranes.
  
  Membranes used in water treatment equipment are fabricated in two forms, as flat sheets or as hollow fibers. 

Figure M.1.  Structure of homogeneous and asymmetric membranes.

 

• MILLIGRAM-EQUIVALENTS PER LITER (m.e./l):  Calculated by dividing mg/l by the equivalent weight of the ions.
   

• MILLIGRAMS PER LITER (m.g./l):  Equivalent to parts per million (ppm).
   

• METHYL ORANGE ALKALINITY:  See "Alkalinity".
   

• MHO:  Unit of Conductivity.  See "Conductivity".
   

• MICROMHO:  One millionth of a Mho.
   

• MICRO-SIEMENS:  Another term for micromho, the unit of conductivity.

 

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N

• NET APPLIED PRESSURE:  See "Pressure, Net Applied".
   

• NET PRESSURE:  See "Pressure, Net".
   

• NONCARBONATE HARDNESS:  See "Hardness".

 

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O

• OHM:  Unit of Resistivity.  See "Resistivity".
   

• O-RING:  A ring of synthetic rubber that is used as a seal within the connectors to join two or more modules together in a pressure vessel.
   

• OSMOSIS:  A natural phenomenon in which water diffuses through a membrane from a less concentrated solution of salts to a more concentrated solution of salts.
   

• OSMOTIC PRESSURE:  When a solution, such as salt water, is separated from pure water by a membrane which is impermeable to the salt, a flow of water will occur from the pure water to the salt solution.  The driving force for this flow is called the osmotic pressure and its magnitude  depends on the number of salt particles in the solution.
  
  Note that the osmotic pressure depends on the number of particles and not on the total mass of particles. For example, 1 g/L of a small solute, such as sodium chloride, will exert a greater osmotic pressure than 1 g/L of a large solute, such as protein. For water to flow from the salt solution to the pure water this solution must be exposed to a hydrostatic pressure greater than its osmotic pressure.    This is the principle of reverse osmosis. 

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P

• PARTS PER MILLION (PPM): Equivalent to milligrams per liter (mg/l).
   

• PERMEATE:  Water from which most of the dissolved solids have been removed by the process of reverse osmosis.
   

• PH:  Water (H₂O) can dissociate into two ions:  hydrogen (H⁺) and hydroxyl (OH^-).  These ions can also be added to water in combination with other oppositely charged ions.  Thus, a solution of hydrochloric acid added to the water provides both H⁺ and the chloride anion, Cl^-.  The concentration of H⁺ in the water is a measure of water's acidity and the concentration of OH^-, a measure of its alkalinity. 
  
  To simplify quantitation of H⁺ differences, where numbers with a wide range of exponents are encountered, scientists devised a logarithmic scale called pH.  The pH values range from 1 to 14.  A pH value of 7 is considered neutral.  Lower values of pH indicate acidic conditions and higher pH values indicate alkaline conditions.  Because pH is a logarithmic scale, and increase of 1 pH unit corresponds to a ten-fold change in acidity.
   

• PHS:  The pH of water at which it is theoretically in equilibrium with calcium carbonate, i.e., saturated.
   

• POLYELECTROLYTE:  A high molecular weight water soluble polymer containing chemical groups capable of undergoing electrolytic dissociation to give highly charged ions.  Polyelectrolytes often have a synergistic effect when used with coagulating agents.
   

• POTENTIOMETRIC TITRATION:  A titration in which a rapid change in pH is used to measure the end point.
   

• PRESSURE, APPLIED: The pressure in the feedwater supplied by the high pressure pump.
   

• PRESSURE DROP:  Expenditure of a certain amount of energy is required for a fluid to flow through any channel, such as a pipe, particle bed, or membrane.  The pressure at any point is a measurement of the energy content of the fluid at that point.  Since some of this energy is expended in flowing to a second point downstream, the pressure at the downstream point is less than at the original point.  The amount of energy expended, and hence the decrease in pressure (or pressure drop), is dependent on the flow rate and viscosity of the fluid, and the size and shape of the channel.  Pressure drops are usually expressed in terms of lb/in² or psi, or in the SI system, kPa (kilopascals).  Pressure drop is sometimes referred to colloquially as "delta P".
   

• PRESSURE, NET: Net applied pressure minus average osmotic pressure.
   

• PRESSURE, NET APPLIED:  The average of the pressure in the feedwater and the pressure in the concentrate upstream from the pressure control valve.
   

• PRESSURE, EFFECT ON OUTPUT:  RO output varies directly with Net Pressure.

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Q

No terms currently listed in this section.

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R

• RECOVERY RATE:  The percentage of water being processed by reverse osmosis that is produced as permeate.
   

• REJECTION RATE:  When hydraulic pressure is applied to water in contact with reverse osmosis membranes, water diffuses through the membranes and the dissolved solids that were in the water are repelled.  The degree to which they are repelled is the rejection rate.   The rejection rate decreases as the feedwater flows through a reverse osmosis unit because the dissolved solids in it are becoming progressively more concentrated.  The net result is that the overall rejection rate depends upon the average concentration of dissolved solids in the entire unit.  It is calculated from the equation:

  % Rejection =  100 (1.0 -

  Permeate Concentration __________________________ Average Feed Concentration

  )

  However, the average feed concentration is not the arithmetic average of the feed and the concentrate, but rather it is the integrated average composition, which is calculated from the equation:

  I.A.C. =	F.C. x 1n	1 _____ 1-R
  	______________ R

  in which

  I.A.C.	=	Integrated average concentration
  F.C.	=	Feed Concentration
  1n	=	Natural (Naperian) logarithm
  R	=	Recovery rate, as a decimal

  
   

• RESISTIVITY:  Resistivity is a measure of the ability of a substance, such as water, to carry an electric current.  It is expressed in units of ohm-cm and is the reciprocal of conductivity.  Resistivity measurements are commonly used to asses the quality of water produced by deionizers.  Like conductivity, resistivity is temperature dependent and should be measured with a  temperature-compensated meter.   The usual reference temperature is 25ºC.

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S

• SILT DENSITY INDEX:  The silt density index (SDI) is a measure of the ability of water to foul a membrane or plug a filter.  SDI is measured using an apparatus which typically consists of an inlet pressure regulator and pressure gauge followed by a filter holder containing a 0.45 µm microporous membrane filter.  Commercial test kits, complete with instructions on how to calculate the index, are available.  Click Here for More Information on Silt Density Index Products!.
   

• STERILIZATION:  See disinfection.
   

• SUPERFICIAL VELOCITY:  The velocity of a fluid flowing through a tan containing a bed of particles is described in terms of the superficial velocity.  The superficial velocity is defined as the velocity which would be achieved by the fluid if it flowed at the same volumetric flow rate through the tank when it was empty of particles.  Mathematically, the superficial velocity (Vs) is given by:
                      Vs= Q/A
  Where:  Q is the volumetric flow rate and A is the cross-sectional area of the empty tank.  For example, if an ion exchange tank has a cross-sectional area of 640 cm² and water is pumped through it at a rate of 64 cm³/sec, the superficial velocity is 64/640 or 0.1 cm/sec.  The actual velocity at the surface of any particle may be greater or less than the superficial velocity because flow will not be uniform throughout the bed and because the particles occupy some of the cross-section.  Nevertheless, engineers have found it useful to calculate superficial velocities in this manner to aid in estimating mass transfer between a flowing liquid and the stationary surfaces of a particle.  (see also Empty Bed Contact Time.)

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T

• TITRATABLE ALKALINITY:  When certain anions, such as carbonate (CO₃⁼), are dissolved in water, they bind hydrogen ions (H⁺) and thus shift the water equilibrium (see definition of pH) to produce free hydroxyl ions (OH^-).  This excess concentration of OH^- is termed alkalinity.  Titratable alkalinity can be measured by determining the amount of H⁺ (in mEq or mmol) which must be added to water to restore the pH to 7.0, the condition of neutrality where [H⁺] = [OH^-].
   

• TOTAL ORGANIC CARBON:  Organic compounds dissolved in water are characterized by their carbon content.  Total organic carbon is the mass of carbon present in a water sample, excluding the carbon present as CO₂ and/or carbonates.  The values are determined by catalytically oxidizing (burning) all dissolved carbon (after CO₂/CO₃⁼ removal by acidification) to CO₂.  The resulting CO₂ may be measured directly by infra-red absorption, or it may be reduced in a furnace with hydrogen to form methane, which is measured by flame ionization detectors.
   

• TURBIDITY:  Turbidity is a measure of the presence of colloidal matter in the water that remains suspended.  Suspended matter in a water sample, such as clay, silt, or finely divided organic and/or inorganic matter will scatter the light from an incident light beam.  The extent of scattering is expressed in Jackson or Nephelometric turbidity units (JTU and NTU, respectively).

U,V,W,X,Y,Z

No Terms currently listed in this section.

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