Project: BAJO Grande AQUATECH INTERNATIONAL CORPORATION
Client: Solidaris, LLC. AQUATECH PROJECT # P-00149
1.3 Common Terminologies
Acids A large class of chemical substances whose water solutions have the ability to react with
cation resins to regenerate exhausted resins which permits the resin to be used over and over
again. Acids are also used to lower the pH of waste water to a desired range, (typically 7±1).
Acids utilized in Aquatech processes are hydrochloric (20° Be HCl) or sulfuric 66° Be H2SO4
technical grade. pH of acids is less than 7.0.
Air Scour - Air enters bottom head of pressure vessel and flow through the strainer plate
nozzles evenly distributed through the vessel’s media. Air agitates the media loosening any
compacted media by breaking any crust formed due to solids.
Anion An ion having a negative charge like sulfate (SO4-), carbonate (CO3-) hydroxide (OH-), and
chloride (Cl-), etc.
Alkalinity capacity of water to neutralize acids, a property imparted by the water's content of
carbonate, bicarbonate, hydroxide, and on occasion borate, silicate, and phosphate. It is
expressed in milligrams per liter of equivalent calcium carbonate (mg/l CaCO3).
Anti-Scalant – is a chemical agent added to the RO feed water to inhibit the precipitation or
crystallization of salt compounds.
Backwash - During the service cycle, the filter media bed collects some suspended impurities
from the water. Some of the media particle/beads breakup into fines and the bed becomes
somewhat compacted. Introducing water at calculated flow rates in the opposite direction to
the service flow lifts the bed that loosens and expands into the free board provided for the
purpose, forcing the suspended particles and the media fines out of the unit. At the same time,
the bed loses its compaction, reducing the chances of channeling that could cause water to
bypass some of the effective media bed. Compaction and fines also cause excessive pressure
drop. Water for the same quality as the influent is introduced from the bottom of the vessel and
is collected at the top and then is directed to the drain. Proper backwash rate is of great
importance since higher than the suggested rate may cause media loss and the lower rate
may not be sufficient to do the proper backwash. Any sudden shock in the backwash cycle
should be avoided, since this may cause media loss.
Bases The opposite of acids with pH > 7.0 and is used to regenerate anion resins and to
upwardly adjust the pH of waste water to the desired level. The Aquatech process uses sodium
hydroxide (50% NaOH) rayon grade.
Biocides chemical agents with the capacity to kill biological life forms. Bactericides,
insecticides, pesticides, etc. are examples
Brackish Water – is water in which the dissolved solids contents fall between that of drinking
water and sea water. Generally the TDS range is 1,000 to 10,000 ppm.
Cation An ion having a positive charges like calcium (Ca++), sodium (Na+), Magnesium (Mg++),
Iron (Fe+3), and Hydrogen (H+).
Page 1 of 7
Project: BAJO Grande AQUATECH INTERNATIONAL CORPORATION
Client: Solidaris, LLC. AQUATECH PROJECT # P-00149
1.3 Common Terminologies
Capacity of a resin is the amount of ions exchanged per regeneration to a selected point, i.e. 20
Kilogram capacity per cubic foot at 8 pounds regenerant per cubic foot dosage. Means that 1
cubic foot of the resin when regenerated with 8 pounds of regenerant would exchange ions
equivalent to 20 Kilograms of calcium carbonate providing a treated water of the selected quality
Chlorination – the addition of small amounts of free chlorine to water for the purpose of killing
harmful microorganisms
Chemical precipitation: (1) the process of utilizing chemicals to produce a separable solid
phases within a liquid medium; in analytical chemistry, precipitation is used to separate a solid
phase in an aqueous solution. (2) The process of softening water by the addition of lime and
soda ash as the precipitants
Conductivity The property of a substance (water) that describes it ability to transfer electricity.
It is the inverse of resistively.
Quality of Water Obtained From Various Sources
Quality (Electrical
Type of Water Resistance In Terms Of
Megaohms-cms.)
Theoretical maximum quality (calculated) 26
Water after 28 distillations in quartz 18.3 25° C
Water treated by strongly acidic-strongly based system 18
Water after three distillations in quartz 2
Water after three distillations in glass 1
Water in equilibrium with the carbon dioxide in the atmosphere 0.7
Water after a single distillation in glass 0.5
Approximate quality of U.S.P. distilled water * 0.1
* The US Pharmacopoeia specifies that USP distilled water must not contain more that 5 ppm
total dissolved solids.
Concentration in solutions, the mass, volume, or number of moles of solute present in
proportion to the amount of solvent or total solution Common measures are: molarity,
normality, percent, molality, and by specific gravity scales.
Dechlorination process a process by which excess chlorine is removed from water to a
desired level. Usually accomplished by chemical reduction through sodium bisulfite, by
passage through carbon beds or by aeration at a suitable pH.
Displacement (Slow) Rinse The process of displacement of regenerants and the eluted ions
from the resin is started at a slow pace, normally at the same rate as the dilution flow of the
regeneration injection. This not only displaces the regenerants through and out of the resin, but
also provides a few more minutes of contact time.
Page 2 of 7
Project: BAJO Grande AQUATECH INTERNATIONAL CORPORATION
Client: Solidaris, LLC. AQUATECH PROJECT # P-00149
1.3 Common Terminologies
Exhaustion/ Regeneration An ion exchanger exchanges ions dissolved in the influent water
with the active ions in its resin, i.e., a zeolite softener unit exchanges calcium and magnesium with
sodium. This slowly reduces the concentration of available active ions. The resin is termed as
exhausted when the active ion concentration reaches a low level and effluent has a pre-selected
high leakage of un-exchanged ions, known as end point leakage. Using sodium chloride, the
exhausted resin is regenerated, bringing back the level of active ion concentration.
Fast Rinse After the slow rinse the resin is rinsed further at a higher flow rate. Rinsing removes
excess regenerant from the resin, at the same time all the eluted ions are displaced from the resin
bed, bringing the resin back to active condition, ready to be put into service.
Fouling the process in which undesirable foreign matter accumulates in a bed of media, clogging
pores and coating surfaces.
Freeboard the vertical distance between a bed of media and the collector for backwash water.
This distance is the height available for bed expansion during back washing. Freeboard is usually
expressed as a percentage of bed depth.
Hardness a characteristic of water, imparted by salts of calcium, magnesium, and iron, such as
bicarbonates, carbonates, sulfates, chlorides, and nitrates that cause curdling of soap, deposition of
scale in boilers, damage in some industrial process, and sometimes objectionable taste. It may be
determined by a standard laboratory procedure or computed from the amounts of calcium and
magnesium as well as iron, aluminum, manganese, barium, strontium, and zinc; expressed as
equivalent parts per million of calcium carbonate.
Temporary hardness is due to calcium and magnesium alkaline salts, such as magnesium
bicarbonates and carbonates. Temporary hardness is also known as "carbonate hardness" or
"alkaline hardness". Mostly, temporary hardness is due to bicarbonates of calcium and magnesium.
Permanent hardness is due to neutral salts of calcium of magnesium that includes chlorides,
sulfates, nitrates, and fluorides of calcium and magnesium. Permanent hardness is also known as
"non-carbonate hardness" or "non-alkaline hardness".
Leakage an amount of un-exchanged ions which are present in the effluent. There is always
some leakage of ions in the effluent from an ion exchange. It varies throughout the service cycle
reaching a maximum at the end of the service cycle. Capacity of a resin is based upon this end
point leakage. The leakage may be as little as 1 PPB (1 parts per billion, i.e., 1 pound of
substance per billion pounds of water).
Langelier Scaling Index (LSI) LSI predicts tendency of water to form calcium carbonate or in
other words how likely it is for calcium carbonate to precipitate. In order to avoid calcium
carbonate scaling, CaCO3 should tend to dissolve in concentrate stream rather than
precipitate. At pH of saturation (pHs), water is in equilibrium with CaCO3. To control calcium
carbonate scaling by acid addition alone, LSI in reject (concentrate) stream must be negative.
LSI = (pH of RO reject) – (pH of saturation for CaCO3)
Page 3 of 7
Project: BAJO Grande AQUATECH INTERNATIONAL CORPORATION
Client: Solidaris, LLC. AQUATECH PROJECT # P-00149
1.3 Common Terminologies
Because a high quality scale inhibitor is available for this particular application concentration
stream can have LSI up to 1.5. Anti-scalant addition will help to reduce or eliminate need for
acid consumption.
Oxidant a chemical agent that oxidizes.
Oxidation in a broad sense oxidation is the increase in positive valence of any element in a
substance. On the basis of the electron theory, oxidation is a process in which an element
losses electrons. In a narrow sense, oxidation means the chemical addition of oxygen to a
substance.
Parts per million (ppm) the unit commonly used to represent the degree of pollutant
concentration where the concentrations are small. Larger concentrations are given in
percentages. 1ppm = 1mg/L. In BOD analysis, the results are expressed in ppm, whereas in
the suspended solids test, the values are expressed in percents. In air, ppm is usually a
volume/volume ratio; in water, ppm represents a weight/volume ratio.
pH control is of critical importance in a large number of industrial operations such as in water
purification. pH is a value taken to represent the acidity or alkalinity of an aqueous solution; it is
defined as the logarithm of the reciprocal of the hydrogen-ion concentration of a solution:
(1)
pH = Log (---------)
(H+)
Pure water is the standard used in arriving at this value. Under ordinary conditions water
molecules disassociate into the ions H+ & OH-, with recombination at such a rate that with very
pure water at 22° C this is a concentration of oppositely charged ions of 1/10,000,000, or 10-7,
mole per liter. This is commonly expressed by saying that pure water has a pH of 7, which means
that its concentration of hydrogen ions are expressed by the exponent 7, without it's minus sign.
When acids or hydroxyl- containing bases are in water solution they ionize more or less
completely, furnishing varying concentrations of H+ & OH- ions, respectively, to the solution.
Strong acids and bases ionize much more completely than weak acids and bases; thus strong
acids give solutions of pH 1 to 3, while solutions of weak acids have a pH of about 6. Strong
bases give solutions of pH 12 or 13, while weak bases give solutions of pH about 8. As the pH
scale is logarithmic, the intervals are exponential, and thus represent far greater differences in
concentration than the values themselves seem to indicate.
Page 4 of 7
Project: BAJO Grande AQUATECH INTERNATIONAL CORPORATION
Client: Solidaris, LLC. AQUATECH PROJECT # P-00149
1.3 Common Terminologies
Examples
Liquid pH Value
Pure water 7
Sea water 7.8 - 8.2
Blood 7.3 - 7.5
Milk 6.5 - 7
Soil (optimum for crops) 6-7
Cola Soft Drinks 2-3
In acid-base titrations, changes in pH can be detected by indicators, such as methyl orange,
etc. Litmus paper can also be used as a rough indication of acidity or alkalinity.
pH adjustment: a means of maintaining the optimum pH through the use of chemical
additives.
Precipitate to cause a dissolved substance to form a solid particle which can be removed by
settling or filtering such as the removal of dissolved iron by oxidation, precipitation and filtration.
Precipitate is also used to refer to the solid formed as a result of precipitation.
Reduction chemical reaction in which an atom or molecule gains an electron; decrease in
positive valence; addition of hydrogen to a molecule.
Reduction Treatment the opposite of oxidation treatment wherein a reductant is used to
lower the valence state of a pollutant to a less toxic form; e.g. the use of SO2 to reduce Cr6+ to
Cr3+ in an acidic solution.
Regenerant Introduction Regenerants of proper concentration are introduced in the tanks to
reactivate the resin. The strength of dilute regenerant and its flow rate are of utmost importance.
Any change in these values compared to the ones specified, may cause resin fouling, capacity
loss, and quality deterioration.
Residual is the amount of a specific material remaining in the water following a treatment
process. May refer to the incomplete removal (such as leakage) or to material meant to remain in
treated water (such as residual chlorine).
Reverse Osmosis (RO) – is the reverse of the natural osmosis process. It is achieved by
external application of sufficient pressure to cause the solvent (water) to flow in the reverse
direction, i.e. from the more concentrated solution to the dilute solution.
RO Membrane – It is the active surface of the element through which the RO feed water is
processed into permeate and concentrate (reject) streams.
RO Array – Each Reverse Osmosis bank consists of an array of 5 vessels followed by a 3
vessels followed by a 2 vessels. Each vessel has 6 membranes.
Page 5 of 7
Project: BAJO Grande AQUATECH INTERNATIONAL CORPORATION
Client: Solidaris, LLC. AQUATECH PROJECT # P-00149
1.3 Common Terminologies
RO Permeate – Within the RO vessel are a series of membranes. Pressurized water flows into
the RO vessel and the pressure forces water through the filtering layers of the membranes and
into the permeate chamber. Permeate comes out both end of the vessel from the center of the
membranes. Permeate connections from each array are headered together. 85% of the feed
water into the vessel becomes permeate water. Permeate will have the majority of suspended
solids, organic material such as bacteria, and dissolved mineral and salts removed.
RO Reject – The remaining water that does not flow into the permeate chamber is called reject
or concentrate. The concentrate has ions which are too large to flow through the membranes.
The concentrate from the first array flows feeds the
second array. As with the first array, the pressure forces some of the concentrate through the
membranes. The concentrate from the second array flows feeds the third array. As with the
second array, the pressure forces some of the concentrate through the membranes. The
concentrate flow leaving the third array is limited to 15% of the feed by adjusting the globe
valve on the RO bank’s reject line.
Recovery – is the amount of feed water recovered as permeate. It is expressed as
percentage (%) recovery.
% Recovery = Permeate Flow / (Permeate Flow + Reject Flow) x 100
Scale – is a coating that forms on surface of membranes due to the precipitation or
crystallization of salt compound or solids. Precipitate that forms on surfaces in contact with
water as the results of a physical or chemical change, often due to the presence of calcium
carbonate (CaCO3) or magnesium carbonate (MgCO3).
Semi-permeable Membrane – is a natural or synthetic membrane that allows only some
molecules in a mixture to pass through it.
Softening the removal of hardness—calcium and magnesium—from water.
Specific Gravity (Sp.Gr.) The ratio of the density of a substance to the density of a reference
substance; it is an abstract number that is unrelated to any units. For solids and liquids, specific
gravity is numerically equal to density, but for gases it is not, because of the difference between
the densities of the reference substances. Which are usually water (1 g/cc) for solids and liquids
and air (0.00120 g/cc, or 1.29 g/l at 0 and 760 mm) for gases. The specific gravity of solids and
liquids is the ratio of their density to that of water at 4° C taken as 1.0 as 1 cc of water weighs 1
gram. Thus a solid or liquid with a density of 1.5 g/cc has a specific gravity of 1.5. Since weights of
liquids and gases vary with temperature, it is necessary to specify both temperatures involved,
except for rough or approximate values.
Suspended solids (1) solids that either floats on the surface of, or is in suspension in, water,
wastewater, or other liquids, and which are largely removable by laboratory filtering. (2) The
quantity of material removed from wastewater in a laboratory test, as prescribed in “Standard
Methods” and referred to as non-filterable residue.
Page 6 of 7
Project: BAJO Grande AQUATECH INTERNATIONAL CORPORATION
Client: Solidaris, LLC. AQUATECH PROJECT # P-00149
1.3 Common Terminologies
Turbidity Foreign suspended particles in water imparting an unsightly appearance and will result
in deposits in water lines, process equipment, etc. It is measured by a nephelometer that which
senses the quantity of light transmitted through a water sample. The units are given as NTU.
Page 7 of 7
