|
Term |
Definition |
|
Action level |
The
concentration of contaminants set by U.S. EPA that if exceeded
requires treatment or other requirements that a water system must
follow. |
| Activity |
The
effective concentration of a species; usually denoted by { }. |
|
Activity coefficients |
The
ratio between the active concentration (activity) of a species
and the actual concentration of a species (Snoeyink and Jenkins,
1980). |
|
Aeration |
Aeration
creates a large interfacial surface area between water and air
in order to accomplish the transfer of gases between the water
and air. |
|
Alkalinity |
Alkalinity
is the ability to neutralize acid. Alkalinity consists of bases
and weak acids. The most common alkalinity forms in natural waters
are bicarbonate, HCO3-, carbonate, CO32-, hydroxide, OH-, and ionized silicic acid, H3SiO4-. |
| AWWA |
American
Water Works Association. |
|
Ballast |
Supplies the proper voltage and current needed
for UV lamp operation. |
| Biodosimetry |
A method used
to find the reduction equivalent dose (RED). A challenge organism
is exposed to UV light in the UV reactor. The inactivation is
then measured and compared to the known dose-response curve. |
| Calcite |
Calcite,
CaCO3, is a major mineral component of
limestone. |
| Calcium
carbonate dissolution potential (CCDP) |
CCDP represents the theoretical concentration
of calcium carbonate that could dissolve into a water. |
| Calcium
carbonate precipitation potential (CCPP) |
CCPP represents the theoretical concentration
of calcium carbonate that could precipitate from a water. |
|
Carbonate saturometer |
A
device used by chemical limnologists and oceanographers to determine
the calcium carbonate saturation state based on electrochemical
approach (AWWA, 1999). |
| Challenge Organism |
The microorganism selected for use in biodosimetry
testing. |
| CND$ |
Canadian
Dollar. |
| Collimated Beam Test |
A bench-scale test designed to determine
the UV dose-response of a microorganism through measurements of
exposure time, UV light intensity and the corresponding log-inactivation
of the microorganism. |
|
Conductivity |
Conductivity is a measure of the ability of a
water to conduct electricity. Conductivity is related to ionic
strength, i.e. the more ions in solution, the higher the conductivity. |
|
Copper |
A metal widely used in household plumbing materials.
Copper is an essential nutrient however it may cause stomach and
intestinal distress, liver and kidney damage and anemia if ingested
at high doses. |
|
Corrosion |
Gradual destruction of metals due to electrochemical
reactions. |
|
Corrosive water |
Corrosive water is a condition of the water’s
quality (such as a low pH value, a low alkalinity, a high specific
conductivity and high temperature) that will cause the water to
dissolve metals from a home’s metallic plumbing at an excessive
rate. All water is corrosive toward lead and copper in some degree
including water that is termed non-corrosive or water treated
to make it less corrosive. The more acidic the water is, the more
corrosive the water will become towards lead and copper. |
|
CSIR |
CSIR is the premier technology and research organization
in South Africa. One of the focus areas of CSIR is a leading center
for scientific research for water management in South Africa.
The researchers of CSIR have developed several technologies to
enable the use of limestone contactor in large water systems such
as SSP and Simplified SSP, and for stabilizing groundwater containing
iron and manganese such as Spraystab. |
| Dark Repair |
A microbial repair process in which enzymes
can regenerate DNA damage by UV light; this process does not require
light. |
|
DESCON |
A computer program written by Letterman and Kothari
(1995) for designing a limestone contactor. |
|
Disequilibrium Index |
Disequilibrium Index also known as General Saturation
Index is one of the indices used to predict the degree of calcium
carbonate saturation in water. For any solid solubility reaction,
it is defined as the logarithmic value of the ion activity product
divided by the solubility constant (AWWA, 1999). |
|
Dissolution |
A reaction where insoluble solid is dissolved
in a solution. |
|
Dissolved inorganic carbon (DIC) |
Typically, the amount of total carbonates (carbon
dioxide gas, CO2 or H2CO3),
bicarbonate ion (HCO3-) and carbonate ion (CO32-) in water and measured
as milligrams of carbon per liter. |
|
Dolomite |
Dolomite is a sedimentary deposit composed mainly
of CaMg(CO3)2 as
compared to limestone which is mainly CaCO3. |
|
Empty bed contact time (EBCT) |
Empty bed contact time is the time it takes for
water to flow trough a limestone contactor if no media is present.
It is the ratio of the volume of an empty contactor to the flow
rate of water flowing through the contactor bed. It is the most
important parameter in the design of a limestone contactor for
insuring adequate contact time in a limestone bed in order to
achieve calcium carbonate saturation. |
|
EPA (same as U.S. EPA) |
U.S. Environmental Protection Agency |
|
Equilibrium |
A state where no change occurs in a system. |
|
Filtration |
A treatment process used to remove suspended
solids from water. |
| Fouling |
Deposits on the lamp sleeve, intensity sensor,
or sensor window from compounds in the water, may decrease UV
light transmittance. |
|
General Saturation Index (same as Disequilibrium
Index) |
General Saturation Index also known as Disequilibrium
Index is one of the indices used to predict the degree of calcium
carbonate saturation in water. For any solid solubility reaction,
it is defined as the logarithmic value of the ion activity product
divided by the solubility constant (AWWA, 1999). |
|
gpm/ft2 |
Gallon per minute per square foot |
|
Hardness |
Hardness in water is caused primarily by the
divalent cations calcium, Ca2+, and magnesium,
Mg2+. Other divalent
cations such as ferrous iron, Fe2+, also contribute
to hardness but its concentration is usually much lower than that
of calcium and magnesium. Hard waters will cause increased soap
consumption for certain kinds of soap as well as the formation
of a precipitate or curd on bathroom fixtures. Hardness can also
cause scaling or encrustations to form in pipes which gradually
reduce the pipe’s diameter and increase the energy losses. |
|
Ionic strength |
Ionic strength is a measure of the concentration
of ions in solution and is used in calculating activities. |
|
KB,8.2 |
KB,8.2 is a term
used by the engineers and scientists in Germany to express the
amount of base needed to titrate water to a pH of 8.2. It is roughly
equivalent to acidity and is one of the parameters used in Germany
to design a limestone contactor. |
|
KS,4.3 |
KS,4.3 is a term used
by the engineers and scientists in Germany to express the amount
of acid needed to titrate water to a pH of 4.3. It is equivalent
to total alkalinity and is one of the parameters used in Germany
to design a limestone contactor. |
| Lamp Sleeve |
A protective sleeve around the UV lamp typically
made of quartz. |
|
Langelier's Index |
Langelier’s Index is used to predict the degree
of calcium carbonate saturation in water. It is the difference
between the actual pH and the hypothetical pH at equilibrium.
|
|
Larson's Ratio |
Larson's Ratio is a ratio of chloride and sulfate
to bicarbonate although some people use the inverse. Some suggest
the ration be less than 0.2 to 0.3 if concentrations are in mol/L. |
|
Lead |
A metal that was used in household plumbing materials
or in water service lines used to bring water from the main to
the home. Lead is toxic to human especially to babies, young children
and pregnant women. If exposed to lead greater than the maximum
contaminant level (MCL), the short term effects may include interference
with red blood cells, delays in the normal development in babies
and young children and interference with the hearing and learning
abilities of children. The long-term effects (if exposed to lead
greater than MCL) may include stroke, kidney disease and cancer.
|
|
Lead and Copper Rule |
A U.S. EPA regulation to control the levels of
lead and copper in drinking water. |
| Long Term 2 Enhanced Surface Water Treatment
Rule (LT2ESWTR) |
EPA rule to be promulgated to regulate Cryptosporidium
in drinking water. Requires 0-2.5 log additional treatment for
filtered systems, depending on the source water Cryptosporidium
concentration, and 2-3 log treatment for unfiltered systems. Provides
requirements for UV reactors for inactivation of Cryptosporidium,
Giardia, and viruses. |
| Low Pressure (LP) Lamp |
Lamp that emits UV light at wavelengths of
254 nanometers. Mercury vapor pressure
optimal at 0.007 torr. |
| Low Pressure High Output (LPHO) Lamp |
Lamp that emits UV light at wavelengths of
254 nanometers but with a higher UV intensity than low pressure
lamps. Mercury vapor pressure
0.76 torr. |
|
Marble Test |
A laboratory based test used to determine the
relative state of saturation with respect to calcium carbonate. |
|
Maximum Contacminant Level Goal (MCLG) |
MCLG is the non-enforceable health goals set
at a level at which it will not result in adverse health effects
on human and allows an adequate margin of safety. |
|
Maximum Contaminant Level (MCL) |
MCL is the maximum allowable concentrations of
specific contaminants that is set and enforceable under the Federal
Safe Drinking Water Act. If the levels are exceeded, treatment
techniques are required. |
| Medium Pressure (MP) Lamp |
Lamp that emits UV light over a range of
wavelengths. Mercury vapor pressure
300-30,000 torr. |
|
MLD |
106
Liter/Day |
| Offline Chemical Clean (OCC) |
Also known as a flush-and-rinse system; method
to clean lamp sleeves where the UV reactor is taken out of service
and a cleaning solution is added. After the cleaning solution
is removed, the UV reactor goes back online. |
| Off-specification operation |
When the UV reactor does not operate within
validated conditions. In most cases, for filtered water the amount
of off-specification operation allowed will be up to the states.
|
| Online Mechanical Clean (OMC) |
Method to clean lamp sleeves where at set
intervals a mechanical wiper cleans the lamp sleeves. |
|
pH |
pH is the negative logarithm of the effective
hydrogen-ion concentration, pH = -log[H+].
|
|
pHc |
pHc is the pH of water that is saturated with
calcium carbonate. |
| Photoreactivation |
A microbial process requiring light in which
enzymes can repair damage caused by UV light. |
|
Precipitation |
Formation of insoluble solids in a solution. |
|
PRO/II |
The computer software that was initially selected
to model the SSP. It modeled all the unit processes involved in
the SSP except for the CO2 stripping from
the sidestream. |
|
R (or ZAR) |
The currency used in South Africa, also known
as South African Rand. |
| Reduction Equivalent Dose (RED) |
The dose observed in a full-scale UV reactor
determined through biodosimetry testing that correlates to a bench-scale
UV dose from collimated beam testing. |
|
Ryznar (Saturation) Index |
Ryznar (Saturation) Index is used to predict
the degree of calcium carbonate saturation in water. It is the
difference between twice the value of hypothetical pH at saturation
and the actual pH (AWWA, 1999). |
|
Saturated |
A saturated solution has dissolved the maximum
amount of a solid, e.g. CaCO3. |
|
Sidestream Stabilization Process (SSP) |
A process developed by South African researchers
to enable stabilization of water using limestone contactors in
large water treatment plants. The process consists of taking a
sidestream of unstabilized water, dosing it with carbon dioxide
and contacting it with limestone. The remaining CO2
is recovered and reused in the process and the stabilized sidestream
blends with the mainstream. |
|
Simplified Sidestream Stabilization Process (Simplified
SSP) |
Simplified SSP is similar to SSP except the CO2
recovery is not included in the process. |
|
Small system |
A small system is
a water system serving 3,300 or fewer people (applies only for
the Lead and Copper Rule). |
| Solarization |
Effect of UV light on the lamp and sleeve
that causes the lamp to become more opaque over time. |
|
Spraystab |
A treatment method developed by researchers in
South Africa to stabilize groundwater with and without the presence
of iron and manganese in the water. |
|
STASOFT |
STASOFT is a computer software used to design,
model and control water treatment processes that involve carbonate
chemistry. It is developed by the Water Research Commission of
South Africa and mainly used to aid in the design of limestone
contactors in South Africa. |
|
Superficial velocity |
The ratio of the water flow rate divided by the
cross-sectional area of the contactor bed in which the water flows
through. |
|
Supersaturated |
A state where a solution contains more solute
than a saturated solution at the same temperature. It will thus
tend to precipitate the solute. |
|
Supporting media |
Supporting media is a term used to describe the
media used to support the limestone bed in a limestone contactor
or the filtration media in a filter such as gravel, rock and garnet.
|
|
Undersaturated |
A state where a solution contains less solute
than a saturated solution at the same temperature. |
| US$ |
U.S.
Dollar |
| UV Absorbance |
The reduction in light intensity due to absorption
by the transmitting medium, e.g. water, lamp sleeves, or air. |
| UV Dose |
The simplest definition is the amount of
ultraviolet light energy per unit area delivered to the water,
typically measured in units of mJ/cm2 or J/m2. UV dose delivered
to a microorganism is the product of the average UV intensity
received by the microorganism from all directions and the exposure
time. |
| UV Dose-Response |
Represents inactivation levels of a microorganism
as a function of the UV dose. |
| UV Intensity |
The power of ultraviolet light per unit area passing through
an area perpendicular to the direction of propagation. Describes
the magnitude of UV light in a UV reactor (USEPA, 2003). |
| UV Intensity Sensor |
A photosensitive device that measures the
UV intensity at a specific location in a UV reactor. |
| UV Light |
Light that is emitted with wavelengths from
200 to 400 nanometers. |
| UV Reactor |
The chamber where water is treated with UV
light. Lamps, lamp sleeves, sensors and wiper cleaning system
are also considered part of the reactor. |
| UV Reactor Validation |
A process for verifying the reactor performance
over a range of operating conditions. |
| UV Transmittance (UVT) |
The fraction of light intensity entering
the water compared to the amount of light leaving. UVT = 10-UVA. |
|
WATCHEM |
WATCHEM is one of the computer programs included
in the STASOFT 4 package used to model the Simplified SSP by the
South African researchers. |
|
ZAR |
The currency used in South Africa, also known
as South African Rand. |
