In industrial water conditioning, chemical analyses are needed to govern
the treatment processes. Analysis should be conducted promptly after sample collection
so that the chemical nature of the sample does not change. On-site testing may
be supplemented by plant central laboratories or GE Water & Process Technologies'
Customer Service Laboratories.
The methods included in this handbook are
suitable for on-site analysis. They involve the use of apparatus
and chemicals that are evaluated, approved, and supplied by GE Water & Process
Technologies. Lists of required materials are provided with each titrimetric,
spectrophotometric, and colorometric procedure. In some cases, other appropriate
equipment may be substituted for the apparatus listed. Substitution of reagents,
unless otherwise noted, is not recommended. Microbiological tests and tests which
are not suitable for on-site analysis have been excluded from this text.
authoritative sources have been referenced in the development of these procedures.
These sources include The Annual Book of ASTM Standards and the APHA-AWWA Standard
Methods for the Examination of Water and Wastewater, along with other well known
and widely accepted analytical methodology. The procedures are not for EPA or
governmental reporting purposes and are not to be used where litigation may be
In order to ensure that results obtained from
an analysis are useful, it is necessary to secure a representative sample from
the system to be tested. Sample lines must be flushed before samples are taken,
and all sampling locations and procedures must be well defined.
tests, the samples should be cooled to room temperature (21-26°C, 70-80°F)
prior to testing. They should also be filtered through 0.2-2.5 µm filters,
METHODS OF ANALYSIS
Historically, titration has been the most common method
of plant control analysis. Titration is based on the use of a buret, from which
a standard solution is added to the sample until an "end point" is reached.
The end point is generally indicated by a color change or detected by potentiometric
device (e.g., pH meter).
Several types of burets are available for plant
- semimicro burets (2.0 or 3.0 mL capacity) are used to titrate
low concentrations of species in the sample
- large burets (25 or 50 mL
capacity) are used to titrate species found in higher concentrations
burets feature a reservoir for "automatic" filling of the buret and an overflow
and reset to 0 mL
Digital titrators provide a more portable approach
to titration in the field. These hand-held units are widely accepted because they
are rugged and easily carried from one location to another. The digital titrator
is equivalent to a buret in the conventional titration methods. The titrator acts
as a plunger and forces concentrated titrant from an attached plastic cartridge.
Each cartidge can perform the same amount of testing as one quart of titrant in
conventional tests. However, in most plant laboratories and testing locations,
automatic burets are still being used.
Photometers or spectrophotometers provide the most accurate means of measuring
the color of a reacted sample. In field analysis applications, simple filter photometers
have been replaced by monochromator-based spectrophotometers. The essential
components of a spectrophotometer include the following:
n a stable
source of radiant energy
- a system of lenses, mirrors, and slits that
define, collimate (make parallel), and focus the beam
- a monochromator,
to resolve the radiation into component wavelengths or "bands" of wavelengths
transparent container to hold the sample
- a radiation detector with an
associated read-out system
Light from a tungsten bulb is reflected
off of a parabolic mirror and dispersed with a double pass through a high-dispersion
prism. The se-lected wavelength is imaged onto a movable slit, ensuring a uniform
tests are not as accurate as the photometric or spectrophotometric methods. Color
comparisons may be used as a backup to on-line or other optical instrumentation.
Colorimetric methods have become popular because of their simplicity and relatively
low cost. However, tight control of most industrial water systems should not be
entrusted to this technique alone.
In a comparator test, a color is developed
that is proportional to the concentration of the substance being determined. The
concentration present in the sample is determined by comparison with sealed color
standards. The color standards are made of colored plastic or glass, or liquids
sealed in air-tight containers.
METHODS USED IN THE LABORATORY
Common new methods of water
analysis often involve highly sophisticated electronic instrumentation not generally
used on-site for plant control.
- Ion Chromatography is used to measure
trace levels of anions in feedwater, steam, condensate, and boiler water.
Absorption Spectroscopy (AA), Inductively Coupled Ion Spectroscopy (ICP), X-ray
Fluorescence Spectroscopy, and other laboratory procedures are used routinely
to measure many elements at trace levels in a fraction of the time required for
wet chemical methods. Some instruments can provide concurrent read-outs of over
40 elements in ppb measurements.
- Gas Chromatography (GC), or Gas Chromatography
and Mass Spectroscopy (GC/MS), quantitatively separates and detects volatile components
(e.g., neutralizing amines) in boiler condensate.
- High-Pressure Liquid
Chromatography (HPLC) permits the separation and detection of trace organic compounds
in antimicrobial applications.
- Total Organic Carbon (TOC) measurements
are used to determine the amount of organic compounds present in water as a result
of water treatments or process leaks. This process is also useful for measuring
organic fouling of resinsin demineralizer systems.
- Nuclear Magnetic Resonance
Spectroscopy (NMR) provides an analytical tool to aid in determining the structure
of organic polymers and other organic water treatment chemicals.
Transform Infrared Analysis (FT-IR) permits the qualitative and quantitative
determination of the composition of boiler and cooling system deposits.
ion electrode detection is an electrometric method that can measure trace amounts
of both anions and cations in water and is within the reach of most laboratories
and testing sites.
The field-testing methods presented in this handbook
are often supplemented by these instrumental methods to optimize treatment effectiveness.