This page provides the answer to the following questions:
What is a PROCESS ANALYZER?
A PROCESS ANALYZER is an analytical instrument used to automatically measure
the chemical content of samples extracted from a variable process, for process
monitoring or process control purposes.
When samples are continuously extracted from the process through a direct connection
to the analyzer, this is called ON-LINE analysis.
How are process analyzers USED?
ChemScan® Process Analyzers are used to measure multiple chemicals at municipal
drinking water treatment plants and municipal wastewater treatment plants or
in an industrial process involving liquids.
Typical applications for process analyzers are characterized by large flow
volumes, a dynamic chemical matrix and a substantial motive to obtain real-time
chemical analysis information.
Motives for use of on-line analysis include economic issues, quality control,
and regulatory compliance.
How is ChemScan® unique?
The ChemScan® Process Analyzer can be thought of as an on-line ultraviolet-visible
spectrometer, designed to collect the full absorbance signature of a sample
at 256 wavelengths.
This is accomplished by drawing a volume of sample into a flow cell, transmitting
known intensities of light through the sample and detecting the intensity of
light that remains at each wavelength in the range.
The standard ChemScan® instrument detects light from 200 nm (nanometers)
thru 450 nm. Special versions of the instrument can increase the number of
wavelengths and extend the range through the visible spectrum.
ChemScan® applies pattern recognition techniques to the full absorbance
signature of a sample in order to detect multiple chemical parameters using
a single analyzer. A manifold system is used to monitor multiple sample points
in a process.
What kinds of CHEMICALS can ChemScan® detect?
ChemScan® can detect any chemical substance that absorbs light in the ultraviolet
or visible wavelength range. Absorbance in this wavelength range is typically
associated with the bond structures of specific molecules.
Ions of nutrients, ions of heavy metals that form coordination compounds in
water, unsaturated (double bonded or triple bonded) hydrocarbons and aromatics
are usually good candidates for analysis using ultraviolet or visible spectrometry.
Chemicals that possess natural absorbance characteristics can be detected
directly using primary absorbance techniques. Chemicals that do not possess
natural absorbance require the assistance of a reagent for indirect detection
using secondary analysis techniques.
ChemScan® has developed many primary and secondary analysis methods that
take advantage of the multiple wavelength detection capability to simplify
the analysis. ChemScan® can also perform multiple primary and secondary
analyses of a sample.
How are the chemicals ANALYZED?
The absorbance signature (shape, wavelength range and intensity) is unique
for each chemical substance that absorbs light. When the change in intensity
for the signature is proportionate to a change in concentration, the substance
is said to follow Beer's Law. The absorbance signature for a solution is a
function of the combined absorbances from all absorbing chemicals in the solution.
A suite of statistical and mathematical techniques called chemometrics is used
to evaluate the combined absorbance from the chemical components in a solution
and to isolate the contribution made by the absorbance from a single chemical
substance to the overall absorbance signature of the solution.
What are typical ChemScan® APPLICATIONS?
Municipal Water applications include control of water blending, chemical feed
control, ion exchange breakthrough monitoring, filtration monitoring and disinfection
control. Specific parameters include:
NATURAL ORGANIC MATTER (NOM) analysis (TOC equivalent)
Municipal Wastewater applications include monitoring and control of nitrification,
biological nutrient removal (BNR), phosphate precipitation, denitrification
and disinfection processes for secondary wastewater treatment, advanced wastewater
treatment and water reuse applications. Specific parameters include:
ORGANICS analysis (TOC/COD equivalent)
PERCENT TRANSMITTANCE analysis