THE NEED FOR FAST REAL-TIME BOD, COD & TOC MONITORING for enhanced process control

SPECTROPHOTOMETRY IN WATER ANALYSIS (CONT'D)

This simple principle of correlating the absorbance
information to concentration can be applied to
measure and monitor many parameters of high
importance for water and wastewater treatment
and management.

Organics show particularly strong potential for
providing high value to water and wastewater
operators, engineers and other stakeholders
involved in the management of water. The primary
reason for this is that traditional laboratory
methods used for measuring organics (BOD and
COD) are time and labor intensive, and have long
turnaround times, which as noted earlier makes
them of little or no value for process control and
decision-making purposes.

As shown in Figure D, most organics absorb
light strongly in the UV region of the spectrum
(particularly 200 to 300 nm) while suspended
solids (turbidity) typically absorb light across
the entire UV-Vis spectrum. Some inorganic
compounds like Nitrite (NO2) and Nitrate (NO3)
absorb light in the deep UV regions of the
spectrum (wavelengths shorter than 250 nm).

By measuring absorbance at different wavelengths
across the UV and visible light spectra, it is
possible to account for interferences while
accurately measuring the concentration of
organics and other parameters of interest.
Accounting for interferences is a function of
measuring absorbance at multiple wavelengths.