Environmental Science & Engineering - www.esemag.com - July 2005
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On-line turbidimeter helps Peel Region comply with new regulation
By Wayne A. Harrison, C.E.T.
Ontario’s Drinking Water Systems Regulation
170/03 was introduced in June 2003, and replaced
Ontario Regulation 459/00 (Drinking Water
Protection Regulation for Larger Waterworks).
One new requirement involves continuously monitoring turbidity
in groundwater sources, following treatment.
The Region of Peel, in the heart of southern Ontario’s
major urban centres, operates water treatment systems serving
more than 1 million residents. This includes a dozen well
sites that serve approximately 50,000 people in the Town of
Caledon, where the region installed 22 TMS 561 turbidimeters
from USFilter Wallace & Tiernan Products in May 2002.
The units provide continuous, on-line measurement of turbidity,
allowing the region to meet the new requirement and
providing for efficient and safer operations.
Undissolved substances such as inorganic or organic particles,
colloids or gas bubbles cause turbidity. As light strikes
these suspended particles, a small amount of light scatters
throughout the fluid. The amount and properties (size, shape
and color) of these particles determine the light’s intensity.
Turbidity measurement is based on the evaluation of the
scattered light’s intensity. The measurement value depends
on the light’s wavelength and either the measuring instruments’
geometry or the measurement angle. In order to
establish an international
turbidity standard,
these parameters
have been defined
by the USEPA (for
U.S. applications)
and ISO (for international
applications).
The TMS 561 turbidimeter
is designed
for continuous on-line
measurement of turbidity.
Its measuring
chamber consists of a
rotational flow assembly
with a replaceable
glass cuvette. A specially
designed flow head eliminates
the need for a bubble trap and
ensures an immediate response
time. Either a white light (USEPA) or infrared light (ISO) lamp
generates a beam of light, which passes through the sample.
This light is measured by two sensors, arranged at a 90-degree
angle. The resulting signal is conditioned by the integral electronics
to provide a turbidity measurement reading in NTU.
When calibrated against a known turbidity standard, the TMS
561 provides a continuous and accurate indication of turbidity.
The turbidimeter can register turbidity as low as 0.10 NTU and
as high as 1,000 NTU.
With the optional data acquisition package, up to 255 turbidimeters
can be networked simultaneously. The turbidimeter’s
one-piece design eliminates the need to mount components
for each turbidimeter.
Continuous Monitoring for Accurate Measurement
TMS 561 turbidimeters now serve all wells currently
operating at Peel’s 12 sites. The units are positioned in close
proximity to each well’s chlorine analyzer, in order to use the
same sample point.
The unit’s integral LCD display provides turbidity levels
as well as messages for guidance in setup, calibration and
troubleshooting. All of the electronics and operator controls
are built into the measurement unit. Each turbidimeter sends
a 4-20 mA signal to the region’s SCADA system, allowing
operators to monitor turbidity levels remotely. Fast response
time provides an early indication of process abnormality. To
comply with the new regulation, the SCADA system can
automatically shut off a well pump at any of the 12 sites if
turbidity exceeds 1 NTU. As optics are not in contact with
the sample, the chance of false low readings is reduced and
the possibility of fouling the measurement detector is eliminated,
says the manufacturer.
Wayne Harrison is Ontario Sales Manager for USFilter
Wallace & Tiernan Products.
Contact e-mail: colangek@usfilter.com
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