3 Monitoring Water Quality
Water quality sensors are used to measure parameters that indicate the symptoms of
possible water degradation. For example, very low dissolved oxygen concentration is
a good indicator of a possible anaerobic condition, which can have a detrimental
impact on aquatic living resources. Diagnostic water quality monitoring is often
performed to obtain baseline water quality information that identifies the possible
causes of water quality degradation. Commonly monitored parameters include measurements of water temperature, pH and conductance, dissolved oxygen content,
turbidity, and algal biomass. Results of diagnostic monitoring are usually used to
plan more elaborate water monitoring programs for water pollution control purposes.
Discrete water quality monitoring involves limited onsite measurements, point
water sampling, and laboratory analysis. Discrete water quality monitoring does not
capture sudden temporal changes in water quality (e.g., spills). Furthermore, discrete measurements are usually implemented during the day when it is practical to
deploy field crews. Because discrete water quality measurements are usually made
during the day, problems such as nighttime changes in dissolved oxygen, hypoxia,
or anoxia often go undetected.
Various types of water quality sensors have been developed for water quality
monitoring. These include physical sensors, chemical sensors, optical sensors, and
biosensors. Water quality sensors can be part of single- or multiparameter handheld
instruments for discrete water quality monitoring, a component of a multiparameter
data sonde which is typically used for continuous and unattended water quality
monitoring, or they can be a single sensor connected to a data collection platform
(DCP) for real-time monitoring. An overview of water quality sensors and their
application is provided below.
3.1 Physical Sensors
Physical sensors can measure physical properties of water such as water temperature and electrical conductivity.
3.1.1 Water Temperature Sensors
Chemical and biological process rates in natural water are temperature dependent
and affect the optimal health of living resources in water. The dissolved oxygen
content of water, rates of photosynthesis and respiration, and living resource
sensitivity to diseases, parasites, and toxins are all temperature dependent. Thermal
stress on living resources can lead to the migration of living resources out of an area
in search of more optimal conditions and in some cases death [7]. Water temperature is a not only a staple measurement for water resource managers, but it is also a
critical sensor in most multiparameter instruments because other sensor measurements are temperature dependent and need to be temperature corrected.
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T. Younos and C.J. Heyer
Water quality sensors are used to measure parameters that indicate the symptoms of
possible water degradation. For example, very low dissolved oxygen concentration is
a good indicator of a possible anaerobic condition, which can have a detrimental
impact on aquatic living resources. Diagnostic water quality monitoring is often
performed to obtain baseline water quality information that identifies the possible
causes of water quality degradation. Commonly monitored parameters include measurements of water temperature, pH and conductance, dissolved oxygen content,
turbidity, and algal biomass. Results of diagnostic monitoring are usually used to
plan more elaborate water monitoring programs for water pollution control purposes.
Discrete water quality monitoring involves limited onsite measurements, point
water sampling, and laboratory analysis. Discrete water quality monitoring does not
capture sudden temporal changes in water quality (e.g., spills). Furthermore, discrete measurements are usually implemented during the day when it is practical to
deploy field crews. Because discrete water quality measurements are usually made
during the day, problems such as nighttime changes in dissolved oxygen, hypoxia,
or anoxia often go undetected.
Various types of water quality sensors have been developed for water quality
monitoring. These include physical sensors, chemical sensors, optical sensors, and
biosensors. Water quality sensors can be part of single- or multiparameter handheld
instruments for discrete water quality monitoring, a component of a multiparameter
data sonde which is typically used for continuous and unattended water quality
monitoring, or they can be a single sensor connected to a data collection platform
(DCP) for real-time monitoring. An overview of water quality sensors and their
application is provided below.
3.1 Physical Sensors
Physical sensors can measure physical properties of water such as water temperature and electrical conductivity.
3.1.1 Water Temperature Sensors
Chemical and biological process rates in natural water are temperature dependent
and affect the optimal health of living resources in water. The dissolved oxygen
content of water, rates of photosynthesis and respiration, and living resource
sensitivity to diseases, parasites, and toxins are all temperature dependent. Thermal
stress on living resources can lead to the migration of living resources out of an area
in search of more optimal conditions and in some cases death [7]. Water temperature is a not only a staple measurement for water resource managers, but it is also a
critical sensor in most multiparameter instruments because other sensor measurements are temperature dependent and need to be temperature corrected.
184
T. Younos and C.J. Heyer