Environmental Engineering Reference
In-Depth Information
water systems are best avoided except when these regions are of direct interest. The
sampling locations should generally be chosen so that the corresponding discharges are
known or can be well estimated. This requirement becomes imperative for programs,
which include the objectives of pollution loads determination.
2.4
The choice of media, parameters and monitoring frequency
Considering the integrated approach to water quality management and the need to protect
all aspects of the environment (water, air and soil), the medium to be assessed may vary,
or the objectives of the program may include monitoring of more than one media, e.g. in
some cases both water quality and sediments quality should be sampled and tested. One
other example is the case of effluents disposal on land, where effluents and soil quality,
together with river and ground water quality might need to be tested, in order to examine
environmental impacts of the disposal. For each specific medium, parameters to be
tested, frequency and methods of monitoring should be identified and specified
separately.
The choice of parameters to be monitored is very important and could influence
considerably the cost of the program. The preparation of a list of selected parameters
involves defining both the type of parameters (pH, dissolved oxygen, etc.) and the
required level of measurement (mg/l, µg/l, and range). The selection of parameters should
be based solely on the need to satisfy the objectives of the program and the appropriate
media to be surveyed, and should consider the available resources. In the case of water
quality monitoring, the selection process should include the following steps:
• Review the water quality criteria (standards) and tolerance limits applicable to the water
body under investigation, or review the performance guidelines where the efficiency
of a treatment operation is under consideration.
• Consult previously reported data, if available.
• Conduct a screening test on the water body under investigation, taking into account,
thermal and material input from tributaries or domestic and industrial discharges in the
case of rivers, and different flow streams in treatment plants.
• Develop a conceptual model of the system under investigation (a set of water quality
characteristics).
• Identify parameters of particular interest to the purpose of measurement, based on
thorough literature and documentary survey.
• Specify levels (range) of measurements for each parameter.
The values obtained by analysis are governed by the methods of analysis used and
therefore all laboratories wishing to obtain comparable results should use the same
method. When selecting a parameter it is necessary to specify the required range of
concentrations. This information is significant in view of the fact that the procedures for
the sampling and analysis of a given constituent in the mg/l range may be completely
different from those used in the µg/l range. The specificity of a parameter is its ability to
define selectively a given chemical or biological species. It is frequently necessary to
provide an explicit statement of the degree of specificity required. For example, it may be
important to state the parameter as “total phosphorus”, “orthophosphate”,
