Science of Water : Concepts and Applications

244 The Science of Water: Concepts and Applications
Drinking water must be monitored to provide adequate control of the entire water drawing/
treatment/conveyance system. Adequate control is defi ned as monitoring employed to assess the
present level of water quality so action can be taken to maintain the required level (whatever that
might be).
We defi ne water quality monitoring as the sampling and analysis of water constituents and
conditions. When we monitor, we collect data. As a monitoring program is developed, deciding the
reasons for collecting the information is important. The reasons are defi ned by establishing a set of
objectives that includes a description of who will collect the information.
It may come as a surprise to know that today the majority of people collecting data are not water
practitioners; instead, many are volunteers. These volunteers have a stake in their local stream, lake,
or other water body, and in many cases are proving they can successfully carry out a water qualitymonitoring
program.
IS THE WATER GOOD OR BAD? *
TABLE 8.3
Total Residual Chlorine (TRC) mg/L
0.06 Toxic to striped bass larvae
0.31 Toxic to white perch larvae
0.5–1.0 Typical drinking water residual
1.0–3.0 Recommended for swimming pools
Source: From Spellman, F.R., Spellman’s Standard Handbook for Wastewater
Operators, Vol. 1, CRC Press, Boca Raton, FL, 1999.
To answer the question “Is the water good or bad?,” we must consider two factors. First, we return
to the basic principles of water quality monitoring—sampling and analyzing water constituents and
conditions. These constituents include:
1. Introduced pollutants, such as pesticides, metals, and oil
2. Constituents found naturally in water that can nevertheless be affected by human sources,
such as DO, bacteria, and nutrients
The magnitude of their effects is infl uenced by properties such as pH and temperature. For
example, temperature infl uences the quantity of DO that water is able to contain, and pH affects the
toxicity of ammonia.
The second factor to be considered is that the only valid way to answer this question is to
conduct tests that must be compared to some form of water quality standards. If simply assigning
a good and bad value to each test factor were possible, the meters and measuring devices in water
quality test kits would be much easier to make. Instead of fi ne graduations, they could simply have
a good and a bad zone.
Water quality—the difference between good and bad water—must be interpreted according to
the intended use of the water. For example, the perfect balance of water chemistry that assures a
sparkling clear, sanitary swimming pool would not be acceptable as drinking water and would be a
deadly environment for many biota. Consider Table 8.3.
* Much of the information in the following sections is based on USEPA’s 2.841B97003 Volunteer Stream Monitoring: A
Methods Manual, 2000b, and on our personal experience.