Science of Water : Concepts and Applications

Environmental Biomonitoring, Sampling, and Testing 287
All of these test procedures are approved methods, and unless prohibited by the plant’s NPDES
discharge permit, can be used for effl uent testing. Based on the current most popular method usage
in the United States, discussion is limited to the following:
1. DPD-spectrophotometric
2. DPD-FAS titration
3. Titrimetric—amperometric direct
√ Note: Treatment facilities required to meet “nondetectable” total residual chlorine limitations
must use one of the test methods specifi ed in the plant’s NPDES discharge permit.
For information on any of the other approved methods, refer to the appropriate reference cited
in the CFRs.
Fluorides
It has long been accepted that a moderate amount of fl uoride ions (F− ) in drinking water contributes
to good dental health—it has been added to many community water supplies throughout the United
States to prevent dental caries in children’s teeth. Fluoride is seldom found in appreciable quantities
of surface waters and appears in groundwater in only a few geographical regions. Fluorides are used
to make ceramics and glass. In large quantities fl uoride is toxic to humans and to some animals.
The chemicals added to potable water in treatment plants are:
NaF Sodium fl uoride, solid
Na2SiF6 Sodium silicofl uoride, solid
H2SiF6 Hydrofl uosilicic acid; most widely used
Analysis of the fl uoride content of water can be performed using the colorimetric method. In
this test, fl uoride ion reacts with zirconium ion and produces zirconium fl uoride, which bleaches
an organic red dye in direct proportion to its concentration. This can be compared to standards and
read colorimetrically.
RECOMMENDED READING
American Public Health Association, 1998. Standard Methods, 20th ed. Washington, DC: American Public
Health Association.
AWWA, 1995. Water Treatment. Denver: American Water Works Association.
Barbour, M.T., Gerritsen, J., Snyder, B.D., and Stibling, J.B., 1997. Revision to Rapid Bioassessment Protocols
for Use in Streams and Rivers, Periphyton, Benthic, Microinvertebrates, and Fish. EPA 841-D-97-002.
Washington, DC: U.S. Environmental Protection Agency.
Bly, T.D. and Smith, G.F., 1994. Biomonitoring Our Streams: What’s It All About? Nashville, TN: U.S. Geological
Survey.
Botkin, D.B., 1990. Discordant Harmonies. New York: Oxford University Press.
Camann, M., 1996. Freshwater Aquatic Invertebrates: Biomonitoring. Available at http://www.humboldt.
edu.
Harr, J., 1995. A Civil Action. New York: Vintage Books.
Hillborn, R. and Mangel, M., 1997. The Ecological Detective: Confronting Models with Data. Princeton, NJ:
Princeton University Press.
Huff, W.R., 1993. Biological Indices Defi ne Water Quality Standard. Water Environ. Technol., 5:21–22.
Huston, M.A., 1994. Biological Diversity: The Coexistence of Species on Changing Landscapes. New York:
Cambridge University Press.
Kittrell, F.W., 1969. A Practical Guide to Water Quality Studies of Streams. Washington, DC: U.S. Department
of Interior.
O’Toole, C. (ed.), 1986. The Encyclopedia of Insects. New York: Facts on File.