-a series of SIX VIDEOS about safe and effective water systems.

Tape #3

Coliform Bacteria

This VIEWER REFERENCE GUIDEis yours to keep!
DO NOT RETURN ITwhen you return the tape.

MRC Catalog #75704

How can I be sure my drinking water is free from harmful bacteria?

If disease-causing organisms are in your water, you can'ttell it by how the water looks or tastes or smells; water testing is the only reliable way to tell if your water is safe!
Have your water tested for coliform bacteria at least ONCE EACH YEAR.
Late spring or early summer are the best times to do it. Coliform contamination is most likely to show up during wet weather.

If coliform bacteria are present in your drinking water, your risk of contracting a water-borne illness is increased.

How do bacterial contaminants get into my water system?

Disease-causing organisms originate above ground.
Soil is nature's water filter.
Normally, after water seeps through 20 feet of soil, it is free of coliforms and disease-causing organisms.
When coliform bacteria show up in a water supply system, a defective well is often the cause.

WELL DEFECTS THAT CAN ALLOW CONTAMINATION OF THE WATER SUPPLY:

1 - missing or defective well cap;
Seals around wires, pipes, and where cap meets casing may be cracked, letting contaminants in.

2 - contaminant seepage THROUGH the well casing;
Cracks or holes in the top 20 feet of the well allow water that has not been filtered by 20 feet of soil to get into the well, contaminating it. (NOTE-This seepage is common in wells made of concrete or clay tile, or of brick.)

3 - contaminant seepage along the OUTSIDE of the well casing;
Open space around the casing should be sealed with grout (a slurry of cement or clay) when the well is constructed.
Most older wells were NOT grouted when constructed.
Grouting old wells is difficult and costly. Consider drilling a new well.

4 - well flooding;
This is a common problem for wellheads located below ground in frost pits that frequently flood during wet weather.

What are some options for dealing with bacterial contamination?

Inspect well for defects and repair them if possible, or construct a new well.
Install continuous disinfection equipment.
Use bottled water for drinking and food preparation.
Connect to regional rural water system, if available.
For more information, see Extension publication Pm-1329, Coping with Contaminated Wells.

How can water be continuously disinfected?

Chlorine treatment-single step method
Use a liquid chlorine injector pump, or a chlorine tablet dispenser to achieve chlorine concentration of about 1 milligram per liter. Adequate TIME MUST be provided (about 35 minutes) for chlorine to kill bacteria before water is consumed. Install baffled tank or long coil of flexible pipe in plumbing system between chlorator and tap to provide sufficient time for thorough disinfection.

Chlorine treatment-two step method (called "superchlorination/dechlorination")
Apply higher chlorine concentration (5 -10 milligrams per liter), to speed disinfection process.
Remove excess chlorine (and the taste and odor it causes) with an activated carbon filter.

Ozone treatment
A small ozone generator produces and injects ozone into water supply.

Ultraviolet light treatment
Water flows past an ultraviolet lamp; light rays kill bacteria.

Distillation
Water is boiled to form steam, which is recondensed to produce purified water.
Heat kills bacteria.

Which disinfection system is best?

None is "perfect." Each has its benefits and drawbacks.

HERE ARE JUST A FEW-

Ozone and ultraviolet light are much faster than chlorine; no need for baffled tanks or pipe coils to retain water in plumbing before consumption.
Chlorine can cause flavors and odors which are objectionable to some people; neither ultraviolet light nor ozone add flavors or odors to the water. Chlorine has "staying power"-it continues to disinfect the water until the water is actually used; ozone and ultraviolet light provide no residual disinfection power.
Test kits can be used to monitor chlorine or ozone level in water; performance of ultraviolet disinfection units is more difficult to monitor.
Distillation uses lots of energy; works best for small batches of water; heat however, is the only disinfectant that can reliably treat cloudy water.

Discuss disinfection options with several water conditioning equipment suppliers to determine which system best meets your needs.

-other sources of information-

Your local county or community environmental/health sanitarian

Iowa Department of Public Health, Lucas State Office Building, Des Moines IA 50319-0075 (515-242-6340)

University of lowa Hygienic Laboratory, Oakdale Hall, lowa City, IA 52242 (319-335-4500)

Geological Survey Bureau, lowa Department of Natural Resources, 123 North Capitol, lowa City, IA 52242 (319-335-1575)

National Sanitation Foundation 3475 Plymouth Rd., P.O. Box 1468, Ann Arbor, Ml 48106 (313-769-8010)

Water Quality Association, 4151 Naperville Rd., Lisle, IL 60532 (708-505-0160)

This material is based upon work supported by the U.S. Department of Agriculture,

Extension Service, under project number 89-EWQI-1-9108

Ames, lowa 50011

AE 3060 July 1991

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