In the mid-1980s several Pennsylvania communities experienced outbreaks of a waterborne disease called Giardiasis. Hundreds of citizens suffered with symptoms ranging from mild nausea to acute, severe intestinal distress. How did the Giardia cysts enter drinking water supplies? Studies showed that the outbreaks occurred in communities with inadequate chlorination systems, improperly operated and maintained filtration equipment, and even unfiltered water supplies. Since water supplies are not regularly tested for Giardia, the contamination was not detected until it was too late and entire communities had been exposed to contaminated drinking water.
From a health standpoint, Giardia has no long-term health effects. However, EPA studies conducted in Pennsylvania communities reveal that even a single Giardia outbreak may require investment in high cost filtration systems.
For residents relying on private wells, the presence of Giardia cysts from unfiltered water, although unlikely, may indicate that other contaminants are making it to the tap, as well. In either case, everyone will agree that the illness-causing cysts must be removed.
Preventing Giardiasis
Detection of Giardia cysts is difficult and is usually not done until an individual becomes infected and is showing symptoms. Testing water for Giardia requires filtering 10 to 50 liters of water and having a trained analyst inspect the concentrated sample with a microscope. This testing typically costs several hundred dollars through an accredited water testing laboratory. Testing water is somewhat limited because the absence of cysts in a single sample is still no guarantee that none exist in the water supply.
The Department of Environmental Protection (DEP) currently samples public water supplies for Giardia and enforces regulations concerning proper operation and maintenance of water treatment plants to insure removal of the cysts. If you suspect that Giardia contamination has occurred, contact your local community water company or the DEP.
For individuals drawing water from private wells, safeguarding the water supply rests on the homeowner. Where deep (greater than 80') groundwater sources are used for water supply, Giardia cysts are usually not a problem. However, if surface water seeps directly into a well, Giardia can contaminate even the deepest well. A well casing that extends above the surface of the ground and is properly grouted will keep surface water out of the well.
Springs and shallow wells have a higher probability of contamination because there is reduced soil filtration of the water flowing into these systems. A recent Penn State study found Giardia cysts in many roadside springs.
Ultraviolet Light (UV)
Ultraviolet or UV light treatment systems pass water through a chamber housing a quartz mercury lamp. Properly sized UV light systems can be effective in treating cysts in water but the sizing of the unit is critical. Other water quality parameters like sediment, iron and hardness can also affect the efficiency of a UV light system and may require pre-treatment.
