The Pennsylvania Safe Drinking Water Act (35 P.S. §§ 721.1 - 721.17) mandates that a public water system supply drinking water that complies with primary and secondary Maximum Contaminant Levels (MCLs), as well as with treatment techniques. Section 109.202 of the Safe Drinking Water regulations (25 Pa. Code Chapter 109) states that. "A public water system shall provide adequate treatment to reliably protect users from the adverse health effects of microbiological contaminants, including pathogenic bacteria, viruses and protozoan cysts." Section 109.202 goes on to specify that. "The treatment technique shall provide at least 99.9 percent removal and inactivation of Giardia lamblia cysts, and at least 99.99 percent removal and inactivation of enteric viruses. Beginning January 1, 2002, public water suppliers serving 10,000 or more people shall provide at least 99 percent removal of Cryptosporidium oocysts."
Giardia lamblia can cause the disease known as giardiasis, of which several outbreaks have occurred in Pennsylvania since the late 1970s. Because of this, Pennsylvania adopted the PA Filter Rule in 1989. This rule requires that filtration and disinfection be provided at all public water systems that use either a surface water source or a groundwater source that is under the direct influence of surface water (GUDI).
Surface waters differ, as well as fluctuate, greatly in pH, alkalinity, hardness, temperature, turbidity, suspended solids and organic matter. Groundwaters, however, exhibit less variation in these parameters. Groundwaters typically are constant in temperature (about 53ºF) and low in turbidity (less than 2.0 NTU). With the exception of limestone aquifers, groundwaters also tend to be slightly acidic (about 6.5 to 6.9 in pH). The pH of limestone groundwaters may exceed 7.0.
Microbiological contaminants, such as Giardia lamblia cysts, have traditionally been associated with various surface waters, such as streams, rivers, ponds and lakes. This is understandably so, since the primary source of Giardia is the mammalian gastrointestinal tract. Another microbiological contaminant of recent concern is Cryptosporidium parvum, which also originates in mammals. Cryptosporidium parvum, which can cause the disease cryptosporidiosis, is resistant to disinfection, thus making filtration all the more crucial. Microbiological contaminants, however, are now being detected in groundwater. Certain geological conditions can serve as a conduit for these microbiological contaminants.
In order to account for groundwater as a source of microbiological contaminants, a definition of GUDI is included in Chapter 109. Section 109.1 defines GUDI as .any water beneath the surface of the ground with the presence of insects or other macroorganisms, algae, organic debris or large diameter pathogens such as Giardia lamblia and Cryptosporidium, or significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity or pH which closely correlate to climatological or surface water conditions... Essentially, any contaminant that may be present in a surface water may be present in groundwater that is directly influenced by that surface water. This may include organic and inorganic compounds.
The purpose of this document is to summarize the filtration technologies that are available to public water systems that have GUDI sources.
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3800-BK-DEP2118 (Rev. 7/2003)
Bureau of Water Standards and Facility Regulation
P.O. Box 8467
Harrisburg, PA 17105-8467