Water Quality Definitions
Maximum Contaminant Level Goal (MCLG) – The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety. MCLGs are set by the EPA.
Maximum Contaminant Level (MCL) – The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology.
Primary Drinking Water Standard – Maximum levels of contaminants that may have an adverse effect on the health of persons; specific treatment techniques adopted in lieu of maximum contaminant levels; the monitoring and reporting requirements that pertain to maximum contaminant levels.
Secondary Drinking Water Standard – An aesthetic quality standard. May apply to any contaminant in drinking water that may adversely affect the odor or appearance of the water and may cause a substantial number of persons served to discontinue its use.
Public Health Goal – The level of a contaminant in drinking water below which there is no known or expected risk to health. PHGs are set by the California Environmental Protection Agency.
Action Level – The concentration of a contaminant that, if exceeded, triggers a treatment or other requirement that a water system must follow.
Aquifer – A geologic unit that can store and supply significant quantities of water in underground formations composed of rock, sand, fractures and gravel. Water is stored in the small spaces between the grains of sand, rock or in the fractures.
Ground Water – The water that is stored in aquifers. Extracted for use by wells.
Well – A bored hole drilled through a geologic formation into an aquifer. Used to extract water from the aquifer.
Surface Water – Water either flowing in an open channel like a river or creek, or confined in a lake.
Watershed – Large areas of land that drain into a particular river, lake, reservoir or aquifer.
Treatment Technique – A required process intended to reduce the level of a contaminant in drinking water Links to
Other Water Related Web Sites
California-Nevada Section, American Water Works Association
American Water Works Association Research Foundation
Association of California Water Agencies
United States Environmental Protection Agency Office of
Ground Water and Drinking Water
Division of Drinking Water and Environmental Management
Regulation
All water utilities are regulated by the EPA and the DOHS. Investor-owned utilities are also regulated by the California Public Utilities Commission (CPUC). The CPUC works in concert with DOHS to assure that high quality water is delivered to customers at the lowest possible cost. This dynamic relationship between CPUC and DOHS provides an extra layer of protection for consumers.
Safe Drinking Water Act
Recognizing a need to address water quality issues in the nation's drinking water supply, the EPA first passed the Safe Drinking Water Act (SDWA) in 1974 regulating 14 contaminants. The SDWA was amended in 1986, bringing the total regulated contaminants to 56, including man-made contaminants like VOCs and SOCs for the first time. This revision primarily targeted surface water systems. Again in 1996, the SDWA was amended with an emphasis on source water protection and ground water sources. By the time this revision has run its course, more than 100 contaminants will be regulated with an ambitious plan in place to monitor and detect emerging contamination threats.
How Contaminants are Measured
The ability to detect and quantify contaminants has experienced enormous progress over the last few decades. Where once we were lucky to detect contaminants at it parts per million level, today it is common to detect contaminants in parts per billion and parts per trillion level, with parts per quadrillion level on the near horizon.
The old wet chemistry methods, while still occasionally used, have been replaced by mass spectrometers and gas chromatographs. Newer instrumentation like hydride generation, inorganically coupled plasma/mass spectrometry, and gas chromatography/mass spectrometry have lead the way. New microbiological methods have been developed to rapidly detect living organisms. New DNA based methods are in development for different types of microbes.
Yet, easy detection and quantification for some contaminants remains elusive, as is the case for the protozoan Cryptosporidium. Progress continues to be rapid and analytical detection methods will continue to improve to help utilities assure the safety of drinking water.
Water Quality
Because water is our business, CWA members work diligently to maintain high water quality standards. Our members maintain strict quality assurance programs aimed at meeting state and federal drinking water standards.
Methods Used to Ensure the Safety of Your Water
All water utilities are regulated by the U.S. Environmental Protection Agency (EPA) and the California Department of Health Services (DOHS).
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Private water utilities are also regulated by the California Public Utilities Commission (PUC).
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Drinking water systems must comply with operator certification requirements as outlined by the state. These requirements ensure that water systems are operated by qualified water technicians.
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Your Right to Know About Your Water — A new federal law requires water suppliers to develop and distribute Consumer Confidence Reports that provide important water quality information.
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Public Notification — Public water systems are required to notify the public whenever there is a violation of a drinking water standard.
The combination of state and federal regulation, coupled with the efforts by CWA member agencies to maintain strict water quality controls, provides public health protection to water consumers. In addition, your water utility plays a role in limiting contaminants or treating water to levels that are not harmful to your health. That is an important job that utilities take very seriously. After all, utility employees and their families also drink the water.
To learn more about your tap water, we encourage you to contact your utility to obtain a Consumer Confidence Report (or Annual Water Quality Report). This report provides specific information on the quality of your water.
Water Treatment Technology
There are many forms of treatment technology, both new and old, that utilities use to treat water. Many are the same technologies that bottled water companies use for their products. Each contaminant, when regulated, has a Best Available Technology or BAT, determined for its removal, when necessary. The quality of the source water dictates what form of treatment, if any, is required. The types of BATs used for different contaminants are listed below. More specific information can be obtained on the DOHS or EPA web pages.
Disinfection (for microbiological contaminants)
Chlorine
Chlorine dioxide
Chloramines (chlorine with ammonia)
Ozone
Perozone (peroxide and ozone)
Potassium Permanganate
Ultraviolet light (UV)
Organic Chemicals (VOCs and SOCs)
Granular Activated Carbon (GAC)
Packed Tower Aeration
Oxidation
Inorganic Chemicals and Metals
Coagulation, sedimentation, filtration
Ion Exchange
Oxidation with pressure filtration
Electrodialysis
Lime Softening
Corrosion Control
Granular Activated Carbon (GAC)
Membranes
Micro-filtration (MF)
Ultra-filtration (UF)
Reverse Osmosis (RO)
Types of Contaminants
Water is the universal solvent. It wants to absorb whatever it comes in contact with, whether minerals in the earth or man-made contaminants improperly discharged to the environment. Many of the naturally occurring contaminants can really only be called contaminants when they exceed certain levels in water. Otherwise, many of the inorganic chemicals and metals that can be found in water are essential to the every day diet of people. Things like calcium, fluoride, selenium, zinc and even arsenic can be found on the ingredient labels of many vitamin supplements, or in your drinking water.
The categories of contaminants are: inorganic chemicals, minerals, metals, radionuclides, physical parameters, microbiological, disinfection by-products (DBPs) and man-made contaminants like volatile organic chemicals (VOCs) and synthetic organic chemicals (SOCs).
For a full listing of regulated chemicals (there are almost 100), check the DOHS web site at www.dhs.cahwnet.gov/ps/ddwem. You can also check EPA, Office of Ground Water and Drinking Water at www.epa.gov/OGWDW.
New Contaminants
Occasionally water utilities, DOHS or EPA find new contaminants that are present in groundwater or surface waters due to improved chemical detection methods or new information on potential contaminant sources. Many water utilities are on the leading edge of research to identify new contaminants. Two such contaminants recently found to be of concern include perchlorate and NDMA.
Perchlorate
Perchlorate is an inorganic compound used as an oxidizing agent in solid rocket fuel. In 1997, concern about the potential for perchlorate contamination in drinking water wells prompted DOHS and utilities to monitor for perchlorate near aerospace facilities or other potential sources of contamination. DOHS investigated drinking water supplies near aerospace, munitions, and fireworks facilities throughout the state. The primary health concern related to perchlorate is its potential to interfere with the thyroid gland's ability to utilize iodine to produce thyroid hormones. Based on the potential health effects in drinking water, DOHS established an Action Level for perchlorate at 18 micrograms per liter.
Further information on perchlorate in California can be found at http://www.dhs.cahwnet.gov/ps/ddwem/chemicals/perchl/perchl_overview.htm.
NDMA
N-nitrosodimethylamine (NDMA) is used in many ways, including a use as a research chemical. It was formerly used as an intermediate chemical in the production of liquid rocket fuel. In 1998, concern about the potential for NDMA contamination prompted utilities to sample for the chemical. A limited number of drinking water wells located near hazardous waste sites or rocket fuel generation and storage sites have detected NDMA in the groundwater. Because NDMA is classified as a probable human carcinogen, in April 1998, DOHS established an Action Level for NDMA at 0.002 micrograms per liter. However, no validated analytical technology exists to detect NDMA levels down to 0.002 micrograms per liter. DOHS recommends utilities detecting any level of NDMA remove the source from service immediately.
Further information on NDMA in California can be found at http://www.dhs.cahwnet.gov/ps/ddwem/chemicals/NDMA/NDMAindex.htm.
Other Contaminants
The EPA and the DOHS are continuously evaluating new information for the potential regulation of emerging contaminants. There is a long list (up to 200) of unregulated contaminants that water utilities routinely monitor. The purpose of this monitoring is to help the regulatory agencies track the occurrence of (or lack of) contaminants in drinking water. When occurrences begin to be detected, the EPA and DOHS begin the process to regulate these chemicals to reduce exposure to the public.
CWA will continue to update you on important information pertaining to new contaminant levels. In a recent development, the DOHS adopted a secondary maximum contaminant level for Methyl Tertiary-Butyl Ether (MTBE). This substance is used in gasoline to promote more complete combustion and reduce exhaust emissions. Over the past several years, this substance has been detected in ground water and surface water in California and throughout the United States. Until a primary MCL is adopted, the DOHS will use its 13-ppb advisory action level to protect against health risks associated with exposures to MTBE in drinking water.