Many different types of water quality standards have been established in the U.S., some state, some federal. Three types of standards will be presented here, drinking water, wastewater, and ambient. In the area of drinking water, a great deal of regulatory activity has recently occurred, and more is planned. This is a direct result of the signing of the Safe Drinking Water Act Amendments of 1986. Environmental impacts from wastewater discharges are controlled through the NPDES (National Pollution Discharge Elimination System) effluent permit system. The writing of effluent permits often requires a case-by-case evaluation. One of two different sets of standards may be used. The first set is the wastewater effluent standards. The second is an ambient surface water quality standard. In a general sense, both of these sets of standards hold. However, depending on site specific characteristics one set will result in more stringent controls, and it is that one that is used to set the NPDES requirements.

1. Drinking Water

In the U.S., ultimate responsibility for drinking water quality resides with the Environmental Protection Agency (EPA). The Safe Drinking Water Act Amendments of 1986 required that EPA promulgate minimum numbers of standards as directed by congress. Primary standards are developed for pollutants that are thought to have an adverse effect on human health. Secondary standards are guidelines for aesthetic, rather than health reasons. The enforceable primary standards are called maximum contaminant levels (MCLs). These are based on maximum contaminant level goals (MCLGs), levels where no adverse health effect would occur with a margin of safety. The MCLs are set as close to the MCLGs as feasible. The secondary (SMCLs) are also non-enforceable.

As of July 1987, there were 30 primary MCLs (including total coliforms and 3 radionuclides). In May 1989, MCLs were proposed for 27 contaminants not previously regulated (Federal Register, 22 May 1989). In addition, several of the earlier MCLs were modified (silver was dropped entirely). This gives a total of 56 MCLs covering 60 regulated contaminants (THM and Rn MCLs are group standards covering 4 and 2 contaminants respectively). In addition, the EPA has recently proposed monitoring requirements for an additional 113 unregulated contaminants (Federal Register, 22 May 1989). Since, the Safe Drinking Water Act Amendments apply to all water systems serving 25 people or more, the potential monitoring effort is enormous. However, considerable discretion is left to the primacy agency in determining monitoring requirements. Currently all of the states have established primacy except Indiana and Wyoming (and the District of Colombia).

2. Wastewater

These are technology-based standards, and are not dependent on the quality of the receiving waters. At the very least, all dischargers must meet these standards. In some areas subject to water quality degradation, more stringent standards are imposed. For municipal plants, the secondary treatment standards (30 mg/L TSS, 30 mg/L BOD) are applied uniformly. Industrial plants are evaluated based on detailed industry-specific wastewater technology evaluations. Standards may be expressed in terms of mass of pollutant per mass of industrial product, or simply in terms of a maximum effluent concentration. These industry-specific standards may be found in the Code of Federal Regulations, Title 40, Parts 402-699.

3. Ambient Water Quality

When the technology-based standards (above) fail to protect a receiving water so that it can no longer support its intended use, water quality-based standards are imposed. These are published in the "Gold Book" which is periodically updated by the USEPA.

Table 8.1

U.S. Selected Water Quality Standards

Table 8.1 (Cont.)

U.S. Selected Water Quality Standards

Table 8.1 (Cont.)

U.S. Selected Water Quality Standards

for European WQ Standards see: Stumm & Morgan, pg. 669 and refs

1. Conventional Pollutants

Significance:

Aesthetics,possibly an internal warning ?

3. protects pathogens during disinfection

2. Metals

Significance:

2. Possible association with Alzheimers Disease

1. suspected carcinogen
1. As(III) is probably more toxic than As(V)

1. Drinking Waters: in US about 80% of population drink finished waters with less than 0.002 mg/L, however, it may rise as high as 0.040 in some groundwaters (Dennis & Evans, 1994)
2. Most prevalent in the Western US, especially in groundwaters
3. Some studies have shown As(V) to be the prevalent form

Source:

1. Dissolution of the mineral, barium sulfate

2. trivalent : very insoluble, rarely found in potable water

Significance:

1. Hexavalent for is an acute systemic poison

3. heptavalent-used to oxidize the divalent form

3. Inorganic Non-metals

Source:

1. fertilizer in agricultural runoff

Source:

1. Partial denitrification of nitrate

2. Partial nitrification of ammonia

3. Industrial

2. excess causes fluorosis,

4. General Organics

Significance:

2. General indicator of anthropogenic pollutants

Significance:

1. toxic, and extremely persistent in the environment.

Source:

Significance:

1. animal carcinogens and mutagens

Source:

Significance:

Source:

5. Volatile Organic Compounds

Significance:

1. human and animal carcinogen

2. acute and chronic toxic effects

Source:

1. synthesis of polyvinyl chloride resins for construction

Significance:

2. carcinogenic and mutagenic activity uncertain

Source:

Significance:

Source:

1. solvent, heat transfer liquid, manufacture of fluorocarbons

Significance:

1. animal carcinogen

2. highly persistent in the environment

Source:

Significance:

1. may be an animal carcinogen

Source:

6. Pesticides

Significance:

1. animal carcinogen (hepatocarcinogen), may also affect CNS

Source:

Significance:

1. animal carcinogen

Source:

Significance:

1. low mamalian toxicity

2. not very persistent in the environment

Source:

Significance:

1. chronic toxicant, epileptic-type convulsions

Source: