76 Chapter 3 Introduction to Engineering Design
3.14 Drinking Water Standards in the United States
The U.S Environmental Protection Agency (EPA) sets the standards for the maximum level of
contaminants that can be in our drinking water and still be considered safe to drink. Basically,
the EPA sets two standards for the level of water contaminants: (1) the maximum contaminant
level goal (MCLG) and (2) the maximum contaminant level (MCL). The MCLG represents
the maximum level of a given contaminant in the water that causes no known harmful health
effects. On the other hand, the MCL, which may represent slightly higher levels of contami-
nants in the water, are the levels of contaminants that are legally enforceable. The EPA attempts
to set MCL close to MCLG, but this goal may not be attainable because of economic or tech-
nical reasons. Examples of drinking water standards are shown in Table 3.8.
See Problem 3.27 for other standards set by the EPA for the so-called Surface Water Treat-
ment Rule (SWTR).TABLE 3.8 Examples of Drinking Water Standards
Contaminant MCGL MCL Source of Contaminant by Industries
Antimony 6 ppb 6 ppb copper smelting, refining, porcelain plumbing
fixtures, petroleum refining, plastics, resins,
storage batteries
Asbestos 7 M.L. ( million 7 M.L. asbestos products, chlorine, asphalt felts and
fibers per liter) coating, auto parts, petroleum refining,
plastic pipes
Barium 2 ppm 2 ppm copper smelting, car parts, inorganic pigments,
gray ductile iron, steel works, furnaces, paper mills
Beryllium 4 ppb 4 ppb copper rolling and drawing, nonferrous metal
smelting, aluminum foundries, blast furnaces,
petroleum refining
Cadmium 5 ppb 5 ppb zinc and lead smelting, copper smelting,
inorganic pigments
Chromium 0.1 ppm 0.1 ppm pulp mills, inorganic pigments, copper
smelting, steel works
Copper 1.3 ppm 1.3 ppm primary copper smelting, plastic materials,
poultry slaughtering, prepared feeds
Cyanide 0.2 ppm 0.2 ppm metal heat treating, plating, and polishing
Lead zero 15 ppb lead smelting, steel works and blast furnaces,
storage batteries, china plumbing fixtures
Mercury 2 ppb 2 ppb electric lamps, paper mills
Nickel 0.1 ppm 0.1 ppm petroleum refining, gray iron foundries,
primary copper, blast furnaces, steel
Nitrate 10 ppm 10 ppm nitrogenous fertilizer, fertilizing mixing, paper
mills, canned foods, phosphate fertilizers
Nitrite 1 ppm 1 ppm
Selenium 0.05 ppm 0.05 ppm metal coatings, petroleum refining
Thallium 0.5 ppb 2 ppb primary copper smelting, petroleum refining,
steel works, blast furnacesCopyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀