Secondary Contaminants In Drinking Water

Secondary contaminants are substances which are not directly health concerns, but may affect the taste, color, odor or some other aesthetic aspect of drinking water. The Secondary Drinking Water Standards are unenforceable federal guidelines regarding these contaminants, and are only suggested levels. Below is a list of the 15 contaminants for which the EPA has developed standards for municipal water systems. The Secondary Maximum Contaminant Level (SMCL) is listed in parentheses after the contaminant. Units are in milligrams per liter or parts per million unless stated otherwise.

Secondary Contaminants

ALUMINUM (0.05 - 0.2 mg/L)
Often added to municipal water in the course of treatment, as well as naturally occurring, high levels of aluminum may cause discoloration of water.

CHLORIDE (250 mg/L)
Found in salt or brackish water intrusion or runoff from road salt, chloride may cause taste and corrosion of pipes.

COLOR (15 color units)
Caused by various minerals or tannin from decayed vegetable matter, color is an aesthetic water quality.

COPPER (1.3 mg/L)
This metal may be leached from copper pipes by corrosive water and cause taste and blue-green staining of porcelain.

CORROSIVITY (non-corrosive)
Aesthetic and water related (corrosive water can leach pipe materials, such as lead, into drinking water.)

FLUORIDE (2.0 mg/L)
Added to municipal water, and occasionally naturally occurring, fluoride in excessive amounts may cause dental fluorosis, a brownish discoloration of teeth.

FOAMING AGENTS (0.5 mg/L)
Usually from soaps and detergents, these substances, while not generally harmful, are aesthetically unpleasing in drinking water.

IRON (0.3 mg/L)
Both naturally occurring and leached from pipes, iron may cause a metallic taste to the water and stain laundry or appliances.

MANGANESE (0.05 mg/L)
Associated with iron, manganese may also cause taste and staining. Manganese stains are very dark and can discolor the interior of dishwashers and other appliances.

ODOR (3 threshold odor number)
The odor of water can be traced to a wide variety of chemical substances as well as certain types of bacteria. Water which smells of rotten eggs usually contains hydrogen sulfide, a very disagreeable, but generally harmless substance. Taste and odor may be removed by a charcoal filter.

pH (6.5 - 8.5 pH units)
pH is a measure of the acidity or alkalinity of water. 7.0 is considered neutral, below 7.0 is acid and above 7.0 is alkaline (or basic). Water of an acidic nature may be corrosive and leach metals such as copper and lead from the plumbing. Basic water may form scale on the inside of pipes.

SILVER (0.1 mg/L)
This contaminant, used in photographic emulsions, can leach from landfills along with other metals. High levels may cause a condition known as argyria, a discoloration of the skin.

SULFATE (250 mg/L)
This naturally occurring chemical may cause taste and have a laxative effect.

TOTAL DISSOLVED SOLIDS (500 mg/L)
High TDS can damage plumbing and limit the effectiveness of soaps and detergents. TDS may also be used as an indicator of corrosivity. (see Hardness)

ZINC (5 mg/L)
Both naturally occurring and as a contaminant, zinc may impart a taste to water.

Other Aesthetic Drinking Water Factors

HARDNESS is a measure of dissolved minerals in water, mainly calcium and magnesium. The hardness scale is as follows: 0-75 soft, 75-150 moderately hard, 150-300 hard, over 300 is very hard.
(Standards taken from the EPA booklet Is Your Drinking Water Safe?, Office of Water (WH-550), September 1991 EPA 570/9-91-005)

Routine Water Testing Program

The Routine Water Testing Program at Fountain Valley Analytical Lab is an easy and inexpensive way of keeping track of your water quality.

Simply call: (410) 848-1014 or (410) 876-4554 or email us at CWM@fval.com for more information.

© 2005 Fountain Valley Laboratory, Inc.
Last update November 27, 2005