Foam -- A cause for concern?

by Dave Courtemanch, Aquatic Biologist (MDEP)

This following is an excerpt from "Foam -- A cause for concern", which appeared in the
Spring, 1979 issue of "Maine Fish and Game" magazine.

    Every summer, one of the most common inquiries made by people to the Department of Environmental Protection's Lakes Division is "does foam on the shore of a lake indicate detergent pollution and declining water quality?"

    Before answering that question, we need to know a little about detergents and the processes which produce foam.

    Foam is created when the surface tension of water (attraction of surface molecules toward the center, which gives a drop of water its round shape) is reduced and air is mixed in, causing bubble formulation.   Many substances, besides soap and detergents, will reduce surface tension.

    "Soap" is generally defined as compounds of fats, fatty acids, and caustic soda.  These materials, by reducing the surface tension of water, increase its cleansing ability and produce suds.

    The term "detergent" usually refers to synthetic compounds which came on the market after World War II.  They also work by reducing surface tension but have the added properties of "softening" water and emulsifying (or mixing with) oils.  The ability to soften water gives detergents their great advantage over soap.  Calcium and magnesium in "hard" waters tend to combine with soap, binding soil particles and causing the characteristic yellowing of clothes.  Phosphates in the synthetic detergents tie up the calcium and magnesium, thus increasing cleaning efficiency.

    The first synthetic detergents to come on the market were usually compounds of alkyl benzine sulfonate (ABS).   In the late 1950s and early 1960s, many communities experienced tremendous foam problems in lakes, rivers, sewage treatment plants, and even water faucets because of contaminated wells.  These events were highly publicized, and foam became a common indicator of pollution.

    Unlike soap, the structure of the ABS molecule was in a branched form which could not be broken down by bacteria.   Hence, the detergent accumulated in the water and was labelled "nonbiodegradable."  To combat this problem, the detergent industry changed the chemical structure to a simple linear form, LAS, which could be attached by bacteria.  Virtually all detergents today are of this simple "biodegradable" form, and great quantities of foam which had occurred from accumulation are thus prevented.

    To answer the original question then:  "No, foam on a lakeshore or in a stream probably is not due to detergent contamination."  Most foam is a product of nature.  Small trout streams often have pools of foam where fish will hide.

    "Natural" foaming occurs when small aquatic organisms (such as algae) die and decompose, releasing a variety of organic compounds.  Organic compounds leached from soil also cause foam.   The Indians were known to have used various materials, such as bark and plant roots, to clean items.  Like soap and ABS, these compounds also reduce surface tension.

    As wind or currents stir the water, foam is produced and may accumulate in quantities on windward shores in coves, or in eddies.  The natural foam has a somewhat earthy or fishy aroma, and it breaks down rather quickly.  Foam from silt or erosion is usually a dirty brown color.   Foam is often seen in the early morning hours and is gone by midday.   Detergent foam, by contrast, will have a noticeable perfumy smell from additives which give your wash that "rosegarden" or "lemon fresh" smell.

    Detergent pollution and foam can be a problem, but the foam will be localized close to the source of the discharge.  A simple experiment demonstrates that wide-spread foaming on a lake is probably not from detergents.  Using two common brands of detergent, we found that it took about 0.07 grams of detergent per liter of water to create suds in the laboratory.   To put this in terms of a lake, it would take about 43,178 kilograms (95,207 pounds) of detergent to suds-up a 40.5 hectare (100 acre) lake with an average depth of 1.5 meters (5 feet).  That's quite a few boxes of detergent!

    -- end of excerpt --