Green Chemistry and the Ten Commandments

water faucet. Furthermore, fish fingerlings were killed by whatever was getting through
the sewage treatment plant.
The culprit in the troublesome incidents of foam associated with sewage was found
to be the surfactant (the active ingredient that makes water “wetter”) in waste detergents,
a material called alkyl benzene sulfonate, ABS, for which the structure is shown below:

C C C C C C C C C C

H

H

H CH 3

CH 3

CH 3

CH 3

CH 3

CH 3

CH 3

CH 3

CH 3

S O- +Na

O

O

H

H

H

H

H

H

H

H

H

ABS

(Recall from Section 5.2 that the hexagon with a circle in it stands for an aromatic
benzene ring.) It is seen in this structure that there is a chain of 10 C atoms (counting
the one that is part of the end -CH 3 group), and attached to alternate C atoms on the
chain are -CH 3 groups. This molecule and similar ones with different C-atom chain
lengths were found to be very effective stable surfactants. There was only one problem,
which is that bacteria hate branched chains and would degrade this compound only
slowly. Hence it stayed around forming foam in sewage treatment plants and significant
amounts remained even after the treated water was discharged.
The solution to the ABS detergent problem was found in the 1960s. Although it
predates the concepts of green chemistry and industrial ecology, it is still cited as one
of the best applications of green chemistry. The solution to the problem created by
chemistry was to use chemistry to devise another kind of molecule, equally effective as
a surfactant, but much more to the liking of bacteria. The substance developed is still
used today and is known as linear alkyl sulfonate, LAS shown below:

LAS

C C C H

H H H

H H H

C

H

H H H H H H H

H H H H H H H H

H C C C C C C C C

O- +Na

O S O

Like ABS, LAS has a chain of carbon atoms. But it is a straight chain, not a branched
one. Bacteria like straight chains, the LAS degraded readily in the sewage treatment
plant, and the problem with surfactants in sewage went away.

7.14. Pesticides in Water

Food producers and gardeners constantly struggle with pests of various kinds that
consume food, ruin crops, compete for space, water, and nutrients, and otherwise make
life difficult and expensive. In addition to insecticides used to kill insects and herbicides

to control weeds, there are many other kinds of pesticides, including bactericides to
control bacteria, slimicides to control slime-causing organisms in water, and algicides
used against algae, all potential water pollutants. When the major water pollution control
laws were enacted around 1970, a great concern was DDT and other very persistent

Chap. 7. Water, The Ultimate Green Solvent 179