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Travel of Synthetic Detergents with
Percolating Water
P. H. McGAUHEY, Chairman
STEPHEN A. KLEIN, Assistant Research Specialist
Civil Engineering Department
University of California
Berkeley, California
INTRODUCTION
The importance of a knowledge of the travel of synthetic detergents with percolating water derives from a number of considerations, all related to the aesthetic
objection to frothing water, and to a growing need to dispel our ignorance of the
ground water polluting potential of polluted surface waters.
As the water needs of our burgeoning populations grow, ground water assumes
an unprecedented importance as a source of supply. A recent study (1) shows that
during the period 1960-1962 the increase in ground water use for domestic purposes
increased 52 per cent in 781 communities with populations of 25, 000 or more. At
the same time the increase in surface water use in these same communities was
but six per cent. In addition, discharge of sewage effluents to the ground is a
growing practice. For example, in 1960, 34 per cent of all housing units in the
United States lacked public sewerage facilities and depended largely upon septic
tanks. These tanks discharge crudely treated waste water underground with no reduction in detergent content between the tank and the percolation field. What is
the ground water polluting potential of this effluent? What happens to the detergent fraction?
The latter question may be directed to treated sewage as well as to septic
tank effluents. Everywhere streams and ponds containing sewage effluent contribute to the ground water, and recharge with water reclaimed from sewage is a
growing practice throughout the southwestern United States and in other parts of the
world. Is there danger that the value of water upgraded in quality through expensive reclamation plants in preparation for recharge will be depreciated by the persistence of detergents in objectionable amounts? In many cases the answer is
obviously "yes" if it is assumed that the detergent applied to the soil surface appears unaltered in the ground water; and conservatism born of ignorance leads to
such an assumption. Does this assumption have any justification? What happens
to detergents in the biologically active mantle of the earth?
Similar questions must be asked concerning the detergent that reaches the
groundwater itself. In contrast with surface water supplies, which may be drawn
from relatively unpolluted sources, or protected from detergent nuisance by the dilution necessary to overcome other polluting fractions ofsewage, groundwater is
subject to little control. It is likewise subject to little treatment, hence any detergent which appears at the wellhead persists into the household of the citizen.
What are the chances of detergent reaching the wellhead in significant concentrations?
Rain waters have been passing through the biologically active mantle of soil
for ages and yet ground waters have been notably free from bacteria. Although
engineers and others were slow to grasp the implications of this fact, it is now well
known that suspended solids and bacteria do not travel far in porous media when
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