25    ON-SITE TREATMENT SYSTEMS FOR AQUIFER
RESTORATION BIOLOGICAL TREATMENT
Paul D. Kuhlmeier, Senior Engineer
Geraghty & Miller, Inc.
Oak Ridge, Tennessee 37922
INTRODUCTION
Enactment of the Resource Conservation and Recovery Act in 1976 prompted a new era of environmental awareness in this country. The original act coupled with its 1984 amendments, CERCLA,
Clean Air Act and Clean Water Act have established rigorous ground water quality protection
standards on industry. In fact the breadth of the problem is still not fully understood. By the end of
1986, 951 sites were listed on EPA's National Priority List; by the end of 1988 this number will top
1500. EPA currently har a backlog of over 15,000 sites that may present a ground water problem, and
these are estimated to represent less than half of the total potentially contaminated sites in this
country. It is easy to comprehend how ground water treatment will grow from its present one to three
percent share of the water/wastewater treatment market to as much as 10-15% by 1992.
Herein lies the paradox between ground water treatment and traditional municipal and industrial
water treatment. While the bulk of treatment schemes used today for ground water treatment are
derived from traditional unit processes the design kinetics and systems costs are diametrically opposite. Classical fixed treatment systems are designed for 20 to 30 years of service; ground water
treatment systems rarely are in service for more than 5 years. This situation gives rise to much higher
ratios of operation and maintenance to capital construction costs. Many ground water treatment
systems dispose of spent chemicals or use them at less than optimal rates rather than go to the trouble
of regeneration or optimization testing.
The relatively small size of ground water systems has been shown to produce significant errors when
using standard design criteria for unit processes such as suspended growth reactors and coagulation
tanks. Consequently more pilot scale testing is necessary for hazardous waste treatment.
The most prominent difference between fixed treatment plants and on-site ground water treatment
is the fact that ground water treatment rarely establishes steady state conditions for any period of
time. Concentrations naturally decline in the influent stream due to dilution. Since most treatment
proceses are based on steady state influent concentrations and minimum chemical or substrate input,
ground water treatment becomes a dynamic process which in turn creates problems in maintaining a
constant effluent quality.
APPROACHES TO TREATING GROUND WATER
In order for any ground-water treatment system to be successful, it must be designed with site-
specific characteristics in mind. This includes an understanding of the mobility and distribution of
contaminants in the subsurface environment, in addition to soil and ground-water properties.
Two general classifications of ground-water treatment will be addressed, in-situ treatment and
above ground treatment. Although the ultimate objectives of these two classes are the same, the
processes used in achieving treatment are quite diverse between the classes and within various subsets
of each class. Specific site characteristics will govern which general class of treatment and the subset
of a given class is applicable. A list of several key parameters are given in Table I. Ultimately these
parameters will determine not only the appropriate cleanup technique but the duration and difficulty
of treatment involved.
In-situ treatment involves neutralization of contaminants by chemical or biological treatment.
Chemical treatment is often accomplished by oxidation with hydrogen peroxide. This method may be
appropriate to treat some organic and inorganic compounds including aldehydes, phenols, and cyanides.
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