C. Remediation of
groundwater contaminants
Physical, chemical, and biological
remediation methods
Objectives:
 Define
remediation and distinguish
among physical, chemical, and
biological remediation techniques
(bioremediation).
 List, describe, and give examples of
contaminated water remediation
techniques.
Remediation of contaminants:
 Definition
– Remediation is the return of an area or
component to as natural a condition as
possible (e.g., contaminated water).
Types of remediation:
 Physical
treatment may include air
striping, filtering of water, etc.
 Chemical treatments include addition of
chemicals that facilitate physical or
biological treatments, or oxidize
contaminants, etc.
 Biological treatment (bioremediation)
utilizes complex biochemical pathways
of various organisms to degrade or
detoxify contaminants.
Techniques for remediation:
 The
method of remediation depends on
the chemical nature of the contaminant:
– Pure-compound recovery is possible when
groundwater is contaminated with a compound that is
not water soluble.
– Pump and Treat methods typically involves
pumping contaminated groundwater out and
treating with appropriate types of treatment
• Air striping
• Chemical oxidation (using ozone, chlorine, etc)
– In-situ Remediation doesn’t involve removal
of the soil and groundwater
Pure-compound recovery:
 Organic
contaminants like oil and gasoline
are less soluble in water and can often be
pumped off the surface of aquifers.
 The specific gravity of the compound may
require pumping from the bottom of a
confined aquifer (if > 1.0).
 Sometimes, the product recovered is still
usable for its original function.
Pump and Treat/In-Situ Remediation
 Soil
vapor extraction (SVE) removes organic
contaminants (primarily from the unsaturated
zone) by flushing with air on site.
 Air sparging (in-situ aeration) uses circulated
air to remove volatile contaminants (primarily
from the unsaturated zone) on site
 Bioventing also introduces air, but only to
speed up natural aerobic microbial
processess.
Bioremediation techniques:
Bioremediation is the use of living organisms
like bacteria, plants, animals, or fungi to
speed up the remediation process.
 A tremendous variety of microbes have been
used for remediation of contaminants.
 In-situ bioremediation introduces microbes
directly into the water which then degrade
contaminants through biochemical
processes.

Examples of bioremediation:
 Microbes
have been used for centuries to
remediate wastewater (biol. treatment).
 Microbes can also degrade and detoxify a
wide variety of synthetic organic
compounds, metals, toxic elements, etc.
 Microbes used to degrade contaminants
include bacteria, and fungi.
 Plants, animals, and mixed populations of
different organisms can also be used .
Advanced treatment techniques:
 More
advanced treatment techniques
may utilize combinations of remediation
techniques.
 Examples include injecting surfactants or
chemicals underground to augment
conventional pump-and-treat techniques.
 These are efforts to integrate in-situ bioremediation with pump-and-treat
techniques.
Genetically-engineered
microbes:
 Attempts
have been made to genetically
engineer microbes so that they degrade
contaminants more efficiently and quickly.
 Microbes have been patented for this purpose
(“superbug” to degrade oil spills).
 There is concern that these “unnatural”
microbes may become pests in the
environment.
Summary:
 Remediation
of water (or return to
“natural” conditions by removal of
contaminants) may use physical,
chemical, or biological techniques.
 Remediation techniques include purecompound recovery, air stripping, pumpand-treat techniques, bioremediation, and
combinations of these.