BIOAUGMENTATION CONSIDERATIONS - Bioaugmentation for Groundwater Remediation - page 155

Table 5.2. (continued)

Injection Wells Direct Push Trenching Fracturing

Capital cost Capital cost is moderate

relative to other passive
approaches
Costs increase
substantially when nested
wells are used to treat
large contaminated
thicknesses

Lowest capital cost for
passive approaches

Highest capital cost of
passive approaches

High capital cost due to
hydraulic fracturing
technology required

Operations and
maintenance (O&M)

O&M is fairly minimal in
passive applications
because injections are
infrequent

O&M is minimal unless
many injections are
required over the life of the
project; as the number of
injection events increases,
O&M of direct-push
injection will approach, and
eventually surpass
injection wells

Low to moderate O&M
required. Recirculation
systems may require O&M
to prevent fouling

No O&M required
Generally fracturing is only
performed one time

Some well rehabilitation
due to biofouling might be
required when injections
occur over several years

Implications for
bioaugmentation

Inoculation into injection
wells is preferred and most
commonly used method

Inoculation into direct-push
points is generally not
preferred

Direct inoculation during
trench installation not
recommended because of
likely exposure to oxygen

Inoculation during
fracturing generally not
performed because high
pressures and high
volumes would create
unpredictable distribution
of low volume inoculum

Few examples of direct-
push inoculation in
literature

Inoculation generally
performed through wells
directly in or just
downgradient of trench Inoculation generally

performed following
fracturing