BIOAUGMENTATION CONSIDERATIONS - Bioaugmentation for Groundwater Remediation - page 139

CHAPTER 5

BIOAUGMENTATION CONSIDERATIONS

Carol E. Aziz, 1 Ryan A. Wymore 2 and Robert J. Steffan 3

1 ENVIRON, Mississauga, Ontario, Canada; 2 CDM Smith, Denver, CO; 3 Shaw Environmental,
Inc., Lawrenceville, NJ

5.1 INTRODUCTION
Bioaugmentation can be employed in bioremediation systems to improve the rate and
extent of solvent remediation. This chapter is intended to assist practitioners by summarizing
the factors that should be considered when selecting and designing a bioremediation approach
employing bioaugmentation.
Several factors can influence the effectiveness of bioaugmentation. These factors include
the environmental site conditions, inoculum volumes and densities, and the overall bioremedi-
ation strategy to be used at the site. In short, practitioners have to make several decisions when
implementing bioaugmentation that can affect the success of the effort, the time required for
effective treatment, or the costs for remediation.
This chapter begins by describing the effects of site conditions on the effectiveness of
bioaugmentation (Section 5.2 ). Section 5.3 (Field Methods) discusses electron donor, buffer and
culture requirements, along with culture injection and initial distribution techniques. The final
section, Section 5.4 , describes typical bioremediation system configurations and the implica-
tions and considerations for bioaugmentation.

5.2 EFFECT OF SITE CONDITIONS ON EFFECTIVENESS
OF BIOAUGMENTATION
Several factors influence the establishment and performance of bioaugmentation cultures
introduced into groundwater environments. These include exposure to oxygen, temperature
and pH, competition for electron donor, chlorinated solvent concentration, the presence of
other chlorinated solvents, and site hydrogeology. These factors are briefly discussed below.

5.2.1 Exposure to Oxygen

Dehalococcoides spp. ( Dhc ) are strict anaerobic microorganisms, and oxygen toxicity can
significantly impact culture viability (Maym ´ -Gatell et al., 1997 ). To prevent oxygen exposure,
delivery of several of the Dhc - containing commercial cultures (such as KB-1 ® and SDC-9 TM )
has been accomplished using shipping canisters that maintain anaerobic culture conditions, and
the culture is typically added to aquifers after anaerobic and reducing conditions have been
achieved. For example, one vendor recommends that groundwater have an oxidation-reduction
potential (ORP) below 75 millivolts (mV) and a dissolved oxygen concentration of less than

0.2 milligrams/liter (mg/L) prior to the injection of the Dhc- containing culture. Other important
ORP indicators prior to bioaugmentation are evidence of nitrate and sulfate reduction.