EP 1110-1-27
27 Jan 00
2-9. Biological Assay
a. Purpose. Biofouling is historically a major or dominant component of corrosion and clogging
impacts on ground water remediation systems (Leach et al. 1991; Smith 1995; Alford and Cullimore
1999). Section 4-6 reviews potential effects of system biological activity.
(1) From a maintenance standpoint, it is well recognized that early detection is crucial to the
management of biofouling problems. However, it has always been difficult to correlate the results of
testing for biofouling components and the degree of deterioration of components of wells. For example,
samples that do not contain biofilm particulate matter and microorganisms do not necessarily indicate an
absence of this material. Cultivating media may not support microorganisms that contribute to fouling,
and sampling may not collect samples representative of the formation's and well system's microbial
ecology.
(2) Smith (1992), Cullimore (1993), Smith (1996), and Alford and Cullimore (1999) discuss and
provide guidance on biofouling assay methods and their utility in maintenance monitoring to provide
useful information. With such information, the following questions can be readily answered:
Is biofouling present?
What types of biofouling organisms are present?
Is the well more or less biofouled than before? The answer to this last question requires
monitoring over time.
b. Mission of biological tests. Biological assay plans have differing strategies depending on the
purpose of the study. Biological assays for maintenance monitoring have goals different from those for
general aquifer ecology or bioremediation planning. Maintenance monitoring methods chosen should be
task-oriented to detect those biological indicators or conditions that lead to reduced well system
performance. For this reason, methods that provide rapid, general insight into biofouling and biocorrosive
conditions are preferred over methods that characterize genetic makeup or metabolic capabilities.
c. Types of biological analyses employed in PM monitoring.
(1) Examination by light microscopy. This has traditionally been the method of choice for
confirming and identifying "iron bacteria" (APHA, AWWA, and WEF, 1998, Section 9240). However, in
many instances, biofouling as a cause of well problems may be difficult to diagnose via microscopy
alone, even with very good tools and skills (Smith, 1996).
(2) Cultural enrichment.
(a) Culturing can provide a means to detect nonfilamentous, metabolically active biofouling
microflora, and also to profile the ecological physiology niches occupied by microorganisms. Currently,
the most promising cultural approach, from a practical application standpoint in the United.States., for
routine maintenance monitoring purposes available in North America is the Biological Activity Reaction
Test (BART) method (Cullimore 1993). This method was found by Smith (1992) in field trials to provide
useful qualitative information in well biofouling events and is increasingly accepted as a standard
biofouling monitoring method (Smith 1996).
(b) The BART method tubes come with a variety of media mixtures. The IRB-BARTTM0 , for
example, is designed to recover anaerobic (sulfur- and nitrate-reducing) and microaerophilic heterotrophic
Fe- and Mn-precipitating microorganisms (iron-related bacteria, IRB). Cullimore (1993), Smith (1992,
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