EP 1110-1-27
27 Jan 00
readily combines with dissolved iron (Fe2+) to form encrusting iron sulfide minerals. Iron oxidation is also
driven anaerobically by denitrification. The CO2 generated by microbial respiration drives carbonate
equilibrium toward bicarbonate saturation. These and other microbial effects tend to complicate
geochemical estimating.
b. The importance of biological assays in maintenance monitoring. These assays provide:
An "early warning" method of predicting biological effects on geochemical transformations
such as predicting ferrous sulfide mineral formation in a 12.9o C (55o F) alkaline carbonate
ground water when SRB are detected.
Means of evaluating changes in biological activity over time. In this, the historic record is
essential.
always straightforward. Because the existing assay tools are inexact, proper interpretation is critical (but
becoming easier). Because interpretation is somewhat subjective and changing over time (e.g., compare
Smith 1992; Cullimore 1993; and Smith 1996), it is useful to involve personnel experienced with this type
of testing in planning an O&M program and in forming the O&M management team (Section 4.5). The
references to literature and web site resources provided (Appendix A) offer a background in the types of
effects to expect.
4-7. Impacts on Plant
The scope of this document does not extend to treatment plant O&M; however, it has become evident that
bio-physical-chemical activity in wells (pumping and injection) has a direct influence on plant and project
mission performance. In addition to the routine effects of pumped water quality on the plant, the
consequences of changes induced by well treatments should also be considered. Treatment effects may
include extended periods of sloughing from the well as damaged clog components are dislodged and
pumped out. In general, treatment plant effects expected should include direct adverse effects on
treatment plant performance, input and output effects, and institutional loss of confidence.
a. Direct adverse effects on treatment plant performance. These effects include:
Excessive organic loading ((biological oxygen demand (BOD), chemical oxygen demand
(COD), etc.)) of the plant.
Acid solution pH shock, which may be particularly disruptive for activated carbon or
biological digestion systems (relying on attached microflora). These should be neutralized to
within stated plant tolerance.
Process disruption due to increased BOD, COD, etc., of the development solution and
subsequent pumpage from wells re-establishing the biogeochemical status prior to the
treatment event.
Low contaminant concentration due to plume disruption.
Sediment production and geochemical alteration of constituents so that they are not as well
addressed by the treatment system. Clogging slugs of biofilm and solids (sand, silt, clay)
developed out of wells may be particularly destructive to membrane and resin bed treatment
systems.
Fouling of piping, sensors, air strippers, granular activated carbon columns, ultraviolet
emission lamps, etc.
Alteration of geochemistry. Rapid flip-flopping of pH can be expected during treatments.
Plants adapted to established reductive water may have to transiently adapt to a more
4-5
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