EP 1110-1-27
27 Jan 00
down to form H2O and O2, and the resultant oxygenation can actually enhance microbial growth away
from the well and the lethal oxidant zone. It may be used in piping system treatment to repress biological
activity. (CEGS 13405 and EM 1110-1-1008).
(d) Potassium permanganate. Potassium permanganate (AWWA B303), another powerful oxidant
used in maintaining industrial process systems and in water treatment (CEGS 13405) for relatively
uncontaminated water, is not used as a primary oxidant in well treatments. Dissolution of metals and
biofilms is more effectively accomplished using acids (Section 6-1c(1)).
(e) Use of heat. In some cases, water heated to 54o C and recirculated over several days is
sufficient without chemicals at least in the short term. Note: Heat propagates from the application source,
but typically accumulates in the well structure due to the poor thermal conductivity of soil materials. Heat
can actually enhance growth away from the thermal shock zone, as well as cause drying and shrinking
clays such as bentonite grout. Using heat alone is also very inefficient in terms of fuel or power to
generate thermal energy. The best approach to using heat is in a process such as the blended chemical
heat treatment method described below (6-1.c) with a prudent selection of chemicals (Alford and
Cullimore, 1999).
(3) Sequestration. In well treatment, these compounds are most properly used in low
concentrations in chemical blends as aids in acidizing mixtures to retain biofilm and metal oxide
components in solution for removal, once they are dissolved and dispersed in the water column. Examples
are various polyphosphates, pyrophosphates, and polyacrylamide-based compounds. In addition, acetic
acid and citric acid (Section 6-1c(1)), and some proprietary acid formulations also have related chelating
properties.
(a) Phosphate-containing compounds are NOT RECOMMENDED for maintenance well
treatment. Residuals of the compounds themselves (higher molecular weight (MW) polymers) and
breakdown products (low-MW pyrophosphate and orthophosphate or phosphate) remain behind in the
formation (attached to clays). The presence of an enhanced phosphate resource induces enhanced biofilm
development, often at the edge of development influence.
(b) Polyacrylamide and similar polyelectrolyte wetting agents provide the desired effects of
dispersing clogging deposits and clay/silt buildup without being phosphate sources. These compounds are
not readily attacked by microorganisms. They should be handled, used, and ultimately disposed of
according to manufacturer/supplier and MSDS instructions.
(4) Reactivity. Consult reactivity tables (e.g., Table 2-4) for problems with ground water
constituents. EM 1110-1-1008 provides guidance in system material reactivity.
c. Blended method treatments. Typically, no one chemical type will address all encrustation and
biofouling removal, suspension, dispersal, and repression needs. Blending approaches can permit more
effective removal of multiple problems, or treat a single difficult problem more effectively (Smith, 1995;
Alford and Cullimore, 1999). Appendix C includes one scenario. The exact blend of chemicals for a
particular well field situation is determined based on an analysis of the needs for cleaning the clogging
materials present and ground water quality.
d. Role of development. It should be emphasized that all chemical mixtures are far more effective
with adequate mechanical mixing and development, and should be specified based on an adequate
analysis of the problem.
6-4