EP 1110-1-27
27 Jan 00
project should employ personnel or contractors to perform well cleaning who cannot clearly demonstrate
competence in use of, and a thorough understanding of the potential reactivity between well cleaning
chemicals, contaminants of concern and other chemicals present on the site.
b. Chemical classes and properties. The following paragraphs summarize chemical purposes and
effects, safety, handling, and effectiveness features.
(1) Acids. Acids are used to dissolve hard encrusting materials, including Fe and Mn oxides and
carbonate deposits. Tables 6-1 and 6-2 list acids most commonly used in well rehabilitation. Table 6-1
lists recommended compounds. Table 6-2 lists commonly used well cleaning compounds not
recommended by the USACE for HTRW well PM treatment.
Table 6-1. Recommended Acid Compounds
Acid
Descriptors
Safety & Handling
Acetic acid
Excellent biocide and biofilm
Safety: Use gloves, splash protection, and
dispersing acid. Relatively safe to
respirator at barrel end*. Does not require
handle. Often a major component of
placarding for shipment.
biofouling "enhancers" and brand-
Handling: These solutions freeze at working
ambient temperatures: glacial at 10o to 12.8o C
name mixtures specified for
(50o - 55o F), 84% at 4.4o C (40o F), 15%
biofouling. Acidizing to pH < 2 with
(working solution) ~ 0o C (32o F). Make the
sulfamic acid recommended (rapidly
loses acid power without). Should use
dilution at an ambient above the stock solution
food or good industrial grade > 85 %
freezing point.
acid. (variation: glycolic or hydroxy-
acetic acid).
Sulfamic
Relatively effective against carbonate
Safety: Relatively safe to transport and handle
acid
scales, and as an acid enhancer for
(solid, dust inhalation should be avoided).
acetic acid. Not effective alone
Handling: Solid, less aggressive than HCl
against biofouling or metal oxides.
(Table 6-2). Use gloves, dust mask and
goggles. Provide proper ventilation. Circulate
during mixing.
Other
For example, oxalic and citric acids.
Safety: Safe to transport.
organic acids Useful as chelating agents. Oxalic
Handling depends on form (typically granular
acid is also effective as a primary
solids). Use gloves, dust mask, and goggles.
acidizer in low-Ca water. Often form
Provide proper ventilation. Circulate during
insoluble precipitates in high-Ca
mixing.
waters.
* Refer to Chapter 7 and health and safety references.
(2) Biocides. These agents are used in the attempt to reduce bacterial populations. As in water
supply well cleaning (Borch, Smith, and Noble 1993), in HTRW well cleaning (maintenance or
rehabilitation), reducing bacterial numbers is typically impractical and no longer considered a primary
objective (Smith 1995; Alford and Cullimore 1999). The reduction of hydraulic impact and other
symptoms for the longest time possible is the primary objective.
(a) Chlorine (typically sodium or calcium hypochlorite (AWWA Standard B300)). Sodium
hypochlorite is liquid and more likely to retain solubility in high total dissolved solids solutions. One
procedure used to limit and remove biological encrustation is termed a "shock" chlorine treatment.
Standard ANSI/AWWA C654-97 covers the procedures for shock chlorination and bacteriological testing
6-2
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