Regulation and Risk Assessment of 1,4-Dioxane - Environmental Investigation and Remediation - page 284

protects POTWs from pollutants that could disrupt the chemical and biological balance necessary
to operate the POTW and prevent introduction of pollutants to the POTW that may pass through the
treatment works untreated. Limiting the chemical load arriving at the POTW improves opportuni-
ties to reuse wastewater and sludges generated by the POTW. Concentration limits for discharge to
sewers are established by USEPA, state, or regional and local sewer districts and municipalities.

6.2.5.1 Industrial Wastewater Discharge Regulations
Pharmaceutical production is among the industries generating wastewater containing 1,4-dioxane.
In 1995, revisions to the Clean Water Act introduced guidelines for efl uent limitations and pretreat-
ment standards for pollutants discharged to POTWs from pharmaceutical manufacturing plants
(USEPA, 1997b). The guidelines addressed 1,4-dioxane discharges by establishing Pretreatment
Standards for Existing Sources, and Best Available Technology Efl uent Limitations, as listed in
Table 6.14.
USEPA's review of chemicals in pharmaceutical manufacturing efl uent noted the occurrence of
1,4-dioxane. Although all six plants surveyed discharged 1,4-dioxane, USEPA determined that the
average loading (0.061% of total loading, about 24,000 pounds annually) did not warrant regulation.
In making this determination, USEPA acknowledged that 1,4-dioxane might pass untreated through
POTWs and therefore solicited data from dischargers regarding the fate of 1,4-dioxane in biological
treatment processes. As a placeholder, USEPA assumed that 1,4-dioxane should be at least as bio-
degradable as tetrahydrofuran on the basis of structural similarities (USEPA, 1998a). Subsequent
research has shown that the i rst-order aerobic biodegradation decay constant for tetrahydrofuran is
approximately twice that of 1,4-dioxane; therefore, 1,4-dioxane is unlikely to degrade as quickly as
tetrahydrofuran (Zenker et al., 2000).
USEPA groups 1,4-dioxane in pharmaceutical wastewater with “alcohols and related pollutants,”
including methanol, ethanol, n -propanol, isopropanol, n -butyl alcohol, tert -butyl alcohol, amyl alco-
hol, formamide, N,N-dimethylaniline, pyridine, aniline, and petroleum naphtha. The economic fea-
sibility of removing this entire group of compounds was evaluated by USEPA, but the cost, $40
million/year, was deemed excessive compared to the benei t, because USEPA assumed all com-
pounds in the group were easily biodegradable.
Substantial efforts have been made to eliminate 1,4-dioxane discharge in treated wastewater
efl uent from the production of polyester i bers. In Spartanburg, North Carolina, the Hoechst
Celanese polyester plant invested millions of dollars in a large-scale treatment system including
construction of a 54,000-gallon holding tank, an azeotropic distillation column for separation of
dioxane from the process wastewater, and a gas-i red thermal oxidizer for the destruction of 1,4-
dioxane (O'Neal Inc., 2007).
1,4-Dioxane is required for efl uent monitoring from leachate treatment at several landi lls, for
example, Laraway Waste Management facility in Elwood, Illinois (IEPA, 2007). At the Lowry
Landi ll Superfund Site in Aurora, Colorado, wastewater containing 1,4-dioxane is permitted for
discharge to the City of Aurora's wastewater treatment plant.

TABLE 6.14
1,4-Dioxane Pretreatment Standards for Pharmaceutical Manufacturing Effl uent

Long-Term Mean
Concentration (mg/L)

Maximum for Any
One Day (mg/L)

Monthly Average
(mg/L) Standard

Best available technology 0.8 8.4 2.6

Pretreatment standards for
existing sources

1240 3160 1760

Source: U.S. Environmental Protection Agency (USEPA), 1997b, Federal Register 62(153): 42,720-42,732.