Permit Guidance 12 BADCT Limits for Volatile Organic Chemicals 11/08/10 Page 1

Permit

Guidance

12

Final

National Pollutant Discharge Elimination System (NPDES);

 BADCT Limits for Volatile Organic Compounds

Statutory references: ORC 6111.01, 6111.03,

6111.04

Rule references: OAC 3745-1-05, 3745-33-07

Ohio EPA, Division of Surface Water

Revision 0, November 8, 2010

This internal guidance does not affect requirements found in referenced rule or statute.

Background and Purpose

Ohio’s Antidegradation rule (OAC 3745-1-05) requires that new discharges be treated to levels

associated with the Best Available Demonstrated Control Technology (BADCT). The rule

specifically defines BADCT for domestic sewage and federal categorical industries. For

cleanups of response action sites contaminated by VOCs, BADCT is defined as treatment

capable of meeting 5 ug/l as a 30-day average for each chemical.

The purpose of this guidance is to define which chemicals are considered VOCs subject to this

treatment standard.

Treatment Used

The process of remediation requires that groundwater or contaminated surface waters are

pumped from their location to a receiving water to meet appropriate health standards for the site

waters. If VOC compounds are present, the discharge is usually treated to remove the VOC

compounds.

VOCs are normally separated from water by physical/chemical processes such as air stripping

or carbon adsorption. The effectiveness of these methods is determined by two

physical/chemical properties of the VOC compound - The Henry’s Law Constant and the water

solubility of the chemical.

Air stripping is designed to remove VOCs based on a ratio of their water solubility (the tendency

of the chemical to stay in solution) to vapor pressure (the tendency to volatilize). This ratio is

the Henry’s Law Constant. Chemicals with lower Henry’s Law Constants require greater

stripping column heights and greater air pressures than those with higher Henry’s Law

Constants.

Carbon adsorption is designed to remove organic chemicals by adsorbing trace materials that

have low water solubilities. Because most of these chemicals do not dissolve easily in water,

they will adsorb to carbon at high rates. Granular activated carbon (GAC) removes VOCs that

adsorb to carbon because the VOCs are carbon-based; the lower the solubility of the VOC in

water, the higher the rate of adsorption will be. Therefore, water solubility is used to predict

which chemicals will adsorb well to GAC.

Treatment Criteria for BADCT Standard

The literature on Henry’s Law Constants and strippability lists a range of values from 0.001 to

0.01 atm-m3/mole as the lower limit for air stripping. The consensus of published reports is that

MTBE, with a Henry’s Law Constant of 5.8 E-04, does not respond well to air stripping. Air

stripping columns appear to be able to remove 1,2-dichloroethane, with a constant of 9.8E-04. 

Chloroform, with a value of 3.7E-03 atm-m3/mole appears to be effectively removable by air
Permit Guidance 12 BADCT Limits for Volatile Organic Chemicals 11/08/10 Page 2

0.0001 0.01 1 100 10,000 1,000,000

0.1

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

Solubility, ppm

Koc

stripping. Likewise the BTEX compounds, with Henry’s Law constants ranging from 5.5E-03 to

7.9E-03 are readily removed by air stripping. Thus 1E-03 (0.001) atm-m3/mole appears to be a

safe threshold value for efficient air stripping.

Organic chemicals with high water solubilities will adsorb to carbon, but at a much lower rate

than less soluble chemicals. These more soluble chemicals can not be expected to meet the

BADCT standard because of this. The literature indicates that chloroform and methylene

chloride, with solubilities of 7,920 and 13,000 mg/l, respectively, are both difficult to remove

using granular activated carbon. Thus, the upper limit of water solubility for GAC removal is

approximately 8,000 mg/l. Note that the solubility of a volatile organic compound varies

inversely with the organic partition coefficient, Koc, which measures the chemical’s affinity for

carbon. Figure 1 shows the relationship between those two values for some common VOCs. 

While we could express the threshold for effective carbon sorption in terms of a minimum Koc,

the solubility limit may be a better measure because that data is more readily available and

generally more precisely measured.

Figure 1. Relationship between aqueous solubility and organic 

partitioning coefficient for VOCs.

Evaluation of Chemicals

Approximately 80 chemicals were evaluated for inclusion in this guidance. In addition to the

physical/chemical parameters listed above, the analytical quantification level (QL) for each

chemical was also reviewed to make sure that the QL was, or was likely to be, less than or

equal to 5 ug/l. The QLs used were those listed in DSW Limits Below Quantification Level

guidance document at www.epa.ohio.gov/dsw/guidance/guidance.aspx. The attached list of

chemicals are those evaluated that meet the three criteria:

1. Henry’s Law Constant > 1E-03, or

2. water solubility < 8,000 mg/l, and

3. analytical QL < 5 ug/l
Permit Guidance 12 BADCT Limits for Volatile Organic Chemicals 11/08/10 Page 3

The chemicals in Table 1 are not a complete list of VOCs. These are the chemicals initially

evaluated by DSW and DERR. Any chemical that meets one of the first two criteria, and meets

the third criterion is covered by this BADCT. Those chemicals in Table 1 with shaded Henry’s

Law Constants are considered to be strippable. Those chemicals with shaded water solubility

values will be sufficiently adsorbed to activated carbon to meet this limit.

Limits in NPDES permits and discharge authorizations under CERCLA records of decision need

to contain 30-day limits of 5 ug/l for any chemical subject to the antidegradation rule. Maximum

limits of 10 ug/l are typically also included in these documents.

Xylenes represent a special case. The three xylene isomers (o-xylene, m-xylene, p-xylene) are

not always able to be separated by USEPA-approved analytical methods. If this is the case,

limits for total xylene of 15 ug/l (30-day average) may be used as BADCT. Maximum limits are

typically set at 20 ug/l in this case.

For chemicals that meet the treatability criteria, but have analytical QLs greater than 5 ug/l, the

30-day limit should be set at the QL, because detections at this level are not expected, given

the treatability data. Maximum limits should be based on a measure of the standard analytical

error at the QL (3 standard deviations above the QL). To determine these values, consult the

DSW QL Guidance Document, USEPA analytical methods [40 CFR 136 or SW-846, as

appropriate], or quality assurance documents and information from Ohio EPA Division of

Environmental Services.

Chemicals not listed in Table 1 that meet the treatability criterion for water solubility, but not for

Henry’s Law Constant are not considered VOCs. These chemicals are treatable by carbon

adsorption, but may or may not be treatable to the BADCT level defined for VOCs. To develop

treatment technology limits for these chemicals using Best Professional Judgment, the following

sources should be consulted:

• Treatability information from DERR’s remedial response program database

• Wastewater treatability information published by U.S. EPA (available in CO-DSW)

• New source performance standards for the Organic Chemicals, Plastics and

Synthetic Fibers Industry [40 CFR Part 414].

Chemicals that do not meet either treatability criterion must be considered case-by-case. Water

soluble organic chemicals that are not strippable must generally be treated using a biological

process, either standard biological treatment processes, or specialized biological treatment

towers or columns. NPDES limits will be based on Permit-to-Install information on treatability

(or similar information for CERCLA sites), Ohio water quality criteria, and projections of CBOD

concentrations and their potential impacts on the receiving water.

For More Information, Contact:

Ohio EPA, Division of Emergency and Remedial Response

Remedial Response Program

Tim Christman (614) 644-2297 timothy.christman@epa.state.oh.us

Ohio EPA, Division of Surface Water

NPDES Permit Program

Eric Nygaard (614) 644-2024 eric.nygaard@epa.state.oh.us
Permit Guidance 12 BADCT Limits for Volatile Organic Chemicals 11/08/10 Page 4

Table 1. Chemicals Specifically Considered VOCs Under OAC 3745-1-05(A)(3)(f)

Shaded values in the Henry’s Law column are those chemicals that can be air-stripped from water.

Shaded values in the water solubility column are those that are amenable to carbon adsorption.

All values are from DERR’s database of chemical constants.

Henry's Law Water Solubility

Chemical Constant (atm-m3/mole) at 25C (mg/l)

Benzene 5.55E-03 1790

Bromobenzene 2.08E-03 410

Bromochloromethane 1.46E-03 16700

Bromodichloromethane 2.12E-03 1290

Bromoform 5.35E-04 3100

n-Butylbenzene 1.59E-02 11.8

sec-Butylbenzene 1.76E-02 17.6

tert-Butylbenzene 1.32E-02 29.5

Carbon Disulfide 1.44E-02 1190

Carbon Tetrachloride 2.76E-02 793

Chlorobenzene 3.77E-03 498

Chloroethane 1.11E-02 5680

Chloroform 3.67E-02 7950

bis-2-Chloroisopropylether 1.30E-04 1700

Chloromethane 8.82E-03 5320

2-Chlorotoluene 3.57E-03 347

4-Chlorotoluene 4.38E-03 1.06

Dibromochloromethane 7.83E-04 2700

1,2-Dibromo-3-chloropropane 1.47E-04 1230

1,2-Dibromoethane 6.67E-04 4150

1,2-Dichlorobenzene 1.90E-03 156

1,3-Dichlorobenzene 2.63E-03 125

1.4-Dichlorobenzene 2.40E-03 76

Dichlorodifluoromethane 3.43E-01 280

1,1-Dichloroethane 5.62E-03 5060

1,2-Dichloroethane 1.18E-03 8520

1,1-Dichloroethylene 2.61E-02 2250

cis-1,2-Dichloroethyene 4.08E-03 3500

trans-1,2-Dichloroethylene 9.38E-03 6300

1,2-Dichloropropane 2.82E-03 2800

1,3-Dichloropropane 1.82E-01 2750

1,1-Dichloropropene 5.00E-02 749

1,3-Dichloropropene 3.55E-03 2800

Ethylbenzene 7.88E-03 169

Hexachlorobutadiene 1.03E-02 3.2

Hexachloroethane 3.89E-03 7.7

n-Hexane 1.81E+00 10

Isopropylbenzene (Cumene) 1.15E-02 61.3

4-Isopropyltoluene 1.10E-02 23.4

Methylene Chloride 3.25E-03 13000

Pentachloroethane 1.94E-03 480

n-Propylbenzene 1.05E-02 52.2
Henry's Law Water Solubility

Chemical Constant (atm-m3/mole) at 25C (mg/l)

Permit Guidance 12 BADCT Limits for Volatile Organic Chemicals 11/08/10 Page 5

Styrene 2.75E-03 310

1,1,1,2-Tetrachloroethane 2.42E-03 1100

1,1,2,2-Tetrachloroethane 3.67E-04 2960

Tetrachloroethylene 1.77E-02 200

Toluene 6.64E-03 526

1,2,3-Trichlorobenzene 1.25E-03 18

1,2,4-Trichlorobenzene 1.42E-03 49

1,1,1-Trichloroethane 1.72E-02 1500

1,1,2-Trichloroethane 8.24E-04 4420

Trichloroethylene 9.85E-03 1100

Trichlorofluoromethane 9.70E-02 1100

1,2,3-Trichloropropane 3.43E-04 1750

1,2,4-Trimethylbenzene 6.16E-03 57

1,3,5-Trimethylbenzene 8.77E-03 48.2

Vinyl chloride 2.78E-02 8800

o-Xylene 5.18E-03 1780

m-Xylene 7.18E-03 1610

p-Xylene 7.53E-03 1620
Permit Guidance 12 BADCT Limits for Volatile Organic Chemicals 11/08/10 Page 6

Table 2. Chemicals Reviewed in Developing this Guidance Document

Shaded values in the Henry’s Law column are those chemicals that can be air-stripped from water.

Shaded values in the water solubility column are those that are amenable to carbon adsorption.

All values are from DERR’s database of chemical constants.

Henry's Law Water Solubility

Chemical Constant (atm-m3/mole) at 25C (mg/l)

Acetone 3.97E-05 1000000

Acetonitrile 3.45E-05 1000000

Acrylonitrile 1.38E-04 74500

Aniline 1.90E-05 36000

Benzene 5.55E-03 1790

Biphenyl 4.08E-04 6.94

Bromobenzene 2.08E-03 410

Bromochloromethane 1.46E-03 16700

Bromodichloromethane 2.12E-03 1290

Bromoform 5.35E-04 3100

Bromoethane 6.24E-03 15200

2-Butanone (MEK) 5.69E-05 223000

n-Butylbenzene 1.59E-02 11.8

sec-Butylbenzene 1.76E-02 17.6

tert-Butylbenzene 1.32E-02 29.5

Carbon Disulfide 1.44E-02 1190

Carbon Tetrachloride 2.76E-02 793

Chlorobenzene 3.77E-03 498

Chloroethane 1.11E-02 5680

Chloroform 3.67E-02 7950

bis-2-Chloroisopropylether 1.30E-04 1700

Chloromethane 8.82E-03 5320

2-Chlorotoluene 3.57E-03 347

4-Chlorotoluene 4.38E-03 1.06

Dibromochloromethane 7.83E-04 2700

1,2-Dibromo-3-chloropropane 1.47E-04 1230

Dibromomethane 8.22E-04 11900

1,2-Dibromoethane 6.67E-04 4150

1,2-Dichlorobenzene 1.90E-03 156

1,3-Dichlorobenzene 2.63E-03 125

1.4-Dichlorobenzene 2.40E-03 76

Dichlorodifluoromethane 3.43E-01 280

1,1-Dichloroethane 5.62E-03 5060

1,2-Dichloroethane 1.18E-03 8520

1,1-Dichloroethylene 2.61E-02 2250
Henry's Law Water Solubility

Chemical Constant (atm-m3/mole) at 25C (mg/l)

Permit Guidance 12 BADCT Limits for Volatile Organic Chemicals 11/08/10 Page 7

cis-1,2-Dichloroethyene 4.08E-03 3500

trans-1,2-Dichloroethylene 9.38E-03 6300

1,2-Dichloropropane 2.82E-03 2800

1,3-Dichloropropane 1.82E-01 2750

1,1-Dichloropropene 5.00E-02 749

1,3-Dichloropropene 3.55E-03 2800

1,3-Dinitrobenzene 3.74E-07 533

2,3-Dinitrotoluene 9.26E-08 220

2,4-Dinitrotoluene 1.30E-07 270

2,5-Dinitrotoluene 9.26E-08 220

2,6-Dinitrotoluene 7.47E-07 182

1,4-Dioxane 4.80E-06 1000000

Ethylene glycol 6.00E-08 1000000

Ethylbenzene 7.88E-03 169

Hexachlorobutadiene 1.03E-02 3.2

Hexachloroethane 3.89E-03 7.7

n-Hexane 1.81E+00 10

2-Hexanone 8.74E-07 1750

Isobutyl Alcohol 9.78E-06 55000

Isopropylbenzene (Cumene) 1.15E-02 61.3

4-Isopropyltoluene 1.10E-02 23.4

Methyl tert-butyl Ether (MTBE) 5.87E-04 51000

Methylene Chloride 3.25E-03 13000

Naphthalene 4.83E-04 3.1

Nitrobenzene 2.40E-05 2090

Nitroglycerine 4.33E-08 1380

Pentachloroethane 1.94E-03 480

n-Propylbenzene 1.05E-02 52.2

Styrene 2.75E-03 310

1,1,1,2-Tetrachloroethane 2.42E-03 1100

1,1,2,2-Tetrachloroethane 3.67E-04 2960

Tetrachloroethylene 1.77E-02 200

Tetrahydrofuran 7.05E-05 1000000

Toluene 6.64E-03 526

1,2,3-Trichlorobenzene 1.25E-03 18

1,2,4-Trichlorobenzene 1.42E-03 49

1,1,1-Trichloroethane 1.72E-02 1500

1,1,2-Trichloroethane 8.24E-04 4420

Trichloroethylene 9.85E-03 1100

Trichlorofluoromethane 9.70E-02 1100
Henry's Law Water Solubility

Chemical Constant (atm-m3/mole) at 25C (mg/l)

Permit Guidance 12 BADCT Limits for Volatile Organic Chemicals 11/08/10 Page 8

1,2,3-Trichloropropane 3.43E-04 1750

1,2,4-Trimethylbenzene 6.16E-03 57

1,3,5-Trimethylbenzene 8.77E-03 48.2

Vinyl acetate 5.11E-04 20000

Vinyl chloride 2.78E-02 8800

o-Xylene 5.18E-03 1780

m-Xylene 7.18E-03 1610

p-Xylene 7.53E-03 1620