National Emission Standards for Hazardous Air Pollutants for Source Categories: Organic Hazardous Air Pollutants From the Synthetic Organic Chemical Manufacturing Industry and Other Processes Subject to the Negotiated Regulation for Equipment Leaks; Proposed Rule Clarifications; Correction

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[AD-FRL-5879-1]

RIN 2060-AC19

National Emission Standards for Hazardous Air Pollutants for

Source Categories: Organic Hazardous Air Pollutants From the Synthetic

Organic Chemical Manufacturing Industry and Other Processes Subject to

the Negotiated Regulation for Equipment Leaks; Proposed Rule

Clarifications; Correction

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule: Correction.

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SUMMARY: On January 17, 1997, the EPA amended certain portions of the

``National Emission Standards for Hazardous Air Pollutants for Source

Categories: Organic Hazardous Air Pollutants from the Synthetic Organic

Chemical Manufacturing Industry and Other Processes Subject to the

Negotiated Regulation for Equipment Leaks.'' This rule is commonly

known as the Hazardous Organic NESHAP or the HON. Among the changes

made to the rule in that action, the EPA added a definition for

``enhanced biological treatment systems or enhanced biological

treatment processes'' to the rule and made clarifying revisions to

appendix C of part 63. This action proposes to revise this definition

in order to clarify its meaning and proposes revisions to appendix C of

part 63 to reflect the clarification of the definition for ``enhanced

biological treatment systems or enhanced biological treatment

processes.'' This action also proposes to revise the compliance

demonstration procedures for biological treatment units to remove

restrictions on the use of the batch test procedure.

These proposed amendments to the rule would not change the basic

control requirements of the rule or the level of health protection it

provides. The rule requires new and existing major sources to control

emissions of hazardous air pollutants to the level reflecting

application of the maximum achievable control technology.

DATES: Comments. Comments must be received on or before September 22,

1997, unless a hearing is requested by September 2, 1997. If a hearing

is requested, written comments must be received by October 6, 1997.

Public Hearing. Anyone requesting a public hearing must contact the

EPA no

[[Page 44609]]

later than September 2, 1997. If a hearing is held, it will take place

on September 8, 1997, beginning at 10 a.m.

ADDRESSES: Comments. Comments should be submitted (in duplicate, if

possible) to: Air and Radiation Docket and Information Center (6102),

Attention Docket Number A-90-23 (see docket section below), Room M-

1500, U.S. Environmental Protection Agency, 401 M Street, SW,

Washington, DC 20460.

Public Hearing. If a public hearing is held, it will be held at the

EPA's Office of Administration Auditorium, Research Triangle Park,

North Carolina. Persons interested in attending the hearing or wishing

to present oral testimony should notify Kim Teal, U.S. Environmental

Protection Agency, Research Triangle Park, NC 27711, telephone (919)

541-5580.

Docket. Docket No. A-90-23, containing the supporting information

for the original NESHAP and this action, are available for public

inspection and copying between 8 a.m. and 5:30 p.m., Monday through

Friday, at the EPA's Air and Radiation Docket and Information Center,

Waterside Mall, Room M-1500, first floor, 401 M Street SW, Washington,

DC 20460, or by calling (202) 260-7548 or 260-7549. A reasonable fee

may be charged for copying.

FOR FURTHER INFORMATION CONTACT: For general questions, contact Dr.

Janet S. Meyer, Coatings and Consumer Products Group, at (919) 541-

5254. For technical questions on appendix C and wastewater provisions,

contact Elaine Manning, Waste and Chemical Processes Group, telephone

number (919) 541-5499. The mailing address for the contacts is Emission

Standards Division (MD-13), U.S. Environmental Protection Agency,

Research Triangle Park, NC 27711.

SUPPLEMENTARY INFORMATION: Comments on the proposed changes to the

NESHAP may also be submitted electronically by sending electronic mail

(e-mail) to: [email protected]. Electronic comments must

be submitted as an ASCII file avoiding the use of special characters

and any form of encryption. Comments will also be accepted on diskette

in WordPerfect 6.1 or ASCII file format. All comments in electronic

form must be identified by the docket number A-90-23. No Confidential

Business Information (CBI) should be submitted through e-mail.

Electronic comments may be filed online at many Federal Depository

Libraries.

I. Regulated Entities and Background Information

A. Regulated Entities

The regulated category and entities affected by this action

include:

------------------------------------------------------------------------

Category Examples of regulated entities

------------------------------------------------------------------------

Industry............................... Synthetic organic chemical

manufacturing industry (SOCMI)

units, e.g., producers of

benzene, toluene, or any other

chemical listed in Table 1 of

40 CFR part 63, subpart F.

------------------------------------------------------------------------

This table is not intended to be exhaustive but, rather, provides a

guide for readers regarding entities likely to be interested in the

revisions to the regulation affected by this action. This action is

expected to be of interest to owners and operators subject to this rule

who plan to use biological treatment to comply with control

requirements for wastewater streams. Entities potentially regulated by

the HON are those which produce as primary intended products any of the

chemicals listed in table 1 of 40 CFR part 63, subpart F and are

located at facilities that are major sources as defined in section 112

of the Clean Air Act. To determine whether your facility is regulated

by this action, you should carefully examine all of the applicability

criteria in 40 CFR 63.100. If you have questions regarding the

applicability of this action to a particular entity, consult the person

listed in the preceding FOR FURTHER INFORMATION CONTACT section.

B. Background on the Rule

On April 22, 1994 (59 FR 19402), and June 6, 1994 (59 FR 29196),

the EPA published in the Federal Register the NESHAP for the SOCMI, and

for several other processes subject to the equipment leaks portion of

the rule. These regulations were promulgated as subparts F, G, H, and I

in 40 CFR part 63, and are commonly referred to as the hazardous

organic NESHAP, or the HON. Since the April 22, 1994 notice, there have

been several amendments to clarify various aspects of the rule. Readers

should see the following Federal Register documents for more

information: September 20, 1994 (59 FR 48175); October 24, 1994 (59 FR

53359); October 28, 1994 (59 FR 54131); January 27, 1995 (60 FR 5321);

April 10, 1995 (60 FR 18020); April 10, 1995 (60 FR 18026); December

12, 1995 (60 FR 63624); February 29, 1996 (61 FR 7716); June 20, 1996

(61 FR 31435); August 26, 1996 (61 FR 43698); December 5, 1996 (61 FR

64571); and January 17, 1997 (62 FR 2721).

In June 1994, the Chemical Manufacturers Association (CMA) and Dow

Chemical Company (Dow) filed petitions for review of the promulgated

rule in the U.S. Court of Appeals for the District of Columbia Circuit,

Chemical Manufacturers Association v. EPA, 94-1463 and 94-1464 (D.C.

Cir.) and Dow Chemical Company v. EPA, 94-1465 (D.C. Cir). The

petitioners raised over 75 technical issues on the rule's structure and

applicability. Issues were raised regarding details of the technical

requirements, drafting clarity, and structural errors in the drafting

of certain sections of the rule. On August 26, 1996, the EPA proposed

clarifying and correcting amendments to subparts F, G, H, and I of part

63 to address the issues raised by CMA and Dow on the April 1994 rule.

On December 5, 1996 and January 17, 1997, EPA took final action on the

amendments proposed on August 26, 1996.

II. Proposed Clarification of Definition of Enhanced Biological

Treatment System or Enhanced Biological Treatment Process

The August 26, 1996 proposed changes to the wastewater treatment

provisions included provisions that provided easier compliance

demonstration options for well-mixed activated sludge systems that are

used to control readily biodegraded compounds. In that proposed change

to the April 1994 final rule, the compounds listed in table 9 of

subpart G were divided into three lists; these lists were presented in

table 36 of subpart G. In the proposal, a performance evaluation would

not be required for an activated sludge system if it met the definition

of ``enhanced biological treatment system or enhanced biological

treatment process'' and if the unit was controlling wastewater streams

that contained only list 1 compounds. The August 1996 proposed

revisions to the rule also required a performance demonstration for

activated sludge systems used to treat a combination of list 1 and list

2 and/or list 3 compounds.

The August 1996 proposal defined an enhanced biological treatment

system as

an aerated treatment unit(s) that contains biomass suspended in

water followed by a clarifier that removes biomass from the treated

water and recycles recovered biomass to the aeration unit. The mixed

liquor volatile suspended solids (biomass) is greater than 1

kilogram per cubic meter throughout each aeration unit. The biomass

is suspended and aerated in the water of the aeration unit(s) by

either submerged air flow or mechanical agitation.

This definition of ``enhanced biological treatment system or enhanced

biological treatment process'' was intended to

[[Page 44610]]

reflect the basis for the simplified compliance approach for some

systems. The 3 lists of compounds in table 36 of subpart G were

developed by modeling performance of an activated sludge system that

was a thoroughly mixed biological treatment unit. (A thoroughly mixed

or completely mixed system is a biological treatment unit where biomass

and wastewater entering the tank are dispersed quickly throughout the

tank such that the system achieves or approaches uniform

characteristics throughout the tank (Docket number A-90-23, item VII-B-

8).) After the August 1996 proposal, the EPA learned that some people

were interpreting the proposed definition of ``enhanced biological

treatment system or biological treatment process'' to apply more

broadly than intended. In the January 17, 1997 final rule, the phrase

``homogeneously distributed'' was added to the second sentence of the

definition to clarify the EPA's intent to define a uniformly well-mixed

biological treatment unit. The EPA thought that this revision would

better reflect the modeling and clarify the EPA's intent to limit the

types of biological treatment units that could use the simplified

compliance option to systems that were similar to the modeled case. The

EPA also believed that this change did not alter the meaning of the

term.

Since January 17, 1997, the EPA has learned that industry

representatives were concerned that the revised definition could be

read to require absolute uniformity in the biomass concentration. These

industry representatives have pointed out that they believe that such a

reading of the definition could preclude any system from using the

simplified compliance approach and the performance evaluation

exemption. It was not the EPA's intent that the phrase ``homogeneously

distributed'' be interpreted in this way. Therefore, the EPA is

proposing clarifying changes to the definition of ``enhanced biological

treatment system or enhanced biological treatment process'' and

proposing parallel conforming changes to appendix C to part 63.

Today's action would revise the definition of ``enhanced biological

treatment system or enhanced biological treatment process'' to read:

Enhanced biological treatment system or enhanced biological

treatment process means an aerated, thoroughly mixed treatment

unit(s) that contains biomass suspended in water followed by a

clarifier that removes biomass from the treated water and recycles

recovered biomass to the aeration unit. The mixed liquor volatile

suspended solids (biomass) is greater than 1 kilogram per cubic

meter throughout each aeration unit. The biomass is suspended and

aerated in the water of the aeration unit(s) by either submerged air

flow or mechanical agitation. A thoroughly mixed treatment unit is a

unit that is designed and operated to approach or achieve uniform

biomass distribution and organic compound concentration throughout

the aeration unit by quickly dispersing the recycled biomass and the

wastewater entering the unit.

The proposed definition includes the following changes made to the

January 17, 1997 definition. The term ``thoroughly mixed'' would be

added to the first sentence and ``homogeneously distributed'' would be

removed from the second sentence of the definition. A sentence would be

added to the end of the definition to clarify the meaning of the phrase

``thoroughly mixed treatment unit'' in the first sentence.

The description of a ``thoroughly mixed treatment unit'' in the new

sentence is intended to convey the concept of an activated sludge

system that is designed and operated to approach or achieve the

characteristics of a completely backmixed system. Because the EPA does

not intend the definition to only allow systems with perfect uniformity

in characteristics, a ``thoroughly mixed treatment unit'' would be

described as a unit that is ``designed and operated to approach or

achieve uniform biomass distribution and organic compound

concentration.'' This description is intended to recognize that well-

designed complete mix systems may still have small insignificant

stagnant zones or other minor deviations from complete mixing. This was

the intended meaning of the definition promulgated on January 17, 1997

as well as the intended meaning of the definition proposed on August

26, 1996.

An example of a system that would meet the enhanced biological

treatment system definition would be a well-designed, well-operated,

and well-maintained activated sludge system that has uniform

characteristics in the aeration unit. The biological treatment unit of

this enhanced biological treatment system would be thoroughly mixed

throughout the unit and biomass and wastewater entering the unit would

be quickly dispersed throughout the unit. The design of the unit would

be such that uniform mixing and quick dispersion of the biomass and

wastewater entering the unit would occur. The design and operation of

the biological treatment unit would take into account mixing, quick

dispersion of the biomass and wastewater entering the unit, the

location of the wastewater inlet with regards to aerators and the

wastewater outlet.

In smaller size units, uniform mixing and quick dispersion could be

achieved with a round or square tank and only one influent. For larger

scale systems, uniform mixing and quick dispersion could be achieved by

having multiple influents of biomass and wastewater. In either case,

the biological treatment unit would have uniform distribution of

organic concentration and mixed liquor volatile suspended solids

(MLVSS) throughout the vessel where the biological reactions occur.

A plug-flow system is an example of a biological treatment system

that does not meet the enhanced biological treatment system definition.

Plug-flow systems typically occur in long tanks with a high length-to-

width ratio in which longitudinal dispersion is minimal or absent

(Docket number A-90-23, item VII-B-8). Plug-flow systems are not

considered acceptable units for the performance test exemption because

they tend to have higher air emissions at the front of the system where

the concentration is higher. The modeling used to develop the

simplified compliance approach for systems meeting the definition for

an ``enhanced biological treatment system or enhanced biological

treatment process'' did not address plug-flow systems. The EPA did not

evaluate the performance of plug-flow systems in the development of the

3 lists for the simplified compliance approach due to the complexity of

plug-flow systems. The wide range in characteristics of plug-flow

systems led EPA to conclude that these systems had to be modeled using

site-specific characteristics. Consequently, these systems are required

to demonstrate compliance through use of the procedures in appendix C.

The exclusion of plug-flow biological treatment systems from the

simplified compliance demonstration should not be interpreted as

implying that a well designed and operated plug-flow biological

treatment system would not achieve the required removal of a compound

and thus not represent an acceptable means of compliance. If correctly

evaluated through the applicable procedures in appendix C to part 63,

they can be acceptable.

Examples of additional biological systems that would not meet the

enhanced biological treatment system definition would be units that are

not thoroughly mixed throughout the aeration unit and that have large

concentration gradients between the inlet and the outlet of the

aeration unit. Such biological units do not quickly disperse the

biomass and wastewater

[[Page 44611]]

entering the unit throughout the unit and tend to concentrate the

volatile organics in a zone with relatively high air stripping rates.

Other examples of units that would not meet the definition include a

unit where the influent is introduced close to an aerator increasing

the opportunity for volatilization prior to biodegradation and a unit

where the influent is introduced close to a discharge point such that

channeling occurs.

The EPA realizes that many units have varying degrees of uniformity

in biomass distribution and organic compound concentration throughout

the biological unit. The EPA is developing additional information to

assist in the determination of whether a biological treatment unit

meets the enhanced biological treatment system definition. The

additional information will be available at the time the final

amendment is issued. The EPA plans to make this material available from

the Air and Radiation Docket and Information Center and to place it on

the EPA's Technology Transfer Network bulletin board as well as on the

Internet.

III. Revisions to Requirements for Determining Site-Specific

Fraction Biodegraded

The EPA is also proposing to revise the requirements in subpart G

for determining site-specific fraction biodegraded (Fbio).

The rule currently only allows biological treatment processes that meet

the definition of ``enhanced biological treatment process'' to use the

batch test procedures in appendix C to part 63. In today's action, the

EPA is proposing to remove that restriction in Sec. 63.145(h)(2) and to

allow use of the batch test procedure in appendix C for any type of

biological treatment system. The EPA is also proposing to allow use of

the batch test procedure to determine compound specific fraction

biodegraded (fbio) for compounds designated as list 3

compounds in table 36 of subpart G. Because this second change removes

the distinction between list 2 and list 3 compounds, today's action

also proposes to revise table 36 by combining the list 2 and list 3

compounds into a new list 2 in table 36. These changes are being

proposed to Sec. 63.145(h) to provide more flexibility and to simplify

this section of the rule.

IV. Revisions to Appendix C to Part 63

In today's action, the EPA is also proposing to revise appendix C

to part 63 to reflect the proposed revision of the definition for

``enhanced biological treatment system or enhanced biological treatment

process.'' There are three sets of proposed changes to appendix C

associated with the proposed change to the definition. First, the

terminology ``uniform well-mixed or completely mixed system'' would be

replaced with ``thoroughly mixed treatment unit'' throughout appendix

C. Second, the description of a uniform well-mixed or completely mixed

system would be removed from section I of appendix C and a sentence

describing a thoroughly mixed treatment unit would be added to section

I of appendix C. Third, based on discussions with industry

representatives, the EPA has concluded that the examples in the second

sentence of the fourth paragraph in section I were not helpful and

should be deleted. Therefore, the second sentence of the fourth

paragraph of section I would be removed and the remaining text in the

fourth paragraph merged with the preceding paragraph.

The EPA is also proposing to revise the instructions for Procedure

1 and Procedure 4 in appendix C to part 63 to allow an owner or

operator to assume that the first order biodegradation rate constant is

zero for any regulated compound(s) present in the wastewater. Appendix

C currently allows the use of this assumption only if the compound(s)

represent a small proportion of the mass of the regulated compounds in

the wastewater. This change would allow an owner or operator to assume

that the biological treatment system achieves no control of a

particular compound. The EPA is proposing this change to make appendix

C consistent with Sec. 63.145(a)(8) of subpart G and to remove a

restriction that might under some circumstances impose an unnecessary

burden to determine rate constants which will have no effect on the

compliance demonstration.

V. Administrative Requirements

A. Paperwork Reduction Act

The Office of Management and Budget (OMB) has approved the

information collection requirements contained in the rule under the

Provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. and

has assigned OMB control number 2060-0282. An Information Collection

Request (ICR) document was prepared by the EPA (ICR No. 1414.03) and a

copy may be obtained from Sandy Farmer, OPPE Regulatory Information

Division; U.S. Environmental Protection Agency (2137); 401 M St., SW;

Washington, DC 20460 or by calling (202) 260-2740.

An agency may not conduct or sponsor, and a person is not required

to respond to a collection of information unless it displays a

currently valid OMB control number. The OMB control numbers for the

EPA's regulations are listed in 40 CFR part 9 and 48 CFR Chapter 15.

The changes included in these proposed revisions to the rule will

have no impact on the information collection burden estimates

previously made. The changes consist of revised definitions,

alternative test procedures, and clarifications of requirements. The

proposed changes are not additional requirements. Consequently, the ICR

has not been revised for this rule.

B. Executive Order 12866 Review

Under Executive Order 12866, the EPA must determine whether the

proposed regulatory action is ``significant'' and, therefore, subject

to OMB review and the requirements of the Executive Order. The Order

defines ``significant'' regulatory action as one that is likely to lead

to a rule that may:

(1) Have an annual effect on the economy of $100 million or more or

adversely affect in a material way the economy, a sector of the

economy, productivity, competition, jobs, the environment, public

health or safety in State, local, or tribal governments or communities;

(2) Create a serious inconsistency or otherwise interfere with an

action taken or planned by another agency;

(3) Materially alter the budgetary impact of entitlements, grants,

user fees, or loan programs or the rights and obligations of recipients

thereof; or

(4) Raise novel legal or policy issues arising out of legal

mandates, the President's priorities, or the principles set forth in

the Executive Order.

The HON rule promulgated on April 22, 1994 was considered

``significant'' under Executive Order 12866, and a regulatory impact

analysis was prepared. The amendments proposed today would clarify the

rule and would remove restrictions on use of an alternative test

procedure. These amendments would not add any new control requirements.

Therefore, this regulatory action is considered ``not significant.''

C. Regulatory Flexibility

The Regulatory Flexibility Act (RFA) generally requires an agency

to conduct a regulatory flexibility analysis of any rule subject to

notice and comment requirements unless the agency certified that the

rule will not have a significant economic impact on a substantial

number of small entities. Small entities include small businesses,

small not-for-profit enterprises, and small government jurisdictions.

This proposed rule would not have a significant impact on a

[[Page 44612]]

substantial number of small entities. See the April 22, 1994 Federal

Register (59 FR 19449) for the basis for this determination. The

proposed changes to the rule merely clarify existing requirements and

therefore, do not create any additional burden for any of the regulated

entities. Therefore, I certify that this proposed action will not have

a significant economic impact on a substantial number of small

entities.

D. Unfunded Mandates Reform Act

Under section 202 of the Unfunded Mandates Reform Act of 1995

(Unfunded Mandates Act), the EPA must prepare a budgetary impact

statement to accompany any proposed or final rule that includes a

Federal mandate that may result in estimated costs to State, local, or

tribal governments in the aggregate or to the private sector, of $100

million or more. Under section 205, the EPA must select the least

costly, most cost-effective, or least burdensome alternative that

achieves the objectives of the rule and is consistent with statutory

requirements. Section 203 requires the EPA to establish a plan for

informing and advising any small governments that may be significantly

or uniquely impacted by the rule.

The EPA has determined that today's proposed action does not

include a Federal mandate that may result in estimated costs of $100

million or more to either State, local, or tribal governments in the

aggregate or to the private sector. Therefore, the requirements of the

Unfunded Mandates Act do not apply to this action.

List of Subjects in 40 CFR Part 63

Environmental protection, Air pollution control, Hazardous

substances, Reporting and recordkeeping requirements.

Dated: August 15, 1997.

Carol M. Browner,

Administrator.

For the reasons set out in the preamble, title 40, chapter I, part

63 of the Code of Federal Regulations is proposed to be amended as

follows:

1. The authority citation for part 63 continues to read as follows:

Authority: 42 U.S.C. 7401 et seq.

2. Section 63.111 is amended by revising the definition of

``enhanced biological treatment system or enhanced biological treatment

process'' to read as follows:

Sec. 63.111 Definitions.

* * * * *

Enhanced biological treatment system or enhanced biological

treatment process means an aerated, thoroughly mixed treatment unit(s)

that contains biomass suspended in water followed by a clarifier that

removes biomass from the treated water and recycles recovered biomass

to the aeration unit. The mixed liquor volatile suspended solids

(biomass) is greater than 1 kilogram per cubic meter throughout each

aeration unit. The biomass is suspended and aerated in the water of the

aeration unit(s) by either submerged air flow or mechanical agitation.

A thoroughly mixed treatment unit is a unit that is designed and

operated to approach or achieve uniform biomass distribution and

organic compound concentration throughout the aeration unit by quickly

dispersing the recycled biomass and the wastewater entering the unit.

* * * * *

3. Section 63.145 is amended by revising paragraph (h) the

introductory text and paragraph (h)(2) to read as follows:

Sec. 63.145 Process wastewater provisions--test methods and procedures

to determine compliance.

* * * * *

(h) Site-specific fraction biodegraded (Fbio). The

compounds listed in table 9 of this subpart are divided into two sets

for the purpose of determining whether Fbio must be

determined, and if Fbio must be determined, which procedures

may be used to determine compound-specific kinetic parameters. These

sets are designated as lists 1 and 2 in table 36 of this subpart.

* * * * *

(2) Fbio determination. If a biological treatment

process does not meet the requirement specified in paragraph (h)(1)(i)

of this section, the owner or operator shall determine Fbio

for the biological treatment process using the procedures in appendix C

to part 63, and paragraph (h)(2)(ii) of this section. If a biological

treatment process meets the requirements of paragraph (h)(1)(i) of this

section but does not meet the requirement specified in paragraph

(h)(1)(ii) of this section, the owner or operator shall determine

Fbio for the biological treatment process using the

procedures in appendix C to part 63, and paragraph (h)(2)(i) of this

section.

(i) Enhanced biological treatment processes. If the biological

treatment process meets the definition of ``enhanced biological

treatment process'' in Sec. 63.111 of this subpart and the wastewater

streams include one or more compounds on list 2 of table 36 of this

subpart that do not meet the criteria in paragraph (h)(1)(ii) of this

section, the owner or operator shall determine fbio for the

list 2 compounds using any of the procedures specified in appendix C of

40 CFR part 63. (The symbol ``fbio'' represents the site

specific fraction of an individual Table 8 or Table 9 compound that is

biodegraded.) The owner or operator shall calculate fbio for

the list 1 compounds using the defaults for first order biodegradation

rate constants (K1) in table 37 of subpart G and follow the

procedure explained in Form III of appendix C, 40 CFR part 63, or any

of the procedures specified in appendix C, 40 CFR part 63.

(ii) Biological treatment processes that are not enhanced

biological treatment processes. For biological treatment processes that

do not meet the definition for ``enhanced biological treatment

process'' in Sec. 63.111 of this subpart, the owner or operator shall

determine the fbio for the list 1 and 2 compounds using any

of the procedures in appendix C to part 63, except procedure 3 (inlet

and outlet concentration measurements).

* * * * *

4. Table 36 of Appendix to Subpart G is revised to read as follows:

* * * * *

Table 36. Compound Lists Used for Compliance Demonstrations for Enhanced

Biological Treatment Processes (See Sec. 63.145(h))

------------------------------------------------------------------------

List 1 List 2

------------------------------------------------------------------------

Acetonitrile Acetaldehyde

Acetophenone Acrolein

Acrylonitrile Allyl Chloride

Biphenyl Benzene

Chlorobenzene Benzyl Chloride

Dichloroethyl Ether Bromoform

Diethyl Sulfate Bromomethane

[[Page 44613]]

Dimethyl Sulfate Butadiene 1,3

Dimethyl Hydrazine 1,1 Carbon Disulfide

Dinitrophenol 2,4 Carbon Tetrachloride

Dinitrotoluene 2,4 Chloroethane (ethyl chloride)

Dioxane 1,4 Chloroform

Ethylene Glycol Monobutyl Ether Acetate Chloroprene

Ethylene Glycol Monomethyl Ether Cumene (isopropylbenzene)

Acetate

Ethylene Glycol Dimethyl Ether Dibromoethane 1,2

Hexachlorobenzene Dichlorobenzene 1,4

Isophorone Dichloroethane 1,2

Methanol Dichloroethane 1,1 (ethylidene

dichloride)

Methyl Methacrylate Dichloroethene 1,1 (vinylidene

chloride)

Nitrobenzene Dichloropropane 1,2

Toluidine Dichloropropene 1,3

Trichlorobenzene 1,2,4 Dimethylaniline N,N

Trichlorophenol 2,4,6 Epichlorohydrin

Triethylamine Ethyl Acrylate

Ethylbenzene

Ethylene Oxide

Ethylene Dibromide

Hexachlorobutadiene

Hexachloroethane

Hexane-n

Methyl Isobutyl Ketone

Methyl Tertiary Butyl Ether

Methyl Ethyl Ketone, (2-

butanone)

Methyl Chloride

Methylene Chloride

(dichloromethane)

Naphathalene

Nitropropane 2

Phosgene

Propionaldehyde

Propylene Oxide

Styrene

Tetrachloroethane 1,1,2,2

Toluene

Trichloroethane 1,1,1 (methyl

chloroform)

Trichloroethane 1,1,2

Trichloroethylene

Trimethylpentane 2,2,4

Vinyl Chloride

Vinyl Acetate

Xylene-m

Xylene-o

Xylene-p

------------------------------------------------------------------------

* * * * *

5. Section I of Appendix C to part 63 is revised to read as

follows:

Appendix C to Part 63--Determination of the Fraction Biodegraded

(Fbio) in a Biological Treatment Unit

I. Purpose

The purpose of this appendix is to define the procedures for an

owner or operator to use to calculate the site specific fraction of

organic compounds biodegraded (Fbio) in a biological

treatment unit. If an acceptable level of organic compounds is

destroyed rather than emitted to the air or remaining in the

effluent, the biological treatment unit may be used to comply with

the applicable treatment requirements without the unit being covered

and vented through a closed vent system to an air pollution control

device.

The determination of Fbio shall be made on a system

as it would exist under the rule. The owner or operator should

anticipate changes that would occur to the wastewater flow and

concentration of organics, to be treated by the biological treatment

unit, as a result of enclosing the collection and treatment system

as required by the rule.

The forms presented in this appendix are designed to be applied

to thoroughly mixed treatment units. A thoroughly mixed treatment

unit is a unit that is designed and operated to approach or achieve

uniform biomass distribution and organic compound concentration

throughout the aeration unit by quickly dispersing the recycled

biomass and the wastewater entering the unit. Systems that are not

thoroughly mixed treatment units should be subdivided into a series

of zones that have uniform characteristics within each zone. The

number of zones required to characterize a biological treatment

system will depend on the design and operation of the treatment

system. Each zone should then be modeled as a separate unit. The

amount of air emissions and biodegradation from the modeling of

these separate zones can then be added to reflect the entire system.

* * * * *

6. Section III of appendix C of part 63, the second paragraph after

(4) is revised to read as follows:

* * * * *

III. * * *

(4) * * *

* * * * *

Select one or more appropriate procedures from the four listed

above based on the availability of site specific data. If the

facility does not have site-specific data on the removal efficiency

of its biological treatment unit, then Procedure 1 or Procedure 4

may be used. Procedure 1 allows the use of a bench top bioreactor to

determine the first-

[[Page 44614]]

order biodegradation rate constant. An owner or operator may elect

to assume the first order biodegradation rate constant is zero for

any regulated compound(s) present in the wastewater. Procedure 4

explains two types of batch tests which may be used to estimate the

first order biodegradation rate constant. An owner or operator may

elect to assume the first order biodegradation rate constant is zero

for any regulated compound(s) present in the wastewater. Procedure 3

would be used if the facility has, or measures to determine, data on

the inlet and outlet individual organic compound concentration for

the biological treatment unit. Procedure 3 may only be used on a

thoroughly mixed treatment unit. Procedure 2 is used if a facility

has or obtains performance data on a biotreatment unit prior to and

after addition of the microbial mass. An example where Procedure 2

could be used, is an activated sludge unit where measurements have

been taken on inlet and exit concentration of organic compounds in

the wastewater prior to seeding with the microbial mass and start-up

of the unit. The flow chart in Figure 1 outlines the steps to use

for each of the procedures.

* * * * *

Appendix C to Part 63 [Amended]

7. In appendix C of part 63, section III, in the second sentence of

C, the phrase ``uniform well-mixed or completely mixed system'' is

revised to read ``thoroughly mixed treatment unit.''

[FR Doc. 97-22367 Filed 8-21-97; 8:45 am]

BILLING CODE 6560-50-P