[Federal Register Volume 62, Number 163 (Friday, August 22, 1997)]
[Proposed Rules]
[Pages 44608-44614]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-22367]


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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