PB88-166798
Waste Minimization Audit Report
Case Studies of Minimization of
Mercury-Bearing Wastes at a
Mercury Cell Chloralkali Plant
Versar, Inc., Springfield, VA
Prepared for
Environmental Protection Agency, Cincinnati, OH
Feb 88
U.S. Depytmod of Commerce
Ratted Tecte&sl toformstbn Service
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WASTE MINIMIZATION AUDIT REPORT: Case Studies of F<
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M. Drabkin and E. Rissmann
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HAZARDOUS WASTE ENGINEERING RESEARCH LABORATORY
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U.S. ENVIRONMENTAL PROTECTION AGENCY EP
CINCINNATI, OH 45268
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EPA/600/2-S8/011
February 1983
WASTE MINIMIZATION AUDIT REPORT
Case Studies of Minimization of Mercury-
Bearing Wastes at a Mercury Cell Chi oral kali Plant
by:
Marvin Drabkin and Edrfin Rissmann
Versar Inc..
Springfield, Virginia 22151
EPA Contract No. 68-01-7053
Work Assignment No. 85
Project Officer:
Mr. Harry Freeman
Hazardous Waste Environmental Research Laboratory
Cincinnati, Ohio 45268
HAZARDOUS WASTE ENGINEERING RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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Notice
This report has been reviewed by the U.S. Environmental Protection
Agency, and approved for publication. Approval does not signify that
the contents necessarily reflect the views and policies of the U.S.
Environmental Protection Agency, nor does mention of trade names or
canpercial products constitute endorsement or reconnendation for use.
\i
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Foreword
The term, "waste minimization," is heard increasingly at meetings and
conferences of individuals working in the field of hazardous waste
management. Haste minimization is an umbrella term that includes the
first four categories of the EPA's preferred hazardous waste management
strategy which is shown below:
1. Waste Reduction: Reduce the amount of waste at the source,
through changes in industrial processes.
2. Waste Separation and Concentration: Isolate wastes from mixtures
in which they occur.
3. Waste Exchange: Transfer wastes through clearinghouses so that
they can be recycled in industrial processes.
4. Energy/Material Recovery: Reuse and recycle wastes for the
original or some other purpose, such as for materials recovery or
energy production.
5. Incineration/Treatment: Destroy, detoxify, and neutralize wastes
into less harmful substances.
6. Secure Land Disposal: Deposit wastes on land using volume
reduction, encapsulation, leachate containment, monitoring, and
controlled air and surface/subsurface water releases.
In general, the idea underlying the promotion of waste minimization is
that it makes far more sense for a generator not to produce waste rather
than develop extensive treatment schemes to ensure that the waste stream
poses no threat to the quality of the environment.
In carrying out its program to er.couragf: the adoption of waste
minimization, the Hazardous Waste Engineering Research Laboratory has
supported a program to carry out waste minimization audits in a wide
variety of industrial settings. This report coitains the results of
waste minimization audits carriec out at two mercury cell chlor-alkali
plants. It will be useful to individuals interested in identifying
opportunities for reducing those waste streams.
If further information is needed, please contact the Alternative
Technologies Division of the Hazardous Waste Engineering Research
Laboratory.
Thomas R. Hauser
Director
Hazardous Waste Engineering Research Laboratory
iii
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ABSTRACT
The USEPA 1s encouraging hazardous waste generators to develop ^
programs to reduce the generation of hazarJou: waste. To foster sue,.
programs, the Agency's Office of Research and Development Hazardous w
Environmental Research Laboratory (ORD/iiWERL) is supporting the
development and evaluation of a modoi hazardous waste minimization aucm
(WMA) procedure using the EPA hierarchy of waste minimization (WM)
options, with source reduction being more desirable and recycle/reuse
less desirable. Treatment options, although not considered WM, were
evaluated if neither of the former alternatives was available. The
procedure was tested initially in several facilities in 1986. WMAs were
conducted at generators of a number of generic hazardous wastes,
including corrosives, heavy metals, spent solvents, and cyanides.
In 1987, the HWRRL WMA program has concentrated on ORO's top priority
RCRA K and F waste list. Audits were conducted at generators of K071 and
K106 wastes (mercury cell chloralkali plants), K048-K052 wastes (sludges
and solids from petroleum refining), F002-F004 wastes (spent solvents),
and FOOS wastes (wastewater treatment sludges from electroplating
operations). The present report covers WMAs carried out at two mercury
coll chloralkali plants (designated as Plant No. 1 and Plant No. 2)
seeking to develop WM options for K071 and K106 wastes.
The audit team was able to develop only one technically and
economically viable source reduction option for K071 waste. Two
treatment options (although not considered WM) appeared to be technically
and economically viable for this waste, allowing it to be delisted by EPA
and thus disposable in a local sanitary landfill. No viable source
reduction or recycle/reuse options were available for K106 waste with one
possible exception - a retorting process which appears capable cf meeting
delisting levels for mercury in the retorted K106 residue has been
successfully tested by Plant No. 1.
iv
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CONTENTS
Notice of Disclaimer if
Foreword i i i
Abstract 1v
Table of Contents v
Figures vi i
Tabl es vi i i
1. Introduction 1-1
2. Waste Minimization Program 2-1
3. Waste Auditing Methodology 3-1
Preparation for the Audit 3-1
Host Site Pre-Audit Site Visit 3-6
Waste Stream Selection 3-6
Host Site Waste Minimization Audit Visit 3-7
Generation of Waste Minimization Options 3-9
Preliminary Evaluation and Rating of Options 3-12
Presentation and Joint Review of Options with
Plant Personnel 3-13
Final Audit Report 3-15
Waste Auditing - Some Do's and Don'ts 3-15
4. Listed Waste K071 Waste Minimization Audit Case
Studies 4-1
Waste Minimization Audit at Plant No. 1 4-1
Facility Description 4-1
Process Description 4-2
Waste Stream Description 4-9
Current Waste Management Profile 4-11
Postulated Waste Minimization Options and
Preliminary Analysis of Their Technical
and Economic Feasibility 4-11
Source Reduction Options 4-13
Recycle/Reuse Options 4-24
Treatment Options 4-24
Summary of Postulated Options for Plant No. 1 4-36
Waste Minimization Audit at Plant No. 2 4-36
Facility Description 4-36
Process Description 4-40
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CONTENTS
Page
Waste Stream Description 4~43
Current Waste Management Profile 4~44
Revamped Waste Management Operation
Based on Current Delisting Effort 4'44
Rationale for No Development of
Wiste Minimization Options 4'47
Summary and Discussion 4"4^
5. Listed Waste K106 - WMA Case Studies 5-1
Waste Minimization Audit at Plant No. 1 5-1
Waste Stream Description 5-1
Current Waste f aiiagement Profile 5-2
Postulated Waste Minimization Options and
Preliminary Analysis of Their Technical
and Economic Feasibility 5-2
Source Reduction Options 5-2
Recycle/Reuse Options 5-4
Treatment Options 5-8
Waste Minimization Audit at Plant No. 2 5-9
Waste Stream Description 5-9
Current Waste Management Profile 5-10
Postulated Waste Minimization Options and
Preliminary Analysis of Their Technical
and Economic Feasibility 5-12
Source Reduction Options 5-12
Recycle/Reuse Options 5-12
Treatment Options 5-14
Summary of Postulated Options for Minimization
of Listed Waste K106 at Plant No. 1 and Plant No. 2 ... 5-17
Summary and Discussion 5-17
6. References 6-1
VI
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FIGURES
Number Page
1 Components of Waste Minimization, Their
Hierarchy, and Definitions 3-10
2 Elements of Source Reduction 3-11
3 NaOH/Thlorine Production Process at P'ant No. 1 4-4
4 NaCl Brine Treatment System at Plant No. 1 4-7
5 KOH/Chlorine Production Process at Plant No. 1 4-8
6 KC1 Brine Treatment System at Plant No. 1 4-10
7 Simplified Schematic of Proposed Membrane Cell
Conversion at Plant No. 1 4-22
8 Proposed Water Washing Process for Plant No. 1
NaCl Saturator Insolubles 4-28
9 Proposed Sulfide Precipitation Option for Removal of
Entrained Mercury from the K071 Brine Purification
Wastes at Plant No. 1 (Applicable to Both NaOH and
KOH Production Facilities) 4-32
10 Proposed Application of the Vulcan Treatment Process
at Plant No. 1 for Entrained Mercury Removal from Both
NaCl and KC1 Brine Purification Wastes 4-35
11 NaOH/Chlorine Production Process at Plant No. 2 4-41
12 Plant No. 2 Newly Instilled K071 Waste
Treatment System 4-48
13 Existing Wastewater Treatment System at Plant No. 1 5-3
14 Proposed Retorting System at Plant No. 1 for Recovery
and Recycle of Mercury from Wastewater Treatment Sludge . 5-7
15 Existing Wastewater Treatment System at Plant No. 2 5-11
16 Proposed Retorting System at Plant No. 2 for Recovery
and Recycle of Mercury from Wastewater Treatment Sludge . 5-15
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TABLES
Number
? 3
1 Waste Minimization Program Elements c
2 Waste Audit Team and Resident Support Groups for
the Two Audits at Facilities Generating Listed
Wastes K071 and K106 2'5
3 Initially Proposed Waste Minimization Audit K-ocedure ... 3-2
4 Recommended Waste Minimization Audit Procedure 3-3
5 Waste Minimization Audits - Information Needs List
for Listed Wastes K071 and K106 at Plants No. 1 and 2 ... 3-4
6 Waste Minimization Audits Generalized List
of Information Sources 3-5
7 Summary of Source Control Methodology for the
A/B Power Formulation Process: Illustration of
Development of Options Rankinq 3-14
8 Typical Rock Salt Composition at Plant No. 1 4-5
9 Typical Analysis of K071 Wastes at Plant No. 1 4-12
10 Summary of Postulated Options for Minimization
of Listed Waste K071 at Plant No. 1 4-37
11 Typical Analysis of Rock Salt Used at Plant No. 2 4-42
12 Total K071 Raw Waste Analysis at Plant No. 2
(Dry Basis) 4.45
13 Summary of Postulated Options for Minimization
of Listed Waste K106 at Both Plant No. 1 and No. 2 5-18
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SECTION 1
INTRODUCTION
The national policy objectives established under the 1984 Hazardous
and Solid Was'ie Amendments to the Resource Conservation and Recovery Act
of 1976 include the goal of reducing or eliminating hazardous waste as
expeditiously as possible. To promote waste minimization activities, the
Hazardous Waste Engineering Research Laboratory (HWERL) of the U.S.
Environmental Protection Agency (EPA), Office of Research and Development,
has undertaken a project to develop and test a waste minimization audit
(WMA) procedure. It is envisioned that such a procedure would be useful
to generators of hazardous waste as they search for waste minimization
alternatives.
A number of authors have recognized the potential value and
desirabili.y of conducting waste audits, although they have suggested
differing approaches and scope limits for such audit activities (U.S.
Congress 1986, USEPA 1986a, Fromm and Callahan 1986, Pojaso'- 1986, Kahane
1986, League of Women Voters, Mass. 1986). This HWERL project expands on
a recently developed and tested audit procedure (EPA 1987, EPA 1987?., EPA
1987b) by conducting actual WMAs in cooperating industrial and government
facilities. The present project includes audits at two industrial
facilities, and is one of several current audit efforts being supported by
HWERL.
Section 2 of this report presents the elements of an overall waste
minimization program, of which the audit procedure is an important
component. Section 3 describes the WMA procedure, its development, and
its final recommenced form. Section 4 presents the results of the WrtAs
performed at facilities that generate listed waste KO/1, and Section 5
contains the results of the WMAs performed at facilities that generate
listed waste K106. Conclusions and recommendations resulting from these
audits are presented in the respective sections.
1-1
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SECTION 2
WASTE MINIMIZATION PROGRAM
Structured programs designed to improve the cost, erergy efficiency,
safety, and other environmental aspects of an industrial undertaking are
not a new concept. During World War II, the General Electric Corporation
developed standardized procurement procedures for reducing product ccst
without sacrificing functionality. Later, similar procedures were
developed and applied to lower the costs of design and construction
projects. This activity, known as value management, value engineering,
or value analysis, is currently a well established government
requirement. In fact, it was mandated by the U.S.EPA for all
construction projects involving wastewater treatment plants. A
subsequent study of 156 treatment plants showed that cost reduction
programs saved $95 million, or a 12 to 1 return on investment (Zimmerman
and Hart 1S82).
Environmental compliance audits and reviews are also becoming more
common and are acquiring the status of an industry norm. Thi? primary
objective of an environmental audit is to determine the states of a
corporation's compliance with Federal, State, and local environmental
laws and regulations (Truitt et al. 1983). Additionally, such audits
often can provide information to aid risk assessment and corporate
planning.
Energy conservation audits are performed to reduce energy consumption
per unit production. It was estimated that energy audits helped save
chemical process industries about $1 billion between 1974 and 1979
(Parkinson 1979). Other related structured programs include safety
reviews, hazard analyses, or failure mode and effects analyses. Waste
minimization programs can be considered to be in the same category as
these programs.
The principal objective of a waste minimization (WM) program is to
reduce the quantity and/or toxicity of waste effluents leaving the
production process in a manner consistent with the goals of protecting
human health and environment. Unlike environmental audit programs, a WM
2-1
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program does not seek to determine or improve the regulatory compliance
status of a facility. Rather, it is primarily oriented toward producing
a set of effective measures to reduce waste generation.
Table 1 presents a breakdown of WM program elements. In the context
of an overall WM program, the waste auditing process (composed of
pre-audit, audit, and post-audit phases) follows the program
initiation/planning phase. During this initiation/planning phase, the
commitment of top management to reduce waste generation must first be
established. This is often done with a formal directive signed by the
chief executive officer of the firm or an administrator of a government
organization. The organizational commitment to start a WM program is
often associated with a goal setting process, e.g., duPont is currently
implementing an annual 5 percent waste reduction goal.
A corporate WM program may be organized in a typical pyramid
structure, with command and monitoring functions centered at the
corporate level and implementation responsibility totally delegated to
individual plants. A corporate-level independent expert task force may
be formed to assist individual plants in setting up and executing their
own WM programs.
At the plant level, the WM program may follow the scheme successfully
used at Union Carbide for energy conservation efforts. At Union Carbide
plants, a plant program coordinator is appointed and supported by a
committee. The coordinator then selects and oversees individuals in each
department who are responsible for devising and/or carrying out WM
activities in their departments (Williams 1976).
This program planning phase should include the selection of audit
teams to carry out the next program phase. The audit team leader should
have d strong technical background, demonstrated problem solving ability,
and, if possible, experience associated with the relevant process(es).
In addition, the leader should possess strong management and
communication skills. It would be preferable for the leader, or at least
some members of the audit team, to have no previous association with the
plant, so as to bring a fresh and unbiased perspective to the audit
process. Such outsiders can be independent consultants or qualified
personnel from other plants.
The audit team must have access to all required documentation and to
a wide variety of plant personnel. During a recent internal workshop on
waste minimization conducted by a major U.S. corporation, the
participants (mostly environmental affairs managers at individual plants)
were asked who should provide support to a waste audit team. The
following responses were obtained:
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Table 1. Waste Minimization Program Elements
Program phase
I. Initiation/
Planning
II. Pre-Audit
III. Audit
IV. Post-Audit
V. Implementation
Jrb plan* phase
Information
Creative
Judgment
Development
Recommendation
Elements
. Secure commitment/authority
. Establish goals
• Establish organization
• Preparation for the audit
. Pre-audit inspection
• Waste stream selection
. Facility inspection
• Generate comprehensive
set of WM options
• Options evaluation
. Selection of options
for feasibility
analysis
• Technical and economic
feasibility analysis
• Report preparation
• Selection of options for
implementation
• Design, procurement,
construction
• Startup
• Performance moniton-g
* Term adopted from value management program.
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Raw material suppliers;
QA/QC department;
Outside consultants;
Customer representatives;
Process engineer;
Safety engineer;
Materials engineer;
Foreman;
Plant manager; and
Purchasing agent.
In short, the organization should be prepared to provide the audit
team with access to a wide range of people both inside and outside the
firm, "ihe teams that carried out the audits described in this report
were composed entirely of employees from outside consulting/engineering
firms. Table 2 depicts the composition of the outside audit teams and
the resident support groups.
The wacte minimization auditing process (Table 1, phases II, III, and
IV), which is described in detail in the next section, provides the key
input to the implementation phaso of the program, i.e., recommendations
on which WM measures are to be implemented. Once a decision is made to
proceed with the implementation of a specific WM measure, subsequent
activities follow a well established, conventional pattern. Detailed
design follows preliminary design; the procurement effort proceeds from
inquiry and definitive bids to bid analysis and the expediting stages;
and construction advances along the patn determined by a detailed
schedule and budget. The budget is controlled through estimates of cost
performed at various project stages; accuracy increases as material and
labor requirements become better defined. Startup follows mechanical
completion. Finally, to ascertain the effectiveness of the changes made,
ongoing performance monitoring is undertaken.
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Table 2. Waste Audit Teams and Resident Support
Groups for the Two Audits at Facilities
Generating Listed Wastes K071 and K106
Plant No. 1 (Mercurv Cell Chloralkali Plant)
1. Outside Audit Team
Chemical engineer*, Ph.D., 37 yrs of experience
Physical chemist, M.S., 20 yrs of experience
Independent consultant**, Ph.D., Metallurgical Engineering, 40 yrs
of experience in metallurgy, process, and environmental engineering
2. Resident Support Team
Plant process engineer
Plant environmental engineer
Company main office staff environmental engineer
Plant No. 2 fMercurv Cell Chloralkali Plant)
1. Audit Team
Chemical engineer*, Ph.D., 37 yrs of experience
Physical chemist, M.S., 20 yrs of experience
2. Resident Support Team
Plant environmental coordinator
Plant process engineer
* Audit team leader.
** Technical support and review function only.
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SECTION 3
WASTE AUDITING METHODOLOGY
As was shown in Table 1, waste minimization audits are a central
feature of a WM program. The auditing process is subdivided into
pre-audit, audit, and post-audit phases. The recommended sequence of
steps shown in Table 1 (also shown in expanded form in Table 4), is based
on modifications of the originally proposed sequence, which is presented
in Table 3. Modifications were made to reflect the experience and
insights gained as a result of actual audit work. The following sections
detail each of the eight sequential steps of the recommended waste
minimization audit (WMA) procedure shown in Table 4.
PREPARATION FOR THE AUDIT
The objective of this activity is to gain background information
about the facility to be audited. Preparation should include examination
of literature references related to the activities performed at the
facility, such as EPA background documents on the industries involved,
plant permit applications, and other relevant documents pertaining to
waste discharge at the industrial facilities of interest. Proper
preparation should result in a wel'i-defir,ed needs list, inspection
agenda, or a checklist detailing v>hat is to be accomplished, what
questions or issues need to be resolved, and what information should be
gathered.
For the host facilities audited in this report, the needs list
(Table 5) was provided to the resident support team in advance of the
site visit. This was very important in ensuring the success (and
efficiency) of the site visit, since it provided time for the facility
personnel to assemble the materials required by the audit team prior to
its visit. A more generalized list of documents and information sources
is given in Table 6.
In tlie audits of the three facilities reported herein, the
availability of the required process documentation v.'as excellent. This
documentation proved to be invaluable in enabling the audit team to
establish a set of waste minimization options.
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Table 3. Initially Proposed Waste Minimization
Audit Procedure
Job plan element
Step
Information phase
Creative phase
Judgment phase
Development phasr
Recommendation phase
1. Preparation for inspection
2. Facility inspection
3. Process and waste stream description
4. Generation of WM options
5. Preliminary evaluation and ranking
of options
6. Presentation, discussion, and joint
review of options with plant
personnel
7. Selection of options for
feasibility analysis
8. Technical and economic feasibility
analysis
9. Final report preparation
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Table 4. Recommended Waste Minimization Audit Procedure
Program phase
Activities
Product
Pre-Audit
1. Preparation for the audit
2. Pre-audit meeting and
inspection
3. Waste stream selection
needs list/
inspection agenda
notes
• process description
• waste descripton
with rationale for
selection
Audit
4. Audit inspection
5. Generation of a compre-
hensive set of WM options
6. Options evaluation and
selection for feasibility
analysis
• notes
• 1ist of proposed
options with written
rationale
• 1ist of selected
options
• options ratings by
audit team and by
plant personnel
• options interim
report
Post-Audit
7. Technical and economic
feasibi1 ity analysis
8. Final report preparation
study or budget
grade estimates 01
capital and
operating costs;
profitability
analysis
final report with
recommendations
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Table 5. Waste Minimization Audits - Information
Needs List for Listed Wastes K071 and K106
at Plants No. 1 and 2
1. Process Flow Diagrams (P.'Ds) with Heat and Material Balances (HMBs).
2. Piping and Instrumentation Diagrams (P&IDs).
3. Plot plan or general arrangement of equipment.
4. Procers description (process flows, liquid and solid wastes
characterizations).
5. Equipment layouts (plan and elevation views).
6. Quantities and costs of chemicals.
7. Dimensions and operating gallonage of all pertinent process vessels
and tankage.
8. Quantities and costs of disposal for all wastes (liquid and solid).
9. Process equipment materials of construction.
10. History of previous waste management projects and any related
documentation.
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Table 6. Waste Minimization Audits Generalized
List of Information Sources
Design process flow diagrams (PFD) with heat and material balances
(HMB) for process and pollution control systems
Equipment list
Piping and instrument diagrams (P&ID)
Materials application diagrams (MAD)
Plot and elevation plans
General arrangement drawings
Piping layout drawings
Operation manuals, process descriptions
Permits and/or permit applications
Emission inventories
Hazardous waste manifests
Annual (or biennial) reports
Waste assays
Operator data logs, batch sheets
Materials purchase orders
Environmental audit/p-eview reports
Production schedules
Organization chart
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Experience with other sites indicates that the availability and
quality of information varies significantly, however. It is importan
allow for this contingency and to have a fall-back position. For
example, if a piping and instrument diagram (P&ID) is not available, i
may be possible to obtain a piping layout plan instead. Similarly,
the information cannot be obtained from the facility, that does not med
that it is unavailable elsewhere. Much information is obtainable rrom
outside vendors, e.g., the costs of bath make-up chemicals or the
phvsical design of the process equipment. If information is truly
needed, it can be obtained with proper initiative and ingenuity, aunouyn
such action may affect project costs and schedules. In light of tms
possibility, it is important to seek only that information which is
necessary to understand the process, to allow for delineation of waste
sources and current waste management techniques, and to characterize
waste generation quantitatively. Requesting unnecessary information
burdens both the provider and user (auditor) and slows down the work.
HOST SITE PRE-AUDIT SITE VISIT
The purpose of this meeting is to become familiar with plant
operations and plant personnel. Initial contacts with plant personnel
should include solicitation of their views on the focus and function of
the audit. This will help to identify waste streams of concern to the
facility. The information needs defined in the previous step should be
discussed here and hopefully met. A guided tour of the facility should
be taken.
At this initial visit, the groundwork for a successful working
relationship with facility personnel must be laid. It should be stressed
that a cooperative attitude and active involvement by host facility
personnel are essential to the success of the audit process. The initial
point of contact at the facility (Plant Manager, Environmental
Coordinator, etc.) must be enlisted as a "Product Champion" for the
program before the audit commences. He/she must be encouraged to relay
the message of cooperation and involvement to others at the facility.
WASTE STREAM SELECTION
Suitable waste streams should be selected either following the
initial conference with plant personnel or after the first plant
inspection. Selection should be based on discussions with plant
personnel and on the independent assessment of the project team. The
criteria used to select a waste stream must include at a minimum:
• Composition;
• Quantity;
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• Degree of hazard (toxirity, flammability, corrosivity, and
reactivity);
t Method and cost of disposal;
• Potential for minimization and recycle; and
• Compliance status.
For the two case studies cited in this report, stream selection was
not a problem. Focusing the audits on two particular wastes (listed
wastes K071 and K106) simplified the selection. Both mercury cell
chloral kali facilities generate only these two hazardous wastes in any
appreciable quantity.
With the selection of the waste streams, the pre-audit stage of the
procedure is completed. At this point, it is recommended that a written
description be prepared of the facility, process, or operation and of the
waste streams. The description should encompass:
• Facility location and size;
• Description of operations or processes cf concern, including
diagrams necessary to detail the pertinent aspects of waste
generation; and
• Waste stream(s) description centering on sources and current
methods of management; this information should be supplemented
with summaries of generation rates, compositions, disposal costs,
and raw macerial costs, and the rationale for waste selection
should be provided.
Descriptions of facility, process, and waste stream(s) for the
facilities involved with audits on "listed wastes K071 and K106 are given
in Sections 4 and 5. Such descriptions summarize all 'he pertinent
information acquired.
HOST SITE WASTE MINIMIZATION AUDIT VISIT
In the course of the pre-audit activities, a general understanding of
the process facility operations and, more important, of waste sources was
established. Also, waste stream selection had been finalized (in most
cases) and the information summarized in a written description of the
facility, process, and waste stream(s).
With the needed comprehension of the process and focus in place, the
audit inspection can now be conducted. Typically, the inspection would
focus on selected aspects of the operation identified through the
pre-audit activities. The governing objective is to obtain a greater
awareness of the principal and secondary causes of waste generation and
to examine the items overlooked in the pre-audit stage.
3-7
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The audit inspection is the ultimate step in the information ^
gathering process. The following guitJolines have been formulated a
result of the work performed on this project:
1. Have an agenda ready. This should cover all points that stil
require clarification following the pre-audit phase.
2. Plan on inspection of the various process operations °.
at different times during the production shift for col?tinuo",11v
processes, in order to observe possible fluctuations in normal ijr
steady state operations. Expect to monitor operations over ^
period of one to two days.
3. Obtain permission to interview the operators, eight-hour shift
supervisors, and foremen directly. Listen attentively and ao not
hesitate to question more than one person if the answer is not ^
forthcoming. Try to assess the operators' and their supervisors
awareness of waste generation aspects of the operation. Note
their familiarity (or the lack thereof) with the impacts their
operation may have on other operations, e.g., t^a effect cf
dumping spills of mercury-bearing brine into the existing
wastewater treatment plant at the chloralkali facility, rather
than metering these solutions at a controlled rate.
4. Obtain permission to photograph the facility. Photogrephs are
especially valuable in the absence of plan layout drawngs. Many
details can be captured in photographs that otherwise could well
be forgotten or inaccurately recalled at a later date.
5. Observe the "housekeeping" aspect of the operation. Check for
signs of spills or leaks. Ask to visit the maintenance shop and
inquire about their problems in maintaining the equipment
leak-free. Assess the overall cleanliness and order of the site.
6. Assess the level of coordination of environmental activities
among various departments.
During the planning stage and the actual audit inspection itself, it
is beneficial to mentally "walk the line" from the suspected source of
waste generation to the point of exit, be it a treatment unit, storage
facility, or haulage to offsite RCRA treatment, storage, and disposal
(TSD) facilities. The audit inspection must result in a c>ar
understanding of the causes of waste generation.
3-8
-------
GENERATION OF WM OPTIONS
Thus far, the audit process has been mainly oriented toward
information gathering and organization. These activities should have
yielded a thorough understanding of the origins of waste generation and
of the process or facility operations in general. The audit activity has
now reached the creative phase.
The objective of this step is to generate a comprehensive set of WM
options. Such activity may take the form of a "brainstorming" session
involving audit team members or may involve separate efforts by
individual members. A combination of these approaches was found to be of
value during the audits conducted for this study. In this stage of the
audit process, it is important to generate as many options as possible.
Current WM measures in the audited facility should also be listed. This
knowledge often leads to the formulation of additional options and
provides valuable insights for the option evaluation step to follow.
In generating options, most of the effort should first focus on
source reduction, followed by recycling and then treatment (if there are
no options available in either of the preferred areas). Such a hierarchy
of effort stems from the fact that environmental desirability favors
source reduction over recycling and recycling over treatment.
Current EPA-proposed definitions ••f waste minimization and key waste
minimization terms are given in Figure 1. A generalized quide map to
various source reduction elements is shown in Figure 2. For a discussion
of the terms and examples illustrating each element, the reader is
referred to the EPA support document for the 1986 Report to Congreis on
Waste Minimization (I'SEPA 1986b).
To develop options, it is often necessary to examine the technical
literature. The reference section of this report lists the sources
consulted for technical material relevant to reduction or elimination of
mercury cell chloralkali mercury-bearing wastes. Options can also be
formulated through discussion with manufacturers of equipment or
suppliers of process input materials.
The result of tho WM options generation step should be a list
identifying each option, together with a brief description of the
rationale for its listing. For the K071 waste studied in this report, a
total of nine relevant options could be determined at both the facilities
audited, while for the K106 waste, a total of five relevant options were
developed at both facilities.
3-9
-------
SOURCE REDUCTION
RECYCLING
J
u>
I
RELATIVE ENVIRONMENTAL DESIRABILITY
GREATER SSSS^SSSSSSSSSSS^^
LESSER
FIRST
ORDER OF EXPLORATION
smssssssssssss^^
SECOND
FIGURE 1. COMPONENTS OF WASTE MINIMIZATION, THEIR HIERARCHY AND DEFINITIONS
-------
SOURCE REDUCTION
1
PRODUCT SUBSTITUTION
EXAMPLE:
CONCRETE MARINE PlINGS
NSTfcAD Of TREATED WOOD
SOURCE CONTROL
NOTE: CAN BE EXTERNAL TO
GENERATOR
WUT MATERIAL OUNCES
o PURIFICATION
osuBSTramoN
o DILUTION
TECHNOLOGY CHANGES
o PROCESS CHANGES
o EOUIPMENT.PIPING OR LAYOUT
CHANGES
o CHANGES TO OPERATIONAL
SETTNGS
o ADD'TICNAL AUTOMATION
o ENERGY CONSERVATION
o WATER CONSERVATION
8
PROCEDURE L/teTnUTONAJ. CHANGES
o PROCEDURAL MEASURfcS
o LOSS PREVENTION
o PERSONNEL PRACTICES
o SEGREGATION
o MATERIAL HANDLING IMPROVEMENTS
Figure 2. Etemenls of sourc* reduction
-------
PRELIMINARY EVALUATION AND RATING OF OPTIONS
Each of the options postulated in the preceding step must
preliminary engineering evaluation and rating. The objective
evaluation is to eliminate the measures that do not merit additional
consideration and to rank the remaining measures in order relative
their overall desirability.
The evaluation should include, at a minimum, consideration of the
following aspects:
. Waste redaction effectiveness (i.e., reduction of waste quantity
and/or toxicity);
• Extent of current use in the facility;
• Industrial precedent;
• Technical soundness;
• Cost (preliminary capital and operating cost evaluation). An
important economic yardstick for option evaluation is the
determination of a "payback period," which is defined here as the
incremental investment divided by the net savings in direct
operating costs due to implementation of the proposed option.
• Effect on product quality;
• Effect on plant operations;
• Implementation period; and
• Resources availability and requirement.
The preliminary evaluation and valuing process would consist of the
following steps carried out by the audit team:
(a) Developing a written rationale for each proposed option
including a clear description of the operating principle,
estimates of waste minimization measured in pounds of waste and
in pounds of waste per unit production, estimates of potential
resource recovery measured in pounds of waste component
recyclable *o the process or salable as a recovered material,
perceived advantages and disadvantages, simplified schematics of
the proposed material flow, material balance calculations,
"order of magnitude" cost estimates, references relating to
prior applications, and other relevant documentation pertaining
to the idea. These steps were carried out as appropriate for
each option developed for minimization of listed wastes K071 and
K106.
3-12
-------
(b) Qualitative rating of each option in three categories: waste
reduction effectiveness, extent of current use, and future
application potential. The ratings are to be done on scale of 0
to 10 by a proponent, then reviewed by the audit team leader.
It is expected that some options may receive ratings low enough to
warrant their withdrawal. The team leader may call a review .neeting to
submit the ratings to a collective discussion or vote. In the case cf
the audits discussed in this report, a number of such op.ions were
withdrawn, as is discussed in Sections 4 and 5.
The product of this effort should be a table summarizing the
preliminary ratings for each option that addresses a particular waste
stream or source, along with the written documentation developed in this
phase of the audit. Table 7 is a sample table illustrating the approach
used to develop such a summary table.
PRESENTATION AND JOINT REVIEW OF OPTIONS WITH PLANT PERSONNEL
Following the technical and economic evaluations of the selected
options by the audit team, these options are prepared in the form of a
Preliminary Audit Report to be submitted to appropriate plant personnel.
Each option in the Preliminary Audit Report should be well described in
terms of the technical rationale and projected "order of magnitude" cost
estimates. Cost estimates are of particular importance to plant
personnel who have to deal with tight operating budgets and must have
some idea of the cost of implementing an attractive-appearing option. In
this regard, calculation of "the payback period" will provide a quick
indication of the economic viability of the proposed option. Cost
estimates are also of importance tc the options belonging to the category
of good operating practices. Availability of preliminary cost data along
with the presentation of this category of option circumvents quick
dismissal of these options as "trivial" by a technology-oriented plant
engineer.
The plant personnel should then be asked to review the Preliminary
Audit Report and independently rate each proposed option, revise them
based on their assessment, and incorporate any additional options they
consider applicable.
The review process would culminate in a joint meeting in which the
audit team would present the proposed options one by one. The
presentation ideally should include a detailed discussion of the
rationale and reasons for selected ratings. The plant engineers would
then present their critique or comments. The discussion should conclude
with a revised rating acceptable to both sides. !f such a conclusion
cannot be reached, a further course of action must be well outlined.
3-13
-------
Table 7 Summary of Source Control Methodology for the A/6 Powder Formulation
Process: Illustration of Developiient of Options RanKing
CO
>—•
-fr
Waste
reduction
Waste source
Ueiq-iina operat 'OP i
2.
3
Wet grind leading 1 .
arij u-oadi'ig 2
3
4
5
6
7.
8
9
Dry grind loading 1
anj unlosdir'j 2 .
3 .
4.
5.
Control methodology effect iveress
Returr ",7,pty containers
Use cre«eighed containers
Use drj" covers
Over;' 1
Use plastic f unnel/col lar or unit
Use sir.:', ler trays, manual operation
Place t'ays on rao. wa^k-ir oven
Use ele.3tor tdLle on ract . walk-in oven
Insta!" Boiler conveyer unaer valve
Instal': fail-close valve on d'scharge
Pump slurry into trays ove1" at oven
Reruce clearing frequency
Pypass dry gr-.nding unit
Overa'"
Use plastic funnel/collar on unit
Do not 'oad while unit is c-erating
Inspect all seals regularly
Use arum covers
Bypass dry grinding unit
Overall
2
2
2
r.oo
i
2
2
\
1
2
2
3
2
1.63
2
3
2
2
4
2.60
Future
Extent of application Fraction of
current use potent'ol total waste
0 2
0 4
2 1
0.67 2-33 0.10
0 4
0 2
0 2
0 1
0 1
0 3
0 1
0 3
0 4
0.00 2.33 0.45
0 4
4 0
3 2
2 3
0 4
1.80 2.60 0 45
Current
reduction
index
0.00
0 00
0.25
0.25
0.00
0.00
0.00
0 00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0 75
0.38
0.25
0.00
0 75
Future
reduction
index
0.25
0.50
0 06
0.50
0 50
0 25
0.25
0 06
0.06
0.38
0.13
0 56
0.50
0.56
0.50
0.00
0.06
0 19
O.QO
0.90
All sources
All rrtthodr.
1.00
0.58
0 71
-------
The objective of the meeting is to obtain an agreement on the ratings
of various proposed options; these ratings would then be analyzed and
used to rank all the options, with the aim of selecting those that
warrant further evaluation by the plant. It also may happen that the
plant personnel may suggest new options or that such options may result
from the joint discussion.
Following the meeting, all appropriate revisions of the options
presented in the Preliminary Audit Report would be made in preparation
for the issuance of a Final Audit Report.
In the present audit effort, both the audit team and the plant
personnel were in agreement on the evaluation of each of the options
presented.
FINAL AUDIT REPORT
In accordance with the workplan, the Final Audit Report will contain,
at a minimum, the following sections:
1. Facility and process description;
2. Description of waste stream(s) origin, composition, and
quantities;
3. Detailed description of all work minimization options considered,
including simplified schematics of revised process flows (if
appropriate) and lists of any new process equipment required;
4. Detailed evaluation of technical feasibility and potential
benefits of all waste minimization options considered, together
with their preliminary economics (capital and operating costs,
estimated payback period) and final rankings (based on audit team
findings and host plant engineers evaluations); and
5. Recommendations including any research and development efforts
needed to further evaluate the recommended options.
WASTE AUDITING - SOME DO'S AND DON'TS
Some of the most important lessons learned in the pilot audits relate
to the human element of the audit process, i.e., to the interaction
between the audit team and the host facility personnel.
Obviously it is vital that host facility personnel become and remain
active participants throughout the audit process. Some non-technical
skills of the audit team personnel, and particularly of the audit team
leader, were found to be extremely valuable here.
3-15
-------
The audit team leader must be an effective and aggressive
communicator as well as a technical expert, because this individual must
serve as a facilitator for the audit team and host facility personnel
alike. A reserved and low key attitude and behavioral style by the au
-------
SECTION 4
LISTED WASTE K071 UNA CASE STUDIES
The focus of this set of case studies is to propose ways to reduce or
eliminate the generation of listed waste K071. This waste Is defined in
40 CFR 261.32 as follows:
- K071: Brine purification muds from the mercury cell process in
chlorine production, where separately prepurified brine is
not used.
Two facilities were selected as host sites for WMAs at generators of
listed waste K071. The two plants involved are mercury cell chloralkali
facilities located in the Southeast. Background information on the
generation of listed waste K071 at mercury cell chloralkali plants can be
found in two Environmental Protection Agency (EPA) documents on this
waste (EPA 1980, EPA 1980a). In this report, the two plants studied are
designated as Plant No. 1 and Plant No. 2.
WMA AT PLANT NO. 1
Facility Description
Plant No. 1 is a mercury cell chloralkali facility located in the
Southeast and has a name plate capacity of 138,000 metric tons of
chlorine per year. The facility operates two parallel mercury cell
electrolytic process production lines one manufacturing sodium
hydroxide (NaOH) as a co-product and the other producing a potassium
hydroxido (KOH) co-product. The capacities of the two parallel
production lines are 310 metric tons of NaOH per day and 246 metric tons
of KOH per day.1
In subsequent sections of this report, reference is made to the
sodium and potassium hydroxide production facilities, with chlorine
being understood as the co-product in both cases.
4-1
-------
The facility uses DeNora type mercury electrolytic cells, some of
which are used for NaOH manufacture and the balance for KOH
production* All cells have been equipped with metal anodes since tne
late 1960s.2
The facility is located near a major river and receives its raw
materials by barge and railcar. Rock salt from Louisiana is receivea oy
barge and stored in outdoor piles prior to use. Potassium chloride from
Canadian sources arrives by rail and is stored in railcars prior to use.
The facility production is almost entirely merchant (i.e., all of the
products produced are sold to other facilities except for a portion or
the produced K071, which is used internally to produce anhydrous
potassium carbonate (K2C03)). Chlorine (C12), caustic soda (NaOH),
KOH, and hydrogen are the only products of the electrolytic process.
Most customer facilities for the C12, NaOH, and KOH are located in the
Southeast. During the winter months, by-product hydrogen is combusted in
the plant boilers generating a portion of the facility's steam
reaiiirements. At other times of the year, part of the hydrogen is sold
over the fence.
Plant No. 1 presently generates a total of about 2,500 tons per year
of listed waste K071 (mercury-bearing brine purification wastes) from
both the sodium and potassium hydroxide production lines, as well as
approximately 2,500 tons per year of listed waste K071 (mercury-bearing
saturator insolubles) from the NaOH production line. All of these wastes
are currently sent offsite to a hazardous waste landfill.
Process Description
Plant No. 1 produces both r.odium and potassium hydroxides, along with
a chlorine co-product in parallel electrolytic mercury cell production
lines. During electrolysis of sodium chloride brine in the mercury
cells, chlorine gas is formed at the anodes and is collected, cooled, and
dried by passing through su'f'.Tic acid and then compressed, liquified,
The present DeNora electrolytic mercury cell design was developed by
Dr. Annunzio DeNora, an Italian technologist, in 1968, and has
become the industry standard for the manufacture of chlorine by
electrolysis of brine using mercury cells. In this cell, a stream
of flowing mercury is used as the cathode, and specialty-designed
metal plates are used as anodes.
4-2
-------
and stored for shipment. Simultaneously, in the cells, a sodium-mercury
amalgam is formed at tlie flowing mercury cathodes. Mercury leaving the
cells, which contains the amalgam, is subsequently reacted with water in
units called denuders. The reaction converts the amalgam to mercury
metal, a 50 percent NaOH solution, and- hydrogen gas. The hydrogen gas is
collected and partially sold and partially burned for fuel; the NaCH
solution is further processed before being shipped to customers, end the
mercury is returned to the cells. Figure 3 is a simplified schematic of
the jNaOH/chlorine production process.
The spent brine leaving the mercury cells (at about pH 5) contains
about 22 percent sodium chloride, versus 25 percent in the incoming
brine. This depleted brine typically containing 6 ppm dissolved
mercury1 is further acidified with hydrochloric acid (to pH 2.5) and
is then dechlorinated using vacuum flash tanks. The chlorine released is
collected and combined with that generated in the mercury cells for
further processing. The dechlorinated brine is then pumped to the
initial portion of the process, where rock salt is added to form a
resaturated brine. Table 8 presents a typical rock salt analysis at
Plant No. 1. The brine has NaOH solution blended with it prior to
entering the dissolver. The NaOH addition adjusts pH from -2.5 to 10.5
to 11 in order to avoid dissolution of silica (as silicates) in the
brine. Rock salt (NaC1) dissolution occurs in a saturator (or dissolver)
tank, where the flow of salt is countercurrent to the brine flow. No
agitation is used in the dissolver tank. In this operation, the sodium
chloride dissolves in the brine and the insolubles present in the rock
salt fall to the bottom of the saturator vessel, from where they are
periodically removed by mechanical means and discharged to the brine
recovery pads (concrete-lined sludge pads for collecting K071 waste
sludges and decanting and recycling excess brine from these wastes).
These insolubles constitute the largest portion of K071 waste and include
insoluble clay and mineral components of the salt feed, together with
precipitated materials formed in the dissolution step and small amounts
of entrained mercury. The dissolution of the salt occurs in brine at a
temperature of about 70°C.
Plant No. 1 has five dissolver tanks in parallel, two of which are in
use at any given time, one of which is en standby, and a fourth, which is
undergoing cleaning to remove collected insolubles (which form a
rock-like mass on the sioes and the bottom of the tanks as they
accumulate). Operation of the fifth dissolver is described below. The
dissolver tanks are 35 feet in height and 30 feet in diameter, and are
cone-shaped at the base.
The mercury can be in as many as three ionic forms: Hg+, Hg++, and
(HgCl4)=.
4-3
-------
NaCI(ROCK SALT)
VENT
DEPLETED NaCI BRINE
SALES
H2
COMPRESSION
H2
BRIN? AREA
RESATURATED
NaCI
BRINE
CELLROOM
NaOH
50%
BOILERS
f
CI2
GAS
CHLORINE
LIQUIFACTION
CI2
LIQUID
-»>SALES
ELECTRICITY
STORAGE
50% NaOH SOLUTION
SALES
FIGURE 3. NaOH/CHLORINE PRODUCTION PROCESS
AT PLANT NO. 1
-------
Table 8. Typical Rock Salt Composition at Plant No. 1
Compound Weight percent
Water Solubles
NaCl 98.5
CaSO* 1.3
Insolubles 0.2
Acid Solubles
NaCl 93.5
CaC03 0.01
CaSO* 1.5
Insolubles 0.00
Mg 38 ppm
Fe <10 ppm
Si <10 ppm
Source: Plant No. 1 in-house data.
4-5
-------
The resaturated brine is next pumped to a treatment tank where sodium
carbonate is added. Calcium, magnesium, and iron ions prasent in In?
brine precipitate as calcium carbonate and magnesium and iron hydroxide*,
respectively. These precipitate? are removed in the treated oriiw
clarifier. The clarifier overflow is then passed through sand ti'Jers lo
remove residual solids. The underflow, containing the P*"601?1*3.:!:,,
solids and small amounts of entrained mercury (a second form of KO/I
waste), is fed to concrete-lined sludge pads, where the solids settle.
The clarification and filtration operations are carried out at 60 to
70'C. The clarifier used is 90 feet in diameter and 15 feet in
height. Tha sand filters operate in the downflow mode, and are
periodically backwashed with brine to flush out accumulated impurities.
The backwash stream is sent to the K071 waste sludge pads, where the
solids settle and the clean brine is returned to the clarifier.
The fifth dissolver tank operates in the "hot-prccess" mode; i.e.,
when the brine flow rate through the system clarifier reacnes its
capacity, this dissolver is put into operation as both a brine
preparation and an impurities precipitation tank. Sodium carbonate is
added to resaturated brine in this dissolver, causing precipitation of
impurities in the added salt as insoluble carbonates, e.g., calcium
carbonate. The treated brine from this tank is pumped to the sand
filters and the settle! solids are discharged to the K071 sludge pads.
The purified brine after filtration is acidified witn hydrochloric
acid to a pH -5 and sent to the electrolytic mercury cells. Figure 4
shows a simplified schematic of the portions of the process generating
K071 waste from the NaOH production line.
The production process for KOH and chlorine at Plant No. 1 is
identical to that described above. Figure 5 is a simplified schematic of
the KOH production process. The following differences exist with respect
to operations that generate the K071 waste:
• Potassium chloride (KC1) of typically 99.5+ percent purity is
used as a feedstock in place of rock salt. As the potassium
chloride is of higher purity, minimal saturator insolublps are
generated in the KCH brine preparation circuit. The processing
equipment and process conditions, however, are identical to those
described above for the NaOH brine preparation system.
• Solids formed during the KC1 brine purification steps are more
Difficult to dewater. As a result, the clarifier underflow going
v.o tha K071 sludge ponds contains a lower percentage of solids,
which settle more slowly. The reason for this problem stems
4-6
-------
NaCL-
NaCl
3ATURATORS
K071
SLUDGE
Na2CO3
REACTION
TANK
BRINE RETURN
NaCl
SLUDGE PADS
< BRINE SLUDGE
-*-K071 SLUDGE
Nad
CLARIflER
BRINE
VACUUM
DECHLORINATION
CI2TO PROCESSING
DEPLETED
BRINE
NaOH
CI2 CONDENSATE
FROM CHLORINE
PROCESSING
HCI
HCI
BRINE
SLUDGE
FILTERS
CELLROOM
FIGURE 4. NaCI BRINE TREATMENT SYSTEM
AT PLANT NO. 1
-------
-------
from the presence of traces of amine anti-caking additives present
In the rr*as>sium chloride feedstock. The amines act like
flotation agents and retard settling of the precipitated
materials. The plant is investigating alternative sources of KC1
feedstock that do not contain traces of amines.
• In the KC1 brine purification step, potassium carbonate and KOH
are added in place of soda ash and NaOH.
Figure 6 is a simplified schematic of the KC1 brine treatment system.
Waste Stream Description
There are two sources cf listed K071 waste in Plant No. 1:
(1) mercury-contaminated saturator insolubles and (2) brine muds from the
brine treatment purification portion of the process.
At Plant No. 1 both the KOH and NaOH production lines generate these
waste streams as follows:
a) Brine saturator insolubles from the NaOH production process
consist of a complex gypsum/sodium sulfate insoluble salt,
undissolved sodium chloride, silica, and other insoluble
materials present in the raw rock salt. The mercury compound
level in this K071 waste is about 10 ppm (as mercury). About
2,500 tons per year of sodium chloride brine saturator insolubles
are generated by the NaOH process train.
b) Brine purification muds from the NaOH production process
(including brine clarifier underflow and brine filter backwash)
consist mostly of calcium carbonate, undissolved sodium chloride,
small quantities of gypsum, other insolubles, and water. Mercury
levels in these K07! wastes are in the 20 to 40 ppm range. About
1,000 to l.jOO tons per year of brine purification muds are
generated by the NaOH process train.
c) The KOH production process generates essentially negligible
quantities of saturator insolubles because of the very high
purity of the potassium chloride feedstock and the processing
done by its manufacturer to remove insoluble materials.
Purification of the potassium chloride brine yields sludge
containing calcium carbonate, magnesium hydroxide, undissolved
potassium chloride, traces of other insolubles, and water.
Mercury levels in this K071 waste are about 15 to 25 ppm. This
waste is more difficult to dewater than the two K071 wastes
generated by the process train (as discussed above under
description of the KOH manufacturing process). Up to 1,000 tons
per year of K071 waste is generated from th. KOH process train.
4-9
-------
1
h-'
o
K2C03
KCI »
KCI
SATURATORS
1 i
i
KO71
SLUDGE
i
i
».
i
\
P
REACTION
TANK
\
F
BRINE
KCI
RETURN
i
KCI
SLUDGE PADS
t
i
> BRINE SLUDGE '
CLARIFIER
^
• CI2TO
BRINE
i
BRINE
SLUDGE
FILTERS
HCI
i
PROCESSING
HFPLETED
VACUUM
DECHLORINATION
t
CI2 COMDENSATE
KOH
BRINE
FROM CHLORINE
l
CELL
ROOM
*»—
1
I
1
HCI 1
PROCESSING I
FIGURE
6. KCI BRINE TREATMENT SYSTEM 1
AT PLANT
NO.
1
-------
Table 9 presents typical ana ys-s of the NaCl brine-related wastes.
Current Waste Management Profile
At Plant No. 1, the K071 wastes are currently managed as follows:
• Saturator insolubles (dry solids) from the NaCl brine treatment
system are periodically removed mechanically from the dissolvers
and combined with the settled brine muds in the K071
sludge-holding basins prior to disposal. Blending of these two
wastes enables a "dry" solid material to be loaded into roll-off
bins for shipment to the hazardous waste landfill.
• Clarifier brine mud/filter backwash from esch of the NaCl and
KC1 brine treatment systems is discharged to separate
concrete-lined sludge-holding basins, where the solids settle and
the liquid phases are decanted and recycled to the brine treatment
systems. Separate mud-holding basins are used for the sodium and
KOH production lines. In general, the muds from the KOH
production lines require longer settling times. This is because
the potassium chloride used contai.is traces of amine anti-caking
agents applied to the KC1 particles during production of this
material in order to prevent caking during storage and shipment.
Trace levels of such agents make the settling process more time
consuming, and result in the KC1 treatment muds having a higher
waver and salt content.
After settling, blending, and air-drying, the muds are retrieved
from the holding basins, containerized, and shipoed to a hazardous
waste landfill for final disposal.
Postulated Waste Minimization Options and Preliminary Analysis of Their
Technical and Economic Feasibility
As a result of initial discussions held with plant personnel at Plant
No. 1 during bovl> the pre-audit and audit visits and subsequent
evaluations by tha audit team, waste minimization (WM) options for
reducing or eliminating the generation of K071 waste were developed under
the approved EPA hierarchy: source reduction options being more
desirable and recycle/reuse options less desirable. Treatment options
for the Plant No. ' hazardous wastes, although not considered waste
minimization approaches, were viewed as alternatives because of
The RCliA legal definition includes treatment as a WM approach. In
the context of this EPA program, however, the much preferred WM
approaches are source reduction and recycle/reuse, with the treatment
approach used only if neither of the former approaches is available.
4-11
-------
Table 9. Typical Analyses of K071 Wastes at
Plant No. 1
Component
Weight percent
NaCl Dissolver Sludge
CaS04
Na2S04
NaCl
H20
Insolubles
Balance (Al, Mg, Fe)
Hg, total
Hg, EP-Tox
34
34
25
5
1
<10 ppm
25 ppb
CaCo3
NaCl
H20
Na2/CaS04
Insolubles
Balance (Al, Mg, Fe)
Hg, total
Hg, EP-Tox
NaCl Clarifier/Filter Backwash Sludqe
37
35
25
1
1
30 ppm
65 ppb
NaCl Clarifier/Filter Backwash Sludqe
CaC03
KC1
H20
K2/CaSO,
Insolubles
Balance (Al , H,, Fe)
Hg, total
Hg, EP-Tox
10
47
40
<0.5
1
2
15 ppm
100 ppb
Source: Plant No. 1 in-house data.
4-12
-------
their potential technical and economic feasibility for detoxifying the
K071 waste, i.e., reduce mercury levels to <12 ppb and/or demonstrated
ability to meat EPA delisting requirements at other mercury cell
chloralkali facilities. The options considertd under the various
categories are presented below. In these presentations, preliminary
economics based on order-of-magnitude cost estimates (±50 percent
accuracy) are included in order to indicate the economic viability of the
respective options.
Source Reduction Options
The following source reduction options have been identified for the
K071 waste stream:
(A) Use of depleted brine side stream treatment for reduction of
NaCl saturator insolubles generation;
(B) Use of prepurifipd salt as a feedstock in place of the rock salt
currently used in NaOH production;
(C) Use of solar salt as a feedstock rather than the higher
impurities-containing rock salt currently used;
(D) Removal of mercury from the depleted brine prior to brine
resaturation and purification; and
(E) Conversion of the electrolytic mercury cells to electrolytic
membrane cells, thus eliminating the generation of both K071 and
K1C6 wastes.
These options are discussed in sufficient detail below to permit a
preliminary assessment of their technical and economic feasibility.
(A) Use of depleted Brine Side Stream Treatment for Reduction of
NaCl Saturator Insolubles Generation.
One of the operational problems at Plant No. 1 related to K071 waste
gsneration is the formation of rock-like masses of insoluble materials
that build up in the cone bottom section of the NaCl saturators during
the rock salt dissolution operation in these units. As a result of the
solids ouildup, periodic shutdown of these saturators is required (every
5 to 6 weeks) in order to allow operators to enter the saturator unit
taken offline and remove the rock-hard saturator insolubles material
using jackhaminers. This is a labor-intensive process and costs Plant
No. 1 approximately $250 000 per year. Table 9 data indicate that the
bulk of tKis material (about 70 percent by weight) is a mixture of equal
4-13
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parts of sodium and calcium sulfates. This material is theorized by
Plant No. 1 personnel to be the double salt Na2S04«CaS04 (also
known as the mineral Glauberite). If the sulfate content of the depleted
brine entering the saturator can be significantly reduced below
saturation level, allowing some sulfate in the incoming salt to dissolve,
this could reduce or avoid the precipitation of the sodium/calcium
sulfate "double salt." With a dissolved sulfate level of 36,000 ppm in
the Plant No. 1 depleted brine, it is proposed to treat a side stream ot
5 percent of the depleted brine flow following dechlorination and pH
adjustment (approximately 150 gpm), using calcium chloride as the
precipitant to remove sulfate as insoluble calcium sulfate. Following
this treatment step (which would require a reactor and clarifier), the
treated side stream, now low in dissolved sulfate (assumed to be
1,500 ppm), would be recombined with the balance of the depleted brine to
achieve an average of approximately 34,000 ppm dissolved sulfate entering
the saturator. In this manner, up to 2,000 ppm equivalent of the
incoming sulfate in the raw salt, e.g., from its calcium sulfate content,
can dissolve, reestablishing the saturated sulfate level, and
correspondingly reducing or eliminating the potential for "double salt"
formation and precipitation in the saturators.
With respect to the operating cost of this side stream operation, the
single biggest cost would be that for the calcium chloride precipitant.
Calculations indicate that the annual cost of this material (based on
$175/ton at the plant) wo'ild be far in excess of the savings resulting
from elimination of the need for an intensive labor operation to remove
built-up deposits in the saturators, i.e., $58,000,000 for calcium
chloride versus a $250,000 labor cost for the present saturator cleanout
operation. This option is obviously not economically feasible. Use of a
much cheaper sulfate precipitant, e.g., lime kiln dust, would require a
far larger side stream treatment system because of the limited solubility
of the latter material. Both precipitants would result in the generation
of large volumes of mercury-contaminated sludges, actually increasing the
amount of K071 to be disposed of, even though the dissolver solids
problem would be considerably mitigated.
(B) Use of Prepurified Salt Feedstock to the Sodium Hydroxide
Production Facility
One way to avoid generation of K071 wastes in the NaOH production
line is to separately prepurify the salt feedstock used, i.e substitute
an essentially pure Nad feedstock for the present rock .salt • iterial,
which now requires a brine purification step (with its resultant
generation of the mercury-contaminated K071 waste). The rav» N:r.'
feedstock (rock salt) would be dissolved in water to prepare <• saturated
brine. The brine would then be filtered to remove insoluble", and treated
4-14
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to precipitate out calcium and magnesium ions as well as other trace
impurities. Precipitated materials would be removed by clarification and
filtration, and the purified brine would then be evaporated to recover a
solid pure sodium chloride, which would then be used as a feed for the
mercury cell process. With a pure salt feed, there would be minimal need
for in-process purification of this material and thus minimization of the
generation of mercury-contaminated brine purification wastes.1
The major cost associated with this option would be for evaporation
of the purified brine. According to plant data, 1.72 tons of salt would
have to be purified per ton of chlorine produced. As saturated brine
contains 25 percent salt and 75 percent water, about 5.16 tons of water
would have to be evaporated per ton of chlorine generate^. Discussion
with a prime vendor of commercial evaporation equipment, indicates that
the use of a quadruple-effect evaporator (with suitable preheat) coupled
to a centrifuge would produce a crystallized salt product and require
approximately 70,000 Ib/hr of saturated steam for this purpose. Using
a cost of $3 per 1,000 Ib of 15 psig steam generated in onsite
facilities, en annual cost of approximately $1.7 million would be
required for steam usage. In addition, there are other direct and
indirect operating costs including labor, supervision, electricity,
maintenance, and depreciation on plant equipment, which would also
contribute significant costs. The facility is currently spending about
$150 per ton to dispose of about 5,000 tons per year of K071 waste at a
commercial hazardous waste landfill. Thus, current, annual disposal costs
are about $750,000. In addition, a labor cost of about $250,000 is
incurred annually to remove the caked rock salt impurities from the salt
dissolver units. Thus, a total amount of approximately $1 million is
available to offset costs of at least $2 million annually incurred by the
use of a salt prepurification step. This approach is thus not
1 Small amounts of impurities remaining after salt purification would
still result in small but measurable quantities of brine
purification muds, i.e., I to 2 tons per year.
2 Personal Communication, M. . Frank Bella, Swenson Process Equipment,
Inc., Harvey, Illinois, May 20, 1987.
4-15
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economically viable.1 It should be noted that a source of waste heat
that could generate low pressure steam (though not presently available)
could change these economics substantially, i.e., lower the cost of
pre-purifying the salt feedstock.
(f) Use of Solar Salt as Feedstock to the Sodium Hydroxide
Production Facility
Another alternative to the use of rock salt for NaOH production would
be the use of solar salt, which is 99.7 percent NaCl with the balance
being soluble calcium and magnesium salts (as compared to the present
rock salt feedstock with 98.5 percent NaCl and a significant amount of
insoluble material). Use of solar salt would eliminate the largest
source of K071 waste (the saturator insolubles), but would still generate
comparable quantities of brine muds - primarily magnesium and calcium
hydroxides with accompanying entrained mercury - as are generated in KC1
brine purification, i.e., approximately 1,000 tons per year. In
addition, the cost of solar salt is $28.70 per ton FOB Bahamas, and
adding an estimated freight cost of $15 per ton would make this material
uneconomical to use as prepurified salt (current rock salt cost at the
plant is under SH per ton).
(D) Removal of Mercury from Depleted Brine Leaving the Mercury Cells
Two proposed in-process modifications "or removal of entrained
mercury from the depleted brine leaving the mercury cells, were discussed
with plant personnel during the audit visit. Either of these, if
technically and economically viable, could reduce or eliminate the
generation of K071 waste. These two options are discussed below:
In this regard, one audit team suggestion was considered, whereby
Plant No. 1 would interest a sufficient number of mercury cell
chloralkali plants in pooling their salt purchasing volume with a
rock salt producer in a cooperative effort to have the producer
prepurify the rock salt for distribution to this group. This group
of chloralkali plants could jointly defray the cost of the new rock
salt purification equipment at the rock salt production site in
return for long-term contractual commitments for the prepurified
salt. One significant problem with this suggestion is the fact that
there is an insufficient number of mercury cell plants within a
reasonable distance of a rock salt producer that cou^d benefit from
this approach. Of the 14 mercury cell plants that could potentially
benefit from access to prepurified rock salt, only one or two in any
given salt producing region would be able to benefit from this
arrangement.
4-16
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(1) The first of these options would involve treatment of depleted
brine from the mercury cells with sodium sulfide (Naj>S) to precipitate
essentially insoluble mercuric sulfide before the depleted brine is
returned to the brine resaturation and treatment portion of the process.
The plant had previously investigated the possibility of removing
entrained mercury from the depleted brine when an experiment was carried
out to test operation of a membrane electrolytic cell at the site. The
need existed to produce a mercury-free brine to be used as feed to this
cell, and sodium hydrosulfide (NaSH) was uced to precipitate mercury as
the insoluble sulfide. The plant was able to produce a mercury-free
brine using this procedure. Adaptation of this procedure as a commercial
process for removal of mercury from the depleted brine prior to the brine
resaturation step was explored for its potential as a viable source
reduction option. Two possible approaches under this option include the
following:
(a) Disposal of the mercuric sulfide waste generated by the sulfide
precipitation step. In this approach, the depleted brine from
the mercury cells following decblorination and pH adjustment
with NaOH solution to a pH of 7 to 8, would be treated in a
number of parallel in-line static mixers with sodium sulfide
(Na^S) to precipitate mercury as insoluble mercuric sulfide
(this reaction is complete within 30 to 60 seconds). Enough
NaoS is added to ensure complete precipitation of the mercury
and reaction with the residual chlorine in the dechlorinated
brine. The resulting slurry would then be fed to a hold
tank where filter aid (diatomaceous earth) and coagulant (if
required) are added, and the mixture is then fed to pressure
leaf filters. The filtered brine now free of entrained mercury
would then be fed to the salt dissolvers, and the brine
treatment and purification process would now generate a
non-hazardous waste, which could be placed in a sanitary
landfill after appropriate delisting.
With an average of 70 ppm of residual Cl2 in the depleted brine
after dechlorination reacting to form hypochlorite ions (OC1~) in
the brine, the (OC1}~ is expected to react with sodium sulfide to
form NaCl and NaoSO^. In the latter reaction (at an alkaline
pH), one mol of Na^S would be consumed in reacting with 4 mols of
NaOCl. Together with the reaction of Na^S with soluble mercury
(assumed to be present as mercuric chloride) in the depleted brine,
a total of 151 tons per year of Na£S (as 100 percent material)
would be required at an approximate delivered cost of $500/ton or
$75,000/year.
4-17
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Approximately 240 Ib/day of mercury would be removed from the
depleted brine as mercuric sulfide. This material wou'' °%
included in a 50 percent solids filter cake (the recovered form
ot this waste) of approximately 24,000 Ib/day (12 tons/day;,
based on data on K106 waste generation in mercury eel I P18""
using sulfido treatment for collected wastewaters. With mercury
valued at about $6/1b (equivalent to $518,000/yr replacement
cost), treatment costs including labor, chemicals (Na2b),
power, and maintenance are estimated to be approximately
$250,000/yr, and a disposal cost of roughly 4,300 tons per year
of this waste at the currently used hazardous waste landfill or
about $645,0;)0/yr, the total annual cost for treating and
disposing of tnis waste would be approximately $1.4 million per
year. This is over double the present cost of K071 waste
disposal from the NaOH production facility ($0.6 million per
year), and the option would therefore not be economically viable.
(b) Recovery of mercury from the mercuric sulfide waste generated by
the sulfide precipitation step. A retort of the multiple hearth
furnace type is commercially available to recover the mercury
from the mercuric stlfide sludge, and would cost approximately
$1.0 million to install based on the Capacity and feed rate
required. The 12 tons per day of mercuric sulfide filter cake
generated in the sulfide precipitation step (having been washed
free of residual NaCl in the filtration step) would be
continuously fed to the retort, the mercury vapor condensed, and
the recovered mercury recycled to the electrolytic cells.
The retorted residue, consisting of about 6 tons per day of
essentially pure filter- aid with traces of iron sulfide, would
be recycled to the sulfide filtering step, with a small amount
of this material (assumed to be 10 percent or approximately 0.6
ton per day) disposed of ?.s a delisted non-hazardous waste to a
local sanitary landfill.2
It is assumed that the mercuric sulfide in the returt wo'ild vaporize
at 1000°F, and, in the praserce of air ;wept through the retort,
would react to form metallic mercury and S02- After the mercury
is condensed, a caustic scrubber would be used to remove the $03
from the residual vent guS. Appropriate monitoring of the vent
gases would be required for residual mercury and S02 emissions.
Based on preliminary Plant No. 1 test data, EP-tox Teachable mercury
from this residue should be less than 12 ppb (assumed to be the EPA
delisting level for this waste).
4-18
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The operating cost of retorting for mercury recovery (assuming a
natural gas-fired retort) is estimated as $100 per ton of dry
feed to the retort.1 These costs include labor, natural gas,
electricity, and maintenance (with the latter assumed to be
60 percent of the total operating cost) and total $216,000 per
year. Other direct operating costs (including labor, NaoS,
power, and maintenance) for the mercuric sulfida precipitation
step are estimated as $250,000 per year. Total direct operating
cost is therefore $358,000 per year. The total installed cost
of the mixer/filter/retort system for mercury precipitation and
recovery is estimated at $1.4 million. The savings in disposal
cost for K071 based on disposal of the delisted mercury-free
saturator insolubles and brine muds and mercury retort residue
in a nearby approved sanitary landfill would be $397,000
annually. Since the total operating costs for this option
exceed the savings in landfill costs, there is no payback
available with this option, and it is not economically viable.
(2) A second possible ip-prccess modification discussed with plant
personnel involves the use of ion exchange resin for dissolved mercury
removal from depleted brine leaving the mercury cells. The significant
problems with this approach include the following:
- the lack of a commercially available resin capable of treating a
depleted brine containing significant levels of residual
chlorine (even after dechlorination) without extensive
pretreatment to remove the chlorine;
This number represents three times the operating cost estimate
developed in 1974 for operation of a similar retort used for tl.is
purpose (EPA 660/2-74-086, p.72). Plant No. 1 onstream time is
assumed to be 360 days per year for all operating cost estimates in
this report.
Disposal cost in a lined sanitary landfill within approximately
30 miles from Plant No. 1 would cost about $33/ton. This cost has
been used throughout the report as that for disposal of delisted
K071 waste in an approved sanitary landfill. "Approved" in this
context i; taken to mean that the landfill is equipped with a clay
or synthetic liner with a permeability of less than 10~' cm/sec.
Payback period is defined in this report as the total incremental
investment for the option considered divided by tne net savings in
annual direct operating costs. In this case, the payback is
(1 400,000/397,000 - 216,000 - 250,000) or -20 years.
4-19
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- the relatively low flow rates available for use with present
commercial resins (10 to 15 bed volumes/hr) requiring very
resin beds; and
- the relatively low mercury adsorption capacity for commercially
available resins before breakthrough occurs (-0.7 percent oy
weight of available capacity for commercial resins evaluated oy
Plant No. 1).
This approach thus appears to be both technically and economically
nonviable.
(E) Conversion of the Mercury Electrolytic Cells t^ Membrane
Electrolytic Cells, Thus Eliminating the Genera*ion of Both K071
and K106 Wastes1
The use of membrane technology in chloralkali plants has become
firmly established, with a total of 12,000 metric tons of caustic
production per day or approximately 11 percent of worldwide capacity
using this technology in 1987.z Although membrane cell technology
appears to be the brine electrolytic cell technology of choice for new
installations worldwide, only about 3 percent of chloralkali capacity in
the U.S. currently uses this process, primarily because of the lack of
growth in the domestic chloralkali industry.L With no new mercury cell
chloralkali plants planned and the existing mercury cell plants in the
U.S. for the most part nearing the end of their useful lives, either
replacement of this capacity with membrane technology or conversion of
the existing mercury cells to membrane cells is becoming a distinct
possibility. An additional incentive for replacement of mercury cells
with membrane cells would be elimination of the generation of K071 and
K106 wastes. A source reduction option was evaluated wherein the
existing mercury cell facility at Plant No. 1 was replaced with membrane
cells incorporating Dupont Nafion perfluorinated membranes.
1 Information in this section is derived from a paper by M. Esayian
and J.H. Austin (Esayian, M. and Austin J,H. 1984).
2 Personal Communication, Mr. David Peet, E.I. Dupont de Nemours and
Co., Inc., Wilmington, Delaware, July 22, 1987.
This does not imply any EPA endorsement of this product.
4-20
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In addition to electrolyzer conversion, a mercury cell to membrane
cell retrofit, based on present technology, is assumed to require three
major changes in auxiliary facilities:
- The use of ion exchange resin in a new secondary brine purification
step to remove dissolved calcium and magnesium to a level of less
than DO ppb. At least two resin beds are required, one bed being
online while the other is being regenerated. This step is well
established technology.
- Evaporation to concent-ate the 32 to 35 percent NaOH or KOH from
the membrane process to the 50 percent product required. This is
assumed to require additional steam generating capacity.
- A caustic recirculation loop to provide temperature control as well
as mixing in order to achieve a uniform concentration profile in
the cathode chamber. Deionized water is added to the catholyte
loop to control the NaOH or KOI.1 concentration.
The existing brine loop can be used in the mercury cell conversion,
although the higher salt conversion capability of the membrane cell
process will significantly reduce the brine hydraulic flow. Selection of
the proper membrane electrolyzer designs should minimize cell room
changes. It is assumed that the present rectifiers and current
conductors at the Plant No. 1 cell room will not require major changes.
Figure 7 is a simplified schematic of the revised chloralkali process
employing membrane cell technology at Plant No. 1. While shown for the
NaOH manufacturing portion of the plant, this schematic would apply to
both NaOH and KOH production facilities.
Based on the process shown in Figure 7, the investment for membrane
conversion at Plant No. 1 is estimated as $61,000/ton/day of 100 oercent
NaOH (or KOH)1. With combined NaOH and KOH production (100 percent
basis) of 307 tons per day, the total investment for the membrane
conversion is $19.0 million. An estimate of direct annual operating cost
was developed based on the following assumptions:
Personal Communication, Mr. David Peet, L. I. DuPont deNemours and
Co., Inc., Wilmington, Delaware, July 22, 1987. This is an estimate
based on a generic plant design that is believed to be of sufficient
accuracy i.e., well within the ±50 percent accuracy used for
estimates in this report, for this preliminary estimate.
4-21
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ROCK
SALT
DISSOLVER
WASTE
SATURATED
BRINE
*
l
ro
PRIMARY
BRINE
PURIFICATION
NON-HAZARDOUS
-». WASTE DISPOSAL
TO SANITARY LANDFILL
LEGEND
EXISTING PROCESS
PROPOSED PROCESS
MODIFICATIONS
ABANDONED
FACILITIES
BRINE
BRINE
PURIFICATION
MUD
y///////////
L/SECONDARY BRINE/
y PURIFICATION /
| (ION EXCHANGE) /
V / //////////
PLANT
WASTE-
WATERS
K106 WASTEWATER
TREATMENT
WASTEWATER
DISCHARGE
(pH ADJUST)
AMALGAM
DECOMPOSITION
CHLORINE
DRYING
COMPRESSION
LIQUIFICATUN
CHLORINE
PRODUCT
HYDROGEN BY-PRODUCT
(FOR INTERNAL USE AND SALES)
SO PERCENT NaOH PRODUCT
FIGURE 7. SIMPLIFIFD SCHEMATIC OF PROPOSED MEMBRANE
CELL CONVERSION AT PLANT NO. 1
-------
- Electric power configuration:
• Mercury cell: 2,950 KWH/metric ton of 100 percent NaOH (or
KOH)
• Membrane rell: 2,200 KWH/netric ton of 100 percent NaOH (or
KOH}1
Electric power cost: 4.9 cent./KWH
- Steam cost: $4.80/1,000 Ib
- Membrane life: 2 years
- Auxiliary power consumption: 260 KWH/metric ton of 100 percent
NaOH (or KOH)
- Steam for evaporation: 200 Ib/metric ton of 100 percent NaOH (or
KOH)
Operating costs shown are in 1985 dollars and are assumed to be
applicable in 1987 dollars.
The difference in direct operating costs resulting from electric
power and steam costs (in the mercury cell case) and electric power,
steam, membrane replacement, and miscellaneous costs (in the membrane
cell case) is estimated as $9.4 million/year. Other direct operating
costs are assumed to be the same for both, cases. With respect to waste
disposal, the difference between K071 and K106 hazardous waste disposal
of approximately 5,000 tons per year (in the mercury cell case) and
disposing of this material in the non-hazardous form (in the membrane
cell case) is about $600,000 per year. With a total savings of about
$10.0 million per year in direct operating costs, the payback period is
(19.0 mill ion/10. "> million) or 1.9 years, making the membrane conversion
economically attractive based on these numbers.
Space requirements for the additional equipment (including one common
stream generating system, two sets of evaporators for the NaOH and KOH
products, and two icn exchange systems for secondary brine purification),
are believed to be adequate for the required plant revarrp at Plant No. 1
if this option were to be adopted.
Current efficiency for KCH production in membrane cell eleUrolyzers
is higher than for NaOH. The figure shown is for NaOH, so 'hat this
is a conservative assumption.
4-23
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Recycle/Reuse Options
There were no recycle/reuse options available for recovery of the
very small daily amount of mercury entrained in the K071 waste
(<5 Ib/day). This amount of mercury (primarily in the ionic form) is
dispersed in approximately 30,000 Ib/day of brine purification muds and
saturator Insolubles.
Treatment Options
While treatment is not a WM option, it is possible that with only one
technically and economically viable source reduction option deemed by the
audit team to be potentially available to Plant No. 1 (replacement of the
mercury cell system with membrane cells and appropriate auxiliary
equipment), consideration should be given to technically and economically
feasible treatment alternatives to the present disposal method at Plant
No. 1 for the K071 waste.1 Such treatment, if it would render the
waste non-hazardous, would permit disposal of the treated material in a
sanitary landfill once the waste was suitably delisted. In this regard,
the August 1938 ban on disposal of these RCRA listed wastes (K071 and
K106) in hazardous waste landfills, lends additional impetus to
consideration by Plant No. 1 of a treatment alternative to the present
method of disposal. Three proposed treatment options were considered:
(1) Use of a washing process to render the NaCl saturator insolubles
portion of the K071 waste nun-hazardous. The waste would be
considered non-hazardous by EPA because of the reduction of
EP-tox Teachable mercury level to <12 ppb. No separate
treatment is planned for the KC1 saturator insolubles, since
this waste is negligible in quantity.
It should be noted that the audit team had no knowledge of the
investment priorities at Plant No. 1 and thus could not judge
whether or not the proposed source reduction option (which would
involve an investment of approximately $20 million) would be given
serious consideration at this time.
In addition to this impetus, BOAT (best demonstrated available
echnology) requirements, when promulgated by EPA for listed wastes
F071 and K106, will require mercury cell chloralkali plants
presently disposing of these wastes in hazardous waste landfills, to
meet much more stringent mercury levels in order to continue
disposal in landfills.
The current maximum level in the EP-tox leachate reqi-ired for
delisting of the K071 waste by EPA at the waste generation level in
Plant No. 1 is 12 ppb of mercury.
4-24
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(2) Use of «-< washing process for the Nad saturator insol'ibles
combined with an experimental chemical treatment process
developed by Plant No. 1 for the brine clarifier mud/filter
backwash solids/hot process treatment solids. The combined
treatment would render the total K071 waste non-hazardous by
reducing the EP-tox Teachable mercury level in this waste to
<12 ppb. The Plant No. 1 experimental process would be used
on both the NaCl brine treatment waste and (separately) on the
KC1 brine waste. In the latter case, onl> the brine
purification muds and filter backwash so1ids would be treated by
the Plant No. 1 experimental process.
(3) Use of a washing process to treat the NaCl saturator insolubles
portion of the K071 waste and a technique used in the Vulcan
Treatment Process to chemically treat the brine clarifier
muds/filter backwash solids/hot process treatment solids portion
of the NaCl brine-based K071 waste. Separate use or the
Vulcan treatment technique would be employed for the KC1
brine-based K071 waste. These procedures would render the
entire K071 waste non-hazardous by reducing the EP-tox Teachable
mercury level i.i this waste to <12 ppb.
It is to be noted that option (1) ?bove is common to all three
proposed treatment options. Plant No. 1 could install option
(1) initially and add either option (2) or (3) at a later date (bul
before the August 1988 RCRA ban on landfilling these wastes), when
delisting of the NaCl saturator insolubles is achieved and small-scale
trials of either option (2) or (3), together with derailed economic
studies of these approaches, er.ables Plant No. 1 to make an appropriate
choice of a treatment step for the brine purification muds. The three
options are discussed in detail below.
A K071 treatment process developed by the Vulcan Chemicals, Port
Edwards, Wisconsin, chlorali.ali facility and available to the
mercury cell chloralkali industry. This process, used by the Vulcan
facility to obtain EPA delisting of their K071 waste, is currently
incorporated in the plant operation.
As a result of adoption of option (1), (2), or (3), wastewater
treatment costs in the K106 treatment operation would show a small
but measurable increase caused by as much as a 10 ton per year
increase in K106 generation.
4-25
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Option (1) Use of a washing process to convert the NaCl saturator
insolubles portion of K071 waste into a non-hazardous rorm.
The largest portion of K071 waste at Plant No. 1 is the NaCl
saturator insolubles. This stream is approximately 50 percent
(2,500 tons per year) of the total hazardous waste shipped offsite. in
optior. (1), a water washing treatment approach was applied to this stream
only. A number of mercury cell chloralkali producers have been
successful in delisting all or part of the K071 waste stream, using a
washing technique utilizing either water or depleted urine.
It is assumed that discharge of the saturator solubles from the Plant
No. 1 offline NaCl saturators could be scheduled so that the proposed
water washing process can be carried out on a continuous basis. This
material would not be mixed with the dilute brine clarifier sludge (as is
done now), but would be stored separately on the existing sludge pad as
the feed point in the proposed treatment option. The brine clarifier
underflow stream and (when generated) the hot process treatment tank
solids discharge (see Section 2 for a description of the hot process
system for NaCl brine preparation) would have to be continuously
combined, clarified, thickened, filtered, and shipped offsite as
hazardous waste, as is discussed below.
It is proposed to water wash the NaCl saturator insolubles material
(characterized in Table 2 - NaCl Dissolvcr Sludge) at the rate of
approximately 7 tons per day (580 Ib/hr). The process would consist of
loading this material from the sludge pad storage area (using a portable
conveyor) into a propeller-agitated slurry tank. In the tank, fresh
water makeup and a recycle dilute brine stream (derived from the residual
salt in the saturator insolubles) would be used to prepare a slurry
(assumed to be 25 percent solids) to be used as feed to a horizontal
vacuum belt filter. Large particulate (rocks, trash, etc.) would be
Stauffer Chemical Co., St. Gabriel, Louisiana, Olin Chemical Co»p.
Charleston, Tennessee, Vulcan Chemicals, Port Edwards, Wisconsin,
and Stauffer Chemical Co., Le Moyne, Alabama. These companys'
respective EPA delisting petitions contain appropriate supporting
data and process information on this approach. The operating
mechanism in the washing process is presumed to be a metathesis
reaction, i.e., the glauberite (Na2S04 • CaSO*) is assumed
to dissolve, soluble calcium ions present would disproportionate the
sodium ions, and calcium sulfate would recrystallize as either
gypsum or anhydrite. Lab-scale tests at Plant No. 1 have tended to
confirm this mechanism.
4-26
-------
periodically drained from the bottom of the slurry tank and held on the
sludge pad for final disposal. Slurry would be fed through a head tank
to the filter where a countercurrent water-washing scheme is achieved.
In this scheme, slurry is continuously delivered to the feed end of the
unit and filtered solids (assumed to be a 75 percent solids cake) are
discharged at the opposite end. Fresh wash water is applied to the cake
near the discharge area, passes through the cake, is collected in a
vacuum receiver, and is reapplied to the cake nearer the feed end of the
filter in countercurrent fashion. Two to four washing stages would
normally be used. Wash liquor discharge from the unit is sent to the
Plant No. 2 wastewater treatment operation described in Section 3.
Based on extensive pilot-scale treatment of a similar saturator
insolubles material, the filter cake would have 1 to 15 ppm mercury and
the EP-tox leachate would have about 5 ppb mercury.2 The filter cake,
once delisted, could be disposed of in a lined sanitary landfill within
about 30 miles from Plant No. 1.
A simplified schematic of the proposed treatment scheme is shown in
Figure 8.
The brine clarifier underflow, filter backwash discharge, and hot
process reactor tank slurry discharge, which, because of the method of
operation, is quite dilute (containing less than 0.5 percent solids in
the combined stream), is presently combined with the saturator insolubles
discharge on the sludge pad to produce a "dry" sludge prior to shipment
offsite to a hazardous waste landfill. Adoption of proposed treatment
option (1) by Plant No. 1 would require that the brine wastes be handled
separately prior to discharge as a final waste. This would involve
discharging the combined brine clarifier underflow/filter backwash
solids/hot process reactor tank solids stream to a separate
clarifier-thickener in order to produce an underflow sufficiently high in
solids to feed to a dewatering filter such as a rotary vacuum filter
(approximately 10 to 20 percent solids in the filter feed is assumed to
be achievable by this technique). The filter cake from this treatment
As a result of adoption of option (1), (2), or (3), wastewater
treatment and waste disposal costs in the K106 treatment operation
would show a small but measurable increase because of an increase in
K1U6 generation of up to 10 tons per year.
Stauffer Chemical Company, St. Gabriel, Louisiana. Delist'ing
Petition to EPA, April 18, 1982, Table III.
4-27
-------
DECHLORINATED
DEPLETED BRINE FROM
MERCURY CELLS
ROCK
SALT
BRINE TREATMENT
AND CLARIFICATION.
FILTER BACKWASH
SOLIDS CLARIFICATION
I
ro
cc
TREATED, PURIFIED
BRINE TO MERCURY CELLS.
HOT
PROCESS
TREATMENT
SOLIDS
/VACUUM^
/ FILTER /
/s s / s s /
LEGEND
n
Y//,
EXISTING PROCESS
PROPOSED PROCESS
MODIFICATIONS
FILTER CAKE (KO71)
»-
TO HAZARDOUS
WASTE
LANDFILL
DISPOSAL
RECYCLED WATER
FROM WASTEWATER
TREATMENT SYSTEM
/HORIZONTAL VACUUM/
/BELT FILTER/WASHF.R/
WASHED NON-HAZARDOUS FILTER
CAKE TO SANITARY LANDFILL DISPOSAL
ROCKS,
TRASH
WASH WATER
TO WASTEWATEH
TREATMENT SYSTEM
FIGURE 8. PROPOSED WATER WASHING PROCESS FOR PLANT NO. 1
NaCI SATURATOR INSOLUBLES
-------
sequence would be discharged as K071 waste to the presently used
hazardous waste landfill and the clarifier-thickener overflow and
filtrate recycled to the brine circuit.1 This treatment sequence is
also incorporated in Figure 8. With respect to the costs entailed by the
adoption of this proposed treatment option, the major capital cost items
include the following:
• Stirred slurry tank for saturator insolubles feed preparation
(1,000 gal);
• Corrosion resistant horizontal vacuum belt filter (200 sq ft
filtration area) for saturator insolubles washing;
• A clarifier/thickener for the combined brine clarifier/hot
process tank solids slurry (30 ft diameter x 10 ft high); and
• A corrosion-resistant rotary vacuum filter (100 sq ft filtration
area).
Together with associated instrumentation, piping, and pumps, the
total installed cost for the proposed saturator insolubles washing
process (including separate treatment of the NaCl brine treatment wastes)
is estimated to be $700,000. Annual direct operating costs (including
labor, electricity, water, and maintenance) are estimated at $50,000 per
year. Cost of disposal of the 2,500 tons per year delisted K071
saturator insolubles at $33/ton is estimated as $83,000 per year. Based
on an assumed production rate of 800 tons per year of K071 brine mud
waste (as a 75 percent solids filter cake), disposal cost in the
presently used hazardous waste landfill is estimated as $120,000 per
year. Net savings (over present disposal cost of $600,000 for the K071
NaCl brine purification muds and saturator insolubles) is thus $380,000
per year, with a payback period estimated as (700,000/380,000-50,000) or
2.1 years. This option thus appears worthy of further detailed
examination as a means of creating a delistable waste.
It is important to note that an additional benefit derived from
implementing this dewatering and filtration technique (if
successful) would be a major reduction in the amount of hazardous
waste sent offsite to the presently used hazardous waste landfill.
Instead of 1,500 tons per year of NaCl brine muds sent offsite
(along with 2,500 tons per year of treated saturator insolubles
wastes), a net production of about 800 tons per year of K071
brine-related waste as a 75 percent solids filter cake may be
achievable. This approach will require some research and
development effort to establish the appropriate operating parameters.
4-29
-------
Consideration of the location requirements for installing the
proposed option for the Nad saturator insolubles, suggests the following
as appropriate for this need:
. An area, presently vacant, believed the NaCl K107 sludge storage
pads, should be available to install the slurry tank, head tank,
and horizontal vacuum belt filter for the saturator insolubles
water washing treatment. An area adjacent to the present NaCl
brine clarifier should be suitable for installation of the new
clarifier/thickener to process the combined NaCl brine clarifier
underflow/filter backwash solids/hot process treatment solids
stream. An existing one story building on the opposite side of the
present NaCl brine clarifier, should be usable to house the
required rotary vacuum dewatering filter.
Option (2) Use of a washing process for the saturator insolubles portion
of K071 waste and a Plant No. 1 experimental process for the
brine purification muds portion of K071 waste in order to
convert these wastes into a non-hazardous form suitable for
delisting.
This option proposes the use of the water washing treatment process
described under treatment option (1) for the NaCl saturator insolubles,
and the addition of an experimental process developed by Plant No. 1 to
treat the total NaCl brine purification and stream (brine clarifier muds,
filter backwash solids, and hot process treatment muds). In a separate
treatment step, the Plant No. 1 experimental treatment scheme would be
used to process the KC1 brine purification muds (brine clarifier mud and
filter backwash solids) in an identical manner. As a result of these
processing steps, the entire K071 treated waste stream would show less
than 12 ppb Teachable mercury in the EP-tox procedure, and would be
suitable for ultimate EPA delisting and disposal in a nearby approved
sanitary landfill.
The experimental process developed by Plant No. 1 (as applied to the
NaCl brine purification waste) involves first treating the combined NaCl
brine clarifier mud/filter backwash/hot process treatment solids through
the clarification/thickening sequence described under option (1) above.
The underflow slurry from the clarifier/thickener would be pumped to a
hold tank where filter aid is added, and the resulting slurry is then fed
to a vacuum filter. The filter cake would be subjected to multiple step
washing on the vacuum filter in oruer to remove as much residual
solubilized mercury as possible. The filter cake wash steps would
include the following:
- One to two washing steps using acid pH wash water to solubilize as
much mercury from the filter cake as possible, with the filtrate
then sent to the plant wastewater treatment system for mercury
removal.
4-30
-------
- A final wash using NaSH solution (following appropriate pH
adjustment) in sufficient excess to precipitate the remaining trace
amounts of solubilized mercury present in the filter cake as
insoluble mercuric sulfide. NaSH solution filtrate would be
recycled with periodic makeup added as requirad.
The discharged filter cake would be low enough in Teachable mercury
such that the EP-tox leachate from the material is expected to indicate
less than 12 ppb mercury. Preliminary tests of this technique at Plant
No. 1 indicated a mercury level in the EP-tox leachate of 2 ppb. The
treated filter cake after suitable delisting would be disposed of in a
nearby sanitary landfill.
A simplified schematic of this proposed option (applicable to both
the NaCl and KC1 K071 brine purification waste streams) is shown in
Figure 9.
The capital equipment requirements for both the NaCl and KC1 brine
purification waste treatment schemes in option (2) are assumed to be
identical, i.e., a clarifier/thickener, a NaSH storage tank, and a
horizontal belt vacuum filter, together with all appropriate
instrumentation, piping, and pumps. A total installed cost of $500,000
is estimated for both treatment lines ($250,000 per treatment line shown
in Figure 8). Annual direct operating cost (including labor, chemicals,
electricity, water, and maintenance) for both waste streams is estimated
as $160,000 per year. Based on disposal of an estimated 1,500 tons per
year of delisted waste filter cake from the combined NaCl and KC1 K071
brine purification wastes from treatment option (2) at $33/ton at a
nearby lined sanitary landfill, as compared to the present combined waste
disposal costs for 2,500 tons per year at $150 per ton in the presently
used hazardous waste landfill, the net savings in disposal cost is
$325,000 per year and overall net savings in annual costs is $165,000.
With respect to the treatment of the NaCl saturator insolubles under
option (2), the capital and operating costs are reduced, since the
equipment designated in option (1) for brine treatment waste handling
prior to disposal as a K071 hazardous waste is now used to produce a
delistable waste from the NaCl brine-derived waste. Overall payback time
for implementation of option (2) on both the NaCl and KC1 production
lines is (500,000 + 500,000/262,000 + 165,000) or 2.3 years. Option (2)
is therefore of interest for further evaluation, in particular with
respect to additional research and development needed to establish the
optimum operating parameters for the NaSH treatment step.
4-3]
-------
I
l~
ro
DECHLORINATED
DEPLETED BRINE
FROM MERCURY CEL
ROCK SALT
OR KCI
TO
PR
1 »
TREATED, PURIFIED NaCI OR *~
LS KCI BRINE TO MFRCURY CELLS
RECYCLED BRINE
1
onmc RESABTmwcTED NaCI OR KCI BRINE ™EATMENT HOT PROCESS TREATMENT
BnlNE BRINE „ AND CLARIFICATION. FILTER -toi H)S <"•<- 1 PHINF ONLf)
SATURATORS |NaC, of KC1) - BACKWASH SOLIDS
CLARIFICATION
NaCI
SATURATOR
(KCI SATURATOR ' ' _,.. ., " «, '///{i »DICICD^ '////
INSOLUBILES ARE //// CLAHIHtH '//// _»
,,Nbl,UWBLE) rn.«,,,.UT *'//// f f f '/,////.
WATER WASHING <*S NEEDE°> "^IDS™
OCESS (FIGURE 9) ^
WATER NaSH
i T;
'//// NaSH / '///
ACIDIC ' '//V//STORAGE/' /// ^
WATER WASH NaSH SOLUTION WASH ///// T»WK "/ ^// "
1 Y////////&7//,
\
////// ////7////
LEGEND
[ | EXISTING PROCESS
[//A PROPOSED PROCESS
\//A MODIFICATIONS
NaSH
SOLUTION
RECYCLE
///^VACUUM/////
////////////// WASHED NON-HAZARDOUS FILTEH CAKE **
WASH WATER To SANITARY LANDFILL DISPOSAL
TO
WASTEWATER
TREATMENT
SYSTEM
V 1
FIGURE 9. PROPOSED SULFIDE PRECIPITATION OPTION FOR REMOVAL OF
ENTRAINED MERCURY FROM THE KO71 BRINE PURIFICATION
WASTE6 AT PLANT NO.1 (APPLICABLE TO BOTH NaOH AND
KOH PRODUCTION FACILITIES)
-------
Consideration of the location requirements for installation of the
proposed treatment option for the NaCl saturator insolubles and both the
Nad and KC1 brine treatment/wastes, suggests the following areas as
appropriate for these needs:
• An area, presently vacant, believed the NaCl K107 sludge
storage pads, should be available to install the slurry tank,
head tank, and horizontal vacuum belt filter for the saturator
insolubles water washing treatment. An area adjacent to the
present NaCl brine clarifier should be suitable for
installation of the new clarifier/thickener and NaSH storage
tank to process the combined NaCl brine clarifier
underflow/filter backwash solids/not process treatment solids
stream. An existing one story building on the opposite side
of the present NaCl brine clarifier should be usable to house
the required washing/dewatering vacuum filter.
• An area behind the KC1 brine sludge pads and near the
wastewater storage tankage, should be available for the
installation of the new clarifier/thickener, NaSH storage
tank, and the washing/dewatering vacuum filter to process the
combined KC1 brine clarifier underflow/filter backwash
solids. A one story structure would need to be built to house
the filter operations.
Option (3) Use of a washing process for the NaCl saturator insoluble
portion of K071 waste and employment of a technique used in
the Vulcan Treatment Process to chemically treat the NaCl
brine clarifier muds/Tiller backwash solids/hot process
treatment solids portion of the K071 waste as well as the
KCl-derived brine purification waste.
This option proposes the use of the water washing process described
under treatment option (1) for the NaCl saturator insolubles, and the
addition of a portion of a commercially available K071 waste treatment
process (developed by Vulcan Chemicals at their Port Edwards, Wisconsin,
chloralkali facility), in order to treat the brine purification wastes
from both the NaCl and KC1 brine production areas. The Vulcan process
involves the use of pH adjustment1 and hypochlorite treatment, on the
Sulfuric acid is used in adjustment of pH to the 2.5 to 3.0 range.
This procedure promotes growth of gypsum crystals, which ensures
minimal entrainment of solubilized mercury in the later
filtration/washing step.
4-33
-------
combined NaCl brine clarifier mud/filter backwash solids/hot process
treatment solids (or the combined KC1 brine clarifier mud/filter backwasn
solids) followed by filtration of the hypochlorite-treated material on a
rotary vacuum filter. The filter cake is washed successively with HC1
and fresh water. By means of this treatment sequence, the filter cake
solids entrained mercury content is lowered to the point where E?-tox
Teachable mercury is below 12 ppb, enabling these portions of the K071
solid waste to be deli:ted.
This treatment procedure is in routine use at the Vulcan Chemicals,
Port Edwards, Wisconsin, mercury cell chloralkali plant and is currently
being installed at the B.F- Goodrich, Paducah, Kentucky, mercury cell
chloralkali facility. The former plant's K071 waste has been fully
delisted by EPA (including both the saturator insolubles, which are
treated using a brine washing technique, and the brine
purification-related muds treated as discussed under this option). The
latter plant will be granted a conditional delisting pending acquisition
of a suitable body of data applicable to a permanent delisting of its
entire K071 waste stream by EPA. Data obtained during a recent EPA BOAT
sampling and analysis effort at the Vulcan Chemicals, Port Edwards,
Wisconsin, plant indicated that the pH adjustment, hypochlorite
treatment, and filtration/washing steps result in a K071 waste that
averaged less than 1 ppb mercury in the leachate when subjected to the
EPA toxicity characteristic leaching procedure (TCLP) test (EPA 1987c).
A simplified schematic of the proposed option (3) applicable to both
the NaCl and KC1 K071 waste streams is shown in Figure 10.
The capital equipment requirements for both NaCl and KC1 brine wastes
treatment processes would be identical, including for each stream:
• Clarifier/Thickener (30 ft diameter x ]0 ft high);
• pH adjustment tank (10,000 gallons), propeller agitator;
• Hypochlorite treatment tank (20,000 gallons), propeller
agitator; and
• Rotary vacuum filter (100 sq ft. filtration area).
Together with associated instrumentation, piping, and pumps, the
total installed cost for the Vulcan Treatment Process portion of option
(3) for both tha NaCl and KC1 wastes is estimated to be $1.4 million.
Annual direct operating costs for the two treatment lines (including
labor, chemicals (HjSO,}, HC1, calcium hypochlorite), power, water,
and maintenance) is estimated as $300,000 per year. Annual savings by
disposal of an estimated combined delisted brine purification waste of
1,000 tons per year at $33 per ton in a nearby lined sanitary landfill,
as compared to present disposal of 2,500 tons per year of K071 combined
4-34
-------
DECHLORINATED
DEPLETED BRINE
FROM MERCURY CELLS
T
K
RECYCLED BRINE
1 ' u
ROCK SALT RES'TUFl
OR KCI BRINE BRIN
* SAIURATORS (NaC| of
NaCI
SATURATOR
INSOLUDLES
(KCI SATURATOR
INSOLUBLES ARE
NEGLIGIBLE)
TO WATER WASHING
PROCESS (FIGURE 9)
H2SO«
^pH ^ADJUSTMENT// _.
^ '. TA ,|K f/ S>L
'///&?////,
ATED NaCI O3 KCI BRINE TREATMENT
E ^ AND CLARIFICATION. FILTER
KCI) BACKWASH SOLIDS
CLARIFICATION
V
SODIUM
HYPOCHLOHITE
i i
JRRY /HYPOCI LORITEV. SLURR
/ TA 'JK /
REATED. PURIFIED NaCI OR *~ LEGEND
Cl BRINE TO MERCURY CELLS ( 1
EXISTING PROCESS
"TTy PROPOSED PROCESS
/// MODIFICATIONS
HOT PROCESS TREATMENT
SOLIDS (NaCI BRINE ONLY)
1 * '//'M^™™///^/
* '/////?***"(*/////<
UNDERFLOW
SOLIDS
I '
HCI WATER
WASH WASH
i t
A//////' .r/ WASHED NON-HAZARDOUS FILTER CAKE
Y ^ />>ROTA;>V/X TO SANITARY LANDFILL DISPOSAL
'//, FILTER //.
WASH WATER TO
HCI LIQUOR TO BRINE WASTEWA-, EH TREATMENT
TREATMENT CIRCUIT, r SYSTEM
FIGURE 10
PROPOSED APPLICATION OF THE VULCAN TREATMENT PROCESS
AT PLANT NO. 1 FOR ENTRAINED MERCURY REMOVAL FROM BOTH
NaCI AND KCI BRINE PURIFICATION WASTES
-------
brine purification waste in the Emelle, Alabama, hazardous waste landfill
at $1DO per ton, is $342,000 per year. Overall net operating savings for
this portion of option (3) is therefore $42,000 per year. Combined with
the respective investment cost and overall net savings of the saturator
insoluble* treatment portion of this option, the overall payback period
is (1,400,000 + 500,000/42,000 + 262,000) or 6.3 years. This option
therefore does not look as attractive from an economic standpoint as the
previous treatment options; however, it is important to note that all cf
the treatment steps appear to have been proven and reduced to practice in
other mercury cell chloralkali facilities. Plant No. 1 may, therefore,
wish to give this approach further study.
Summary of Postulated Options for Minimization of Listed Waste K071
A total of seven source reduction options were developed by the audit
team at Plant No. 1 for listed waste K071, as well as three
detoxification treatment options for this waste. Table 10 summarizes
these options and results of the preliminary evaluation by both the audit
team and plant personnel. One source reduction option (option E) and two
treatment options (options (1) and (2)) appear worthy of detailed
evaluation by Plant No. 1 for minimization of listed waste K071 at. this
site.
WMA AT PLANT NO. 2
Facilitv Description
Plant No. 2, located in the Southeast, is a mercury cell chloralkali
plant built in 1966 and has a name plate capacity of 116,000 metric tons
per year of chlorine. Sodium hydroxide (NaOH) is produced as a
co-product and plant capacity is approximately 354 metric tons per day.
Louisiana rock salt, received by barge, is the raw material used.
The chloralkali facility employs DeNora type mercury cells equipped
with mecal anodes. All of the chlorine produced is used captively in an
adjacent chemical complex. The co-product NaOH is sold primarily to
external customers in the Southeast.
In this regard, Plant No. 1 personnel have expressed concern with
the very high IDS in the Port Edwards plant wastewater effluent. The
•Port Fdwards plant discharges approximately 20,000 mg/1 of various
soluble cations including sodium, potassium, calcium, and magnesium,
as well as about 100,000 mg/1 of chloride (the Vulcan process
characteristically generates high levels of TDS). Plant No. 1
believes that its State permitting requirements would not allow such
high levels of dissolved salts in its effluent.
4-36
-------
pre-.e't
co-jt of
(t ,'}
t'><"r> ' f:' t ei'if n/it!Dn
•- '.V.l'l ' C '1 r..1'te
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-------
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tcc.ic
-------
' ^'.- 'e ID ;C Tint ir_,fcj )
Potentla
savings
ever
presert
cost of
waste
d'sprfal
(J/r)
J-e
-1 VN z. ', " 1 r ^
" " rpr: ,^- t r *
* > ' - L,' , r. *.
k. irr^ e. coTt-t M I ' ,-prcvei p'Ciecs
tri! r,",' ! l' ,_ .: !!( '".ir.'J Ci" c lj'0-"'
PL.- : 3- c( •:';..! •= f...j'.i:.'e
Pctenti: clelj> ir ichievng EPA
of -st ir:i becijse of k'ltby procedure
2o3.CJO
c.1,,1' :• per'c" I? >t-i';J. 5cace
jvi 1' 11 •( > <=t lt-f r 'di t fc- •
•__'"L 'e: tre,i''T--it "ro:e:s ':- rot a
£-'f-c!fc treatnent sfep fcr
PJ'-f icat'0' xjci-j is cc-mer
ur'prcve" La:- 0* proven t
P'o:esc CTjIu cltU, up E?*
iJ~C: r. !ij *C' '-dt^jtC' T".oljt.lt;
Vul: -. pro.-H'- < '^"e-c --i 1 ly prcve'i
anc -i e/pectt;. tc re r"AI tcr k.171
wd^te ip^.e ovd i ^ii 11 11 y a* p'a-"it
fc- CD"! me:l "C-itre-t p'orcs- is ro
P'CD 'e-
Ecoirrics c' Vj:Cdr prccess *or
crTrr.i i fidC ' *-•.' t>; i t."ne stream
pi." r ^Cat -.0" mj-Jt appej'S unf avorab'e
at this t •^e Vu'cj^ p-ocess may a ;so
P'a-'t l.c ! tin ;tatt »•!! a'lo*
-------
Plant No. 2 presently generates approximately 5,400 tons per year of
listed waste K071, including about 1,080 tons per year of saturator
insolubles and 4,320 tons per year of brine treatment sludges. The plant
also generates about 75 tons per year of listed waste K106
(mercury-bearing wastewater treatment sludges). All of this waste is
currently sent offsite to hazardous waste landfills. The focus of this
study is to propose ways to reduce or eliminate the generation cf K071
and K106 wastes.
Process Description
Plant No. 2 produces bot'i NaOH and a chlorine co-product in a mercury
cell electrolytic production line. During electrolysis of sodium
chloride brine in the mercury cells, chlorine gas is formed at the anodes
and is collected, cooled, and dried by passing through sulfuric acid and
then compressed, liquefied, and stored fo- shipment. Simultaneously, in
the cells, a sodium-mercury amalgam is formed at the flowing mercury
cathodes. Mercury leaving the cells, which contains the amalgam, is
subsequently reacted with water in units called denuders. The reaction
converts the amalgam to mercury metal, a 50 percent NaOK solution and
hydrogen gas. The hydrogen gas is collected, partially shipped to other
production units in the chemical complex, and partially burned for fuel;
the NaOH solution is further processed before being shipped to customers,
and the mercury is returned to the cells. Figure 11 is a simplified
schematic of the NaOH/chlorine production process.
The spent brine leaving the mercury cells contains about 22 percent
sodium chloride versus 25 percent in the incoming brine. This depleted
brine typically containing 20 ppm dissolved mercury (primarily as
mercuric chloride) is further acidified with hydrochloric acid (to pH
2.5) and is then dechlorinated using vacuum flash tanks. The chlorine
released is collected and combined v»itn that generated in the mercury
cells for further processing. The dechlorinated brine is then pumped tc
the initial portion of the process, where rock salt is added to form a
resaturated brine. Rock silt is dissolved in the dechlorinated brine
from the mercury cells. Table 11 presents a typical rock salt analysis
at Plant No. 2. The depleted brine has 20 percent NaOH solution blended
with it prior to entering the dissolver. The NaOH addition adjusts pH
from -2.5 to near neutral (pH 5 to 6) in order to avoid dissolution of
silica (as silicates) in the brine. Rock salt (Nad) dissolution occurs
in a saturator (or dissolver) tank, where the flow of salt is
countercurrent to the brine flow. No agitation is used in the dissolver
tank. In this operation, the sodium chloride dissolves in the brine and
the insolubles present in the rock salt fall to the bottom of the
saturator vessel. These insolubles include clay and mineral components
of the salt feed, together with precipitated materials formed in the
4-40
-------
NaC!(ROCK SALT)
VENT
DEPLETED NaCI BRINE
SALES-*-
H2
COMPRESSION
BRINE AREA
RESATURATED
HaCI
BRINE
CELLROOM
NaOH
50%
BOILERS
CI2
GAS
CHLORINE
LIOUIFACTION
LIQUID
-»-SALES
ELECTRICITY
STORAGE
50% NaOH SOLUTION
SALES
FIGURE 11. NaOH/CHLORINE PRODUCTION PROCESS
AT PLANT NO. 2
-------
Table 11. Typical Analysis of Rock Salt Used at Plant No. 2
Component Concentration
**
Bromine
Carbon organic
Chlorate as NaC103
Chloride as NaCl
Fluorine
Iodine
Silicon
Sulfate as Na2S04
Aluminum
Barium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Potassium
Strontium
Titanium
Vanadium
Zinc
HoO insolubles
Loss 9 110'C
Phosphate
56
15
<1.0
97.7 percent
<1.0
-------
dissolution step and small amounts of entrained mercury. The dissolution
of the salt occurs in brine at a temperature of about 70'C.
Plant No. 2 has two dissolver tanks in parallel, one of which is in
use at any given time and the other on standby. The dissolver tanks used
are 45 feet in height and 28 feet in diameter, and are cone-shaped at the
base. The accumulated saturator insolubles are periodically sluiced from
the bottom of these tanks for treatment and disposal.
The resaturated brine flows by gravity to a series of four treatment
tanks where sodium carbonate solution is added. Calcium, magnesium, and
iron ions are present in the brine precipitate as calcium carbonate and
magnesium and iron hydroxides, respectively. These precipitates are
removed in the treated brine clarifiers. The clarifier overflow is then
passed through pressure leaf filters to remove residual solids, and the
filtered brine is then pumped to the mercury cells. The brine claririer
underflow, containing the precipitated solids and small amounts of
entrained mercury (a second form of K071 waste), is fed to the K071 waste
treatment system.
The clarification and filtration operations are carried out at 60 to
70°C. The clarifier used is 80 feet in diameter and 15 feet in
height. The pressure leaf filters are periodically backwashed with brine
to flush out accumulated impurities. The filter backwash stream (another
portion of the K071 waste since it also contains entrained mercury) is
sent to the K071 waste treatment system as well.
Waste Stream Description
There are two sources of listed waste K071 in Plant No. 2:
(1) mercury-contaminated saturator insolubles and (2) brine treatment
muds from the brine purification portion of the process. At Plant No. 2
these waste streams consist of the following:
(1) Brine saturator insolubles consist of gypsum, sodium sulfate,
silica, and calcium carbonate, as well as less than 1 percent
undissolved salt. Trace quantities of mercury (both soluble and
insoluble) of up to 5 prm (dry basis) are also found in this
waste. Abouv 1,080 tons per year (as a 40 percent
moistjre-60 percent solids material) of these insolubles are
generated at Plant No. 2.
(2) Brine purification muds are made up mostly of calcium carbonate,
with smaller quantities of gypsum and less than 1 percent salt
and sodium sulfate. Mercury levels present are below 30 ppm
4-43
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(dry basis). About 4,320 tons per year (as a 40 percent
moisture-60 percent solids material) of these muds are generated
at Plant No. 2, including approximately 4,120 tons per year of
brine clarifier underflow solids and 200 tons per year of filter
backwash solids.
The caturator insolubles and brine purification muds are combined at
present prior to disposal; however, the plant is undergoing significant
modifications to the K071 waste treatment system, as is described in
detail in the Waste Management Profile section below.
Table 12 presents typical analyses of the K071 brine-related wastes.
Current Waste Management Profile (in Effect Until the Fall of 1987)
Following the selection of Plant No. 2 for a WM audit, the audit team
made a pre-audit plant visit on February 24, 1987, and learned at that
time (and in more detail during a subsequent visit by plant personnel to
the audit team offices), that waste management practices for the K071
wastes were undergoing significant change. The plant had recently
decided to install its version of the Vulcan Treatment Process for
treatment of all the brine-related K071 wastes.1 This process (when
fully operational) will replace the current practice of dewatering all of
the K071 wastes (including the saturator insolubles and brine
purification wastes) on a rotary vacuum filter and shipping the K071
waste offsite to a hazardous waste landfill for disposal. The revamped
waste management scheme for Plant No. 2 K071 waste is described below.
Revamped Waste Management Operation Based on Current Delisting Effort
Officials as Plant No. 2 have recently applied to EPA for a
conditional deli^iing of their treated K071 wastes based on installing
and operating their version of the Vulcan Treatment Process. A
conditional exclusion (notice of which will appear in the Federal
Register) is expected to be obtained from EPA by the fall of 1987. At
that time, plant management will begin to assemble the needed treatment
data to gain a final delisting of the treated wastes. Corporate plans
call for disposal of the treated brine purification wastes in a nearby
sanitary landfill following receipt of the EPA conditional exclusion.
A K071 waste treatment process developed by the Vulcan Chemicals,
Port Edwards, Wisconsin, chloralkali facility and available to the
mercuty cell chloralkali industry. Operational information and
mercury levels data in this report were obtained from the Vulcan
delisting petition and its amendments.
4-44
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Table 12. Total K071 Raw Uaste Analyses at Plant No. 2 (Cry Basis)*
Sample Location and Date: Saturator insolubles 7/23/80
Analysis
Mercury
Sodium chloride
Calcium sulfate
Calcium carbonate
Sodium sulfate
Insolubles (silica)
•Jnits
ppm
percent
percent
percent
percent
percent
Analysis
3.4
<1
62
16
<1
20
Sample Location and Date: Brine clarifier s"1. ids 7/23/80
Analysis
Mercury
Sodium chloride
Calcium sulfate
Calcium carbonate
Sodium sulfate
Units
ppm
percent
percent
percent
percent
Analysis
26.5
<0.1
17.9
82.1
<0.1
Sample Location and Date: Backwashed solids from brine filters 7/29/80
Analysis
Mercury
Sodium chloride
Calcium sulfate
Calcium carbonate
Sodium sulfate
Units
ppm
percent
percent
percent
percent
Analysis
14.8
\8.2
81.8
*Source: Plant No. 2 in-house data.
4-45
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For the K071 treatment process as installed at Plant No. 2 and
expected to be fully operational by the fall of 1987, the following
treatment steps will be included:
• The saturator insolubles will be collected every few days in a
dumpster, with each batch then washed using depleted acidic
brine. The mercury compounds present in the saturator insolubles
dissolve in the brine. The brine will then be drained from the
washed saturator insolubles and recycled to the mercury cell
process. Residual levels of mercury in the treated insolubles
should be about 3 ppm based on results obtained with the process
at the Vulcan Chemicals Plant in Port Edwards, Wisconsin. The
treated saturator insolubles are expected to show less than 12 ppb
in the EP-tox leachate from this material.
• The brine purification muds {both brine clarifier underflow
solids and brine filter backwash solids) will be collected and
pumped to a pH adjustment tank for treatme.it. The pH adjustment
tank serves as a storage vessel to equalize feed rate
fluctuations, and as a reaction vessel where spent sulfuric acid
(a chlorine drying by-product) is added. The brine treatment
precipitated solids are acidified to a pH of 2 to 3 to promote the
growth and precipitation of calcium sulfate crystals. All calcium
carbonate is chemically converted to calcium sulfate and magnesium
hydroxide is converted to magnesium sulfate in the acidification
step. The calcium and magnesium sulfates' crystal structure
characteristics allow these materials to be more readily filtered,
thereby enhancing solubilized mercury removal.
• The acidified calcium sulfate slurry from the pH adjustment tank
will be further treated with sodium hypochlorite (a chlorine
liquefaction/emergency scrubber by-product) to solubilize tne
mercury in a hypochlorite treatment reactor. In this tank, the
addition of sodium hypochlorite will ensure conversion of the
mercury to a soluble mercuric form. Any residual chlorine
generated in this tank will be veatc-d back to the plant chlorine
recovery system. Following the hypo addition step, the treated
slurry will be pumped to a rotary vacuum filter that separates the
solubilized mercury from the treated solids, the former then being
discharged in the filtrate, which is sent to the wastewater
treatment system.
• A spray wash system on the rctary vacuum filter will further
reduce mercury content by ensuring solubilization of mercury and
by removing mercury-bean 17 liquids from the filter cake. The
spray wash system will consist of a low-p'H acid wash (a pH of 4
4-46
-------
achieved by the use of a dilute HC1 solution), followed by two
water washes. The filter cake solids will have thus been
successively treated with sulfuric acid and sodium hypochlorite,
and then washed under conditions comparable to an extraction
process likely to be found in any landfill under worst-case
conditions. Residual mercury level in the filter cake is expected
to be about 2.5 ppm based on data supplied by the Vulcan Chemical,
Port Edwards, Wisconsin, plant. EP-tox leachate from the filter
cake solids is expected to be <12 ppb.
Figure 12 presents a simplified schematic of the K071 treatment
process currently becoming operational at Plant No. 2.
Rationale for No Development of Waste Minimi..ation Options
As discussed above, management at Plant No. 2 had made a decision on
handling its various brine purification wastes so as to remove them from
the K071 waste category. The plant is installing the Vulcan brine sludge
treatment process and expects that it will be fully operational by the
fall of 1987.
In selecting this technology, the facility management had also
investigated a number of other options, such as a simple washing process,
purchase of prepurified salt, and potential in-situ brine treatment
processes for removal of mercury from the brine. All of these
alternative options were rejected in favor of the Vulcan process because
of either cost or technological factors.
Since the treatment technology to detoxify K071 wastes has already
been selected and installed at Plant No. 2, no additional WM options were
considered for this waste.
In addition to findings similar to most of those presented above for
Plant No. 1 on source reduction options for K071 waste, i.e.,
technically and/or economically infeasible options that caused their
rejection by Plant No. 2, economic studies by the latter on adoption
of the Vulcan K071 waste treatment process showed that a savings of
approximately $16,000 per week would be available if the K071 waste
was delisted by EPA, allowing disposal of this material in a local
sanitary landfill (Personal Communication from Plant No. 2
personnel).
4-47
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I
CO
KO71 BRINE PURIFICATION SOLIDS TREATMENT SYSTEM
VEN1
(TO PROOUC
BRINE CLARIFIER SLOWDOWN '
SULFURIC SQDIUH
ACID HYPOCHLORITE
BRINE < 4 y
Cl* WATER WASP
RECOVERY) >
ACID \
"£? tX F.L-RATE
^f ^\ TO PLANT WASTEWATER "
TT \ TREATMENT SVSTFU
n'^rKW*™ BR'NE PM r HYPOCHLOR|TE 1 J VACUUM \ , .
BACKWASH CLAHIFiEH SOLIDS fr ADJUSTMENT 1» TREATMENT
COLLECTION TANK TANK TANK
i ' '
J-l FILTER I ^ IHtAltO SOLIDS
\ / ^ TO LOCAL
\ y SANITARY LANDFILL
BACKWASH
COLLECTION
TANK
... .... K071 SATUHATOR IMSOLUHLES TREATMENT SYSTEM
DEPLETED ACID BRINE
1
BRINE SATURATOR 1 > | ( TREATE
SATURATOR SOLIDS SOLIDS
TREATMENT TANK TO LOC
(DUMPSTER) , SANITA
1 ANPFI
FIGURE 12. PLANT NO. 2 NEWLY INSTALLED KO71 W
(THIS SYSTEM IS CURRENTLY BECOMINC
ACID BRINE RECYCLE
•*• TO N«CI BRINE
SYSTEM
D
iTOR
AL
HY
LL
ASTE TREATMENT SYSTEM
i OPERATIONAL)
-------
l i Waste generated at mercury cell rhlnpaiK?1i pli.it- i» a
liatn • ? / ""tc ^'"yi'iy several thousand tons per year of inert
twn- i ipnnciPally calcium carbonate and calcium sulfate) for the
rana Atoi' and contaminated with levels of mercury in the 30 ppr.i
range. At Plant No. 1, less than 5 pounds of mercury per day are
entrained in approximately 30,000 pounds per day of inerts. The depleted
orine stream that carries the entrained mercury to the resaturaticfi and
suosequent brine purification step is also a large stream, typically
amounting to 1,000 to 2,000 gallons per minute circulation rate and
containing 5 to 10 ppm entrained mercury. In-plant removal or recovery
°{ merc"ry from these streams is clearly not economically feasible,
although this may be possible to accomplish from a technical standpoint.
Replacement of the rock salt feed material with pre-purified salt (in
order to avoid the generation of K071) also is not economically feasible.
In summary, the results of WMAs conducted at Plants No. 1 and 2 by
the EPA-sponsored audit team clearly indicated that WM options (source
reduction and/or recycle options) for minimization of K071 waste at
mercury cell chloralkali plants are extremely limited. The only
technically and economically feasible source reduction option available
to Plant No. 1 to eliminate generation of K071 waste is highly capital
intensive, i.e., an investment of approximately $20 million to replace
the mercury electrolyic cells with membrane cells (and required auxiliary
equipment). Installation of this option by Plant No. 1 would result in a
potential savings of about $600,000 annually in disposal cost of K071 and
K106 wastes in hazardous waste landfills, and a payback period of less
than 3 years. No WM options were developed at Plant No. 2 since this
facility is currently phasing in a K071 waste treatment process (the
Vulcan Treatment Process), which will result in this waste's being
delisted by EPA and allow disposal in a local sanitary landfill.
Since the audit team's investigations in the desired areas of WM for
the K071 waste were relatively nonproductive, consideration was also
given to treatment options. A commercially-established washing process
for the saturator insolubles portion of the K071 waste (treatment option
(I)), either used alone or coupled with an experimental sulfide treatment
process for the brine purification solids portion of this waste
(treatment option (2)), was considered both technically and economically
feasible in the preliminary evaluation. More pilot-scale effort will be
necessary to establish operational parameters for the sulfide treatment
process. Potential annual savings in hazardous waste disposal costs for
Plant No. 1 would range from $325,000 per year (treatment Option (1)) to
$380,000 per year (Treatment Option (2)), with payback periods of less
than 2.5 years in either case.
4-49
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uy removing mercury to low ppm levels in the treated K071 waste
(<5 ppm), TCLP (or EP-tox) leachate has been shown to be <12 ppb, a level
sufficiently low to allow delisting of this waste by EPA, thus enabling a
mercury cell chloralkali plant to dispose of the treated waste in a
sanitary landfill. Approximately 14 such plants may be able to benefit
from this approach at the present time.
4-50
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SLCTION 5
LISTED WASTE K106 KMA CASE STUDIES
The focus of this set of case studios is to propose ways to redure or
eliminate the generation of listed waste K106. This waste is defined in
40 CFR 261.32 as follows:
- K106: Wastewater treatment sludge fio.n the mercury cell process in
chlorine production.
Two facilitiec were selected as host sites for WMAs at generators of
listed waste K106. The two plants involved are mercury cell chloralkali
facilities located in the Southeast. Background information oil the
generation of listed waste K106 at mercury cell chloralkali plants can be
found in two EPA documents on this waste (IPA 1930, [PA 1980a). In this
report, the two plants studied are designated as Plant No. 1 and Plant
No. 2.
WMA AT PLANT NO, 1
Facilitv Doscript ion
(See Section 4)
Process Description
(See Section 4)
Wac.te Stream Description
A common wastewater treatment system is used to handle dll mercury-
containing wastewaters from both the NaOH and KOH production lines. Th-:
streams with the highest conct-ntrat ions of mercmy and volumes of water
are cell room washwater and mercury cell end box purge wate-. Waste
streams that contain little cr no mercury contamination, such as
rainwater collected in the brine purification area, are also treated.
The wastewater treatment consists of the addition of hydrazii.e to 60 to
5-1
-------
90 gpm of alkaline wastewater. The normal concentration of hydrazine in
the wastewater during treatment is 0.5 ppm. With exposure to air,
hydrazine spontaneously decomposes to form water and nitrogen gas. The
hydrazine reacts with dissolved mercury salts present in the wastewater
to yield mercurous hydroxide, which precipitites. Filtration of the
treated wastewater generates a sludge that is primarily composed of
carbon (used as filter precoat material), diatomaceous earth (filter
aid), water (approximately 50 percent of the cake weight), dirt from the
various sumps, and the collected mercury (as mercurous hydroxide). The
concentration of hydrazine in the treated sludge has been found to be
below detectable limits. This sludge is the listed hazardous waste K106,
with mercury levels typically in the 0.5 percent range. The treated
wastewater effluent from the system contains approximately 0.04 to
0.08 ppm mercury, and is discharged to a river under an NPDES permit with
a mercury limit of 0.082 pounds per day (0.041 kg/day) (monthly
average). An average of about 20 tons per year of K106 waste is
generated at the facility. Figure 13 is a simplified schematic of the
existing wastewater treatment system at Plant No. 1.
Cm rent Waste Management Profile
The K106 waste is recovered as a filter cake from a plate and frame
filter press in the wastewater treatment area of Plant No. 1. This waste
is containerized and sent to a hazardous waste landfill for final
disposal.
Postulated Uaste Minimization Options and Preliminary Analysis of Their
Technical and Economic feasibility
Discussions were held with Plant No. 1 personnel on the potential for
minimizing or eliminating the generation of K106 waste from plant
wastewater treatment. Results of these discussions and further
evaluations by the audit ;<-am are presented below.
Sourcp Reduction Options
As described above, K1C6 waste at Plant No. 1 derives from the
various wastewaters collocted from plant operations, as well as rainwater-
runoff from production areas involved with mercury or mercury compounds
processing. There appears to be no feasible way for the plant to
minimize or modify the process-related sources of this wastewater, as
these sources have unavoidable impurities builduo requiring a periodic
purge, e.g., wastewater from mercury cell end boxes. The other sources
of wastewater are housekeeping-related, e.g., cell room wash downs;
accidentally generated, e.g., brine spills; or incidentally generated.
e.g., rainwater runoff. Therefore, it appears chat source reduction
options are not available to reduce or eliminate this waste.
5 2
-------
STORAGE
WASTEWATERS
FROM CELLROOM,
BRINE TREATMENT, ETC.
FILTERS
CARBON
ADSORPTION
TREATED
WASTEWATER
TO OUTFALL
(NPDES)
HYDRAZINE K106 SOLIDS TO HAZARDOUS
WASTE LANDFILL
FIGURE 13. EXISTING WASTEWATER TREATMENT SYSTEM
AT PLANT NO. 1
-------
Recvcle/Reuso Options
The raw mercury-bearing wastewaters generated in Plant No. 1 appeared
to be amenable to one recycle/reuse option for mercury recovery and
recycle to the plant. The wastewater treatment sludge (K106) generated
in the wastewater treatment process seenecl to be amenable to one
recycle/reuse option for mercury recovery and recycle to the plant.
These two options are discussed below:
(a) Use of a suitable ion exchange resin for removal of mercury from
trie combined wastewater generated by Plant No. 1, followed by
recovery of the mercury in a form suitable for recycle to the'
mercury cell system. In this proposed option, a suitable ion
exchange resin (such as the IMAC TMR resin manufactured by Ak20
Zout Chemie, Rotterdam, The Netherlands) would be used to remove
mercury from the combined wastewater stream, following suitable
pretreetment of the wastewater to enable the resin to function
efficiently. This resin is claimed to be in use in over 20
mercury cell chloralkali plants worldwide for mercury removal
from wastewater (DoJong and Rekers 1974).
In chloralkali plant wastewater, mercury can occur as metallic and
ionic mercury, e.g., mercuric chloride. Tnere can be large variations in
pH, salt, and chlorine content, and significant amounts of solids
present, which could plug the ?on exchar.no rosin. In orde.~ to
accommodate these variables, the proposed ion exchange mercury recovery
process would incorporate the following protreatment steps in treating an
average of 75 gpm of wastewater with an average mercury level of 10 ppm:
• Oxidation/pH adjustment us'ng HC1 ar.d hypochlorite;
• Filtration using sand filcers:
• Two-stage dechlorination using NaHSC3 (or Na2i>C>3) followed
by activated carbon treatment; and
• Ion exchange treatment consisting of two bed; of IMAC TMR resin
in series. This process includes nercury recovery, desorption cf
bound mercury as mercuric chloride, and resin regeneration. The
long cycle time of the resin is claimed to provide ample cycle
time to regenerate the fir-:t column before the second column
breaks through.
The existing wastewater cleanup process (described above) world act
as a backup system in the event that the iin exchange process hod to be
taken offline because of sudden resin failure. Resin failure can occut
5-4
-------
as a result of sudden excursions in the free chlorine level of the
wastewater, which are unable to be controlled by the pretreatment
system. The resulting excess chlorine could destroy the activity of the
resin.
With regard to ion exchange economics, a recent Akzo quote (i?85
dollars) for a complete plant to handle a 250 gpm wastewater treatment
rate1 has been prorated for the average 7b gpni feed rate in Plant
No. 1, using the 0.6 factor. The plant design referred to treated a feed
stream with an average 10 ppm mercury content and produced an effluent
containing <5 ppb mercury. The adjusted plant cost for the 75 gpm feed
site at Plant No. 1 is $1.7 million installed. Annual direct operating
costs were estimated as $350,000 per year, including labor, chemicals,
resin replacement, power, and maintenance costs. Present disposal costs
of the mercury-bearing waste from wastewater treatment, based on a
maximum of 40 tons per year of K106 wasto (containing approximately
0.5 percent mercury) at 5150 per ton sent to the present hazardous waste
disposal site, are estimated as $6,001 per year. Maximum recovered value
of mercury at $6 per Ib (as elemental mercury) is estimated as $2,000 per
year. Overall savings using the proposed recycle option for the mercury
in the K106 waste would be about $8,000 per year. Since the direct
operating costs of $350,000 per year far exceed the savings available,
this recycling/reuse option is not considered economically viable.
(b) The use of a retorting process to treat the K106 waste for
recovery of elemental mercury and disposal of the mercury-free
residue as a delisted non-hazardous waste in a nearby approved
sanitary landfill.
Between 20 and 40 tons per year of wastewater treatment sludge (K106)
are generated at Plant No. 1 as a filter cake. This material contains
50 percent water, 49 plus percent inerts including: filter aid
(diatomaceous earth), carbon from filter precoating, and dust from the
various wastewater collection sumps, as well as approximately 0.5 percent
mercury (primarily as mercurous hydroxide from the hydrazine treatment
step). A recycle option is proposed wherein this material would be
retorted in a special retort in use in other mercury cell chloralkali
plants of Plant No. 1's parent corporation. The retort operates under
vacuum in an inert steam-injected atmosphere and is gas-fired. The
mercurous hydroxide decomposes at a temperature of 700 to 800°F,
Personal Communication, Mr. H.G.J 3jrville, Akzo Engineering,
Rotterdam, Netherlands, to plant personnel at Plant No. 2,
February 12, 1985.
5-5
-------
forming mercury vapor and water. Mercury condensation is accomplished by
cooling, using a water-injected venturi scrubber. The residual
noncondensable vent gases are passed through an activated carbon column
for final trace mercury removal. Based on a limited number of
plant-scale tests of this process, leathate from the residue from the
retorting step has been shewn to contain less than 12 ppb mercury by
EP-tox test, so that the retort residue should be able to be delisted by
EPA. A small schematic of the proposed process is shown in Figure 14.
A retort to recover approximately 0.2 ton per year of mercury
(400 Ib/year) from a maximum of 40 tons per year of K106 waste would have
to operate intermittently because of the small quantity of waste material
involved. It is proposed to accumulate the filter cake over a 90-day
period, at which time the retort would process this waste on a batch
during the day shift (8 hours per day) at the rate of about 1,000 pounds
per day. The retort system is estimated to cost $100,000 installed.
Annual direct operating cost (including fuel, power, labor, and
maintenance) for 180 d?ys per year operation, is estimated as $36,000 per
year. With maximum recovered mercury valued at $2,400 per year ($6 per
Ib) and savings in hazardous waste landfill disposal costs at $6,000 per
year (see discussion under recycle option (a)), there is a net deficit in
operating this unit (6,000 + 2,400 - 36,000) of $27,600 per year, so that
no payback period is available. This option is thus not economically
viable unless the retort was required for processing a sufficient volume
of contaminated mercury (spills) or other mercury-contaminated waste
materials. By increasing the retort throughput in this manner, mercury
recovery from K106 waste could be potentially economical.
In point of fact, Plant No. 1 has recently submitted a petition for
proposed conditional delisting of K106 waste to LPA (July 20, 1987)
using this retorting technique. Based on limited plant-scale data,
the petition claims that EP-tox levels will be below the level
specified for mercury in 40 CFR 261.24, Table 1 (0.2 ppm), that no
other EP-tox metals exceed the Table 1 limits, and that there are no
Appendix VIII hazardous constituents present above detectable
limits. The state environmental authorities have advised Plant No.
1 that the proposed retorting plant will not require an air emission
permit. The petition provides no specifics on retorting operation
conditions nor on whether the K106 waste would be the sole material
processed in the retort. This petition thus confirms the audit
team's belief in the technical viability of the mercury retorting
option, but leaves open the question of the economic viability of
this process.
5-6
-------
LEGEND
[ I EXISTING PROCESS
V7T( PROPOSED PROCESS
""" MODIFICATIONS
WASTEWATERS
FROM CELLHOOM,
BRINt TREATMENT. ETC.
FLUF
FLUE
GAS
RETORT
RESIDUE
TO SANITARY
LANDFILL
+ DISPOSAL
TREATED
WASTEWATFR
TO OUTFALL
(NPDES)
WATER TO
WATER TOT
CONDENSERS
'VASTEWATER
TREAT*EHT
RECYCLE TO
MERCURY CELLS
FIGURE 14. PROPOSED RETORTING SYSTEM AT PLANT NO. 1 FOR RECOVERY AND RECYCLE
OF MERCURY FROM WASTEWATER TREATMENT SLUDGE
-------
Treatment Options
While treatment is not a WM option, there do not appear to be any
economically viable source reduction or recycle/reuse options available
to minimize or eliminate the generation of K106 waste at Plant No. 1. A
treatment option wherein the K106 waste could be detoxified enabling it
to be delisted and thus be disposed of in a sanitary landfill, may be the
only technically and economically viable alternative to the present
disposal of K106 in a hazardous waste landfill. One such proposed
treatment option is presented below.
(c) Use of a solidification/stabilization technique to render the
K106 waste non-hazardous and permit disposal in a sanitary
landfill following suitable delisting.
In this proposed option, the K106 filter cake produced as a result of
wastewater treatment at Plant Nc. 1 would be combined with a cementatious
material such as lime kiln or cement kiln dust in order to solidify the
waste material in an insoluble matrix, which would pass the EP-tox test
for Teachable mercury, i.e., <12 ppb mercury for EPA delisting.
Preliminary laboratory work in connection with the current EPA BOAT
effort in mercury cell chloralkali plant hazardous waste treatment,
indicates that it may be possible to immobilize the mercury in the K106
waste, using this method. Preliminary results from TCLP leach tests of a
blend of one-third by weight lime kiln dust and two-thirds by weight K106
waste, showed Teachable mercury to be less than 10 ppb. The
solidified material met the 50 psi strength criterion as a low-strength
concrete. The results shown here, while preliminary in nature, appear to
offer a good possibility for a treatment alternative to disposal of K106
waste in hazardous waste landfills.
Preliminary economics were developed for a solidification/
stabilization system based on the results given above. Blending of lime
kiln dust and K106 waste would be done on a concrete pad, using a small
dedicated concrete mixer. The blending operation could be done or.ce per
week, blending approximately 0.5 ten of the waste with about 0.25 ton of
lime kiln dust. The lime kiln dust would be stored in a pre-fabncated
metal building holding about 3 months supply (3 to 5 tons) of this
Personal Communication, Mr. M. Arozarena, P£I, Inc., Cincinnati,
Ohio, April 29, 1987. The K106 waste was produced by wastewater
sulfide treatment at the Vulcan Chemical Plant, Port Edwards,
Wisconsin, chloralkali facility. This technique would have to be
applied to other K106 wastes and be given more in-depth testing to
establish its viability.
5-8
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a9S< h b1ended material would be allowed to cure on a
ri°r t0 bein9
ho i?m!al-?d 50st for a suitable prefabricated storage building to hold
ivoi ?! I" dust 1S "tinted as $2,000. A small, portable concrete
thoro • "timated to cost approximately $3,000. It is believed that
whTrh \ ?!r2Uate Space on the existing concrete sludge holding pads
™
-------
streams that contain little or no mercury contamination, such as
rainwater collected in the brine purification area, are also treated.
The wastewater treatment consists of the addition of sodium hydrosulfide
(NaSH) to 250 to 300 gpm of wastewater, which has been acidified to pH
2.5 -'3.5 using sulfuric acid. The NaSH reacts with the dissolved
mercury salts present in the wastewater to yield mercuric sulfide, which
precipitates. Two-step filtration of the treated wastewater (including
filtering the precipitated sulfide/filter aid slurry through a precoated
porostone filter followed by periodic filter back wash and final
filtration of the backwash through a plate and frame filter press)
generates a filter cake that has the following approximate composition:
Filter cake Approximate
component weight percent
Water 40
Filter Aid/Carbon 54
Brine Muds/Sump Dirt 3
Residual Sulfide <0.5
Mercury 1-3
This filter cake is the listed hazardous waste K106. Figure 15 is a
simplified schematic of the existing wastewater treatment system at Plant
No. 2.
Current Waste Management Profile
The wastewater effluent from the system (following treatment through
an activated carbon bed system) is discharged to a river under on NPDES
permit with a total daily average mercury limit of 0.032 kg/day
(0.07 Ib/day) and a total daily maximum mercury limit of 0.073 kg/day
(0.16 Ib/day).1 About three drums per week (75 tons per year of K106
filter cake) are generated at Plant No. 2. Th:s material is currently
disposed of, with the K071 waste being sent a hazardous waste landfill.
However, when the K071 waste treatment system becomes fully operational
in the fall of 1987, disposal costs for this small volume of hazardous
waste could range up to $300 per ton because of the low volume and great
distance to the disposal site. As a result. Plant No. 2 is interested in
developing alternative WM options or detoxification treatment
technologies for this waste (tho latcer allowing the waste to be
delisted).
Spent activated carbon is periodically removed from the system and
sent to a hazardous waste landfill for disposal.
5-10
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H2SO4 N»SH SOLUTION
NaOH
1
PRE
r
SULFIDE
&
CIPITATU
1
?
DN
^
FILTERS
WASTEWATERS
FROM CELLROOM,
BRINE TREATMENT. ETC.
i
— ^-
FlU
P
ADJ
AL ACTIVATED
UST ADSORPTION
TREATED
WASTEWATEH
TO OUTFAIL
fNPDFSt
K.OS SOLIDS TO LANDFILL
FIGURE 15. EXISTING WASTEWATER TREATMENT SYSTEM
AT PLANT NO. 2
-------
Postulated Waste Minimization Options and Preliminary Analysis of Their
Technical and Economic Feasibility
Discussions were held with Plant No. 2 personnel on the potential for
minimizing or eliminating the generation of K106 waste from plant
wastewater treatment. Results of these discussions and further
evaluations by the audit team are presented below.
Source Reduction Options
As described above in Section 5 under source reduction options for
K106 waste generated at Plant No. i, the identical wastewater generation
situation at Plant No. 2 precludes development of any source reduction
options to reduce or eliminate this wastp.
Recycle/Reuse Options
The raw mercury-bearing wastewaters generated in Plant No. 2 appeared
to be amenable to one recycle/reuse option for mercury recovery and
recycle to the plant. The wastewater treatment sludge (K106) generated
in the wastewater treatment process seemed to be amenable to one
recycle/reuse option for mercury recovery and recycle to the plant.
These two options are discussed below:
(d) Use of a suitable ion excnange resin for removal of mercury from
the combined wastewater generated by PUnt-No. 2, followed by
recovery of the mercury in a forn suitable for recycle to the
mercury cell system. This option would be carried out in an
identical fashion to that described under option (a) in
Section 5, above, for Plant No. 1. The only difference would be
the wastewater flow rate to the process proposed for option (a),
i.e., 250 gpm for Plant No. 2, as compared to 75 gpm for Plant
No. 1.
With regard to the economics of the proposed ion exchange system for
mercury removal and recovery at Plant No. 2, a recent Akzo Engineering
quote (1985 dollars) for a complete plant to handle a 250 gpm wastewater
treatment rate is available to permit estimating installed capital
cost.1
The plant design referred to treats a feed stream with an average
10 ppm mercury content and produces an effluent containing <5 ppb
mercury. The adjusted plant cost in 1987 dollars for a 250 gpm feed rate
Personal Communication, Mr. j.B.J. Durville, Akzo Engineering to
plant personnel at Plant No. 2, February 12, 1985.
5-12
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ooeratina ™J 1S estimated as $3.3 million installed. Annual direct
chemicals rw? !fre estiina'ed as 51 ? million per year, including labor,
costs * Prp« t J"9 fes1n rePlacer....'. power, and maintenance
wastewatPr trn.t ai*P°sal costs of the ,,iercury-bearing waste from
an averaae !j"tment' ba"d on 75 tons per year of K106 waste (containing
P?ese5tl? u?L hPerCSnt mercury) at $80C Per ton delivered to the
oer war Th h"ardous waste disposal site, are estimated as $60,000
aWf^imatJ t™C2«ered value of mercury in the K106 waste would be
minion Jlr Y V00 Per year" Since th* direct operating costs of $1.2
on on if Lf 3r far, exceed the savin9S available, this recycling/reuse
option is not considered economically viable.
(e) The use of a retorting process to treat the K106 waste for
recovery of elemental mercury and disposal of the mercury-free
residue as a delisted non-hazardous waste in a nearby approved
sanitary landfill.
Approximately 75 tons per year of wastewater treatment sludae (K106)
are generated at Plant No. 2 as a filter cake. From Plant No. 2
characterization data on this material (see above), an average of
2 percent mercury (primarily as mercuric sulfide from the NaSH treatment
step) is assumed to be present in this waste. It is proposea to retort
this material in a special reto.t developed for this curpose and in use
in a number of other mercury cell chloralkali plants.3 The retort
operates under vacuum and Is gas-fired. The mercuric sulfide is assumed
to decompose at a temperature of about I.UCO'F, forming mercury vapor
and S02 in the presence of air. Following mercury cordensation, the
residual vent gases are passed successively through a caustic scrubber to
remove S02 and an activated carbon column to remove any residual
mercury.4 Based on plant-scale tests of this retort (on a
This estimate is based on Akzo-developed direct operating costs of
approximately $O.OC6/gal of treated wastewater in 1979 dollars
increased by 50 percent for equivalent 1987 dollars.
Based on discussions with Plant No. 2 personnel, this value would be
a worst-case cost.
It is assumed that the retort design in question would be available
under license.
If monitoring of mercury and SC^ omissions is required, this could
be intermittent, using absorption trains to measure these
pollutants. It is believed, however that information from a Plant
No. 1 conditional delisting petition indicates that an air emissions
permit may not be required.
5-13
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mercurous hydroxide waste at another chloralkali plant), the residue from
the retorting step is expected to contain less than 12 ppb mercury and
should be able to be delisted by EPA. A simplified schematic of the
proposed process is shown in Figure 16.
A retort to recover approximately 1.5 tons per year of mercury
(3,000 Ib/yr) from 75 tons per year of K106 waste would have to operate
intermittently because of the small quantity of waste material involved.
It is proposed to accumulate the filter cake initially over a 60-day
period, at which time the retort would process this waste during the day
shift (8 hours per day) in batches at the rate of about 1,000 pounds per
day. The retort system is estimated to cost $100,000 installed. Annual
direct operating :^t (including fuel, power, labor, and maintenance) for
150 days per year opc?-*'on, is estimated as $45,000 per year. Recovered
mercury value (ba:ed on Vo ner Ib) is $18,000 per year. After achieving
a suitable delisting of the "etorted material from EPA, available savings
in hazardous waste landfill disposal costs would be approximately 560,000
per year.' There would thus bt an overall net savings in operating
this unit (60,000 + 18,000 - 45,000) of $33,000 per year. The payback
period in this case wou.d be (100,000/33,000) or 3.0 years, and this
option thus may be economically viable. Plant No. 2 should consider this
option as a possible alternative to disposal of K106 in the- hazardous
waste landfill.
Treatment Options
While treatment is not a UM option. Plant No. 2 n.ay want to consider
a potentially available treatment alternative to option (e) in order to
avoid the capital expenditure involved, as well as the possibility of
being required to maintain a complex air monitoring system for potential
mercury and S02 emissions from the retort used in option (e). A
treatment option wherein the K106 waste could be detoxified, enabling it
to be delisted and thus be disposed of at a sanitary landfill, may be a
technically and economically attractive alternative to the present
disposal of K106 in a hazardous waste landfill. One such proposed
treatment option is presented below.
It is assumed that the retorted filter cake residue would be
disposed of at nominal cost in } local sanitary landfill available
for use by Plant No. 2, i.e., combined with the delisted K071 waste
that will be disposed of in this landfill (as discussed in
Section 4). The 560,000 annual savings is the same amount as
discussed under Option (d).
5-14
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in
i
HjS04
WASTEWATERS
FROM CELLROOM.
BRINE TREATMENT, ETC
EXISTING PROCESS
PROPOSED PROCESS
MODIFICATIONS
NaSH SOLUTION
FINAL
pH
ADJUST
ACTIVATED
CARBON
TREATED
WASTEWATER
TO OUTFALL
(NPDES)
K106 FILTER CAKE
X MERCURY '.
NiOH
SOLUTION
VENT OASES
TO ATM
RETORT
RESIDUE TO
SANITARY
LANDFILL
DISPOSAL
/CONDENSERX
SPENT
SCRUBBER
SOLUTION
TO WASTE
DISPOSAL
*
/CIRCULATION;,
WATER TO
CONDENSERS
LIQUID MERCURY
V/ATER TO
WASTEWATER
TREATMENT
RECYCLE TO MERCURY CELLS
FIGURE 16.
PROPOSED RETORTING SYSTEM AT PLANT NO. 2 FOR RECOVERY AND RECYCLE
OF MERCURY FROM WASTEWATER TREATMENT SLUDGE
-------
(f) Use of a solidification/stabilization technique to render the
K106 waste non-hazardous and permit disposal in a sanitary
landfill following suitable delisting.
In this proposed option, the K106 filter cake produced as a result of
wastewater treatment at Plant No. 2 would be combined with a cementatious
material such as lime kiln or cement kiln dust in order to solidify the
waste material in an insoluble matrix, which would then pass the EP-tox
test for Teachable mercury, i.e., <12 ppb mercury for EPA delisting.
Preliminary laboratory work in connection with the current EPA BOAT
effort to establish mercury cell chloralkali plant hazardous waste
treatment technologies, indicates that it may be possible to immobilize
the mercury in the K106 waste, using a solidification/stabilization
method. Preliminary results from TCLP leach tests of a blend of
one-third by weight lime kiln dust and two-thirds by weight K105 waste,
showed Teachable mercury to be less that 10 ppb.1 The solidified
material met the 50 psi strength criterion as a low-strength concrete.
The results shown here, whiie preliminary in nature, appear to offer a
good possibility for a treatment alternative to disposal of K106 waste in
hazardous waste landfills.
Preliminary economics were developed for a solidification/
stabilization system based on the results given above. Blending of lime
kiln dust and K106 waste would be done on a concrete pad, using a small
dedicated concrete mixer (portable type). The blending operation could
be dene once per week, blending approximately 1 ton of the waste with
about 0.5 ton of lime kiln dust. The latter would be stored in a storage
building holding about 3 months supply (5-10 tons) of the latter material
in bags. The blended material would be allowed to cure on a concrete
storage pad for 1 to 2 months prior to being shipped offsite to the
nearby sanitary landfill available to Plant No. 2.
Personal Communication, Mr. M. Arozarena, PEI, Inc., Cincinnati,
Ohio, April 29, 1987. The K106 waste was produced by wastewater
sulfide treatment at the Vulcan Chemical Plant, Port Edwards,
Wisconsin, chloralkali facility. This technique would have to be
applied to other K106 wastes and be given more in-depth testing to
establish its viability.
This material, following submission of suitable TCLP leachate data
to EPA, would be delisted and thus be suitable for disposal in a
sanitary landfill. It is assumed that a permit would be required to
operate as a TSD facility in order to carry on this operation.
5-16
-------
Mi/fhfV" L- ed cosl for a suitable prefabricated storage building to
hold the lime kiln dust, a small portable concrete mixer, and a concrete
?« m Jnn ,]e?d1ng and curing the solidified K106 waste, is estimated
iuii * believed that there is adequate space adjacent to the
«r?. i?"generation area to perform these operations. Annual operating
«t!»a» ! «?2 abor* 11me kiln dust- fuel- and maintenance) is
eiumaiea as $10,000 per year. Savings in disposal cost for the delisted
MUO would be approximately $55,000 per year based on disposal in the
nr«n«y 5a*Udry landfi11- Overall annual savings available if the
proposed treatment option was implemented, is estimated as $45,000 per
a™!' * t pa^back Period of approximately 4 months. This option
Appears to be worthy of further evaluation, including research and
oeveiopment to establish the appropriate operating parameters for tho
soiiaitication/stabilizaticn reaction involving K106 waste and lime kiln
oust (or other suitable solidification/stabilization material).
iummarv nf Pnc».,^tpd QDtions for Minimization of K106 Waste at Plant
JO. 1 anrl Pl,nt No ? —
A total of three recycle/reuse options as well as two detoxification
treatment options were developed by the audit team for listed waste K106
« Plants No. 1 and 2. Table 13 summarizes these options and results of
tne preliminary evaluation by both the audit learn and respective plant
personnel. One WM option (recycle/reuse) involving retorting of K106
waste for mercury recovery and one treatment option (detoxification
treatment of K106 using staoilization/solidification) appear worthy of
further evaluation for minimization of this waste at both Plants No. 1
and 2.
.Summary and Discussion
The K106 waste generated at mercury cell chloralkali plants is a
low-volume waste, variable in quantity, and ranging between 10 and 100
tons per year depending on plant size. This material (wastewater
treatment sludge) typically contains approximately 50 percent water, with
the balance inerts (diatomaceous earth and carbon) with mercury
content-typically in the form of the insoluble sulfide (Plant No. 1 is an
exception in its use of hydrazine as the mercury precipitant) ranging
from 0.5 to 5 percent. The wastewater from which this sludge derives
(after the precipitation treatment step) is a re atively su-all stream,
typically in the 50 to 100 gpm range, with 5 to 10 PPm levels of mercury.
Source reduction options are not available to reduce or eliminate the
wastewater; recycle/reuse options for the low levels ojJ^rcury in Je
wastewater, i.e., ion exchange wastewater are jot economica "> feasible
for orimarv removal of mercury, ion exchange or activated carbon
tSatleS has beeused Is a polishing step following primary treatment
of was?ewater bj processes such as sulfide or hydrazine precipitation.
5-17
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Table lj. Summary o' Postulated Options for Minimization of Listed Waste K10G at Plants No. 1 and No. 2
Description
Type of
option
Disadvantages
Potential
53. 'ngs
over
present
ccst o*
waste
disposal
(d) !o" excrange treatment
cf raw wastemter for
reiio*al and recovery c~
trt'curj (applicable to
tcth PU-its (o. 1 ,a.nj
Ho. 2)
Recycle/ Process demonstrated co
-------
Table 13. (Continued)
Potential
sav -ngs
over
Opt ion
Description
Type of
opt ion
Advantages
cost of
waste
disposal
Disadvanta;es
Same as (b) 'or Plant
He. 2
Recycle/ Process has been in commercial use ir
reuse sfvera) nercury ce'l cnlo-aH.ali
plants fo' suK icie-Lased w.^stei.ater
treatment sludge. Kei.overed reta 11 ic
mercury c-Jf. be reeve led to mercery
cells. Capable ot producing residue
"o* enouyh. m irercurj to a Hoi.
ciel 1st ing by CFA. Cojld have
ftivor3ble economics (paybaCK period)
due to potentially high cost o' KlOf
disposal cr.ce it carrot be cor* ned
with n.071 waste (when the latter is
delisted at Plo-.t No. 2) for shipment
to the hazardous waste landfill.
May require extens've stack emissions
monitor inq systfn for "••.-rcurj and
SO, eTissions.
60.000
Same as (c) for Plant
Ho. ?
Treatment
bare as (c) .
Same as (c).
-------
In summary, the results of WMAs conducted at Plants No. 1 and No. 2
by the EPA-sponsored audit indicated that only one WM option is availat^e
for minimization of K106 waste at mercury cell chloralkali plants:
retorting of K106 waste sludge (in the form of a filter cake) for mercury
recovery and recycle to the process with delisting and disposal of the
retort residue in a local sanitary landfill. This option is technically
well-proven and iray be economically feasible at Plant No. 2. Plant No. 1
appears ready to adopt this option in order to succeed in ultimately
having this waste delisted by EPA, irrespective of process economics.
Adoption of this option at Plant No. 2 can potentially result in savings
(as compared to che present cost of disposal in a hazardous waste
landfill) of $60,000 annually with a payback period of about 3 years.
With only one WM option available to Plants No. 1 and 2 for K106
waste minimization, the audit team investigated the possibility of using
a treatment option to detoxify this waste. Current preliminary EPA BOAT
investigations indicate that a solidification/stabilization technique
using lime kiln dust can produce a solidified waste that, upon TCLP
extraction, shows Teachable mercury in the <12 ppm range, offering the
potential for EPA to delist the stabilized waste. A commercial process
incorporating this procedure would show a $4,500 and $55,000 annual
savings in waste disposal costs, respectively, for Plant No. 1 and Plant
No. 2 ivith payback periods in the 3-year range. Additional research and
development will be required to establish mercury Teachability results on
•i wide variety of K106 wastes, as well as the required operational
parameters for optimum stabilization results.
5-20
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SECTION 6
REFERENCES
De-ong, G.J., and Rekers, C.J.N. 1974. Thf Akzo process for the removal
of mercury from wastewater. Proceedings of the First World Mercury
Congress, Vol. 1, p. 377. Barcelona, Spain, Kay 1974.
Esayian, M., and Austin, J.H. 1984. Membrane technology for existing
cnloralkali plants, E.I. Dupont de Nemours and Co., Inc., presented at
the 27th Chlorine Plant Managers Seminar, Washington, O.C., February
Fromni, C.H., and Callahan, M.S. 1986. Waste reduction audit procedure
a methodology for identification, assessment and screening of waste
minimization options, Hazardous Materials Control Research Institute,
Conference Proceedings, pp. 427-435, Atlanta, Ga., March 1986.
Kahane, S.W. 1986. Waste minimization audits. Proceedings of the
Conference on solvent waste reduction, Santa Clara and Los Angeles,
Calif., October 1986.
League of Women Voters. 1986. Proceedings of the conference on waste
reduction - the untold story, sponsored by the Leaoue of Women Voters
of Massachusetts, Woods Hole, Mass., June 1986.
Parkinson, G. 1979. Presenting The enp"gy audit. Chem. Eng.
86:25-27, December 31, 1979.
Pojasek, R.B. 1986. Waste minimization planning, auditing and
implementation. In Hazardous and solid waste minimization.
Washington, D.C.: Government Institutes Inc.
Truitt, T.H., et al. 1983. Environmental audit handbook, basic
principles of environmental compliance auditing, 2nd ed. New York:
Executive Enterprises Publications Co.
U.S. Congress. 1986. Office of Technology Assessment. Serious
reduction of hazardous waste for pollution prevention and industrial
efficiency. OTA-ITE-313. Washington, D.C.: U.S. Government Printing
Office.
6-1
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USEPA. 1980. U.S. Environmental Protection Agency. Office of Solid
Waste, RCRA capacity background document, Wastes K071, K106,
Washington, O.C.
USEPA. 1980a. U.S. Environmental Protection Agency. Office of Research
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Multi-media assessment of the inorganic chemicals industry, Contract
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USEPA. 1986a. U.S. Environmental Protection Agency. Office of Solid
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USEPA. 1986b. U.S. Environmental Protection Agency. Waste
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USEPA. 1987. U.S. Environmental Protection Agency. Office of Research
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waste minimization audit report: waste minimization audit at
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USEPA. 1987a. U.S. Environmental Protection Agency. Office of Research
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Waste minimization audit report: Case studies of minimization of
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USEPA. 1987b. U.S. Environmental Protection Agency. Office of Research
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Waste minimization audit report: Case studies of minimization of
solvent waste from parts cleaning and from electronic capacitor
manufacturing operations. Report in publication.
USEPA. 1987c. U.S. Environmental Protection Agency. Office of Solid
Waste. Waste Treatment Branch. Onsite engineering report of treatment
technology performance and operation for Vulcan Materials Corp., Port
Edwards, Wisconsin. Draft report in publication. Washington, D.C.:
U.S. Environmental Protection Agency, May 20, 1987.
Williams, M.A. 1976. Organizing an energy conservation program. Chem.
Eng. 83:149-152, October 11, J976.
Zimmerman, L.W., and Hart, G.D. 1982. Value engineering, a practical
approach for owners, designers and contractors. New York: Van
Nostrand Reinhold Co.
6-2
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