National Center for Environmental Health: Chemical Weapons Elimination | Reports - VX Report - Attachment #4

Attachment #4

Report for Congress: Review of the U.S. Army Proposal for Off-Site Treatment and Disposal of Caustic VX Hydrolysate From the Newport Chemical Agent Disposal Facility

Assessment of the Treatability of Caustic VX Hydrolysate at the DuPont Secure Environmental Treatment Facility

By

Carmagen Engineering, Inc.
in consultation with the
Centers for Disease Control and Prevention
November 3, 2004

SUMMARY

To completely ascertain the capability and effectiveness of the DuPont Secure Environmental Treatment (SET) facility to treat caustic VX hydrolysate (CVXH), the Centers for Disease Control and Prevention (CDC) and Carmagen Engineering, Inc. (Carmagen), recognized that, in addition to reviewing the DuPont treatability test results, the Newport Chemical Agent Disposal Facility (NECDF) destruction process and the analytical methodologies for CVXH clearance also had to be assessed to ensure that the hydrolysate being shipped to the SET facility will be adequately characterized and that VX and EA 2192 levels in the CVXH will meet Army clearance specifications. Please note that in this report, the more technically accurate term CVXH generally is used in place of Newport caustic hydrolysate or NCH. These assessments were considered essential elements to ensure safe SET facility operations. Therefore, the Carmagen Team (Team) focused its review in three areas consisting of (1) process issues at NECDF, (2) analytical methods, and (3) CVXH treatment at DuPont. The review comprised several meetings with people from the Army, Chemical Materials Agency, Parsons, and DuPont at which presentations were made, followed by in-depth discussions. These meetings were followed up by written questions and requests for additional documentation. Documentation received in response to the Team’s questions and requests for additional information was substantial.

The major findings from the three areas examined by the Team are shown below. These findings are valid only for an 8% diisopropylcarbodiimide (DIC)-stabilized VX hydrolysate. The current database is insufficient to allow extrapolation to other VX loadings or stabilizers.

Process Issues (Chapter 2)

Only laboratory/bench-scale runs have been completed for the process, and scale-up to the integrated full-size facility is based on anticipated processing conditions. Recently, several safety studies were completed that recommended changes in the design and operation of the NECDF. The impact of the responses to these recommendations and possible facility changes on the final process is unknown.

Finding 2.1. The database supports the efficacy of neutralizing DIC-stabilized VX using sodium hydroxide at the 8% VX-loading rate. Scale-up of the process from laboratory/bench scale to pilot scale should be operationally feasible. However, because the NECDF will be a pilot facility, changes must be anticipated in operating mode and hydrolysate composition sent for off-site treatment.

Finding 2.2. VX loading (weight percent) and the specific stabilizer (DIC; dicyclohexyldicarbodiimide [DCC]) employed significantly impact the process, hydrolysate composition, analytical methods validation, and possibly solids formation. Scale-up of the process from 8% to 16% VX loading is of particular concern (because of the similarity of the organic-phase volumes from 16% to 33% VX-loading batches), the potentially high VX concentration in the resulting organic layer, and the analytical problems identified with 33% VX loading.

Finding 2.3. The impact is unknown of solids formation during hydrolysis on operations (potential for blockage of the in-line static mixer, control valves, and sampling system), VX analytic methods, and off-site hydrolysate treatment. The transition from 8% to 16% VX loading, as well as stabilizer change, is of concern and requires additional detailed studies.

Analytical Methods (Chapter 3)

The purpose of the review and evaluation of the analytical methods was to define the adequacy of the proposed NECDF analytical methods to meet current programmatic requirements for detecting and quantifying VX and EA 2192 in the CVXH.

Finding 3.1. The methods for analyzing VX and EA 2192 in 8% VX-loaded, DIC-stabilized CVXH are adequate to detect and quantify at the established clearance levels for VX and EA 2192 (non-detected with a U.S. Environmental Protection Agency (EPA) method detection limit (MDL) of ≤20 parts per billion [ppb] for VX and ≤1 part per million [ppm] for EA 2192).

Finding 3.2. The use of the EPA’s method detection limit (MDL) for clearance levels does not preclude analytical instrument detection of low levels of VX and EA 2192 (generally <20 ppb VX and <1 ppm EA 2192) in the CVXH. The perception that the MDL clearance criteria indicate absence of analytically detectable VX and EA 2192 could be misleading. While CDC believes that utilizing the MDL approach would not result in public health concerns, the Army needs to address potential public misperceptions regarding the detection or non-detection of VX in CVXH. A simpler reporting scheme (i.e., non-detected, detected at <20 ppb, or detected at >20 ppb) should be considered.

Finding 3.3. The overall quality assurance (QA) and quality control (QC) plan and procedures for the NECDF laboratory are well designed and documented. However, NECDF laboratory personnel must continue to implement the QA/QC plan by developing day-to-day operational QC data to demonstrate that all analytical systems are operational and under control before plant startup.

Caustic VX Hydrolysate Treatment (Chapter 4)

Once transported to the SET facility, CVXH will be further treated to adjust the pH and remove the organic by-products by a series of physicochemical and biologic processes. The DuPont treatability studies were designed and executed to obtain scale-up parameters for engineering design and regulatory compliance, rather than (except for a few specific species) to assess fate, transport, and biodegradability of environmental contaminates. The treatability studies also investigated the capability of the SET facility to treat alternating hydrolysate feeds from Aberdeen (sulfur mustard [HD]) and Newport (VX).

Finding 4.1. The SET facility effectively treats the CVXH generated from an 8% VX loading with DIC stabilizer (i.e., pH adjustment, thiolamine destruction, conversion of ethyl methylphosphonic acid to methyl phosphonic acid [MPA]), except for MPA, for which only minimal reduction is demonstrated.

Finding 4.2. The SET facility treatment performance should be unaffected when treatment of hydrolysate feeds from Aberdeen (HD) and Newport (VX) is alternated.

Finding 4.3. The DuPont treatability studies have not yet demonstrated the effective treatment of 16% VX-loaded CVXH, nor of 8% VX-loaded CVXH with DCC or a mixture of DIC and DCC stabilizers.

Table of Contents

Summary
Table of Contents

1. Introduction
    1.1. Background
    1.2. Nature of the Caustic VX Hydrolysate
    1.3. Clearance
    1.4. Analytical Methods
    1.5. Carmagen Engineering, Inc.
    1.6. Report Outline
2. Process Issues
    2.1. Introduction
    2.2. Process Description
    2.3. Process Chemistry
    2.4. Findings
3. Analytical Methods
    3.1. Introduction
    3.2. Sampling Representativeness
    3.3. Analysis of VX in Caustic VX Hydrolysate
          3.3.1. Data Evaluation/Interpretation Criteria
          3.3.2. Method Description and Documentation
    3.4. Analysis of EA 2192 in Caustic VX Hydrolysate
          3.4.1. Data Evaluation/Interpretation Criteria
          3.4.2. Method Description and Documentation
    3.5. Use of Analytical Data for Clearance
    3.6. Quality Assurance and Quality Control Procedures
    3.7. Findings
4. Caustic VX Hydrolysate Treatment
    4.1. Introduction
    4.2. Extent of Treatment
          4.2.1. pH Adjustment
          4.2.2. Hydrogen Peroxide Oxidation
          4.2.3. PACT® Biotreatment
   4.3. Environmental Persistence and Agent Loading Effects
   4.4. Findings
5. Major Findings
6. References

1. Introduction

1.1 Background

The Newport Chemical Depot, Newport, Indiana, stockpile comprises the chemical nerve agent O-ethyl S-[2- (diisopropylamino) ethyl] methyl phosphonothiolate (VX) stored in bulk quantities (1269 tons in 1690 containers). VX contains phosphorus double-bonded to an oxygen atom and single-bonded to a carbon atom. VX is stabilized with several percent of either diisopropylcarbodiimide (DIC) or dicyclohexyldicarbodiimide (DCC) to protect against decomposition. Forty-six percent of the stockpile at Newport consists of VX stabilized with DIC (potentially with small amounts of DCC stabilizer as a contaminant), 16% stabilized with DCC, and 38% stabilized with both DIC and DCC. VX is highly toxic and lethal in both liquid and vapor forms. Because munitions containing agent and energetics are not present at Newport, the process requirements for disposing of only ton containers of agent are less demanding than the processing requirements for the more complex stockpiles at most sites.

The Newport Chemical Agent Disposal Facility (NECDF) was designed and is to be operated as a pilot-plant facility because the process has been demonstrated only at a laboratory/bench scale. Production operation will begin only after pilot-scale operations have been completed, the data reviewed and assessed, and approval granted by the State of Indiana and the federal government. Because pilot-plant operations generally uncover unknown elements, the probability is high of process modifications and change— including possible changes in the analytical methods and procedures used to support plant operations and hydrolysate clearance—during this piloting period.

The NECDF was designed to destroy VX using caustic hydrolysis in a hot (194 degrees Fahrenheit [°F]) solution of sodium hydroxide. Initially the plan was to further treat the resulting hydrolysate on-site by Supercritical Water Oxidation (SCWO) and to ship the final SCWO effluent (brine) to a Treatment, Storage, and Disposal Facility (TSDF). Mechanical problems encountered in the SCWO engineering-scale test, conducted in Corpus Christi, Texas, in 2000, led to initiation of studies to directly ship the NECDF hydrolysate to an off-site treatment facility as an alternative to on-site SCWO treatment. The terrorist attacks of September 11, 2001, and continuing questions about the feasibility of implementing SCWO on-site in any reasonable timeframe supported the decision to adopt “Project Speedy Neutralization.” This involves shipment of the neutralized product (i.e., caustic hydrolysate) off-site for further treatment.

Detailed testing of the caustic hydrolysis process began with the Alternative Technologies and Approaches program in the 1990s. The “recipe” for NECDF agent destruction using sodium hydroxide was tested on a laboratory scale, and an agent loading of 33% was chosen for the program.

Confirmation of the efficiency of destruction of VX depends on the analytical methods available to monitor for residual VX and EA 2192 levels in the resultant hydrolysate. During the past ten years changes in analytical techniques and instrumentation, coupled with increased personnel experience with these analyses, have lowered the detectable concentration of VX to the low parts per billion (ppb) levels and the detectable concentration of EA 2192 to the low tenths of parts per million (ppm) levels for 8% VX loading hydrolysate. However, the complexity and variability of the 33% VX loading hydrolysate continued to complicate the VX analysis.

By October 2003, the Project Manager for Alternative Technologies and Approaches had begun to investigate the use of reduced VX loading to preserve resources and obviate the need to resolve differences in data and data interpretation for the 33% VX-loading hydrolysate. The program plans to begin operations at 8% VX loading of DIC-stabilized agent and then, through a carefully monitored ramping-up process, move to 16% VX-loading, DIC-stabilized agent.

1.2 Nature of the Caustic VX Hydrolysate

The hydrolysate that will result from the caustic hydrolysis of VX at the NECDF comprises an aqueous phase and an organic phase. The organic phase exists both as an emulsion with droplets distributed throughout the continuous aqueous phase and as a visible organic layer that floats on top of the continuous aqueous phase. The extent to which a separate organic phase floats on the lower aqueous layer depends on the VX loading. As the VX loading increases, the quantity of organic phase available to form an organic layer (above that which forms a stable [or metastable] emulsion) increases.

At 33% agent loading (weight percent), the organic layer was significant (3%–5% by volume). The VX concentration in this organic layer was approximately 20 times the concentration in the bulk hydrolysate (>20 ppb), although disagreement exists within the program about the validity of the measurements (Wojciechowski, 2003). For 16% agent loading, the organic layer was 2–3 volume percent; for 8% agent loading, the separate “organic layer” was only a sheen at the surface of the hydrolysate. The “organic layer” has not been analyzed at 8% and 16% agent loadings; only mixed (homogenized) samples were analyzed. Obtaining samples of this organic layer for 8% agent loading poses significant technical difficulties. Centrifugation of a 550-milliliter (mL) sample of 8% CVXH showed that the maximum organic layer that could be “separated” was 0.45%–0.5%. These differences demonstrate the significant impact of agent loading on hydrolysate characteristics.

1.3 Clearance

Since its inception, a key tenet of the Army Chemical Demilitarization program has been safety of the workers and public. Department of the Army (DA) Pamphlet (PAM) 38561, entitled “Toxic Chemical Agent Safety Standards,” defines the approach for verifying the thoroughness of the neutralization process as using laboratory analyses to ensure that the chemical agent is ≤20 ppb. This concentration is measurable and is a quantifiable upper limit concentration in drinking water (20 ppb criterion is for soldiers). However, the procedure and methodology to verify the 20 ppb criterion in CVXH have been a challenge (see Section 3). As stated in the Low Level VX (LLVX) panel report (Science Applications International Corporation [SAIC], 2003):

The panel is not aware of any document that clearly states the exact criteria for offsite shipment of VX hydrolysate from NECDF or any document that codifies the Army’s commitment to the public for offsite shipment.

The report, Generation and Clearance of Hydrolysate for Treatability Studies in Support of Newport Operations, states:

To clear the hydrolysate, the analytical results must be non-detect for VX with a method detection limit (MDL) of less than or equal to 20 parts per billion (ppb). Non-detect is defined as the absence of a signal in the VX retention time window for ion 128, or a signal with a signal-to-noise (S/N) ratio of less than or equal to 3, or a concentration below the calculated MDL.

These criteria are incompatible in that an analytical response for VX could be classified as “analytically detected” by implementation of the “analyte retention time/signal-to-noise (S/N) ratio equal to or greater than 3” detection criteria, but reported as “nondetect” by the “less than the established MDL” criterion (see Section 3).

1.4 Analytical Methods

Significant resources were expended for almost a decade to develop an analytical method that could reliably and accurately measure VX concentration in CVXH at lower and lower levels for a 33% VX agent loading without success. The newer analytical methods demonstrated the presence of detectable levels of VX in 33% DIC-stabilized CVXH and the inability to demonstrate an MDL of ≤20 ppb. This unexpected result led to an aggressive investigation of the causes and possible solutions for addressing the issue to bring the plant into operation.

An independent assessment panel was convened in October 2003 to evaluate the significance of the observation of “persistent” LLVX in caustic hydrolysate at the 33% agent loading level and to determine whether data were sufficient to confirm whether VX forms in CVXH (SAIC, 2003). Two conclusions of the panel were:

There are significant uncertainties in the Solid Phase Extraction (SPE)/gas chromatography-ion trap mass spectrometry (GC-ITMS) method that make it difficult or impossible to quantify LLVX.

It is not possible to determine the origin of the “persistent” LLVX in VX hydrolysate from the currently available data. The panel could not rule out formation of VX in VX hydrolysate or the hypothesis that has been advanced that there is a quasi steady state concentration of VX in VX hydrolysate due to a competition between agent destruction and formation. The current data from the analytical method did not enable the panel to determine if detectable VX was originating from VX hydrolysate (that is, either residual untreated VX or formation within the VX hydrolysate matrix) or was formed during the analytical procedure.

Consequently, efforts during the past year have been devoted to evaluating the effect of reduced VX loading on

VX caustic hydrolysis destruction,
VX reformation during long-term storage, and
VX formation after a reduction in pH accompanied by a concomitant formation of an organic layer.

This evaluation has paralleled the development, evaluation, and validation of analytical methodologies for measuring VX and EA 2192 in the 8% DIC-stabilized CVXH. At the time of this writing, methods for analyzing VX and EA 2192 in 8% DIC-stabilized CVXH and VX in 16% DIC-stabilized CVXH had been established in the NECDF laboratory, and the performance of these methods had been validated through various precision and accuracy studies. Implementation and validation of methods for ethyl methylphosphonic acid (EMPA), methyl phosphonic acid (MPA), and thiolamine in 8% DIC-stabilized hydrolysate are expected to be completed shortly. Similar work on other methods required for 16% DIC-stabilized hydrolysate and 8% DCC-stabilized hydrolysate were scheduled for completion later in 2004. Validated methods for anticipated processing conditions are essential to ensure that hydrolysate shipped off-site to a TSDF meets Army criteria.

1.5 Carmagen Engineering, Inc.

The Centers for Disease Control and Prevention (CDC) engaged Carmagen Engineering, Inc. (Carmagen) to assemble a group of knowledgeable experts (Team) to help evaluate the DuPont Technical Assessment on U.S. Army Newport (Indiana) Project (March 2004). The Team consisted of a former chairman of the National Research Council Stockpile Committee, a retired assistant director for the CDC/NCEH Division of Laboratory Sciences, a retired Program Manager for Chemical Demilitarization, a professor at Stevens Institute of Technology, a retired regional laboratory director for EPA, and a former environmental health and safety manager/process design manager for ARCO Chemical. Specifically, Carmagen was asked to evaluate the “Treatability of Newport (Indiana) Caustic Hydrolysate” portion of the DuPont report.

To ascertain the capability and effectiveness of the DuPont Secure Environmental Treatment (SET) facility at Chambers Works (Deepwater, New Jersey) to treat CVXH, the Team recognized that an assessment of the NECDF destruction process and an examination of the analytical methodologies to be used for CVXH clearance were required to ensure that the hydrolysate being shipped to the SET facility will be adequately characterized and that VX and EA 2192 levels in the CVXH will meet Army clearance specifications. These assessments were considered essential elements to ensure safe SET facility operations. Therefore the Carmagen Team focused on three areas:

Process Issues (NECDF),
Analytical Methods, and
Caustic VX Hydrolysate Treatment (DuPont).

The review comprised several meetings with people from the Army, Chemical Materials Agency, Parsons, and DuPont at which presentations were made and discussed in depth. These meetings were followed up by written questions and requests for additional documentation. Documentation received in response to the Team’s questions and requests for additional information was substantial.

1.6 Report Outline

The report contains five chapters.

Introduction—Discusses the historical evolution of the NECDF project and the charge to and approach taken by the Carmagen Team.
Process Issues—Discusses the impact of VX loading on the process, i.e., nature and extent of the two-phase CVXH, VX partitioning to the organic layer, clearance quality assurance (QA) and quality control (QC), scale-up, and storage.
Analytical Methods—Reviews and evaluates the use and data quality objectives of VX and EA 2192 measurements, sampling procedures, validation of methods, and QC of the analytical processes.
Caustic VX Hydrolysate Treatment—Describes pH adjustment, oxidative pretreatment, PACT® biotreatment, and VX and EA 2192 destruction.
Major Findings—Presents major findings.

2. Process Issues

2.1 Introduction

Although the primary purpose of this report is to examine issues associated with the treatability of the hydrolysate produced by the Newport facility, as noted in the Introduction, a discussion of processing issues is important. The composition of hydrolysate sent for treatment depends on the nature of the VX being hydrolyzed (i.e., agent loading, stabilizer), neutralization process, process operating conditions, process effectiveness, and consistent process operation. Confirmation of the composition of the hydrolysate (efficacy of treatment) is related to the accuracy of the analytical methodologies (see Chapter 3) and whether the sample(s) used for the analysis represent the batch being processed. The satisfactory treatment of each batch is determined on the basis of analysis of the hydrolysate samples.

Only laboratory/bench-scale runs have been completed for the process, and scale-up to the integrated full-size facility is based on the anticipated processing conditions. At startup, NECDF intends to operate the reactor at a VX loading of 8%, rather than the 33% originally planned. This has process and operational consequences that are discussed later in this chapter. The Army proposes that VX loading will be increased to 16% as experience is gained with the process and equipment, and when analytical methodologies and successful off-site treatment capability demonstrated at the higher loading are validated. The change from the proposed 33% VX loading to 8% VX loading will increase substantially the total quantity of hydrolysate to be treated and the length of time the Newport facility will operate.

2.2 Process Description

The process for VX neutralization at Newport uses batch processing (Figure 2-1). Each batch consists of the following sequential steps:

The reactor is charged with caustic.
The reactor is heated to approximately 194ºF.
The reactor circulation loop is activated, and the agitator in the reactor is started.
Agent is added to the reactor using a feed line in the recirculation piping. The amount of agent added is determined by the VX loading target for a given batch. Two phases are present in the reaction mixture—an aqueous phase and an organic phase. The relative volumes of the two phases are determined by the VX loading.
VX and caustic are mixed by the agitator in the reactor and by the static mixer in the recirculation piping. The static mixer is designed to achieve an organic droplet size of approximately 10–30 microns (µm).
After the reaction has been circulated at temperature (194ºF) for a period of time sufficient to complete the hydrolysis reaction, the mixture is cooled and a sample taken from the recirculation line. If the sample meets the criteria for VX and EA 2192 destruction, the resulting mixture (the hydrolysate) is pumped from the reactor to storage. If the VX and EA 2192 destruction criteria are not met, then the mixture is reheated, and processing continues. This is repeated until the batch is successfully processed.
After the batch is processed, it will be transferred to intermediate storage, and then shipped off-site for final treatment.

Diagram illustrating the components of a Hydrolysate reactor

Figure 2-1. Hydrolysate reactor

Texas A&M performed a safety study of the Newport facility using fault-tree techniques. One scenario examined was “Offsite Transfer of Hydrolysate Containing Excess VX Concentration.” The Executive Summary of this report stated:

Fault tree analysis techniques were applied to the VX project speedy neutralization (PSN) process and related process support systems in order to estimate the frequency that the cited hazard scenario can be expected to occur. The study results indicate that the best estimate for an annual frequency of this undesired event is 5 x 10^-5.

The annual frequency is estimated at 1 in 20,000 chance for CVXH being outside of specification for VX (>20 ppb). The existing design does not detect contamination of acceptable hydrolysate after the batch sampling procedures have been completed. The amount of potential contamination is minor and not thought to present a public health risk. This issue could be corrected by good engineering practices such as physical isolation using piping blinds, spool pieces or a double block and bleed valve configuration or by development of a sampling method at the storage tank. CDC has alerted Army representatives regarding this design issue as part of the normal oversight activity. Any potential design changes to the facility and schedule impacts need to be balanced by the national security risk associated with extended storage of the VX.

At the time of this report, the recommendations in Safety Study Reports by Texas A&M and other safety studies relating to the design and operation of the Newport facility were still being evaluated for implementation.

2.3 Process Chemistry

The process chemistry involved with VX neutralization is complex when an extremely high destruction of VX is required. At the time this report was written, investigations into the process chemistry are still under way, and not all of the details of the main and side reactions involved (e.g. solids formation) were fully understood. The major variables that affect the chemistry include the agent loading (i.e., the relative amount of agent per unit volume of caustic in the reactor at the start of the batch) and the type of stabilizer present in the agent being processed. (The stabilizers used to minimize the decomposition of the VX during storage were DIC or DCC or DIC + DCC).

The main reaction by which VX is neutralized by caustic is well understood and is pseudo-first order with respect to VX concentration. However, the presence of two phases (organic and aqueous), the presence of VX in the organic phase, the creation of EA 2192, and the presence of stabilizers complicate the physical and chemical process. If all other system parameters and the composition of initial caustic solution remain constant, then the size, composition, and partitioning of the reaction products between the aqueous and organic layers depend on the VX loading. Mass transfer limitations become more pronounced as the droplet size increases and the organic layer is formed. This will affect the rate, as well as the pathways of the reactions, and may produce different final products. In addition, some of the ton containers are now known to contain gelled/solid material. How much of this material will be removed with the VX and how much will remain in the ton container is uncertain. The effect of any gelled/solid material on the chemistry or operation of the neutralization reactor mixing process and sampling system also is unknown.

The purpose of the agitator and the static mixer are to mix the phases and to transform the organic phase into tiny droplets. The smaller the droplet size, the faster the diffusion processes in leaching and neutralizing the VX in the organic droplets. Therefore, VX is rapidly destroyed at the start of the batch operation; then a slower, diffusion-limited process follows as the VX in the organic phase droplets is neutralized. Moreover, the size and chemical compositions of the dispersed droplets and the organic layer will differ for the various VX loadings and stabilizer types.
In a response to questions from CDC, the Army and its contractor (Parsons) summarized these issues:

Because of the highly reactive nature of hot caustic, less than 0.1% of the VX added to the reactor during the FILL period accumulates in the reactor with virtually all of this residual VX removed during the first minute of REACT. Additional REACT time is needed to destroy residual VX that partitions into the organic phase during FILL, and to ensure that EA2192 is non-detect. ………. It is expected that the NECDF’s full-scale pilot reactor will provide the necessary mixing and droplet size to produce non-detectable levels of both VX and EA2192. This conclusion is based on laboratory-scale results and full-scale pilot plant calculation results provided herein. The actual reaction time required to obtain non-detectable levels of both VX and EA2192 will be determined during Controlled Start-up testing of the full-scale NECDF pilot plant. If the reaction time required to obtain non-detectable levels of both VX and EA2192 determined during Controlled Start-up differs from that which was predicted during laboratory-scale testing, the types and configuration of the elements within the static mixer and the volumetric flow rate through the recirculation line can be changed, as needed.

This response accurately describes the process, neglecting the effect of any gelled/solid materials in the feed to the reactor or generated within the reactor.

As previously noted, the reaction originally was designed to have used a 33% agent loading in each batch. However, studies demonstrated that, at 33% agent loading, a significant organic phase (3%–5% by volume) formed during the reaction, and this organic layer separated from the aqueous phase during storage and floated on top. Remaining (un-neutralized) VX partitioned into this organic phase, and the VX concentration in this organic phase was approximately 20 times the VX concentration in the bulk hydrolysate (nominally <20 ppb). Therefore, operation with 33% agent loading could have resulted in a “significant” volume of organic phase with a “high” VX concentration in storage tanks and during transportation. This was considered unacceptable, and modifications to the process were proposed and implemented.

Additional investigation showed that operation at 16% agent loading reduced the organic layer to approximately 2–3 volume percent. At 8% agent loading, the organic layer was only a sheen on the surface of the hydrolysate (approximately 0.5% by volume determined by centrifuging the sample). The VX concentrations in the organic phase for 8% and 16% agent loadings had not been determined at the time this report was written.

Significant changes in organic liquid loading occur between 8% VX loading and 16% VX loading (approximately a 1:5 volume ratio at a minimum) and between the 16% and 33% VX loading (approximately 1:1.5 ratio). The physical and/or chemical processes involved and the reason(s) for such a significant increase in organic loading between 8% and 16% VX loading have been the subject of some investigation, but no conclusion has been reached.

Laboratory studies have demonstrated that the reaction times required to complete neutralization vary with agent loading and stabilizer. With DIC-stabilized agent (approximately 46% of the Newport stockpile), the reaction times are 2.5–4 hours for 8% loading and 4–6 hours for 16% loading. With DCC-stabilized agent, the reaction time is 10–14 hours for 8% loading. The reason(s) for the apparent additional processing time required by DCC-stabilized agent is (are) not fully understood. The amount of stabilizer in each ton container also can vary significantly. Therefore, what is valid for 8% VX loading stabilized with DIC may not be valid for 16% VX loading case and other stabilizers. The data do not warrant generalizations that apply to all VX loadings and stabilizers.

In addition, laboratory studies have determined that solids are generated during the neutralization process. These solids have been variously described as a sticky gel and as a more coherent material. The amount of solids, their composition, and the amount of VX, (if any) these solids contain have not been determined.

The presence of solids in the hydrolysate within the reactor may be problematic in the full-scale unit and impact plant operations. Concern has been expressed that the solids may precipitate onto the surfaces of the agitator in the reactor and result in an imbalance that could cause mechanical failure of this item. A more likely source of concern may be the potential blockage of the in-line static mixer or deterioration of the performance of control valves, particularly the three-port valve that controls the introduction of chemical agent to the reactor and the transfer of the hydrolysate to the storage tanks. The in-line mixer is constructed deliberately with small flow paths (10–30 µm) to break up the organic phase into small droplets. Any solids formation could result in blockage, with the potential for reduced production rates and the need to remove the in-line mixer for cleaning. Solids also can also be deposited on the surfaces of the internal parts of the three-port valve, impacting valve closure and enabling leakage of agent, thereby contaminating previously sampled and acceptable hydrolysate batches as they are transferred from the reactor to the storage tanks. Another possibility is that modification of the process equipment to incorporate an upstream filter may be required. Furthermore, the solids may negatively impact the sampling system and the analytic measurements and treatment of the hydrolysate.

Appendix K of the documentation, provided in response to CDC Question 1, discusses solids formation. The “Conclusions” section of this document states

Formation of solids in 8 weight % hydrolysate have (SIC) the potential to impact process throughput due to reactor hardware plugging in the pumps or static mixer. Preventative maintenance needs to be scheduled as experience determines.
Difficulties have been encountered clearing the hydrolysate with gelatinous material. When hydrolysate fails to clear, more processing is required. Detailed analysis of the gelatinous material may lead to procedures that could expedite clearance.
Further testing is underway to characterize the observed solids and identify whether stabilizer type (DCC vs. DIC) or VX loading causes changes in solid volume or content.
At [the Chemical Agent Munitions Disposal System (CAMDS)], twenty five batches of DCC hydrolysate and one batch containing DIC hydrolysate were processed without process failure due to these solids. (Note—Whether a static mixer with very small passages [such as at Newport] was installed at CAMDS) is not known)

In the subsystem hazard analysis of the process, the following finding (Failure Mode and Effects Analysis [FMEA] Item 01-04-134) was noted:

Over-or Under-Reaction Creates Gelatinous Matrix in Neutralization Reactor Containing VX

Several mis-operations and reaction inconsistencies can result in the creation of a gelatinous matrix in the neutralization reactor (1- and 2-L401). It might not be possible to completely prevent this occurrence. A study is being performed to identify ways to dissolve or solubilize
any gelatinous matrix that might form. Additional information or data from the study could determine methods to prevent the polymer formation and ways to mitigate such a formation if it occurs. This evaluation addresses FMEA Item 01-04-134.

Whether this finding in the safety studies documenting issues associated with solid/gel formation in the reaction system has been addressed at the time this report was completed is not known.

Except for solids formation and its possible effects, the scale-up of the reactor from laboratory to full-scale operation should succeed. Adequate heating and cooling have been provided for the reactor system, the equipment is simple in design and the batch will be run until the analytic methods demonstrate that VX and EA 2192 have been adequately destroyed. However, the effect of gelled/solid material in the ton containers passed into the reactor does not appear to have been examined in detail. Therefore, no conclusion can be reached about the effects of such material on the neutralization reaction, the destruction efficiency, and the operation of the reaction system.

2.4 Findings

Scale-up of the process for 8% VX loading from laboratory-scale data should be operationally feasible. The database supports the efficacy of neutralizing 8% VX (stabilized with DIC) using sodium hydroxide. However, the Newport facility will be a pilot operation when it starts operation, and changes must be anticipated in operating mode and hydrolysate composition sent for off-site treatment.
VX loading and the specific stabilizer employed significantly impacts the process, hydrolysate composition, analytical methodology, and possibly solids formation. Scale-up of the process from 8% to 16% VX loading is of particular concern (because of the similarity of the organic-phase volumes between 16% and 33% VX loading batches) and the analytical problems identified with 33% VX loading.
The effects of solids formed during the hydrolysis reaction in the process on the hydrolysate and on the efficacy of treatment at a TSDF are unknown. The solids may contain VX. The impact of solids formation on the operation of the reaction system and, in particular, the potential for blockage of the in-line static mixer and other components (including the sampling system) is unknown. In addition, the presence of solids may impact the VX analytics, as well as the off-site hydrolysate treatment process.
At the time this report was written, all the findings from safety studies had not been fully addressed. In particular, findings relating to possible solids formation in the reactor and the required process modifications to provide additional assurance that no off-specification CVXH is shipped from the Newport facility may affect the CVXH composition shipped off-site.

3. Analytical Methods

3.1 Introduction

The purpose of this review and evaluation is to define the adequacy of the proposed methods for the analysis of VX and EA 2192 in the CVXH to meet the programmatic requirements of the NECDF. The scope of this review is limited to laboratory analyses of hydrolysate from the neutralization of DIC-stabilized VX at the 8% VX-loading level. Adequate analytical data were not available to evaluate analyses of hydrolysate related to other VX-loading levels or stabilizers.

3.2 Sampling Representativeness

We recognize that the validity of the clearance process depends on the sample taken and delivered to the laboratory for analysis; the sample must truly represent the total hydrolysate process batch. To evaluate the sample procurement process, all available documents describing the design and operation of the equipment and the sampling procedures were reviewed. We also had detailed discussions with NECDF personnel.

NECDF personnel believe the sampling will be highly representative on the basis of the mixing capability of the reactor, the design and operation of the sampling equipment, and the detailed protocols that have been established. On the basis of our understanding of reviewed information, we agree—as long as solids formation does not block the sampling points. The planned sampling program should provide representative samples for CVXH batches to the laboratory for analyses.

QA/QC procedures are in place to ensure and document adequate training of personnel, performance of sampling equipment, availability and quality of supplies, proper and complete recordkeeping, establishment and maintenance of chain of custody, and the safety of plant and laboratory personnel.

Maintaining representativeness of the analytical sample during transfer of the 5-mL analytical portion from the plant batch sample will be challenging because of the potential for separation of an organic layer. The laboratory method for VX analysis in CVXH calls for the analyst to “verify hydrolysate is as homogeneous as possible” during the subsampling process. This process can be highly subject to analyst technique error and will require careful QC.

3.3 Analysis of VX in Caustic VX Hydrolysate

3.3.1 Data Evaluation/Interpretation Criteria

Instrument or qualitative detection as defined in Laboratory Field Instruction (LAFI)-A-30-053:

Consider VX present in the sample if the following criteria are met:

Retention time of analyte peak within +/- 0.1 minute of average standard VX retention time.
The m/z 128 ion, the m/z 139 ion, and the m/z 167 ion maximize within 0.05 minute of each other.
The m/z 139 and 167 ions may not be present at concentrations <1 microgram per milliliter (µg/mL) in the sample.
The m/z 128 ion response must be at least three times the background noise level, i.e., S/N ratio 3 or greater.

Quantitative criterion as defined by the Army is as follows:

MDL, calculated according to U.S. Environmental Protection Agency (EPA) procedure published in the Code of Federal Regulations (40 CFR, Part 136, Appendix B) <20 ppb.

3.3.2 Method Description and Documentation

LAFI-A-30-053 provides a comprehensive, step-by-step description of the method for analyzing VX in CVXH. The method is based on multiple hexane extractions of the hydrolysate, followed with solid-phase extraction techniques for initial fractionation of the extract, then final separation and detection of the VX using gas chromatography (GC) coupled with ion-trap (IT) mass-spectrometry/mass-spectrometry (MS/MS) techniques. The use of high-resolution capillary GC coupled with the dual-phased MS/MS IT techniques gives this method extremely high selectivity and sensitivity for VX in the hydrolysate. Stated in layman’s terms, the method can detect and quantify VX in the highly complex CVXH mixture at <20 ppb with a high level of confidence against both false positives and false negatives.

The laboratory QC procedures defined in LAFI-A-30-053 and in Section 11.2 of the NECDF Laboratory Quality Control Plan, Revision 2, are consistent with procedures and requirements published in EPA SW-846. Implementation of these procedures should provide the QC data needed to define the overall validity of the analytical results.

Evaluation of MDL data for 8%VX-loaded, DIC-stabilized hydrolysate shows that, with this type of hydrolysate, the NECDF laboratory can consistently generate MDL values below the 20-ppb criterion. In a study to characterize batch-to-batch variation, the NECDF laboratory generated three MDL values for each of two batches of hydrolysate. The six MDL values ranged from 6 to 17 ppb, with a mean of 11 ppb, with no appreciable differences between the two hydrolysates.

In summary, the current method for analyzing VX in CVXH is adequate to detect and quantify VX well below the established clearance level of 20 ppb. The GC/IT/MS/MS technique provide a method with extremely high analyte selectivity and sensitivity. The method consistently shows an instrument detection limit below the 5–10 ppb range.

3.4 Analysis of EA 2192 in Caustic VX Hydrolysate

3.4.1 Data Evaluation/Interpretation Criteria

Instrument or qualitative detection as defined in LAFI-A-30-030:

Consider EA 2192 present in the sample if the following criteria are met:

Retention time of analyte peak is within +/- 1.0 minute of the average retention time of the standard EA 2192 during instrument calibration.
The m/z 162 ion is present with a 128/162 ion ratio of 0.3.
At EA 2192 concentrations <1 mg/mL the 128/162 ion ratio may not equal 0.3, but m/z 162 ion must be present.
The m/z 128 ion response must have a minimum S/N ratio of 3.

Quantitative criterion as defined by the Army:

MDL, calculated according to EPA procedure published in 40 CRF, Part 136, Appendix B, <1 ppm.

3.4.2 Method Description and Documentation

LAFI-A-30-030 provides a comprehensive, step-by-step description of the method for analyzing EA 2192 in CVXH. The method consists of a simple 1:25 dilution of the CVXH sample, followed by analyte separation using liquid chromatography (LC) techniques, with final detection and quantification using dual-phase IT/MS/MS. The use of LC/IT/MS/MS techniques results in a highly sensitive, extremely selective analysis of EA 2192 in the CVXH.

Laboratory QA/QC procedures defined in LAFI-A-30-030 and the NECDF Laboratory Quality Control Plan are consistent with those published in EPA SW-846. Analytical data characterizing the performance of this method are limited. MDL data show values of 0.23 ppm and 0.09 ppm; both well below the clearance level of 1 ppm. Precision and accuracy data show overall very good precision of the method with analyte recoveries ranging from 82% to 95%.

In summary, the current method for analyzing EA 2192 in CVXH is adequate to detect and quantify EA 2192 in laboratory-generated hydrolysate well below the established clearance level of 1 ppm. Data also indicate that the qualitative (analytical presence) instrument detection limit of the method is consistently <0.1 ppm.

3.5 Use of Analytical Data for Clearance

The Army has stated its intended use of VX and EA 2192 analytical data in the clearance of CVXH for off-site shipment, as follows:

Since its inception, a key tenet of the Army Chemical Militarization program has been the safety of the workers and the public. Department of the Army (DA) Pamphlet (PAM) 385-61, entitled “Toxic Chemical Agent Safety Standards,” defines the approach for verifying the thoroughness of the neutralization process as using laboratory analysis to assure that the chemical agent is at a level less than or equal to 20 ppb. This level has been deemed protective of soldiers and Department of Defense personnel. The Project Manager for Alternative Technologies and Approaches (PMATA) elected to use the standard EPA method detection limit (MDL) as the means for determining whether the detection limit specified in the DA PAM has been met. Thus, the requirement for successful neutralization of VX is that the hydrolysate must be non-detect for VX with an MDL of 20 ppb or less.

The Army also has stated that EA 2192 must be “non-detect with an MDL of 1 ppm or less.”

As discussed in Sections 3.3 and 3.4, we believe that NECDF methods LAFI-A-30-053 for VX in CVXH and LAFI-A-30-030 for EA 2192 in CVXH can provide valid qualitative and quantitative data for detecting and quantifying VX and EA 2192, respectively, in the concentration ranges needed for programmatic clearance of the hydrolysate material for off-site shipment. NECDF’s intended practice for measuring and reporting “non-detects” is potentially misleading. Specifically, we are concerned with the Army’s plan to classify and report analytical results above the instrument detection level, but below the established MDL, as “non-detects.” While CDC believes that utilizing the MDL approach would not result in public health concerns, the Army needs to address potential public misperceptions regarding the detection or non-detection of VX in CVXH. A simpler reporting scheme (i.e., non-detected, detected at <20 ppb, or detected at >20 ppb) should be considered.

The Army’s clearance criteria of “non-detect with an MDL less than an established concentration level” combines two related, but different, analytical chemistry concepts. First, “instrument or analytical detection” is a qualitative-based “yes or no” criterion. Second, MDL is a statistically calculated, quantitative criterion.

The first criterion, “detection,” addresses two questions: (a) Was an instrument response observed at the expected retention time of the analyte? and (b) If so, was the level of that response greater than three times the background noise (S/N ratio >3)? If the answers to both of these questions are “yes,” then according to instructions in LAFI-A-30-053 and LAFI-A-30-030, the analyte (either VX or EA 2192) is considered “present” or “detected.” If the answer to either question is “no,” then the result of the analysis is a “non-detect.”

The second criterion, MDL, addresses the level of confidence in the quantitative value calculated from the observed instrument response using an established calibration curve for the instrument. EPA’s definition of an MDL, calculated according to the published procedures in 40 CFR, Part 136, Appendix B, is the minimum concentration of a substance that can be measured and reported with 99% confidence that the analyte concentration is greater than zero. This is a highly conservative criterion designed to all but completely eliminate false-positive results. Failure to meet the quantitative-based MDL criterion does not negate the analytical “presence” established by the “detection” criterion.

Our issue is that the Army, through its current use of the EPA MDL concept, could improperly classify analytical data as “non-detects” when, in fact, the data have been determined analytically as “detects.” Although EPA-prescribed uses of the MDL concept may be appropriate for many applications in regulatory monitoring, in this public health-driven application, it is open to criticism when low-level instrument detects are discarded.

We are not suggesting that using the MDL concept and reporting “analytical detects” as “non-detects” will compromise the process of clearing the CVXH concentration at 20 ppb for VX and 1 ppm for EA 2192. Rather the issue is improper classification of analytical results. Usually no issue would involve MDL, if the MDL was used only to help determine a quantitation level at which a reliable number can be provided to help make an action decision. In this case, the Army used “detection,” not a quantitative level, as its primary clearance criterion. We stated in sections 3.3 and 3.4 that the current NECDF methods can support a clearance process on the basis of quantifiable measurements. The Army could report analytical results as “less then,” rather than as “detects” and “nondetects,” which would more accurately represent the analytical data.

3.6 Quality Assurance and Quality Control Procedures

The Laboratory Quality Control Plan clearly defines the comprehensive laboratory QA/QC procedures and techniques. This document defines the procedures for: preparation and verification of analytical standards; the certification, maintenance, and calibration of analytical instruments; the certification of methods and personnel; and the QC procedures, techniques, and samples used to define the operational status of the analytical processes and the basic validity of the analytical data. The overall QA/QC plan and procedures are well designed and documented.

3.7 Findings

The planned sampling program should provide representative samples for CVXH batches.
The current method for analyzing VX in CVXH (LAFI-A-30-053) is adequate to detect and quantify VX in laboratory-generated, 8% VX-loaded, DIC-stabilized hydrolysate well below the established clearance level of 20 ppb.
The current method for analyzing EA 2192 in CVXH (LAFI-A-30-030) is adequate to detect and quantify EA 2192 in laboratory-generated, 8% VX-loaded, DIC-stabilized hydrolysate well below the established clearance level of 1 ppm.
The use of EPA’s MDL for clearance levels does not preclude analytical instrument detection of low levels of VX and EA 2192 (generally <20 ppb VX and <1 ppm EA 2192) in the CVXH. The perception that the clearance criteria (defined as “non-detected” with a MDL of ≤20 ppb VX or ≤1 ppm EA 2192) indicate absence of analytically detectable VX and/or EA 2192 could be misleading. While CDC believes that utilizing the MDL approach would not result in public health concerns, the Army needs to address potential public misperceptions regarding the detection or non-detection of VX in CVXH. A simpler reporting scheme (i.e., non-detected, detected at <20 ppb, or detected at >20 ppb) should be considered.
The overall QA/QC plan and procedures are well designed, and documented. NECDF laboratory personnel must generate day-to-day operational QC data to demonstrate that all analytical systems are operational and under control before plant startup according to written plans and procedures.

4. Caustic VX Hydrolysate Treatment

4.1 Introduction

The CVXH is the liquor obtained from the alkaline hydrolysis of the chemical agent VX at elevated temperatures. The details of the processes that generate the CVXH at the Newport facility are described earlier in this report. Once transported to the DuPont SET facility, CVXH will be further treated to remove the organic by-products by a series of physicochemical and biologic processes. The exact composition and phase characteristics of the CVXH received at the SET plant will depend on the stabilizer type and VX loading used in the NECDF process batch. The major parameters and characteristics of 8% VX– loaded, DIC-stabilized hydrolysate (which is the main focus of this report), as received by DuPont, are given in the Table 4.1 for two separate CVXH samples.

pH	TOC, mg/L	COD mg/L	TN mg/L	EMPA mg/L	MPA mg/L	Thiolamine mg/L
>13	33,852	61,000	6,739	39,135	2,789	11,200
13.1	44,147		4,334	35,937	2,826	42,900

total organic carbon (TOC), total nitrogen (TN), milligrams per liter (mg/L)

Table 4.1 Characteristics of caustic VX hydrolysate generated from 8% VX loading with DIC stabilizer

The DuPont treatability studies were designed and executed to obtain scale-up parameters for engineering design and regulatory compliance. Because of their relatively high concentrations in the CVXH, only thiolamine, EMPA, and MPA were analyzed or monitored within the treatment train or in the process effluent. Trace contaminates, such as VX and EA 2192, were not monitored during the studies. (Note: Because of the high 1500- to 2000-fold dilution factor in the DuPont SET process, monitoring of these compounds may not be analytically possible.)

The pH adjustment and neutralization of the CVXH is the first step of the pretreatment process before introduction of the waste to the biologic treatment system. CVXH neutralization is followed by peroxide treatment to destroy odorous substances. The most recent biotreatability studies, the final step in the treatment train, use two-stage PACT®-activated sludge systems that are operated under conditions emulating the actual plant flow rate and hydraulic retention time. In addition to CVXH, the reactors received mustard (HD) hydrolysate from the Aberdeen operations because an alternating treatment scheme may be implemented at the DuPont SET facility.

The studies described in the two DuPont treatability reports (March 3, 2004, and July 19, 2004) were performed with different types of hydrolysates. The inconsistencies in the samples used to conduct the treatability studies make evaluation of the entire treatment process on the same basis and extrapolation of the treatability studies to pilot-plant performance challenging. For example, the pH adjustment and neutralization experiments reported in the Basic Data Summary Report (July 19, 2004) were conducted using 16% VX–loaded, DIC-stabilized CVXH (actual), but the biotreatability studies were performed with 8% VX-loaded, DIC-stabilized CVXH (actual). Although 20% sulfuric acid was used in the pH-treatment experiments, DuPont proposes to use 5% acid in the full-scale process. The heat of reaction for acidification was measured for 8% and 16% VX-loaded CVXH (reformulated)1 with DCC stabilizer, not DIC, which is the focus of our investigation. In summary, the studies reported in the Technical Assessment and the Basic Data Summary Report suffer from inconsistencies with respect to the type of CVXH used in each test. The experimental findings do not support the assumption that the CVXH has identical physical and chemical properties regardless of the VX loading and stabilizer type. The volume of the organic layer formed, which differs for 16% VX-loaded CVXH and 8% VX-loaded CVXH, clearly indicates that the system chemistry differs depending on how much VX is added to the caustic solution. Moreover, the volume of the organic layer formed during hydrolysis is not directly proportional to the VX loading. Therefore, linear extrapolations of the experimental results obtained in the preliminary treatment studies should not be used to predict performance at higher agent loadings, and equating the 8% VX-loaded 7000-gallons per day (gpd) CVXH with 16% VX-loaded 3500-gpd CVXH (Table 5, Basic Data Summary Report) for design and modeling purposes should be avoided.

Because the Army’s stated objective is to begin operations with 8% VX-loaded, DIC-stabilized CVXH, the assessment of the DuPont treatability studies focused mainly on treatment of the CVXH at this condition. Occasionally, however, other data and material reported by Parsons on the VX alkaline hydrolysis treatment are cited to support the main findings of this assessment. Data are insufficient to assess treatment of CVXH at other VX loadings and for other stabilizers. In the following sections, the hydrolysate acidification process, the peroxide oxidation, and the biologic treatment studies are evaluated and the major findings presented.

4.2 Extent of Treatment

4.2.1 pH Adjustment

The CVXH acidification experiments were conducted with actual CVXH (16% VX-loaded, DIC-stabilized) titrated with 20% sulfuric acid to a final pH of 4–6. The titration curve obtained from the actual CVXH was compared with the aqueous layer from a centrifuged sample after separation of the organic layer. The heat of reaction also was computed, but for 8% and 16% VX-loaded, DCC-stabilized (reformulated) CVXH. The results of these experiments demonstrated that

The organic layer is destroyed. pH adjustment produces a homogeneous amber yellow clear solution.
The process generates 3.07 calories per gram (cal/g) during the titration of 8% VX-loaded, DCC-stabilized (reformulated) CVXH, producing a temperature increase of 6.4 ºC. This energy is expected to dissipate through heat losses during plant operation, and cooling and heat exchanger installation will be unnecessary.
Removal of the organic layer lowers the buffering capacity of the mixture (hydronium ions appear to be consumed during destruction of the organic layers).
The process increases the volume of the CVXH waste by about 30%. If 5% sulfuric acid is used, as DuPont proposes to avoid cooling the reaction mixture, the volume increase will be close to 100%, further diluting the sample by a factor of 2. The effect of the 5% sulfuric acid on the organic treatment is unknown; the available reports did not present data using 5% sulfuric acid.

In response to the May 25, 2004, clarification questions (Responses to CDC Clarification Questions, Final, 17 June, 2004), Parsons indicates that pH adjustment does not destroy the organic layer. DuPont’s 3 March 2004 report, “Treatability of Newport (Indiana) Caustic Hydrolysate” (Reich et al), confirmed that the adjustment of pH without additional treatment measures aggravates the odor of hydrolysate. Furthermore, the uncharged form of thiolamine is poorly-soluble and results in the formation of a large organic layer, on the order of 10% by volume. This organic layer is presumed to have a low flashpoint, which would add risk to the shipping process.

However, DuPont and its treatability study as presented in the Basic Data Summary Report, states

The sample was observed to change from a yellowish cloudy color
to a slightly amber clear color once a single phase was formed
which occurred around pH 6.0. Once a single phase formed, there
was no longer any organic material coating the glass.

Addition of a strong acid to the CVXH profoundly affects the physical and chemical stability of the organic droplets dispersed in the hydrolysis liquor and the dissipation of the organic layer. Attachment 1, “Characterization of Droplets Resulting from NECDF Static Mixers,” of the Parsons report (July 22, 2004) states that the average size of the colloidal droplets ranges from 5 to 10 µm, with specific gravity of about 0.87 and strong negative charges. This charge most likely keeps the droplets suspended, preventing efficient collisions and subsequent aggregation. The electrophoresis experiments to determine the particle surface charge were performed with 16% VX- loaded, DIC-stabilized CVXH (actual). No experimental data are presented in the Parsons white paper on the properties of the droplets formed in the hydrolysate from the 8% VX-loaded, DIC-stabilized CVXH. The Parsons reports documented, and experimental observations by DuPont verified, that the volume of the organic layer and the size distribution and dispersion of the droplets in the final CVXH depends on the VX loading. The higher the loading rate the larger the resulting organic layer volume. However a direct proportional relation does not appear to exist (i.e., doubling the VX loading does not increase the volume of the organic layer by a factor of two). Visual observations by Parsons personnel of the formation of the organic layer estimated that the layer thickness remains unchanged for up to 4 months. However, no kinetic information is provided about the rate of formation of the organic layer.

Given that the organic droplets carry an overall negative charge, addition of hydronium ions should compress the electrical double layer that typically exists in the boundary of the organic-aqueous interface and allow the attraction forces to take over. Because this is not observed, i.e., addition of sulfuric acid does not appear to enhance flocculation or layer formation and separation, we can conclude that either the solubility of the organic phase is higher or its components become chemically unstable and decompose at lower pH or both. The disappearance of the organic phase during pH adjustment supports this.

The exact composition of the organic layer is not known, but the response of the whole (as received) CVXH to the addition of sulfuric acid suggests that it imparts alkalinity to the sample, probably because of weak organophosphorous acids and carbonates in the process water. More sulfuric acid (about 30 grams [g]) is required to reduce the pH of the whole CVXH sample than the aqueous layer to a pH of 8 (Figure 1 of the Basic Data Summary Report). However, the two titration curves intersect at a pH of 7 indicating that the same amount of acid is needed to bring the solutions to this endpoint. From that point, further addition of small amounts of acid brings about a steep pH drop in the aqueous layer but has little effect on the whole CVXH (as received), until about 380 g acid (x-axis of Figure 4-1), where pH drops substantially. This behavior is consistent with a chemically reactive solution. The organics exert a hydronium ion demand in excess of the amount required to neutralize the base. The organic layer appears to react with the hydronium ions participating in a chemical reaction rather than to be simple acid-base equilibrium chemistry. Moreover, the observation that this step modifies the odorous intensity of the mixture provides additional evidence that the organic components undergo significant chemical changes during pH adjustment.

Chart illustrating caustic CVHX titration curves

Figure 4-1 Caustic CVXH titration curves provided by DuPont in the Basic Data Summary Report.

4.2.2 Hydrogen Peroxide Oxidation

Once the pH of the hydrolysate is adjusted to a pH of 4–6, the mixture is treated with 10% peroxide to control objectionable odors emanating from the CVXH caused mainly by the volatilization of thiolamine. Peroxide and the free radicals formed by its addition to the reaction mixture attack the organics present in the hydrolysis liquor and initiate thiolamine destruction. Again, these studies were conducted with 16% VX- loaded, DCC-stabilized CVXH (actual or reformulated). Thiolamine is destroyed quickly by the peroxide, with most of the compound depleted within the first minute of reaction (Figure 4-2). After 20 minutes, the concentration drops below the detection limit of 5 ppm. The degradation products of thiolamine are presented in the Technical Assessment Report (March 3, 2004). Four compounds were identified as possible thiolamine degradation products: acetic acid, diisopropyl amine, urea, and 2-diisopropylaminoethyl ethyl disulfide. Acetic acid and urea are readily biodegradable compounds and are expected to break down in the two-stage PACT^® bioreactors. However, the biodegradability of isopropyl amine and the 2-diisopropylaminoethyl ethyl disulfide is not documented in the Technical Assessment Report or the Basic Data Summary Report; only qualitative references (page 49 of the Technical Assessment Report) state that samples analyzed from the effluent of one of the bioreactors had no detectable amounts of thiolamine or any of its oxidation products. No other information is provided that confirms the biodegradation of these two by-products. EMPA and MPA remain unaffected by the peroxide process.

Chart illustrating the destruction of Thiolamine by hydrogen peroxide oxidation over time.

Figure 4-2 Destruction of thiolamine by hydrogen peroxide oxidation.

The oxidation step is an exothermic process releasing approximately 14 cal/g of heat. This value was obtained from a reformulated 16% VX–loaded, DCC-stabilized, CVXH that was first treated with 20% sulfuric acid to a pH of 6.4, then subjected to 20% weight equivalent of 10% hydrogen peroxide solution. Gas-generation measurements conducted in 2-liter flasks showed that the amount of gas generated during the peroxide oxidation is negligible. The lack of gas evolution suggests that the degradation of thiolamine is incomplete; in other words, the compound is not mineralized to the simple innocuous carbon dioxide and water.

4.2.3 PACT^® Biotreatment

Two sets of biodegradation experiments were conducted using one- and two-stage PACT^® bioreactors. The first treatability study was performed with CVXH; in the second, both CVXH and HD hydrolysate from Aberdeen were tested to determine the effect of alternating the bioreactor feeds on the performance of the biologic system. Co-processing will be necessary when both types of hydrolysates will be sent for treatment to DuPont’s SET facility. The objectives and the criteria of both studies were stated in the Basic Data Summary Report:

To confirm that the anticipated rates of CVXH can be processed successfully through the SET [wastewater treatment plant (WWTP)], enhancing the database provided by the original treatability study;
To assure that the CVXH can be processed at appropriate rates while HD hydrolysate from Aberdeen is being managed at the WWTP using a plan to either alternately campaign each hydrolysate or process the pretreated hydrolysates simultaneously;
To ascertain the degree of improvement in treatment that can be anticipated with a two stage PACT^® system.

As for the earlier Treatability Study there were three general criteria for judging the treatment of CVXH to be successful:

Ability to maintain satisfactory control of wastewater and sludge odors.
Ability to maintain control of SET WWTP operations (e.g., effective dissolved organic carbon [DOC] removal, manageable foaming, pH control, solids management, etc.)
Ability to assure permit compliance (e.g., effluent BOD5 [5-day biochemical
oxygen demand], BOD5 percent removal, effluent TSS, effluent NH3-N and
WET). In addition the fate of EMPA, MPA and thiolamine were monitored.

As mentioned before, the studies were designed to provide information about system performance in terms of regulatory compliance and to obtain design parameters for scaleup.

To ensure adequate treatment, two PACT^® bioreactors were operated in series. This biologic system, in addition to the microbial degradation, was dosed with activated carbon, which in general enhances the treatment capacity by removing recalcitrant compounds that are resistant to biodegradation. Six reactors were set up to evaluate various treatment scenarios using 8% VX-loaded, DIC-stabilized CVXH and the HD hydrolysate. The flow rate and retention time in the bioreactors were set to simulate actual plant conditions treating 7000-gpd CVXH and 15,000- and 25,000-gpd HD hydrolysate. A large dilution of the hydrolysate, to the order of approximately 2000 times, occurred at introduction of the pretreated CVXH to the biologic PACT^® system. Appropriate controls were used throughout the study, and all pertinent system parameters were monitored to assess system performance. However, the fate of individual compounds as they pass through the bioreactors is not as well documented. Only EMPA and MPA were monitored in the pilot-plant effluent.

The data presented in figures 7, 8, 9, and 10 and tables 8 and 9 of the Basic Data Summary Report indicate that, after a short acclimation period, the removal efficiency, as measured by DOC and BOD reduction, stabilizes to an average of about 85%–90% in all reactors. Even during the acclimation period, the removal does not drop below 75%. This high-removal efficiency also is observed in the alternating Aberdeen/DIC CVXH influents, indicating that the biologic system is not affected by these input changes. The 7000–gpd, 8% VX-loaded CVXH is equated to 3500–gpd, 16% VX-loaded CVXH (Table 5). However no evidence suggests that this is a valid approach. See Section 4.3 for a discussion of the potential differences on the composition and general chemistry of the 8% and 16% VX-loaded CVXH.

The Technical Assessment and Basic Data Summary reports clearly document the conversion of EMPA to MPA. Both compounds remain unaffected by the pH reduction, and conversion during peroxide treatment appears to be limited. Biologic treatment by the two-stage PACT^® process converts essentially all of the EMPA to MPA but appears not to affect the MPA decomposition. Data are sufficient to support this conclusion. The slight decrease in MPA effluent concentration most likely results from partitioning in the organic sludge.
DuPont’s Technical Assessment and Basic Data Summary reports contain no information about the fate of VX or EA 2192 during treatment of the CVXH in the DuPont SET facility. The presence of these two compounds in the plant effluent in trace amounts cannot be excluded.

4.3 Environmental Persistence and Agent Loading Effects

The major hydrolysis products of VX are well characterized, and the reaction rate and pathways depend strongly on solution pH and temperature (Figures 4-3 and 4-4). With solubility of approximately 30 grams per liter (g/L), VX is considered to be highly mobile in the environment and can persist for days or even weeks in slightly acidic waters. Other VX hydrolysis products in the CVXH include EMPA, which has a half life in soils of about 8 days, with MPA being the major transformation product.

Chart illustrating the pH dependence of apparent rate constant for VX hydrolysis

Figure 4-3 pH dependence of apparent rate constant for VX hydrolysis

Chart illustrating the temperature dependence of apparent rate constant for VX hydrolysis at a pH of 7.7

Figure 4-4 Temperature dependence of apparent rate constant for VX hydrolysis at a pH of 7.7.

As discussed in Section 4.2.3, the treatability studies with the 8% VX-loaded CVXH demonstrates conversion of EMPA to MPA in the activated sludge bioreactors. MPA is stable in the environment because it is resistant to hydrolysis, photolysis, and thermal decomposition. It is also soluble in water and has a low coefficient for sorption onto soil particles. Therefore, it can migrate easily in the soil and groundwater (Munro et al., 1999). Another major by-product of the hydrolysis of VX at neutral and high pH values, is EA 2192 (S-(2-diisopropylaminoethyl)methyl phosphonothioic acid), an environmentally persistent highly toxic compound with infinite water solubility.

Some of the hydrolysis products, namely EA 2192, EMPA and MPA, are stable at neutral pH; whether these, or other byproducts that are not identified or exist at low concentrations, can react and form stable VX molecules is questionable. This is a concern because the CVXH is adjusted to a pH below 6 in preparation for the oxidation and biologic treatment. Parsons attempted to partially address this concern by studying the CVXH over a 5-hour period at a pH of 10 or 71 days at a pH of 14. These conditions, however, do not represent the low (<6) pH range in the system after pH adjustment. Neutral pH is a worst-case scenario because of the stability of the by-products at those conditions and the possibility of recombining to reform VX. Thermodynamic analyses also should have been performed to assess the tendency of the pH-adjusted CVXH to move toward VX reformation. Because experimental data are not presented, the questions regarding possible VX reformation remain unanswered.

4.4 Findings

The 8% VX-loaded, DIC-stabilized CVXH is treated by pH adjustment to a pH <6 to eliminate the two-phase mixture, followed by hydrogen peroxide oxidation to destroy the odor-causing thiolamine, and finally biologic treatment to convert most of the EMPA to MPA.
The DuPont SET facility effectively treats the CVXH generated from an 8% VX loading with DIC stabilizer, except for MPA, for which only minimal reduction is demonstrated.
Alternating feeds from Aberdeen HD hydrolysate and CVXH did not affect the performance of the DuPont bench-scale reactor.
The effects of the SET facility on the destruction of any trace quantities of VX and EA 2192 in the CVXH are unknown. In addition, the fate of diisopropyl amine and 2-diisopropylaminoethyl ethyl disulfide through the SET plant is not well documented.
The possibility of VX reformulation at acidic (<6) pH conditions (after pH
adjustment) in the Dupont SET treatment process has not been adequately investigated and remains unresolved.
Effective treatment of 16% VX-loaded CVXH and 8% VX-loaded CVXH with DCC or DIC/DCC stabilizers were not demonstrated in the DuPont studies.

5. Major Findings

NECDF was designed to destroy VX using caustic hydrolysis in a hot solution of sodium hydroxide. Initially the plan was to further treat the resulting waste on-site by SCWO and to ship the SCWO effluent to a TSDF. After the terrorist attacks of September 11, 2001, the plan was modified to eliminate on-site SCWO treatment and ship the resulting hydrolysate directly off-site for treatment at a TSDF. Critical to this modified plan was the development and validation of analytical methods to clear the hydrolysate for shipment. The stringent Army clearance levels for VX and EA 2192 proved challenging to the analysts. The original plan to operate at 33% VX loading was abandoned, and the program plans to begin operations at 8% VX loading and move to 16% VX loading.

This programmatic change has necessitated an intensive effort to develop the analytical methods needed to assess process performance and suitability of the hydrolysate for off-site shipping, process modification to ensure adequate mixing and VX droplet size, and search for a TSDF capable of treating the hydrolysate. The current plans are for NECDF to ship the CVXH to the DuPont SET facility in Deepwater, New Jersey.

CDC engaged Carmagen Engineering, Inc., to assemble a team of experts (Team) to assist in the evaluation of the DuPont SET facility’s treatment of the CVXH. The Team recognized that an assessment of the NECDF destruction process and an examination of the analytical methods to be used for CVXH clearance were required to ensure that the hydrolysate being shipped to SET will be adequately characterized and that VX and EA 2192 levels in the CVXH meets Army specifications.

The Team addresses its findings in chapters 2–4 of the report. The reader is encouraged to review all of the findings, as well as the supporting documentation in each chapter. The major findings follow.

Process Issues (Chapter 2)

Finding 2.1. The database supports the efficacy of neutralizing DIC-stabilized VX using sodium hydroxide at the 8% VX-loading rate. Scale-up of the process from laboratory/bench scale to pilot scale should be operationally feasible. However, because the NECDF will be a pilot facility, changes must be anticipated in operating mode and hydrolysate composition sent for off-site treatment.

Finding 2.2. VX loading (weight percent) and the specific stabilizer (DIC, DCC) employed significantly impact the process, hydrolysate composition, analytical methods validation, and possibly solids formation. Scale-up of the process from 8% to 16% VX loading is of particular concern (because of the similarity of the organic-phase volumes from 16% to 33% VX-loading batches), the potentially high VX concentration in the resulting organic layer, and the analytical problems identified with 33% VX loading.

Finding 2.3. The impact is unknown of solids formation during the hydrolysis process on operations (potential for blockage of the in-line static mixer, control valves, and sampling system), VX analytic methods, and off-site hydrolysate treatment. The transition from 8% to 16% VX loading, as well as stabilizer change, is of concern and requires additional detailed studies.

Analytical Methods (Chapter 3)

Finding 3.1. The methods for analyzing VX and EA 2192 in 8% VX-loaded, DIC-stabilized CVXH are adequate to detect and quantify at the established clearance levels for VX (20 ppb) and EA 2192 (1 ppm).

Finding 3.2. The use of EPA’s MDL for clearance levels does not preclude analytical instrument detection of low-level VX and EA 2192 (generally <20 ppb VX and <1 ppm EA 2192) in the CVXH. The perception that the MDL clearance criteria indicate absence of analytically detectable VX and EA 2192 could be misleading. While CDC believes that utilizing the MDL approach would not result in public health concerns, the Army needs to address potential public misperceptions regarding the detection or non-detection of VX in CVXH. A simpler reporting scheme (i.e., non-detected, detected at <20 ppb, or detected at >20 ppb) should be considered.

Finding 3.3. The overall QA/QC plan and procedures for the NECDF laboratory are well designed and documented. However, NECDF laboratory personnel should continue implementing the QA/QC plan by developing day-to-day operational QC data to demonstrate that all analytical systems are operational and under control before plant startup.

Caustic VX Hydrolysate Treatment (Chapter 4)

Finding 4.1. The SET facility effectively treats the CVXH generated from an 8% VX loading with DIC stabilizer (i.e., pH adjustment, thiolamine destruction, conversion of EMPA to MPA), except for MPA, for which only minimal reduction is demonstrated.

Finding 4.2. The SET facility treatment performance should be unaffected when treatment of hydrolysate feeds from Aberdeen (HD) and Newport (VX) are alternated.

Finding 4.3. The DuPont treatability studies have not yet demonstrated the effective treatment of 16% VX-loaded CVXH, nor of 8% VX-loaded CVXH with DCC or DIC + DCC stabilizers.

6. References

DuPont. DuPont Technical Assessment on U.S. Army Newport (Indiana) Project. 3 March, 2004.

DuPont. Basic Data Summary Report for Newport Caustic Hydrolysate. 19 July, 2004.

Munro, N.B., Talmage, S.S., Griffin, G.D., Waters, L.C., Watson, A.P., King, J.F., and Hauschild, V. The sources, fate, and toxicity of chemical warfare agent degradation products. Environ Health Perspect. 1999;107(12):933–974.

Parsons. CVXH Analytical Testing Results (Response to CDC Request for Information: Item No. 1). 15 May 2004.

Parsons. Sampling Protocols (Response to CDC Request for Information: Item No. 2). 14 May 2004.

Parsons. Analytical Methods for VX in Hydrolysate (Response to CDC Request for Information: Item No. 4). 14 May 2004.

Parsons. Newport, Indiana Process Variability Impact on Secondary Treatment (Response to CDC Request for Information: Item No. 6). 14 May 2004.
Parsons. Responses to EPA Questions to DuPont [16 questions]. 14 June 2004.

Parsons. Responses to Additional CDC and EPA Questions [9 EPA questions, 19 CDC questions]. 17 June 2004.

Parsons. Responses to CDC 29 June, 2004 Questions [11 requests and 5 questions]. 22 July 2004.

SAIC. Assessment of Low-Level VX in CVXH LLVX Independent Assessment Panel. October 2003.

Texas A&M University System. Quantitative Subsystem Hazard Analysis of Potential for Off-Site Transfer of Hydrolysate Containing VX Above the 20 ppb Method Detection Limit. Draft Report. August 2004.

Wojciechowski P, Mokos J. Analysis for VX in Hydrolysate at NECDF. Presentation to CDC, 27 March 2003.

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