Progress Report

CICEET Progress Report for the period 9/15/04 Through 3/15/05

Project Title: In Situ Sediment Ozonator for Remediation of PCB, PAH, DDT and Other Recalcitrant Chemicals
Principal Investigator(s): Andy Hong
Additional Investigator(s): Don Hayes
Project Start Date: September 1, 2004

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Tables
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Project Objectives for This Reporting Period
Objectives
On The Chemical-Biological Process
  • Can ozone degrade the target contaminants PCB, DDT, PAH?
  • Can ozone completely degrade the contaminants and interemediates?
  • What are the intermediates and products formed during ozonation?

On the In Situ Sediment Ozonator (ISO) Equipment
To provide answers to the following questions concerning operating parameters of the equipment:

  • What are the key equipment operation parameters?
  • What are the operation parameters that should be tested individually?
  • What are the sedimentation and thickening characteristics of the sediments?

On the Chemical-Biological Process
To provide answers for these follow-up questions:

  • Are the intermediates and products amenable to biodegradation?
  • Are nutrient supplements helpful for subsequent natural bioremediation?
  • What are the important process parameters and treatment efficiency accordingly?

On the ISO equipment
Finalize the design concept for sediment flow through the ISO system including the counterflow reactors.

Tasks to meet objectives
On The Chemical-Biological Process

  • Ozonated pure PCB and DDT compounds dispersed in CCl4 solvent.
  • Characterized contaminated sediments obtained from NERR sites including Narragansett Bay NERR (Dyer Island; NBDI), Elkhorn Slough NERR (Monterey Bay; MBES), and Wells NERR, respectively, for treatment test in this project.
  • Characterized sediment samples from 3 contaminated sites at different parts of the country.

On the In Situ Sediment Ozonator (ISO) Equipment

  • Gathered and characterized sediments to use in pumping tests
  • Conducted counterflow reactor tests at various sediment concentrations to determine hydraulic properties and identify maximum feasible pumping concentrations
  • Preliminary assessments on potential sand trap designs to simplify pumping efforts

On the Chemical-Biological Process

  • Biodegradability tests for the intermediates and products
  • Biodegradability tests with nutrient supplements for the intermediates and products
  • Characterize treatment efficiencies according to varying treatment parameters

On the ISO equipment

  • Select a target solids concentration for use in the system design
  • Construct and operate a combined system including dilution, pumping, reactor(s), and settling tank

Progress on Tasks
On The Chemical-Biological Process

  • Completed degradation studies of Aroclor 1242, Aroclor 1260, DCB (decachlorobiphenyl), and DDT by ozone in CCl4
  • Completed identification of intermediates and products from ozonation of contaminants Aroclors (1242 and 1260) and DDT.
  • Completed characterization of sediment samples from 3 NERR sites and from other parts of the country.

On the In Situ Sediment Ozonator (ISO) Equipment

  • Sediments were gathered from Utah Lake and the Jordan River to use for in the pumping tests to avoid depleting our “stockpile” of contaminated sediments and simplify laboratory handling. Physical sediment properties (grain size distribution, specific gravity, etc) were determined for the sediments.
  • Counterflow tests were conducted at solids concentrations ranging from 20% to 50% solids. Although sediments could be pumped at all of these concentrations the tests identified settling of coarse particles as an issue at any concentration.
  • Designed a trap to remove coarse sediments from pumped feed line to counterflow reactor. Conducted a series of tests at various flowrates using different sediments. In general, simple traps were able to remove most coarse particles; adding agitation within the trap improved its ability to segregate fine and coarse particles.

Difficulties
On The Chemical-Biological Process
The sediment samples were heterogeneous in nature and variations among samples can be significant. This difficulty is overcome by slight modifications of EPA’s analytical protocol and cleanup procedures, with substantial replicates.

On the In Situ Sediment Ozonator (ISO) Equipment
The presence of sand in the sample presented a challenge and required some redesign of the counterflow reactor system. Also, the testing process has taken more time than anticipated for this portion of the project.

Project Objectives for Next Reporting Period

Objectives

Tasks to Meet Objectives

Work Plan for Next Reporting Period
On the Chemical-Biological Process
The development is on track. We will continue development as proposed:

  • Will characterize biodegradability of intermediates from target contaminants by performing BOD, COD, and Toxicity tests
  • Will characterize biotreatment with varying amounts of added carbon and oxygen source
  • Will characterize treatment performance by varying treatment parameters such as contact time, ozone concentration, solid concentration, and mixing intensity, etc.

On the ISO equipment

  • Conduct extended duration flow tests of sediment slurries to help isolate the best “target” solids concentration. Current results suggest about 30% solids may be best, so efforts will initially focus on this concentration.
  • Construct a complete flow system that includes sediment dilution, a sand trap, pumping the slurry through a countercurrent reactor, then into a settling chamber, sedimentation to a reasonable sediment density, then return to dilution.
  • Operate the flow system with several sediment types and at multiple solids concentrations so its overall performance can be evaluated under different conditions.

Anticipated Success in Meeting Project Objectives
On the Chemical-Biological Process
We expect to successfully carry out the planned tasks for the next 6 months, in which we expect to see increased BOD (i.e., increased biodegradability), as well as decreasing toxicity, following ozonation. We also expect to add insights to how various process parameters and ranges that will contribute to more effective treatment.

On the ISO equipment
The above tasks and work plan will lead us to a preliminary system design, the primary project objective for this component of the research.

Overall Project Timeline Update
On the Chemical-Biological Process
Our development is on track as originally proposed, and we don’t find any changes to original schedule necessary.

On the ISO equipment
No project timeline updates anticipated at this time.

Preliminary Data
Degradation of Aroclor 1242 in Carbon Tetrachloride
Procedures:

  • 3.3 mM of Aroclor 1242 were introduced into ozone pre-saturated CCl4 solution.
  • Samplings were conducted at 1,2,3,5,10 min
  • Reaction was stopped by adding indigo blue solution in methanol (that immediately consumed remaining ozone)
  • The samples were concentrated by a gentle N2 stream
  • GC/MS analyses were performed

Results and Conclusions

  • Figure 1: Concentration, as Ln([A]/[A]0), vs. time profiles for various congeners of Aroclor 1242, with the slopes indicating pseudo-first order rate constants of congeners with ozone.
    Conclusion: The results show that when PCBs are dispersed in solution, they are readily degraded by molecular ozone within minutes.

  • Figure 2: Formation and destruction of several intermediates during ozonation of Aroclor 1242, as modeled by a consecutive reaction model.
    Conclusion: The compounds as identified are intermediates during the degradation of PCBs by ozone. The compounds are also completely removed within short contact time.

  • Figure 3: Concentration vs. time profiles for various congeners and total PCBs of Aroclor 1242 in the presence of varying amounts of added t-butyl alcohol during ozonation.
    Conclusion: The results with the free radical scavenger t-butyl alcohol show that the degradation mechanism is mostly via attack by molecular ozone attack, rather than by secondary free radical oxidants possibly formed from ozone.

  • Table 1: Second-order rate constants for reactions of various PCB congeners with ozone ([O3] = 65 mg/L). Conclusion: The basic reaction rate constants between various congeners with ozone had been nonexistent in the literature, but they are now available as reported in the Table.

  • Table 2: Second-order rate constants in formation and depletion of various intermediates as mediated by O3 ([O3] = 65 mg/L).
    Conclusion: The intermediates are also degradable by ozone, with the reported basic rate constants.

  • Table 3: Congeners and intermediates during degradation of Aroclor 1242 by O3 at different O3 to PCBs ratio.
    Conclusion: Even under limited supply of ozone, PCBs are degraded to various extents with some intermediates remaining. These intermediates will be further tested for subsequent biological remediation.

Degradation of Aroclor 1260 in Carbon Tetrachloride
Procedures:

  • 1.1 mM of Aroclor 1260 were introduced into ozone pre-saturated CCl4 solution.
  • Samples were taken at 1,3,5,8,10min
  • The reaction was stopped by sparging N2
  • The samples were concentrated by a gentle N2 stream
  • GC/MS analyses were performed

Results and Comments/Conclusions

  • Figure 4: The total concentration (mM) of PCBs in Aroclor 1260 vs. ozonation time (min) profile.
    Conclusion: Complete degradation of Aroclor 1260 occurred within 20 min of ozonation.

  • Figure 5: Concentration, as Ln([A]/[A]0), vs. time profiles for various congeners of Aroclor 1260, with the slopes indicating pseudo-first order rate constants of congeners with ozone.
    Comments: The degradation of Aroclor 1260 conforms to a pseudo-first order profile, which confirms the bimolecular reaction between the PCB molecule and the molecular ozone.

  • Figure 6: Formation and destruction of several intermediates during ozonation of Aroclor 1260.
    Comments: The intermediates formed during degradation of various PCB congeners were also degraded by the end of 40 min of ozonation.

  • Figure 7: Profiles of total PCB concentration (mM) in Aroclor 1260 vs ozonation time (min) without TBA and with 9 times mole ratio TBA.
    Comments: TBA serves as a free radical trap and should significantly suppressed degradation mediated by free radical mechanisms. TBA showed some effect; however, the results seemed to suggest significant degradation reaction that occurred via attack by molecular ozone and not by free radical pathways.

  • Table 4: The initial concentration and first order rate constants of PCB congeners in Aroclor 1260.
    Comments: The basic constants pseudo first-order and second order constants of various congeners with ozone are now available.

  • Table 5: Byproducts of PCB Congeners in Aroclor 1260 detected by GC/MS.
    Comments: Various intermediates formed during degradation by ozone were detected, and they were also completely degraded by ozone.

  • Table 6. Congeners during degradation of Aroclor 1260 by O3 at different O3 to PCBs ratio.
    Comments: Intermediates were found at various limited or excess ozone concentrations.

Key Conclusions:

  • Aroclor 1260 (1.4 mM) can be completely degraded by ozone within 40 min.
  • Ozone can degrade high-chlorinated PCBs (about 60% by weight in Aroclor 1260).

Results of Decachlorobiphenyl (DCB) in Carbon Tetrachloride

Procedures: Similar to the ozonation of Aroclor 1260 in Carbon Tetrachloride

  • Figure 8: The concentration of DCB (mM) vs. time (min) profiles with various added TBA amounts in ozone pre-saturated CCl4 Solution
  • Figure 9: The DCB concentration vs. ozonation time (min) profiles in CCl4 olution without pre-saturation with ozone

Key Conclusions:

  • Even DCB, a fully chlorinated PCB, can be degraded by ozone.
  • The reaction pathways may have involved free radical reactions
Results of DDT in Carbon Tetrachloride
  • Figure 10: DDT concentration (mM) vs. ozonation time (min) profiles during ozonation of DDT in CCl4 Solution with and without pre-saturation with ozone

Conclusions

  • DDT is degradable by ozone, and 0.3 mM of DDT can be completely degraded by ozone within 10 min.

Characterization of PCBs, DDT, and PAHs in Various Sediment Samples:

  • Table 7: Concentrations of PCBs, PAHs and DDT found in sediments from various sites of the country.

Procedures:

  • Replicates of tests conducted for sediments collected from different sites.
  • The sediments were first dried on a steam table and grounded.
  • The sediments were Soxhlet-extracted for 24 hrs.
  • The extracts were cleaned up following EPA Method 3665--Sulfuric acid/permanganate cleanup, EPA Method 3660B of Sulfur removal and EPA Method 3620B of Florisil cleanup
  • GC/MS or GC/FID analyses were performed

Conclusions:

  • Only low levels of PCBs, DDT, or PAHs or none were found in sediments collected from NERR sites and Other-3 site.
  • Significant amount of PCBs and PAHs were found Other-1 site sediments
  • High levels of PAHs were found in the sediments of Other-2 site.

Dissemination
Publications:
Reaction Kinetics and Products of Arochlor 1242 with Ozone A. Hong, H. Xu, D. Hayes, submitted to Ind. Eng. Chem. Res.

Conferences:
The 15th AEHS meeting and West Coast Conference on Soils, Sediments, and Water. March 14-17, 2005, San Diego, CA Presentation title, “In-situ Chemical-Biological Treatment of PCB-Contaminated Sediment. A. Hong, D. Hayes, H. Xu

Contact with End Users:
This report will be reviewed by Dr. Kerstin Wasson, Research Coordinator for Elkhorn Slough NERR, CA.

Patent, Copyright, Invention Disclosure Activity:
Hong, Hayes, In Situ Sediment Ozonator for Contaminants Remediation. U#3287. Prov. Appl. 12/2004.

Expenditures
Our expenditures are in the range of anticipated, and as proposed.

End User Advisor Feedback
Name: Dr. Kirstin Wasson
Organization: Elkhorn Slough NERR, CA
Location: Elkhorn Slough National Estuarine Research Reserve 1700 Elkhorn Road, Watsonville, CA 95076
Phone number: 831 728 5939
E-mail: research@elkhornslough.org

1) At this stage, what are the potential applications for this research? Please discuss how you and others could potentially use the technology.
Past studies have revealed high levels of pesticides and other pollutants at Elkhorn Slough. If there were affordable ways of cleaning up the sediments in situ, that would be very appealing for improving ecosystem health and ensuring further contaminants don’t entire the foodweb and affect sensitive organisms such as waterbirds and marine mammals.

2) What, if anything, has changed about this project's potential applicability since the last reporting period (not applicable to the first Progress Report)?
None.

3) Do you see any key challenges that the researchers may want to address or keep in mind?
The instrument would have to be capable of operating in areas with a mix of substrate types. Our most polluted areas have rip rap and oysters and other hard substrate chunks mixed in with the soft sediment. It would also be important to determine possible short-term negative impacts on benthic communities (clams, oysters, etc.) and the organisms that feed on them (sharks, otters, seabirds, etc.).

4) Does this report offer you enough information to adequately address the above questions?
Fine for a first report.

5) Other feedback?
The sediment buckets are very heavy ­ I needed to find strong guys to help me carry the mud from the shore into my car and from the car to the mailing area. This is something to keep in mind when making arrangement with researchers to collect sediments: be sure they are physically qualified, not just mentally willing!