dnapl and groundwater remediation technology annual review

ORICA DNAPL and Groundwater Remediation Technology Annual Review No. 14 1

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DNAPL AND GROUNDWATER REMEDIATION TECHNOLOGY ANNUAL REVIEW NO. 14

ORICA BOTANY GROUNDWATER CLEANUP PROJECT

REPORT NO. EN.1591.61.PR084

30 APRIL 2020


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DNAPL and Groundwater Remediation

Technology Annual Review No. 14

James Stening

Senior Environmental Technologist

Orica Australia Pty Limited

30 April 2020


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DOCUMENT CONTROL

DNAPL and Groundwater Remediation Technology Annual Review No. 14

Botany Groundwater Cleanup Project SharePoint Folder

Revision 0, Issued 30 April 2020

Distribution List

NAME POSITION

1 Matthew Hart Senior Operations Officer – Metro South

NSW Environment Protection Authority

2 James Fairweather Head – Environmental Remediation

Corporate Affairs, Orica Australia Pty Ltd

Reviewer: James Fairweather Reviewer Position Title


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CONTENTS

1. EXECUTIVE SUMMARY 5

2. INTRODUCTION 7

3. BOTANY GROUNDWATER STRATEGY REVIEW 9 3.1 2007, 2011 and 2014 Workshops 9

3.2 2017 Workshop 9

3.3 Work Arising from the 2017 Workshop 10

3.4 2020 Workshop 12

4. TECHNOLOGIES CURRENTLY IN USE 14 4.1 Groundwater Treatment Plant 14

4.2 In Situ Groundwater Treatment 14

4.3 DNAPL 14

5. TECHNOLOGIES UNDER EVALUATION 15 5.1 Groundwater Treatment Plant 15

5.2 In Situ Groundwater Treatment 16

5.3 DNAPL 17

6. ONGOING INVESTIGATION 18

7. REFERENCES 19

A1 GROUNDWATER TREATMENT PLANT 22

A2 BIOREMEDIATION OF GROUNDWATER 25

A3 DNAPL CLEANUP TECHNOLOGIES 27


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1. EXECUTIVE SUMMARY In the Voluntary Management Proposal (VMP) issued by Orica Limited to the NSW Environment Protection Authority (EPA) in November 2010 and subsequently updated in August 2015 Orica committed to “Provide an annual report to EPA that would assess the practical application and effectiveness of appropriate technologies in relation to the remediation”. In accordance with that commitment, Orica has submitted a series of annual reports under successive VMPs. This report constitutes the thirteenth annual report.

Under the VMP Orica is also committed to convening a Strategy Review Workshop every three years to which it will invite a minimum of three overseas experts in the field. The review process will involve consideration by the experts of the annual reports prepared by Orica and worldwide developments in technology in order to assess whether any current or emerging technologies (including developments in technology and its applications) are likely (individually or in combination) to provide a practicable solution and justify the conduct of field trials of those technologies.

Strategy Review Workshops have been held in December 2007, February 2011, February 2014, February 2017 and March 2020. The outcomes of the 2020 Workshop are described in this report, as well as progress against actions arising from the 2017 Workshop. As recommended by the 2017 Workshop, a large amount of soil and groundwater data were collected in the latter part of 2017, 2018 and 2019, which have been used to further develop understanding of the natural attenuation mechanisms and assimilation capacity of the aquifer. A transect of nested monitoring wells was installed downgradient of the C1 Source Area to enable collection of data relating to contaminant mass flux from the source area. Soil samples were also collected from the drilled core samples, which were used to create column tests to evaluate the processes of diffusion/back-diffusion and sorption/desorption in the lower-permeability layers found in the aquifer. The outcomes of this work by Geosyntec Consultants in Canada were reported to the 2020 Workshop. They reported that the bulk mass attenuation behaviour at the Botany Site is a complex balance of competing contaminant mass attenuation mechanisms, and that that balance is evolving over time. The rate of DNAPL dissolution will vary over time as a result of changing composition as more soluble components preferentially dissolve over less soluble components. Biological degradation processes will both enhance dissolution of DNAPL in some areas and be inhibited by elevated dissolved-phase concentrations in others.

Peat and clay layers initially provided mechanisms for dissolved-phase contaminant mass loss through sorption and diffusion, but more recently, are acting as persistent secondary sources of mass as contaminants are released to groundwater through desorption and back-diffusion, which are much slower and are leading to tailing of plume concentrations and mass reductions over time.

Multiple lines of evidence point to the occurrence of biologically-mediated degradation in many areas. Other lines of evidence also point to inhibition of microbial activity, related to elevated EDC concentrations and chloroform (a known inhibitor of microbial activity), in some areas.

Various indicators suggest that CTC will be the least persistent of the three primary DNAPL components, and that PCE is likely to persist the longest. However, once the chloroform concentrations reduce below inhibitory levels, biological attenuation may be enhanced, leading to faster attenuation of the total mass over time.

A number of actions from the Workshop also related to updating the numerical modelling of the fate and transport of contaminants in the aquifer. The existing numerical model has not been updated for a number of reasons. Numerical modelling was further discussed in the 2020 Workshop.

The 2017 Workshop also recommended evaluation of a number of possible amendments to the current remediation approach to enhance DNAPL dissolution and dissolved phase contaminant removal. A screening level review of the suggested remediation technologies was completed by Golder. The remediation options assessment concluded that none of the identified technologies is likely to provide a solution to achieving the primary goal of reducing the cleanup timeframe in a reliable, cost effective and sustainable manner.

This report describes treatment technologies currently in use and under evaluation.

The Orica Botany Groundwater Cleanup is being achieved by groundwater extraction along three containment lines and ex situ treatment of the water in the GTP.


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During 2015 Orica divested its Chemicals business. The Chemicals business is now known as Ixom Operations Pty Ltd (Ixom). At Botany Industrial Park, the ChlorAlkali Plant is now owned and operated by Ixom. As part of the transition at Botany, personnel at the GTP transferred to Ixom. Consequently, although the GTP continues to be owned and funded by Orica, it is now operated under a service contract by Ixom.

The efficacy of the hydraulic containment and treatment system is not discussed herein, but is reported in biannual progress reports prepared by Orica and its environmental consultants. The GTP comprises a number of unit processes designed and operated to treat the various contaminants – natural and anthropogenic – in the extracted groundwater.

Investigations and improvements to the GTP unit processes since the GTP’s commissioning in 2006 are described in these annual reports. Operationally, the GTP is a mature plant, and the number of enhancements to its operation have decreased year by year since its commissioning in 2006. In the reporting period specifically covered by this report, investigations and improvements have been made in the following areas:

• A feasibility study for replacing the front end of the GTP (air stripping, thermal oxidation and gas scrubbing) with Moving Bed Biofilm Reactor (MBBR) technology commenced. This biological treatment technology is significantly less energy and capital intensive than the existing plant, and its application has become more feasible as feed concentrations of chlorinated hydrocarbons (CHCs) to the GTP have decreased.

• Seawater membranes have been installed in Array 1 of each Primary RO skid along with both Arrays of Secondary RO skids to address rising salinity of extracted groundwater, and has improved the RO operation better in handling high salinity groundwater.

No full-scale in situ groundwater treatment technology is currently in use at the BIP. However, work continues to investigate and develop techniques and technologies to remediate groundwater in situ, particularly natural attenuation processes. Additional sampling and analysis of groundwater has been undertaken to improve characterisation of the aquifer properties that may affect the fate and transport of contaminants through the aquifer. Work undertaken as a result of the actions arising from the 2017 Strategy Review Workshop has complemented these investigations. The outcomes of this work by Geosyntec were presented in detail in the 2020 Botany Groundwater Strategy Review Workshop held in early March 2020.

No full-scale Dense Non-Aqueous Phase Liquid (DNAPL) removal technologies are currently in use at the BIP. The 2017 Strategy Review Workshop proposed an evaluation of a range of potential enhancements to the current remediation approach to increase DNAPL dissolution and dissolved phase contaminant removal. A review of remediation options for DNAPL source zones was carried out by Golder (2020) and presented to the 2020 Strategy Review Workshop. The remediation options assessment concluded that none of the identified technologies is likely to provide a solution to achieving the primary goal of reducing the cleanup timeframe in a reliable, cost effective and sustainable manner.


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2. INTRODUCTION Under the subheading of Best Practice Technology, Condition 7E of Notice of Clean Up Action (NCUA) No. 1030326 (issued by the NSW EPA under Variation of Notice of Clean-Up Action no. 1052882) stated

Orica must consider best practice technology in the remediation of DNAPL and groundwater containing dissolved phase contaminants, through:

a) continued review of relevant, emerging technologies; and b) ongoing investigation of the practical application and effectiveness of these technologies in

relation to the remediation.

Condition 7F of the NCUA additionally stated

Orica must provide an annual written report to the EPA on the progress of actions required by Condition 7E, with the first report to be provided to the EPA no later than 28-Feb-2006.

In November 2010 the NCUA was replaced with a Voluntary Management Proposal (VMP), which was subsequently updated in August 20151. Under the heading of "Source Area Management" in the VMP Orica made the following commitments:

• Conduct ongoing review of developments in remediation technologies and techniques for treatment of Dense Non-Aqueous Phase Liquid (DNAPL), sorbed mass and dissolved phase CHC contamination, and their practical applicability to the Botany Groundwater Cleanup Project.

• Convene a Strategy Review Workshop every three years to which it will invite a minimum of three international experts in the field. The EPA will be consulted on the selection of the experts prior to the experts being engaged. The review process will involve consideration by the experts of the annual reports prepared by Orica (see bullet point below) and worldwide developments in technology in order to assess whether any current or emerging technologies (including developments in technology and its applications) are likely (individually or in combination) to provide a practicable solution and justify the conduct of field trials of those technologies. Appropriate representatives of the Independent Monitoring Committee (IMC) (as agreed with the Orica Botany Liaison Committee (OBLC) – refer P4) and the EPA will be invited to attend the workshop. The outcome of the Remediation Strategy Review Workshop will be considered in determining whether field trials of one or more remediation technologies should be conducted.

• Provide an annual report to the EPA that would assess the practical application and effectiveness of appropriate technologies in relation to the remediation. Every three years, this would also include a detailed summary of the outcomes of the Strategy Review Workshop (refer R3).

In early December 2005 Orica submitted to the NSW EPA a copy of its report on DNAPL Source Area Remediation Technical Mission, USA and Canada, May 2005 (Orica, 2005). That report constituted the first report issued under NCUA Condition 7F.

The following annual reviews of Orica’s progress against NCUA Condition 7E and the subsequent VMP commitment have been submitted to the NSW EPA:

• The first on 28 February 2007 (Orica, 2007); • The second on 29 February 2008 (Orica, 2008); • The third on 27 February 2009 (Orica, 2009); • The fourth on 26 February 2010 (Orica, 2010);

1 The VMP has since been updated in accordance with the five-yearly review cycle (Approval Notice number 20201704).


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• The fifth on 29 April 2011 (Orica, 2011a). The 2011 report was the first issued under the VMP. The later submission date was agreed with the EPA due to the timing of the Strategy Review Workshop held in late February 2011;

• The sixth on 29 February 2012 (Orica, 2012); • The seventh on 28 February 2013 (Orica, 2013); • The eighth on 30 April 2014 (Orica, 2014a). The later submission date was agreed with the EPA due

to the timing of the Strategy Review Workshop held in February 2014; • The ninth on 27 February 2015 (Orica, 2015); • The tenth on 29 February 2016 (Orica, 2016); • The eleventh on 28 April 2017 (Orica, 2017a); • The twelfth on 28 February 2018 (Orica, 2018); and • The thirteenth on 28 February 2019 (Orica, 2019).

This report constitutes the fourteenth annual report. Being an update report, it does not provide as much background information as provided in the 2007 report (Orica, 2007). Furthermore, brief progress summaries have been included in the biannual Groundwater Cleanup Plan Progress Reports issued under Condition 4BA of the NCUA and the subsequent VMPs.

This report discusses cleanup technologies that are currently being employed in full-scale applications (Section 4), technologies that are currently under review by way of desktop evaluations through to pilot-scale or field trials (Section 5), and ongoing investigation Orica is undertaking into innovative applications of existing technologies and emerging technologies (Section 6).


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3. BOTANY GROUNDWATER STRATEGY REVIEW

3.1 2007, 2011 AND 2014 WORKSHOPS The 2007, 2011 and 2014 Botany Groundwater Strategy Review Workshops have been previously described (Orica, 2008, 2011b and 2014b).

3.2 2017 WORKSHOP A report of the fourth Workshop (Orica, 2017b) was attached to the 2017 annual report (Orica, 2017a). The Executive Summary of the 2017 Workshop report is reproduced below.

On 21 and 22 February 2017 Orica Ltd (Orica) conducted the fourth Botany Groundwater Strategy Review Workshop. This followed the inaugural Workshop held in December 2007 and subsequent Workshops in February 2011 and February 2014. It fulfils a commitment to conduct regular Workshops under a VMP, which the NSW Environment Protection Authority (EPA) approved in November 2010.

The 2017 Workshop was attended by four international groundwater and DNAPL experts (two of whom attended one or two of the previous Workshops), local environmental consultants, representatives of the NSW EPA, a member of the Independent Monitoring Committee (IMC, which provides specialist advice to the Orica Botany Liaison Committee), and Orica environmental specialists and senior managers. It was facilitated by a professional consultant.

Over the two days presentations were made by:

• Orica personnel and the local environmental consultants – to provide a background to the Orica Botany Groundwater Project and an update since the previous Workshop (including a tour of the GTP, BIP and surrounds;

• A representative from the NSW EPA – to provide the Regulator’s perspective; and • The four international experts – to provide their views on the current remediation strategy and

achievements of the Orica Botany Groundwater Project to date, observations from comparable sites overseas, updates on available and emerging cleanup technologies, and views on whether any changes to the strategy would be warranted.

Attendees of the Workshop then participated in a facilitated discussion of recent developments and application of cleanup technologies, and what – if any – could be the best alternative strategies for long-term management and remediation.

The principal outcomes of the 2017 Workshop are:

• Pump and treat remains the most effective way to manage the groundwater contamination and achieve the objective of protection of human health and the environment;

• Notwithstanding the fact that a significant amount of contaminant mass has been removed from the aquifer since 2005, the cleanup will still take a long time;

• There are currently no other cleanup technologies for DNAPL and dissolved phase remediation available that clearly warrant further investigation;

• More characterisation of the contamination source areas is required to better understand their architecture, contaminant mass flux, and rate of depletion; and

• The fate and transport of contamination in the aquifer needs to be further investigated. In particular this requires a deeper understanding of the natural attenuation processes – biological and abiotic – occurring in the aquifer, and whether they can be used to predict potential remediation endpoints for the Botany Groundwater Cleanup Project.


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3.3 WORK ARISING FROM THE 2017 WORKSHOP The 2017 Workshop also suggested a range of actions. Orica is working through these, having prioritised them according to which provide greatest value to progress understanding of the mechanisms and rates of aquifer cleanup, and potential for enhancement of the current approach, in development of a targeted work plan. As new data and information about the aquifer conditions come to hand, the process of implementing the actions is refined.

Some of the suggested actions are refinements or corollaries to the mass loss investigations work that that had been undertaken as a result of actions arising from the 2014 Workshop. The status of these is described below:

• Consider re-evaluating the 2005 and 2015 contaminant mass estimates with the same size of data sets. This work has been undertaken as a larger program of work that includes the evaluation of natural attenuation processes occurring in the aquifer and the attenuative capacity of the receiving environment. The work builds upon the data assessment undertaken by Geosyntec arising from the outcomes and actions of the 2014 Workshop, and includes additional data acquired during the biennial and annual (and supplemental) groundwater monitoring events in September 2017, September 2018 and September 2019, and from soil core samples collected in late 2017 (see below). Geosyntec presented their work to the 2020 Workshop (Sections 3.4 and 5.2).

• When undertaking the soil and groundwater sampling and analysis for the mass loss investigations, collect more data to increase understanding of attenuation mechanisms and aquifer assimilation capacity. As described above, the groundwater monitoring events in September 2017, 2018 and 2019 were supplemented with additional groundwater sampling and analysis from a large number of existing monitoring wells on and in the vicinity of the BIP. This included the extraction and hydraulic monitoring wells in each of the three containment lines. The number of analytes was also expanded to include additional parameters such as anions and cations, metals, dissolved hydrocarbon gases, functional gene quantitative polymerase chain reaction (qPCR – a laboratory technique used to evaluate biodegradation potential or activity in contaminated environments) and fraction of organic carbon, to provide more information about the factors that can influence attenuation and assimilation.

• Use a multi-component analysis of existing and new soil concentration data to assess DNAPL presence. In October 2017, a transect of six nested monitoring wells were installed on the downgradient side of the C1 Source Area (associated with the former Vinyls Plant operations). Sonic drilling was used to maximise recovery of undisturbed soil core samples. Detailed sub-sampling of the soil cores was undertaken to provide specific samples for various types of analysis. Samples were also collected for establishment of column tests by Geosyntec Consultants to assess contaminant sorption and diffusion into and desorption and back-diffusion out of lower permeability aquifer materials, which can affect the fate and transport of both DNAPL and dissolved-phase contaminants. The well transect is being used to collect samples of groundwater flowing from the C1 Source Area on an annual basis. These data will shed light on the mass flux from the source area and allow inferences to be made about the distribution of DNAPL in the source area. Geosyntec presented the outcomes of their data analysis to the 2020 Workshop (Sections 3.4 and 5.2).

• Simulate PCE fate and transport in the numerical model to improve understanding of plume longevity. Previous numerical modelling of the fate and transport of contaminants in the Botany aquifer has been limited to ethylene dichloride (EDC, 1,2-dichloroethane) and carbon tetrachloride (CTC). Perchloroethylene (PCE, tetrachloroethene) is also one of the significant contaminants associated with Orica’s historical operations, and has a lower solubility and higher propensity to sorb to aquifer materials than either EDC or CTC. Therefore, PCE is likely to take the longest to be remediated.


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Numerical modelling of PCE will commence once the numerical model has been further refined to take into account more of the aquifer properties (see below).

• Convert the numerical model to incorporate discrete geological layers. The current numerical model of the Botany aquifer incorporates several layers, for which specific transport parameters have been assigned. However, these layers are all modelled as transmissive layers, and lower-permeability layers have not been specifically included in the model. It was proposed in the 2017 Workshop to increase the vertical discretisation across the model such that geological layers are included in the model. The soil coring mentioned above was undertaken in part to provide detailed information about the geological sequencing of the aquifer and the specific properties of each of the layers. As reported previously, Orica had consulted with groundwater specialists and came to the view that this development of the numerical model is not warranted at this time. The work by Geosyntec has helped to enumerate some of the aquifer properties that could influence contaminant fate and transport, which are heterogeneous and variable. The effort and benefits of using numerical models were discussed in the 2020 Workshop.

• Consider linking/modelling geochemical conditions to variable biodegradation rates. The abovementioned heterogeneity and variability in aquifer properties mean that this exercise is not being considered.

• Investigate development of numerical model(s) to incorporate matrix diffusion. Notwithstanding the comments above about the numerical model, RemChlor-MD is a software tool that is being considered for evaluating the effect of matrix diffusion in discrete locations (as opposed to a three-dimensional model).

The following additional actions will also be considered for inclusion in the work plan:

• Update the 6 Step Capture Zone Analysis to incorporate more up-to-date data and modelled capture targets. Hydrogeological consultants JBS&G have prepared an updated hydraulic assessment report for the Botany Groundwater Cleanup Project using the US EPA’s Six-Step Capture Zone Analysis methodology. The report was submitted by Orica to NSW EPA in September 2018. Once reviewed by NSW EPA, the hydraulic assessment will be incorporated into the hydrogeological assessments routinely undertaken as part of the Surface Water and Groundwater Monitoring Program.

• Using the existing extraction well transects, evaluate the mass flux from the source zones. This is discussed above.

• Subject to assessment of practicability, perform clean water field injection tests in certain plumes to assess the effects of back-diffusion, non-linear/non-equilibrium sorption, and preferential flow on the number of pore volumes needed to lower the concentrations to specified levels. The practicability of such trials was assessed later in 2019. Significant difficulties (e.g., well fouling due to aerobic bacterial growth as a result of the oxygenated water injected) were experienced with similar trials in the Groundwater Injection and Recovery (GIR) System several years ago. It was decided not to proceed with clean water field injection tests.

• Investigate optimisation of the hydraulic containment system. At this point in time Orica has no plans to modify the hydraulic containment system. In the BIP and PCA it is performing sufficiently to achieve the remedial objective of maintaining hydraulic containment of the contaminant plumes. At the SCA containment line the opportunities to optimise performance are significantly constrained by two factors:

o Available land to install wells, which is limited to the median strip along Foreshore Road. There is no available land to extend the containment line to the east; the northern (landward) side of the road is occupied by extensive subsurface infrastructure (pipelines and electricity cables) and Orica is not granted access to Botany Gold Course; and the southern side is too close to the foreshore (see salinity below).


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o Salinity, which is drawn into the extraction wells from the wedge of saline water that extends increasingly landward with depth beneath the foreshore dunes. Salinity adversely affects the groundwater treatment processes at the GTP, especially the RO units. Pumping groundwater too hard, too deep or too close to the foreshore all increase the intake of saline water. Effective hydraulic containment of the contaminant plumes is therefore balanced against saline intrusion.

Furthermore, the day-to-day operation of the hydraulic containment system is being continually optimised on a pump-by-pump basis. In 2018 an operating philosophy was developed for the ‘pump and treat’ system that set out the key performance objectives, prioritised extraction wells in terms of groundwater flux and contaminant concentrations, and identified operating constraints (e.g., drawdown limitations, salinity, etc.), whilst at the same time recognising the dynamic nature of the operations and the environment in which they operate. Operating performance is formally reviewed on a fortnightly basis, and operating setpoints are adjusted accordingly. This adaptive management of the GTP and associated hydraulic containment infrastructure aims to achieve optimal operation at all times.

• Evaluate a range of amendments to the current remediation approach (such as low-level heating, mass extraction wells, biosparging, directed groundwater recirculation, and addition of electron donor, iron sulphide and/or nitrate) to enhance DNAPL dissolution and dissolved phase contaminant removal. A screening level review of the abovementioned remediation technologies has been completed by Golder. Their findings were reported to the 2020 Workshop (see Section 5.3). The remediation options assessment concluded that none of the identified technologies is likely to provide a solution to achieving the primary goal of reducing the cleanup timeframe in a reliable, cost effective and sustainable manner.

3.4 2020 WORKSHOP A report of the fifth Workshop, held on 2 and 3 March 2020, is attached to this report (Attachment 1). The Executive Summary of the 2020 Workshop report (Orica, 2020) is reproduced below.

On 2 and 3 March 2020 Orica Australia Pty Ltd (Orica) conducted the fifth Botany Groundwater Strategy Review Workshop. This followed the inaugural Workshop held in December 2007 and subsequent Workshops in February 2011, February 2014 and February 2017. It fulfils a commitment to conduct regular Workshops under a Voluntary Management Proposal (VMP), which the NSW Environment Protection Authority (EPA) approved in November 2010 (and which was updated in 2015).

The 2020 Workshop was attended by three international groundwater and Dense Non Aqueous Phase Liquid (DNAPL) remediation experts, local and overseas environmental consultants, representatives of the NSW EPA, a member of the Independent Monitoring Committee (IMC, which provides specialist advice to the Community Liaison Committee) and Orica environmental specialists and senior managers.

Over the two days presentations were made by:

• Orica personnel and the environmental consultants – to provide a background to the Orica Botany Groundwater Project and an update since the previous Workshop;

• A representative from the NSW EPA – to provide the Regulator's perspective; and

• The three international experts – to provide their views on the current remediation strategy and achievements of the Orica Botany Groundwater Cleanup (BGC) Project to date, observations from comparable sites overseas, updates on available and emerging cleanup technologies, and views on whether any changes to the strategy would be warranted.

Attendees of the Workshop then participated in a facilitated discussion of recent developments and application of cleanup technologies, and what - if any - could be the best alternative strategies for long-term management and remediation.


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The primary conclusions for the 2020 Workshop are:

• The existing remedial strategy (hydraulic containment effected through large-scale ‘pump and treat’ of groundwater) is appropriate, effective and concluded to remain the most viable option for containment and source reduction through the foreseeable future;

• No recent remediation technology developments, or complementary technologies, are identified at this time that would merit exploration of their applicability to the Orica Botany Groundwater Cleanup Project; and

• The review of source zone remediation options indicates uncertain performance relative to the current situation and high cost.

Notwithstanding the above outcomes, it was also noted that:

• Flushing and mass extraction alone (i.e., without natural attenuation) will not likely achieve remediation end goals in the short or medium term;

• In situ degradation is contributing to faster decay of the plumes and sources; while

• The mechanism of ‘back-diffusion’ and desorption create secondary sources which long-term persistence of plumes and plume response to GTP pumping.

Accordingly, a series of actions were captured in the context of moving towards an enhanced project direction aimed to:

• Optimise GTP performance in key areas of the plumes where practical and cost beneficial;

• Continue to investigate and enumerate existing back-diffusion/desorption and natural attenuative processes with the goal of defining a transition condition that could allow for cessation of operating the GTP;

• Continue to evaluate options to enhance natural attenuative processes to accelerate the rate of cleanup progress; and

• Continue to evaluate timing, metrics and potential effects on the receiving environment of shutting down the ‘pump and treat’ system

while maintaining the ‘pump and treat’ system for the medium to long term.


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4. TECHNOLOGIES CURRENTLY IN USE

4.1 GROUNDWATER TREATMENT PLANT The 2007, 2011 and 2014 Botany Groundwater Strategy Review Workshops have been previously described (Orica, 2008, 2011b and 2014b).

The Orica Botany Groundwater Cleanup is being achieved by groundwater extraction along three containment lines – BIP, SCA and PCA – and ex situ treatment of the water in the GTP.

During 2015 Orica divested its Chemicals business. The Chemicals business is now known as Ixom Operations Pty Ltd (Ixom). At Botany the ChlorAlkali Plant is now owned and operated by Ixom. As part of the transition at Botany, personnel at the GTP transferred to Ixom. Consequently, although the GTP continues to be owned by Orica, it is now operated under contract by Ixom.

The efficacy of the hydraulic containment and treatment system is not discussed herein, but is reported in biannual progress reports prepared by Orica and its environmental consultants.

The GTP has been previously described (Orica, 2007, 2008, 2009, 2010, 2011a, 2012, 2013, 2014a, 2015, 2016, 2017a, 2018 and 2019). A summary of the technologies employed in the GTP is provided in Appendix A1.

4.2 IN SITU GROUNDWATER TREATMENT No full-scale in situ groundwater treatment technologies are currently in use at the BIP.

4.3 DNAPL No full-scale DNAPL removal technologies are currently in use at the BIP.


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5. TECHNOLOGIES UNDER EVALUATION

This section describes research and development efforts that have been undertaken over the last twelve months, as well as historical work that enables understanding of the current work in context.

5.1 GROUNDWATER TREATMENT PLANT Since start-up of the GTP a number of operational and maintenance issues provided challenges to achieving sustained effective groundwater extraction and treatment. A range of trials and improvements were undertaken to address these issues are detailed below. Historical work is also included where necessary to give context to recent and ongoing work. Operationally, the GTP is a mature plant, and the number of enhancements to its operation have decreased year by year since its commissioning with groundwater feed in 2006.

Moving Bed Biofilm Reactor

The front end of the GTP (air stripping, thermal oxidation and gas scrubbing) is a high energy user and utilises an aggressive process (>900oC, hydrochloric acid vapour) which drives increasing energy costs and high sustenance capital requirements. Since 2005 contaminant concentrations in the feed to the GTP have decreased from more than 200 mg/L to less than 30 mg/L. This reduction in feed concentration and developments in biological treatment technology have provided an opportunity to investigate alternatives to treat the extracted groundwater.

Pilot trials were undertaken in 2010 with a Membrane Bioreactor (MBR). At the time the decision was made not to proceed with this particular technology. In 2017 Hydromantis Environmental Software Solutions, Inc was engaged to carry out computer model studies a Moving Bed Biofilm Reactor (MBBR), a variant of the MBR technology. The modelling verified that biological treatment would now be feasible and provided sufficient information to estimate preliminary project costs. The MBBR process comprises a number of agitated atmospheric vessels, containing packing for biofilm support, and a separator to remove sludge. In concept it is similar to an effluent treatment plant for the food industry. It is inherently lower in capital cost than the MBR process because it avoids the use of membrane separation and uses specialised packing for biofilm growth.

Orica engaged Microvi to carry out laboratory tests using a biocatalyst, which has been shown to be infeasible at full scale, but could still be used as a polishing step. Orica engaged Hydroflux to provide a pilot plant that treats up to 1% of the GTP total feed, using the configuration from the Hydromantis simulation, i.e. anaerobic followed by aerobic reactors. The pilot is now in operation.

Reverse Osmosis Membrane Fouling

Fouling of the Reverse Osmosis (RO) membranes has been significantly reduced from initial operation by reduced flux and recovery, chloramine dosing and upstream conversion of multimedia filters to BAFs. However, membrane cleaning and element replacement intervals are still well below general wastewater expectations and iron and Total Organic Carbon (TOC) levels are still above recommended levels for RO membranes.

Trials of alternative anti-scalant formulations to determine whether the iron scaling could be reduced led to adoption of one particular formulation.

An intermittent caustic flush was introduced several years ago to target biofouling. This extends the run time between cleaning events, which reduces chemical use and may extend the life of the membrane elements. The caustic flush program has since been fully automated.

In 2016/17 a biodispersant was trialled on the secondary RO membranes. While this provided only minor benefits, it identified that the foulant was more likely to be organic than biological. Further investigations are ongoing.


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In 2017 overall water recovery was increased from 89% to 91%, yielding an additional 0.13 ML/day of treated water, and reducing reject to sewer by the same volume. To offset increased fouling potential, the configuration of RO skids was changed to provide further reductions in membrane flux. Under the new configuration the GTP runs three primary skids and one secondary skid at a time (compared with two and one, respectively, previously).

Brackish water membranes have been replaced with seawater membranes in three of the four RO stages to address increasing groundwater conductivity (due to salinity from the SCA) and have increased recovery of treated water.

Automation of a clean-in-place (CIP) process for the RO skids is now complete. Previously, CIP of the RO systems was a semi-automatic operation, with significant operator interaction and monitoring duration of each step. Manual adjustment of flows can result in hydraulic shock which reduces membrane life, and variability in CIP operation which is difficult to troubleshoot or improve. The operation also required waste solution to circulate through the cleaned system to pass to waste, which reduces the effectiveness of the clean, and also sacrifices a cartridge filter on each occasion. The waste solution is either acidic or alkaline, and requires neutralization in the GTP effluent system before discharge to the site effluent system.

The automated CIP process includes automated valves for diverting and controlling flows around the RO skids, waste solution neutralization before discharge to the GTP effluent system. The neutralised waste will bypass the cartridge filters and the clean RO membranes.

A pilot media filter is being installed to assess alternate filter media to improve RO feed quality.

5.2 IN SITU GROUNDWATER TREATMENT Outside the GTP, work has been done to investigate and develop techniques and technologies to remediate groundwater in situ. The work carried out to develop enrichment cultures that could be used augment the naturally-occurring biological processes in groundwater is summarised in Appendix A2.

As discussed in Section 3.3, Geosyntec Consultants were engaged to evaluate the contaminant mass removal processes occurring at Botany, including natural attenuation, and how and when those processes could be enhanced. Their findings (Geosyntec, 2020) were presented to the 2020 Strategy Review Workshop. Geosyntec reported that, from the investigations completed to date, it is apparent that the bulk mass attenuation behaviour at the Botany Site is a complex balance of competing contaminant mass attenuation mechanisms, and that that balance is evolving over time. The presence of multiple DNAPL sources provide persistent sources of mass that are dissolving into groundwater. The rate of DNAPL dissolution will vary over time as a result of changing composition as more soluble components preferentially dissolve over less soluble components. Biological degradation processes will both enhance dissolution of DNAPL in some areas and be inhibited by elevated dissolved-phase concentrations in others.

Peat and clay layers provided mechanisms for early-time sinks (during expansion of the C1 plume) for contaminant mass through sorption and diffusion, but more recently, are acting as persistent secondary sources of mass as contaminants are released to groundwater through desorption and back-diffusion, which are much slower and are leading to tailing of plume concentrations and mass reductions over time.

Multiple lines of evidence (e.g., isotopic enrichment downgradient of sources, presence of dechlorinating bacteria, presence of elevated daughter product concentrations, formation of daughter products concurrent with disappearance of parent products in treatability studies) point to the occurrence of biologically-mediated degradation in many areas of the site (31% of locations sampled are likely to have higher activity, up to 80% of locations sampled appeared to have at least some degradation activity). Other lines of evidence (e.g., low diversity and bacteria counts, limited daughter product formation, lack of dechlorinating bacteria) also point to inhibition of microbial activity, related to elevated EDC concentrations and chloroform (a known inhibitor of microbial activity), in some areas of the Site (~20% of locations sampled). Because of the microbial inhibition caused by high EDC concentrations, flushing may be the primary mechanism for dissolution of EDC DNAPL in the C1 source.

Various indicators suggest that CTC will be the least persistent of the three primary DNAPL components, and that PCE is likely to persist the longest. However, once the chloroform concentrations reduce below


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inhibitory levels, biological attenuation may be enhanced, leading to faster attenuation of the total mass over time.

5.3 DNAPL No DNAPL cleanup technologies have been evaluated in the year for the Botany Groundwater Cleanup Project. A summary of DNAPL removal technologies that Orica has evaluated is provided in Appendix A3.

As discussed in Section 3.3, a transect of six nested monitoring wells was installed downgradient of the C1 Source Area in late 2017. As part of these works, soil samples from the drilling cores were collected for analysis. The results of the soil and groundwater analyses are being assessed to provide information about the structure of the DNAPL source, the mass flux from it, and the effects that the aquifer properties have on the fate and transport of the dissolved-phase contaminants. This information should improve understanding of the expected longevity of the source area and possibly what – if any – steps could be taken to accelerate its depletion. Geosyntec presented their findings (Geosyntec, 2020) to the 2020 Strategy Review Workshop.

An additional action arising from the 2017 Strategy Review Workshop (Section 3.3) proposed an evaluation of a range of potential enhancements to the current remediation approach to increase DNAPL dissolution and dissolved phase contaminant removal. These include low-level heating of the source zone (e.g., to around 40oC), mass extraction wells to remove contaminant mass directly from the source area, biosparging (primarily to enhance destruction of contaminants that may be aerobically biodegraded), directed groundwater recirculation, and addition of electron donor, iron sulphide and/or nitrate (to stimulate biodegradation) directly into the source area. This evaluation was carried out by Golder (2020) and presented to the 2020 Strategy Review Workshop. The remediation options assessment concluded that none of the identified technologies is likely to provide a solution to achieving the primary goal of reducing the cleanup timeframe in a reliable, cost effective and sustainable manner. It recommended that ongoing evaluation of potential technologies or approaches should be undertaken from time to time as part of future Strategy Review Workshops. Such evaluations should be limited to technologies and approaches that can reduce the mass in the southern sources zones which are ultimately the key driver for the overall project remediation timeframe.


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6. ONGOING INVESTIGATION Orica continues to evaluate other groundwater and source area remediation technologies. The principal means of doing this include

• Review of technical journals and articles; • Subscription to email-based technical discussion groups (e.g., regarding bioremediation and

environmental health); • Networking and consultation with local and international specialists; and • Attendance at industry seminars and conferences.


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7. REFERENCES Geosyntec (2020). Letter report. Summary of Contaminant Attenuation Behaviour and Plume Persistence Drivers at the Orica Botany Facility, Matraville, NSW; Geosyntec Project: GSY0035. Geosyntec Consultants Pty Ltd. 26 February 2020.

Golder (2020). Orica Botany Groundwater Project – DNAPL Source Zones - Review of Remediation Options, report no. 19135339-R-001-Rev 0. Golder Associates Pty Ltd. February 2020.

Orica (2005). DNAPL Source Area Remediation Technical Mission, USA and Canada, May 2005, report no. EN1591.61.PR011, Rev. 2. Orica Australia Pty Ltd. November 2005.

Orica (2007). DNAPL and Groundwater Remediation Technology Annual Review No. 1, report no. EN1591.61.PR017, Rev. 0. Orica Australia Pty Ltd. February 2007.




Orica (2011a). DNAPL and Groundwater Remediation Technology Annual Review No. 5, report no. EN1591.61.PR041, Rev. 0. Orica Australia Pty Ltd. April 2011.

Orica (2011b). 2011 Botany Groundwater Strategy Review Workshop Summary Report, report no. EN1591.61.PR042, Rev. 0. Orica Australia Pty Ltd. April 2011.










Orica (2019). DNAPL and Groundwater Remediation Technology Annual Review No. 13, EN1591.61.PR080, Rev. 0. Orica Australia Pty Ltd. February 2019.


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Orica (2020). 2020 Botany Groundwater Strategy Review Workshop Summary Report, report no. EN1591.61.PR085, Rev. 0. Orica Australia Pty Ltd. April 2020.


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APPENDICES


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A1 GROUNDWATER TREATMENT PLANT

Commissioning of the Groundwater Treatment Plant (GTP) commenced in late 2005 and groundwater was first introduced into the plant in January 2006. The principal unit processes employed in the plant at the time were:

• Air stripping for removal of volatile organic compounds (VOCs); • Thermal oxidation of VOCs, waste heat recovery and gas scrubbing; • Actiflo® based iron and aluminium removal; • Sand/anthracite filtration for suspended solids removal; • Activated carbon digestion/adsorption for non-volatile organics removal; • Sand/anthracite filtration for suspended solids removal; • Cartridge filtration for finer solids removal; and • Reverse osmosis (RO) for dissolved salts rejection.

It has been reported previously (Orica, 2008, 2009, 2010, 2011a, 2012, 2013, 2014a, 2015, 2016 and2017a) that trials had been conducted and a number of modifications to improve operating conditions and plant configurations had been undertaken since 2007. Further investigations and improvements in this reporting period are described in Section 5.1.

In 2007 monochloramine (NH2Cl) dosing into RO feedwater was implemented to mitigate biological fouling in cartridge filters and RO membranes. High concentrations of monochloramine proved effective at limiting biological fouling. However, as the monochloramine was found to pass into the RO permeate (i.e., the treated water produced by the GTP), a dechloramination system was installed to remove monochloramine from the treated water before discharge to the environment. The ammonia generated by dechloramination was the subject of a Pollution Reduction Program. The Program was successfully completed, and removed from the Environment Protection Licence.

In 2008 five of the activated carbon filters were converted to Biological Aerated Filters (BAFs) to remove readily biodegradable organics and thereby reduce the potential for biological fouling, reduce the need for monochloramine dosing, and improve product water quality. It has been previously reported (Orica, 2008, 2009 and 2010) that the BAFs allowed a significant reduction in monochloramine addition, and in conjunction with selective replacement of worn RO membranes, had allowed the plant to achieve very low Total Organic Carbon (TOC) concentrations in the treated water. Since 2016 expanded clay media has been installed in all vessels. The improved biological process has resulted in partial nitrification (ammonia converted to nitrate). While this has negligible impact on water quality for users, it affects the ability to discharge excess treated water to the environment if the need arises.

As reported in previous annual reports (Orica, 2008 and 2009), two modes of fouling have been observed within the air stripping units: inorganic (iron precipitation) and biological, which are best controlled with low and higher groundwater pH, respectively. In 2009 trials were undertaken to evaluate the effect of chlorine dioxide (a strong oxidising agent and a potent disinfection agent used in water treatment) on reducing biofouling in the air strippers. After a successful trial involving one air stripper Orica initiated a project for a full-scale dosing system with provision for bulk storage of chemical reactants. By late 2010 the project delivered the desired outcome of minimal biofouling and run times between cleaning events of 4 to 6 months rather than 4 to 6 weeks. Further improvements in reducing air stripper fouling, including optimising chlorine dioxide dosing have been described in previous annual reports (Orica, 2012, 2013 and 2014).

An added benefit of chlorine dioxide is that the product is formed in an excess of hydrochloric acid. When dosed to the air strippers the pH falls from 4.9 to less than pH 4. The lower pH effectively minimises iron precipitation, as evident from prolonged run times between cleans.

As reported previously (Orica, 2013 and 2014), a downside to chlorine dioxide dosing has been carryover from the strippers and accelerated corrosion of the downstream off-gas piping. This has been addressed by dosing the stripper off-gas with weak ammonia solution, and a phased replacement of the piping with duplex


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stainless steel for improved corrosion resistance. The replacement program was completed during the annual maintenance shutdown in March 2017.

In 2008 Orica developed a concept of Temporary Aquifer Storage and Recovery (TASR) – renamed Groundwater Injection and Recovery (GIR) in early 2009 – to ensure consistent hydraulic containment even during protracted GTP shutdowns. Using the GIR System enables Orica to reinject extracted groundwater into the aquifer upgradient of the Botany Industrial Park (BIP) containment line if the GTP is unable to treat groundwater for an extended period of time (i.e., several months), and then recapture the groundwater when it reaches the BIP containment line. The GIR System is not designed to provide backup for hydraulic containment on all containment lines; it is designed to provide a system to enable continued extraction of groundwater from critical locations (primarily in the Secondary Containment Area (SCA)) in the event of a prolonged outage of the GTP. Development and trials of the system are described in previous reports (Orica, 2010, 2011, 2012 and 2014a). A full-scale trial was conducted in October 2013 during a scheduled GTP maintenance shutdown, which confirmed that the GIR system could be used at design rates (400 m3/day) for a protracted period (ten days) without loss of injection rates due to well fouling, etc. and achievement of relatively flat or reversed hydraulic gradients at the targeted hydraulic containment wells in the eastern SCA.

It is noted that the effectiveness of the GIR system will be influenced by external variable factors including pumping performance prior to the GTP shutdown and recharge. Therefore, the most appropriate pumping and injection regime should be refined on a case-by-case basis prior to full-scale operation of the GIR system.

It had been previously reported (Orica, 2009) that cartridge filter life had been unacceptably short – one to two weeks, rather than three months – due to residual iron and the susceptibility of the filter structure to flow restrictions by even small amounts of biofilms, and that investigations and trials had been implemented through 2009-2011 to improve run times between filter changes (Orica, 2010, 2011 and 2012).

Since 2012 cartridge filter run times of three months have been achieved. The primary reason is thought to be effective removal of Total Organic Carbon (TOC) in the BAFs and GAC filters such that the residual TOC in the RO feed water is at historical lows. Encouraged by the longer run times, in 2014 Orica began trialling the use of 10 μm filters in place of 40 μm cartridge filters. This was unsustainable, and the plant reverted to 40 μm filters. In more recent times, though, improvements to upstream iron removal (Orica, 2016) have allowed this trial to be resumed. 20 μm filters have been proven. 10 μm filters were evaluated in 2017. On the basis of those trials, it was determined that 20 μm filters are preferred.

Investigations of reduced pump performance in the SCA in 2009 revealed that increased pressure in the Foreshore Road and Southlands pipelines was due to a combination of inorganic fouling (iron from carbon steel pipes and silt in the groundwater) and biological fouling (due to acetate and sulphate nutrients in the groundwater). In mid-August 2009 the pipelines in Southlands were cleaned by forcing a plug through the pipelines with high pressure water, which is called “pigging”. This resulted in significant improvements in line pressures, and consequently improved groundwater extraction at the SCA. Several campaigns of “pigging” have been carried out since. Pigging of the Primary Containment Area (PCA) and SCA pipelines is now regarded as a routine activity.

Concurrently, a project was implemented to replace the Southlands pipelines with SAF2205 duplex stainless steel. This material offers superior corrosion protection and decreases the potential for biofilm attachment (and microbially-induced corrosion beneath the biofilm) compared to the original carbon steel pipelines. The new pipelines have provisions that better accommodate pigging activities.

A piping replacement programme has been initiated to replace the BIP pipelines with 316 stainless steel, to address similar corrosion issues as those noted above. Replacement of all riser pipes (from pumps to the header) and most of the header have been completed, with ongoing work planned over the next few years.

In mid-2010, a backpressure control valve was installed on the BIP containment line. By providing a constant back pressure the BIP pumps operate more consistently and reduce the likelihood of maintenance. In 2013 automated backpressure valves were also installed on the PCA and SCA containment lines. Containment line extraction and GTP performance have now evolved to the stage where more predictable, routine operation has been achieved. This is reflected by the lack of significant operating issues and major plant modification works since mid-2010.


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Iron and biomass removed from the stripped water in the Actiflo and filtration steps are collected in a buffer tank, and fed to a gravity thickener to concentrate the solids fraction. The original plant design included return of the water fraction to the plant, but the higher volumes of wastewater required to address biofouling issues overload the thickener, and wastewater is discharged with trade waste.

Starting with a workshop test rig in 2012, a trial was initiated to investigate the use of progressive cavity pumps to replace multistage centrifugal pumps (which create high shear conditions that are conducive to proliferation of microbes). Field trials commenced in 2013 with replacement of one of the BIP extraction wells. A further four BIP extraction wells were subsequently fitted with identical pumps to evaluate long-term maintenance requirements.

In 2014 a membrane ultrafiltration (UF) unit was installed to remove iron and biomass from the wastewater from the Actiflo and filtration steps, thus allowing recovery of the water back into the plant. The UF unit recovers approximately 75% of the wastewater stream.

In 2015 hypochlorite dosing was switched from the backwash water to the feed stream to reduce the backwash and cleaning frequencies. In 2016, finer (55 μm) pre-filter discs were successfully trialled to reduce the loading on the membranes. To offset the increased loading on the pre-filters, two additional units were installed. This has reduced membrane cleaning frequency from three-weekly to greater than three-monthly, and has provided increased utilisation and hence increased recovery of the wastewater.

In 2016 and 2017 sacrificial anodes were installed in the SCA pipework to provide cathodic (corrosion) protection against the saline water being drawn into the SCA extraction wells.

Since the GTP’s construction and commissioning, maintenance and monitoring activities in the SCA had been challenged by the lack of permanent access to the below-ground infrastructure in the median strip of Foreshore Road. Following several years of negotiation with Roads and Maritime Services, Orica finally gained approval to install permanent protective barriers along the entire length of the SCA containment line. Work on the permanent barriers’ installation was completed in mid-2017, which enabled an extensive inspection and maintenance program to be executed at the SCA containment line in the latter part of 2017.


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A2 BIOREMEDIATION OF GROUNDWATER

Previous annual reports (Orica, 2007, 2008, 2009, 2010, 2011a, 2012, 2013, 2014a and 2015) described developmental work by UNSW intended to assist with groundwater treatment in the future. Ongoing work since 2006 has focused on developing enrichment cultures derived from microbial consortia recovered from the bioremediation field trials conducted in Orica Southlands in 2004-2005. The enrichment cultures are intended to enable augmentation of full-scale bioremediation should it be employed as part of the Orica Botany Groundwater Cleanup Project. Three different cultures have been developed:

• For degrading high concentrations (around 1,000 mg/L) of EDC at low pH (4.5 to 5); • For degrading chloroform at concentrations that are typically inhibitory to biodegradation (i.e., up to

50 mg/L chloroform at pH 7 has been biodegraded at a rate of 3.5 mg/L/day); and • For fully degrading tetrachloroethene (PCE, also known as perchloroethylene).

Bioaugmentation Trials at Southlands

Field trials to augment the biological degradation of contaminants in the shallow aquifer took place in the northern end of Block 2 of Southlands in 2010. Conclusions from the trial (UNSW, 2010) were that:

1. Dechlorination occurs at slow rates when nutrients and pH are modified from the initial conditions; 2. Addition of the EDC degrading culture grown in vitro by UNSW significantly increased the

dechlorination rate; 3. The EDC degrading culture colonised the aquifer matrix in the vicinity of WG176I during Pilot Trial 2;

and 4. The inoculated area around WG176I released EDC degrading bacteria into the groundwater.

In March 2011 a second in vitro microcosm study was conducted – eight months after the first – using groundwater collected from groundwater wells in the initial bioaugmentation trial area to study long-term viability of biomass established during that first trial. There was strong evidence that the culture had colonised – and persisted in – the inoculated well. Species identification of the microbial community indicated that a strain of Desulfitobacterium (most closely related to Desulfitobacterium metallireducens) was the main bacterium degrading the EDC.

Bioaugmentation Trials at Penrhyn Estuary Foreshore

In 2012 Orica entered a collaborative research agreement with UNSW and a number of other parties to study in situ bioremediation solutions for Australia’s organochlorine contaminated aquifers. The study has included injection of the UNSW cultures into a number of aquifers in Australia. Work has been undertaken to evaluate the suitability of the chloroform-degrading culture for injection near Penrhyn Estuary, where the chloroform concentrations are in the order of 15 mg/L. This level of chloroform is inhibitory to some organohalide respiring bacteria (ORB). The chloroform-degrading culture, which has been isolated and genetically characterised (Dehalobacter restrictus UNSWDHB), degraded up to 300 mg/L chloroform in laboratory microcosms, including in saline conditions similar to those in Penrhyn Estuary.

Permission was granted by relevant landholders in late 2015 to conduct a bioremediation field trial in the vicinity of Penrhyn Estuary. The groundwater at the site is suboptimal for bioremediation because the pH is acidic (pH 5). The pH was successfully neutralised with 1000 L of sodium bicarbonate solution, and it remained in a biologically favourable range for around 20 days. This time window is theoretically long enough for ORB to remove organochlorines at the site. 100 L of the chloroform degrading culture was introduced to the subsurface along with electron donors (emulsified vegetable oil and propylene glycol) in mid-February 2016. However, bioaugmentation with UNSWDHB did not result in chloroform attenuation. Laboratory microcosm experiments showed that in situ electron donor production (hydrogen) was not a limiting factor. Stepwise addition of MWF17D groundwater to strain UNSWDHB (in its optimal growth medium) revealed complete inhibition of chloroform respiration at 50% (v/v) groundwater to medium. Furthermore, microcosm tests revealed that sulfate reducing bacteria (SRB) might produce an ORB inhibiting substance. Further work would be required to understand the inhibition of ORB by SRB and to develop a


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mitigation strategy that enables enhanced ORB activity in the vicinity of Penrhyn Estuary. Additional investigations have also pointed to inhibition due to elevated groundwater salinity in the trial location.

A report of the bioaugmentation field trials (UNSW, 2017) was submitted to the EPA.


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A3 DNAPL CLEANUP TECHNOLOGIES

In the past Orica has evaluated a number of Dense Non-Aqueous Phase Liquid (DNAPL) removal technologies.

Direct Recovery

Investigations into the use of direct recovery of DNAPL at the Botany Industrial Park (BIP) have been previously described (Orica, 2011).

It was concluded that this technique of DNAPL removal was unlikely to have further application at this location. Pooled DNAPL has not been found in any other locations on the BIP.

Hydraulic Displacement

Also known as water flooding, this approach consists of the injection of water into a source zone to gradually dissolve the DNAPL, with the resultant dissolved phase contaminants being intercepted and extracted at a downgradient hydraulic containment line. The presence of the hydraulic containment lines and Groundwater Treatment Plant (GTP) on the BIP makes this treatment option more feasible than it might otherwise have been.

This is not a remediation treatment that is considered to have significant application for the Botany Groundwater Cleanup Project. No further work has been done in relation to hydraulic displacement in this reporting period.

In Situ Chemical Oxidation (ISCO)

It was previously reported (Orica, 2009) that the injection of solubilised chemical oxidant – in this case activated sodium persulphate – into the source zone to chemically destroy the DNAPL in situ had been evaluated in laboratory bench-scale tests, and also that the Groundwater Cleanup Project strategy review in late 2007 had concluded that ISCO with base catalysed persulfate is not a practicable option for full-scale DNAPL source zone treatment, with regard to cost, efficacy of the remedy and impacts on the aquifer. As a result, no further work has been done to evaluate ISCO for full-scale DNAPL source zone treatment.

Direct Thermal Treatment (DTT)

As for ISCO, the 2007 Groundwater Cleanup Project strategy review process concluded that although DTT is a feasible technology, it would not be able to completely treat all source zones due to significant access constraints. The benefits of attempting DNAPL source depletion at Botany using DTT are unquantifiable and likely to be marginal in terms of the long-term cleanup of the aquifer (Orica, 2009).

Nano-Scale Zero Valent Iron (nZVI)

Development of a process for manufacturing nZVI has been previously reported (Orica, 2007, 2008 and 2009). The DNAPL Technical Mission Report (Orica, 2005) identified nZVI as being potentially applicable to DNAPL source area removal in the context of admixture with clay (bentonite or kaolinite) and augering into DNAPL source areas, and emulsified zero valent iron (EZVI, created by mixing together food grade surfactant, vegetable oil and nano-scale or micro-scale iron). Neither of these technologies is currently being considered for application in the BIP source areas.

Electrokinetics

As previously reported (Orica, 2008, 2009 and 2010), Orica had funded research at the University of Western Australia in the field of innovative use of electrokinetics (EK) for the remediation of NAPL source zones in heterogeneous and low permeability soil. EK relates to the application of an electrical current between electrodes installed in the aquifer profile to create an electrical gradient that can be used to facilitate rapid and uniform migration of reductants or oxidants (e.g., nZVI, potassium permanganate, sodium


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persulphate, etc.) through targeted zones – particularly in low permeability geological formations – totally independently of hydraulic conductivity. The principal conclusions were reported previously (Orica, 2010).

As Orica has no immediate plans for using ISCO at Botany, Orica is not participating in any further research of EK at this time.


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ATTACHMENT 1

2020 STRATEGY REVIEW WORKSHOP

REPORT

dnapl and groundwater remediation technology annual review

Documents