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Treatment of contaminated land using a biochar/media mixture

Periodic Reporting for period 1 - TOOLBOX (Treatment of contaminated land using a biochar/media mixture)

Reporting period: 2017-07-10 to 2019-07-09

Waste disposal and treatment is a major source of contamination of soils, surface and groundwater, and accounts for 35% of the 1.1 million contaminated sites in Europe. Leaching of the organic solvent trichloroethylene (TCE) into groundwater has been identified as a primary issue with unlined landfills, affecting up to 70% of leachates tested. Human exposure to TCE affects the central nervous, immune and endocrine systems. Mainly used as a metal degreaser and dry-cleaning reagent, TCE is difficult to treat; current treatment methods, such as anaerobic digestion or air stripping, are ineffective and/or expensive.
This project investigated the use of waste materials, including biochar produced from waste material, for the treatment of TCE contaminated water, as a novel, low-cost alternative to current treatment options.

To address this, this proposal used an interdisciplinary approach to address three Research Objectives (RO):
RO1 - Identify the appropriate amount/type of biochar, or combinations of other amendments, for TCE adsorption.
RO2 - Optimise the technology for use of biochar to treat TCE contaminated leachate plumes and surface water.
RO3 - Quantify the impact of biochar addition on the physical, biochemical and biological properties and processes in soil, including nutrient content and bioavailability, and indigenous microbiota.

The experimental results were exciting, demonstrating the potential for biochar use for remediation of TCE-contaminated landfill leachate plumes.
The project was carried out in six work packages (WPs).

WP1 addressed Management, Training and Transfer of Knowledge. The primary role of this WP was to ensure that a high quality standard was maintained throughout the project, to provide the experienced researcher with excellent training and career development opportunities to enable reintegration into the EU research community, and to maximise the benefit to the experienced researcher and host by exploring all current & future opportunities. Significant portions of this WP involved writing and co-writing funding applications, developing and enhancing a collaborator network across Europe, and reestablishing the experienced researchers career in the EU.

WP2 involved the dissemination, exploitation, communication and public engagement aspects of the project, which are detailed in a separate paragraph below.

WP3 was an experimental work package, using batch scale analysis to determine adsorption capacities of a range of materials for TCE. This research identified several biochars that should high capacity for TCE adsorption, and used mathematical modelling to determine maximum adsorption capacity, and also optimal equilibrium time. These data was the topic of an invited conference presentation.

WP4 was a column scale experimental work package, using two biochars identified in WP3 for a sub-surface flow study. The study compared raw landfill leachate influent with autoclaved landfill leachate influent, and showed that the columns were capable of supporting biologically mediated TCE dechlorination. Final analysis of the microbial community supported by the biochar is completed.

WP5 was adapted in response to to the data generated by WP3, and involved a competitive adsorption batch study, investigating the impact of mixed waste streams. In particular, this study investigated the impact of the presence of TCE in the adsorption of lead, cadmium and zinc by biochar.

WP6 involved a holistic evaluation of the methodology, in comparison to existing treatment technologies.

To progress this research, Dr Siggins and Prof Healy have recently been awarded a collaborative Environmental Protection Agency Research Grant (PEST-MAN) to work with industry and goverment agencies in this research area.

Dissemmination and communication activities:
The experienced researcher availed of multiple opportunities to engage the wider community in her research.

She delivered workshops on the topic of her research to over 280 school students at both Engineering and Science outreach events. These included 10 workshops for primary school students as part of the Galway Science and Technology Festival, and two workshops for primary and secondary school students as part of Engineers Week Ireland. These workshops involved discussions of the fate of the ingredients of household products once they enter the environment, and activities around understanding product ingredient lists, environment risk of ingredients, and making safer alternatives and better choices.

She presented her MSCA research at the Ryan Institute Centre for One Health Conference at NUI Galway in September 2019. (Siggins, A., Abram, F. and Healy, M. Use of Pyrolysed waste to treat environmental trichloroethylene contamination). This was a multi-disciplinary research centre, and had attendees from a broad range of research areas. She developed new contacts with relevant industry (Environmental Consultancy) with ongoing discussions about future collaboration opportunites.

The first manuscript from this research is under a third round review with the Journal of Hazardous Materials for their upcoming special issue “Emerging applications of biochar: A way forward to attenuate environmental pollution and contaminant toxicity”.
The experimental work and data analysis are complete for WP4 and a manuscript is currently in advanced draft stage for likely submission to Water Research.
Currently, technologies such as permeable reactive barriers use fill materials such as zero valent iron or granular activated carbon. These materials are typically produced purposely for this use, and have a high associated cost. In addition, zero valent iron may have negative environmental impacts associated with changes in pH downstream from the barrier.

This study demonstrated that pyrolysed waste materials have high capacity for TCE adsorption. Indeed, several biochars showed a higher TCE adsorption capacity than granular activated carbon. Prior to this study, research knowledge on the interaction of TCE with biochar was extremely limited, and didn't consider impacts of biochar on microbial community structure and function. These fields were characterised as medium-to-low knowledge, respectively, with medium-to-high priority for future research, respectively, and inclusion of these research questions in this proposal was a novel approach to the use of biochar for TCE remediation. Our study demonstrated that the microbial community in environmental systems interacted with biochar. Our column study identified biofilm growth on and within the biochar matrix, and this is currently being characterised to determine which species were associated with biochar colonisation. Biological dechlorination of TCE was apparent when raw landfill leachate was a component of the influent, but not when the landfill leachate was autoclaved, indicating that the microorganisms capable of at least partial dechlorination of TCE were present in the landfill leachate, and were functioning in the columns.

TCE is a priority pollutant, with potential to cause significant human health impacts by negatively affecting the central nervous, immune and endocrine systems. This research has identified a lower cost, novel adaptation of a treatment technology that would reduce the risk of TCE contaminated landfill leachate from reaching groundwater and drinking water supplies.