Location: Agricultural Water Efficiency and Salinity Research Unit
Project Number: 2036-12320-011-004-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 15, 2022
End Date: Mar 15, 2024
Objective:
The objectives of the cooperators project are as follows:
(i) Treat a variety of real and/or synthetic wastewaters using specifically designed wastewater polishing systems, comparing influent and effluent concentrations of the constituent antibiotics to quantify system removal efficacy.
(ii) Use influent and effluent solutions to irrigate different soil types and quantify the dissemination of antibiotics and antimicrobial resistance (AMR) determinants into the gut of earthworms from each soil/effluent combination.
(iii) Quantify the risk mitigation potential offered by the polishing systems in terms of AMR dissemination in the wastewater–soil–earthworm continuum.
Approach:
Our wastewater polishing system is customizable in terms of its constituent materials, which are selected based on the characteristics of the wastewater to be treated. Owing to their high adsorption potential for organic compounds, biochars are highly cost-effective materials for use in this system. We have therefore compiled a database of the antibiotic adsorption properties and physical/chemical characteristics of various engineered biochars prepared in-house using different feedstocks, pyrolysis temperatures, and post-pyrolysis modifications. From this database, the most suitable materials (most adsorptive) can be selected for the specific antibiotic compounds present in a given wastewater. As such, various (4–6) real and synthetic wastewaters with differing antibiotic concentrations will be selected and a laboratory-scale (50-cm height × 12-cm diameter) biochar-based polishing system will be specifically designed and constructed for each. The wastewaters will be treated by upwards pumping through the polishing system, with influent and effluent water samples collected for analysis.
Influent and effluent solution antibiotic concentrations will be measured using highly sensitive LC–MS/MS techniques to determine the removal efficacy of the designed systems for the range of antibiotics present in the various wastewaters.
This approach is novel in that the polishing systems will have been designed using adsorptive materials specific to the antibiotics present in the wastewaters (i.e., the systems are custom built based on a prior understanding of (i) the antibiotics initially present in the wastewater and (ii) the best materials for adsorbing those antibiotics); therefore, a high level of antibiotic removal is expected.
We hypothesize that the high effectiveness of the polishing systems will limit the potential for anitmicrobial resistance (AMR) development and dissemination in soil systems. To test this, the influent and effluent solutions will be used in microcosm experiments wherein earthworms are exposed to soils wetted using the wastewaters collected before and after polishing treatment. Earthworms represent an ideal sentinel organism for assessing soil contamination as they exist in direct contact with soil and soil solution, tend to migrate over only short distances, and are widely distributed in soils around the globe. The protocol used will broadly follow OECD Guideline 317. We have used this approach previously to study the effectiveness of biochars in mitigating the transfer of antibiotics from soil to earthworms and are currently assessing AMR development in those systems. In the proposed work, the various influent and effluent wastewaters will be used to adjust and maintain the moisture contents of three differing soils (e.g., differing textures and organic matter contents), which will then be used for earthworm (Eisenia fetida) exposure tests. Temporal changes in AMR development and dissemination within and between the various soil/wastewater combinations and the earthworms will be quantified by periodic destructive sampling.
