Stormwater is an important contributor of contaminants of concern (COCs) such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), Cu, and Zn to receiving water bodies. Although a fraction of these COCs bind to stormwater particulate matter, which can be removed through filtration by traditional media in stormwater control measures, the dissolved portion of COCs requires special attention, such as engineered treatment measures and media. Biochar is a highly porous sorbent produced from a variety of organic materials. It is gaining increasing attention as a stormwater geomedium due to its high potential for adsorption and simultaneously relatively low cost compared to activated carbon. However, biochar is not a uniform product and selection of an appropriate biochar for removal of specific contaminants can be a complex process. Biochars are synthesized from various feed stocks and using different manufacturing methods (i.e., pyrolysis temperature and surface treatment) that can significantly affect biochar properties. These properties can affect the capacity of biochar to remove stormwater contaminants. The local availability of biochar products is another important consideration for the application of biochar in stormwater bioretention cells. To address these issues, we developed a decision framework to select readily available biochars based on criteria obtained from in depth literature survey to identify promising candidates for future laboratory and field testing. As an example, plant-derived biochars contain less nutrient and potential contaminants (such as heavy metals and micropollutants) than sludge and manure based biochars. This can affect the biochar capacity to remove or release nutrients in stormwater. Therefore, the sludge/manure based biochars are not suitable for stormwater treatment. Pyrolysis temperature is considered as the most significant parameter affecting the adsorption of contaminants. Increase in pyrolysis temperature favors ash content, microporous structure, fixed carbon content, pH, and surface area. Generally, biochar produced at low pyrolysis temperature (&lt;400°C) is suitable for the adsorption of inorganic contaminants whereas, relatively high pyrolysis temperature (&gt;700°C) enhances the adsorption of organic contaminants. Information about these basic characteristics have been applied to select suitable biochars for further laboratory experiments.

Decision framework for biochar selection to remove PCBs, PAHs, Cu and Zn from stormwater

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.