Realistic and field scale applications of biochar for water remediation: A literature review

Biochar has received increasing attention in recent years as a potentially cost-competitive adsorbent for removing various contaminants from surface water and groundwater. However, most published studies have been conducted in the laboratory on a bench scale. Laboratory conditions do not necessarily reflect the complex, heterogeneous, and dynamic field conditions of actual contaminated surface water and groundwater environments. There is a lack of comprehensive literature review regarding the performance of biochar for contaminant removal, especially under realistic field conditions and at field scale. Here, we evaluated 31 studies on realistic applications of biochar for water remediation by searching the keywords: pilot scale, field scale, and mesocosm scale combined with biochar and water remediation. Biochar was found to be incorporated into a variety of water remediation technologies for treating both inorganic and organic contaminants, such as nutrients, heavy metals, pesticides, and pharmaceuticals in polluted waters and wastewaters. Also, biochar showed the potential to be effective on a field scale or in realistic remediation technologies, although it is not always as effective as other sorbents, such as activated carbon (AC). This is partially because AC has better physicochemical characteristics such as higher surface area and more micropores. Effectiveness for contaminant removal varies according to the targeted contaminants, the type and dosage of biochar used, and the treatment technology incorporating biochar. Finally, knowledge gaps and future research areas are identified. For example, more field scale studies are needed to test the effectiveness of biochar as an adsorbent under realistic conditions to pinpoint specific characteristics suitable for target contaminants. Physicochemical characteristics of the biochar can also change over time during the treatment process due to weathering, which may negatively affect the treatment performance. The effects of scaling up production on biochar quality should therefore also be further investigated, as physicochemical characteristics can be affected by varying the synthesis conditions. Regeneration and disposal of spent biochar is another active research area to determine the overall treatment costs.