Biochar and zero-valent iron sand filtration simultaneously remove contaminants of emerging concern and Escherichia coli from wastewater effluent

Authors: ZHU, LINYAN - University Of Maryland; CHATTOPADHAY, SUHANA - University Of Maryland; AKANBI, OLUWASEGUN - University Of Delaware; LOBO, STEVE - University Of Delaware; PANTHI, SURAJ - University Of Maryland; MALAYIL, LEENA - University Of Maryland; CRADDOCK, HILARY - University Of Maryland; ALLARD, SARAH - University Of California, San Diego; Sharma, Manan; MONGODIN, EMMANUEL - University Of Maryland School Of Medicine; CHIU, PEI - University Of Delaware; SAPKOTA, AMIR - University Of Maryland; SAPKOTA, AMY - University Of Maryland

Submitted to: Biochar
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2023
Publication Date: 7/19/2023
Citation: Zhu, L., Chattopadhay, S., Akanbi, O.E., Lobo, S., Panthi, S., Malayil, L., Craddock, H., Allard, S.M., Sharma, M., Mongodin, E.F., Chiu, P.C., Sapkota, A., Sapkota, A.R. 2023. Biochar and zero-valent iron sand filtration simultaneously remove contaminants of emerging concern and Escherichia coli from wastewater effluent. Biochar . 5:41. https://doi.org/10.1007/s42773-023-00240-y.
DOI: https://doi.org/10.1007/s42773-023-00240-y

Interpretive Summary: Sustainable approaches to irrigation water is an agricultural priority. Advanced treated wastewater – wastewater that has been treated to remove harmful contaminants – can be a sustainable source of irrigation water for fresh fruits and vegetables. In work described here the objective was to use two technologies which had been applied to remove contaminants from soils and apply them to wastewater. Biochar (BC) and zero-valent iron (ZVI) were used in in sand filters containing nano-silver to determine if they could reduce chemical and bacterial contaminants from the water. Filters which contained sand + BC, sand + BC and ZVI, sand + BC and ZVI and nano-silver all reduced chemical contaminants and Escherichia coli, an indicator of fecal contamination. The filtration options identified here provide technologies that can reduce chemical and bacterial contaminants from recycled wastewater, providing a reliable source of irrigation water for farmers. This work benefits farmers by providing another cost-effective filtration option to improve the quality of recycled wastewater to be used for irrigation.

Technical Abstract: Advanced treated municipal wastewater is an important alternative water source for agricultural irrigation. However, the possible persistence of chemical and microbiological contaminants in these waters raise potential safety concerns with regard to reusing treated wastewater for food crop irrigation. Two low-cost and environmental-friendly filter media, biochar (BC) and zero-valent iron (ZVI), have attracted great interest in terms of treating reused water. Here, we evaluated the efficacy of BC-, nanosilver-amended biochar- (Ag-BC) and ZVI-sand filters, in reducing contaminants of emerging concern (CECs), Escherichia coli and total bacterial diversity from wastewater effluent. Six experiments were conducted with control quartz sand and sand columns containing BC, Ag-BC, ZVI, BC with ZVI, or Ag-BC with ZVI. After filtration, Ag-BC, ZVI, BC with ZVI and Ag-BC with ZVI demonstrated more than 90% (> 1 log) removal of E. coli from wastewater samples, while BC, Ag-BC, BC with ZVI and Ag-BC with ZVI also demonstrated efficient removal of select CECs. Lower bacterial diversity also was observed after filtration; however, differences were marginally significant. In addition, significantly (p<0.05) higher bacterial diversity was observed in wastewater samples collected during warmer versus colder months. Leaching of silver ions occurred from Ag-BC columns; however, this was prevented through the addition of ZVI. In conclusion, our data suggest that the BC with ZVI and Ag-BC with ZVI sand filters, which demonstrated almost 100% removal of both CECs and E. coli without silver ion release, may be effective, low-cost options for decentralized treatment of reused wastewater.