Biochar filters as an on-farm treatment to reduce pathogens when irrigating with wastewater-polluted sources

Luis Fernando Perez-Mercado; Cecilia Lalander; Abraham Joel; Jakob Ottoson; Sahar Dalahmeh; Björn Vinnerås

doi:10.1016/j.jenvman.2019.109295

Biochar filters as an on-farm treatment to reduce pathogens when irrigating with wastewater-polluted sources

J Environ Manage. 2019 Oct 15:248:109295. doi: 10.1016/j.jenvman.2019.109295. Epub 2019 Aug 1.

Authors

Luis Fernando Perez-Mercado¹, Cecilia Lalander², Abraham Joel³, Jakob Ottoson⁴, Sahar Dalahmeh², Björn Vinnerås²

Affiliations

¹ Department of Energy and Technology, Swedish University of Agricultural Sciences, Box 7032, 75007 Uppsala, Sweden; Center for Water and Environmental Sanitation (Centro de Aguas y Saneamiento Ambiental, CASA), Universidad Mayor de San Simon, Calle Sucre y Parque Latorre, Cochabamba, Bolivia. Electronic address: fernando.perez@slu.se.
² Department of Energy and Technology, Swedish University of Agricultural Sciences, Box 7032, 75007 Uppsala, Sweden.
³ Department of Soil and Environment, Swedish University of Agricultural Sciences, Box 7014, 75007 Uppsala, Sweden.
⁴ Department of Risk Benefit Assessment, National Food Agency, 75126 Uppsala, Sweden.

PMID: 31376612
DOI: 10.1016/j.jenvman.2019.109295

Abstract

Microbial contamination of vegetables due to irrigation with wastewater-polluted streams is a common problem around most cities in developing countries because wastewater is an available source of water and nutrients but wastewater treatment is often inadequate. On-farm treatment of polluted water is a feasible option to manage microbial risks in a multi-barrier approach. Current evidence indicates good suitability of biochar filters for microbe removal from wastewater using the hydraulic loading rate (HLR) designed for sand filters, but their suitability has not been tested under on-farm conditions. This study evaluated the combined effect of several variables on removal of microbial indicators from diluted wastewater by biochar filtration on-farm and the correlations between removal efficiency and HLR. Columns of biochar with three different effective particle diameters (d₁₀) were fed with diluted wastewater at 1x, 6x, and 12x the design HLR and two levels of water salinity (electrical conductivity, EC). Influent and effluent samples were collected from the columns and analyzed for bacteriophages (ɸX174 and MS2), Escherichia coli, Enterococcus spp., and Saccharomyces cerevisiae. Microbe removal decreased with increasing HLR, from 2 to 4 to 1 log₁₀ for bacteria and from 2 to 0.8 log₁₀ for viruses, while S. cerevisiae removal was unaffected. Effective particle diameter (d₁₀) was the main variable explaining microbe removal at 6x and 12x, while EC had no effect. Correlation analysis showed removal of 2 log₁₀ bacteria and 1 log₁₀ virus at 3x HLR. Thus biochar filters on-farm would not remove significant amounts of bacteria and viruses. However, the design HLR was found to be conservative. These results, and some technical and management considerations identified, can assist in the development of a scientific method for designing biochar filters for on-farm and conventional wastewater treatment.

Keywords: Biochar filtration; Nutrient recycling; On-farm treatment; Pathogens; Wastewater irrigation.

MeSH terms

Charcoal
Farms
Filtration
Saccharomyces cerevisiae
Waste Disposal, Fluid*
Wastewater*

Substances

Waste Water
biochar
Charcoal