Browsing by Autor "Cecilia Lalander"

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Biochar filters as an on-farm treatment to reduce pathogens when irrigating with wastewater-polluted sources
(Elsevier BV, 2019) Luis Fernando Perez-Mercado; Cecilia Lalander; Abraham Joel; Jakob Ottoson; Sahar Dalahmeh; Björn Vinnerås
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.
Erratum to “Willingness among food consumers to recycle human urine as crop fertiliser: Evidence from a multinational survey” [Sci. Total Environ. 765 (2021), 144438]
(Elsevier BV, 2021) Prithvi Simha; Melissa A. Barton; Luis Fernando Perez-Mercado; Jennifer McConville; Cecilia Lalander; Maria Elisa Magri; Shanta Dutta; Humayun Kabir; Albert Selvakumar; Xiaoqin Zhou
Managing microbial risks in informal wastewater-irrigated agriculture through irrigation water substitution
(Elsevier BV, 2022) Luis Fernando Perez-Mercado; Cecilia Lalander; Abraham Joel; Jakob Ottoson; Mercedes Iriarte; Björn Vinnerås
On-farm measures can be used in multi-barrier schemes to manage microbial risks from consumption of wastewater-irrigated vegetables, especially where informality of the practice determines minimal external support for farmers. Evidence indicates that cessation of irrigation greatly reduces microbial contamination on leafy vegetables, but at the expense of produce quality. Replacing wastewater with higher-quality irrigation water during the last days of cultivation is an alternative to cessation of irrigation that does not compromise produce quality. This study evaluated the effect of wastewater substitution under on-farm conditions on different indicators of microbial contamination of lettuce. Lettuce was cultivated in experimental plots and irrigated with three water sources: spring water, water from a wastewater-polluted river and effluent from a primary wastewater treatment plant, but with the river water replaced by spring water in half the plots about two weeks before harvest. The experiment was repeated four times in different seasons. Irrigation water samples collected during cultivation and lettuce samples collected at harvest were analysed for helminth eggs, Escherichia coli and coliphages. Variables characterizing the irrigation practices and environmental conditions were recorded. There were no significant differences in helminth egg or E. coli concentrations on lettuce (medians ranged from −0.7 to −0.1 log10 eggs g−1 and 0.6–1.4 log10 cfu g−1, respectively) between any of the treatments involving wastewater irrigation; no statistical analysis was possible for coliphages because concentrations on lettuce were mostly at or below the detection limit (94% of samples). Variables associated with temperature and soil explained helminth egg and E. coli concentrations on lettuce, while number of days of irrigation with spring water (representing wastewater substitution) was significant only for E. coli. It was concluded that the experimental conditions were suboptimal for successful implementation of wastewater substitution for on-farm microbial risk management, but key variables for successful implementation were identified.
Pathogens in crop production systems irrigated with low-quality water in Bolivia
(UWA Publishing, 2018) Luis Fernando Perez-Mercado; Cecilia Lalander; Abraham Joel; Jakob Ottoson; Mercedes Iriarte; Carla Oporto; Björn Vinnerås
In dry areas, the need for irrigation to ensure agricultural production determines the use of all available water sources. However, the water sources used for irrigation are often contaminated by untreated or minimally treated wastewater. Microbial risks from reusing wastewater for vegetable irrigation can be addressed by installing environmental barriers that pathogens must cross to reach humans in the reuse system. Knowledge of pathogen flows inside the system and pathogen removal potential is the first step towards devising a risk management strategy. This study assessed microbe prevalence in farming systems in the Bolivian highlands that use wastewater-polluted sources for irrigation of lettuce. Samples of soil, lettuce and different water sources used in the farming systems were taken during one crop season and concentrations of coliphages, Escherichia coli and helminth eggs were measured. The results showed high spread of these microorganisms throughout the whole system. There was a significant correlation between microbial quality of water and of the harvested produce for several microorganisms. The microbial prevalence in protected shallow wells was found to be significantly lower than in other water sources. These findings can help formulate feasible risk management strategies in contexts where conventional technologies for microbial removal are not possible.
Willingness among food consumers to recycle human urine as crop fertiliser: Evidence from a multinational survey
(Elsevier BV, 2020) Prithvi Simha; Melissa A. Barton; Luis Fernando Perez-Mercado; Jennifer McConville; Cecilia Lalander; Maria Elisa Magri; Shanta Dutta; Humayun Kabir; Albert Selvakumar; Xiaoqin Zhou
Source-separating sanitation systems offer the possibility of recycling nutrients present in wastewater as crop fertilisers. Thereby, they can reduce agriculture's impacts on global sources, sinks, and cycles for nitrogen and phosphorous, as well as their associated environmental costs. However, it has been broadly assumed that people would be reluctant to perform the new sanitation behaviours that are necessary for implementing such systems in practice. Yet, few studies have tried to systematically gather evidence in support of this assumption. To address this gap, we surveyed 3763 people at 20 universities in 16 countries using a standardised questionnaire. We identified and systematically assessed cross-cultural and country-level explanatory factors that were strongly associated with people's willingness to consume food grown using human urine as fertiliser. Overall, 68% of the respondents favoured recycling human urine, 59% stated a willingness to eat urine-fertilised food, and only 11% believed that urine posed health risks that could not be mitigated by treatment. Most people did not expect to pay less for urine-fertilised food, but only 15% were willing to pay a price premium. Consumer perceptions were found to differ greatly by country and the strongest predictive factors for acceptance overall were cognitive factors (perceptions of risks and benefits) and social norms. Increasing awareness and building trust among consumers about the effectiveness of new sanitation systems via cognitive and normative messaging can help increase acceptance. Based on our findings, we believe that in many countries, acceptance by food consumers will not be the major social barrier to closing the loop on human urine. That a potential market exists for urine-fertilised food, however, needs to be communicated to other stakeholders in the sanitation service chain.