Browsing by Autor "Abraham Joel"

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A CSM-Based Procedure for Identifying Segments of Agricultural Drainage Ditches to Be Prioritized in Maintenance Work
(2023) Daniel Bernardo Aviles Ribera; Ingrid Wesström; Abraham Joel
Highlights Maintenance of agricultural ditches is important to secure food production. To reduce costs, ditch segments in most need of maintenance should be prioritized. CSM measurements can help prioritize maintenance of agricultural ditch segments. Abstract. Productive agricultural land is vital for food production. To help secure the productivity of drained agricultural soils, diches need to be intermittently maintained. Maintenance work is costly, however, so ditch segments in most need of maintenance should be prioritized. Here, we present a procedure for identifying drainage ditch segments likely to need maintenance based on susceptibility to soil erosion by water flowing in the ditch, evaluated using a cohesive strength meter (CSM). An important part of the procedure is to relate the pressure of the CSM jets to pressures acting on the soil. The relationship between CSM jet pressure and pressures at the soil surface was established based on measurements made with a pressure sensor plate and was applied to obtain several values for pressure at the surface, which were used in turn to estimate critical shear stress for erosion. The results showed that the CSM-based method was able to identify differences in critical shear stress for erosion for different field soils. This information can be useful in identifying drainage ditch segments that should be prioritized for maintenance work. Keywords: Drainage data acquisition, Drainage maintenance, Drainage performance evaluation, Soil erosion.
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.
Effect of liming products on soil detachment resistance, measured with a cohesive strength meter
(Taylor & Francis, 2019) Daniel Avilés; Kerstin Berglund; Ingrid Wesström; Abraham Joel
Good soil structure is important for achieving high productivity of agricultural land and also affects the ability of soil to withstand erosive forces. Given the importance of soil structure, efforts are commonly made to improve it, usually by application of amendments of different kinds (e.g. lime, biochar, compost, manure etc.). However, little is known about the effect of these amendments on the soil resistance to detachment. This study assessed the resistance to detachment of soil cores treated with different liming products, using a cohesive strength meter (CSM) which measures the rate of soil detachment under the action of water jets at different pressures. The amount of soil removed by the water jets was taken as an indirect measure of soil resistance to detachment, under the assumption that more resistant soils will lose less material than more susceptible soils at a given water jet pressure. The results showed that all soil amendments studied reduced detachment of particles under the action of water jets compared with unamended soil (control).
Effect of Vegetation Removal on Soil Erosion and Bank Stability in Agricultural Drainage Ditches
(Multidisciplinary Digital Publishing Institute, 2020) Daniel Avilés; Ingrid Wesström; Abraham Joel
Maintenance of agricultural drainage ditches can be difficult to optimize if farmers have no guidelines on where to target their maintenance efforts. A main concern is whether ditch banks will experience soil erosion or mass movement (failure). In order to help identify sites that are more likely to experience soil erosion and/or mass movement, soil susceptibility to detachment was assessed in this study using a cohesive strength meter (CSM) and measurements of shear strength in unsaturated direct shear tests. The results showed that soil roots play an important role in stabilizing ditch banks against mass movement and in reducing the rate of soil detachment. A positive stabilizing effect was detected by CSM and confirmed by shear strength measurements. The conclusion is that native vegetation should be maintained on ditch banks, instead of being removed during maintenance work as is currently the case.
Impact of Land Use Change on Non-Point Source Pollution in a Semi-Arid Catchment under Rapid Urbanisation in Bolivia
(Multidisciplinary Digital Publishing Institute, 2021) Benjamin Gossweiler; Ingrid Wesström; Ingmar Messing; Mauricio Villazón; Abraham Joel
Changes in pollution pressure exerted on the Rocha River in Bolivia from diffuse sources were assessed using potential non-point pollution indexes (PNPI) for 1997 and 2017. PNPI is a simple, low-effort, time- and resource-saving method suitable for data-scarce regions, as it works at catchment level with commonly available geographical data. Land use type (obtained by Landsat imagery classification), runoff (determined by runoff coefficient characterisation) and distance to river network (calculated at perpendicular distance) were each transformed into corresponding indicators to determine their relative importance in generating pollution. Weighted sum, a multi-criteria analysis tool in the GIS environment, was used to combine indicators with weighting values. Different weighting values were assigned to each of the indicators resulting in a set of six equations. The results showed that higher PNPI values corresponded to human settlements with high population density, higher runoff values and shorter distance to river network, while lower PNPI values corresponded to semi-natural land use type, lower runoff coefficient and longer distances to river. PNPI values were positively correlated with measured nitrate and phosphate concentrations at six sub-catchment outlets. The correlation was statistical significant for phosphate in 2017. Maps were produced to identify priority source areas that are more likely to generate pollution, which is important information for future management.
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.
Spatial and Temporal Variations in Water Quality and Land Use in a Semi-Arid Catchment in Bolivia
(Multidisciplinary Digital Publishing Institute, 2019) Benjamin Gossweiler; Ingrid Wesström; Ingmar Messing; Ana Romero; Abraham Joel
Increasing pressures caused by human activities pose a major threat to water availability and quality worldwide. Water resources have been declining in many catchments during recent decades. This study investigated patterns of river water quality status in a peri-urban/rural catchment in Bolivia in relation to land use during a 26 year period. Satellite images were used to determine changes in land use. To assess water quality, data in the dry season from former studies (1991–2014), complemented with newly collected data (2017), were analysed using the National Sanitation Foundation-Water Quality Index method and the Implicit Pollution Index method. The highest rates of relative increase in land use area were observed for forest, urban, and peri-urban areas, whereas relative decreases were observed for water infiltration zones, bare soil, shrubland, and grassland areas. The water quality indices revealed clear water quality deterioration over time, and from catchment headwaters to outlet. Statistical analyses revealed a significant relationship between decreasing water quality and urban expansion. These results demonstrate the need for an effective control programme, preferably based on water quality index approaches as in the present study and including continuous monitoring of runoff water, mitigation of pollution, and water quality restoration, in order to achieve proper water management and quality.