Microbial Risk Assessment for Agricultural Production Cycle of On-site Resource Oriented Sanitation Systems: A Case of Burkina Faso

On-site resource oriented sanitation system is one of expectable concepts to address a protection of water resources in developing countries due to low installation cost and resource recovery from human excretes. The present study investigated fates of indicators and pathogens originated from greywater and compost in soil to assess microbial risks when the greywater and compost are reused. Compost and greywater obtained from pilots in Burkina Faso were amended in experimental field with lettuce cultivation and the fate of pathogens in the soil was measured. The results suggested that (i) bacterial fates in compost reuse were fitted to log normal linier and those in greywater were maintained in field soil (ii) the bacterial end-off kinetics in Soudano-Sahelian climate were more rapid than that of reference values. (iii) The reduction of E. coli and Salmonella in the present condition was significantly different but that of Salmonella and Enterococci had no difference. (iv) Effect of contaminated soil on annual risk probability was lower than direct handling of greywater and compost but not negligible. The present assessment also suggested that presented current model were required further technical improvement from the view of the biological risks

A Theoretical Analysis of the Geography of Schistosomiasis in Burkina Faso Highlights the Roles of Human Mobility and Water Resources Development in Disease Transmission

We study the geography of schistosomiasis across Burkina Faso by means of a spatially explicit model of water-based disease dynamics. The model quantitatively addresses the geographic stratification of disease burden in a novel framework by explicitly accounting for drivers and controls of the disease, including spatial information on the distributions of population and infrastructure, jointly with a general description of human mobility and climatic/ecological drivers. Spatial patterns of disease are analysed by the extraction and the mapping of suitable eigenvectors of the Jacobian matrix subsuming the stability of the disease-free equilibrium. The relevance of the work lies in the novel mapping of disease burden, a byproduct of the parametrization induced by regional upscaling, by model-guided field validations and in the predictive scenarios allowed by exploiting the range of possible parameters and processes. Human mobility is found to be a primary control at regional scales both for pathogen invasion success and the overall distribution of disease burden. The effects of water resources development highlighted by systematic reviews are accounted for by the average distances of human settlements from water bodies that are habitats for the parasite's intermediate host. Our results confirm the empirical findings about the role of water resources development on disease spread into regions previously nearly disease-free also by inspection of empirical prevalence patterns. We conclude that while the model still needs refinements based on field and epidemiological evidence, the proposed framework provides a powerful tool for large-scale public health planning and schistosomiasis management

Recyclage des eaux usées en irrigation:potentiel fertilisant, risques sanitaires et impacts sur la qualité des sols

The present study takes place in Ouagadougou (Burkina Faso), a typical Sub-Saharan city where water shortage and food crisis necessitate wastewater reuse in urban agriculture. Different issues linked to this practice were studied in two components separated in two experimental sites. The first part treats about agronomic and sanitary aspects and take place in the 2iE (International Institute for Water and Environmental Engineering) experimental site of Ouagadougou. The second component was emphasised on industrial effluents impacts on irrigated soil quality and takes place in Kossodo, an industrial suburb of Ouagadougou. The 2iE site is supply with treated wastewater from domestic origin. The effluent was used to realise the following objectives: (1) managed wastewater fertilizers to fit the plant needs; (2) assess different crops sanitary quality and the effectiveness of methods used for this assessment. Three treatments were tested: (i) irrigation with the treated wastewater (ii) irrigation with the treated wastewater and fertilizers management, adjusted to plant needs and (iii) conventional treatment i.e. fresh water irrigation and total doses of commercial fertilizers. Each treatment was tested on three different crops: lettuce (Lactuca sativa), carrot (Daucus carota) and eggplant (Solanum melongena). The first objective was achieved by comparing crops yields (on basis of wet and dry matter) obtained with the different treatments. The three crops, irrigated with only wastewater, led to yield reduction between the first and the second year. At the contrary, the adjusted treatment showed higher yield for lettuce, with comparable values to conventional treatment yield. However, the effects on carrot and eggplant did not demonstrate better results; indicating that further investigations must be completed for crops with longer growing periods. Most likely, the fertilizers management should better correspond to the crop period demand. The sanitary assessment (second objective) was performed by measuring the heavy metals concentration (Cd, Cu, Pb, Ni, Cr) and the faecal levels (faecal coliform, Escherichia coli and four pathogens among which Salmonella typhimirium and Vibrio cholerae). Chromocult Coliform Agar medium was used for simultaneous detection of faecal coliform and Escherichia coli whereas pathogens were analysed by Polymerase Chain Reaction (PCR). From methodological point of view, faecal coliform were not sufficiently discriminatory in the case of this study since they were naturally present in the soil as well as in the fresh water. At the contrary, Escherichia coli were better linked to wastewater contamination. However, some "false positive" results were detected meaning that each presumptive colony of Escherichia coli must be confirmed. Nevertheless, microbial quality assessment indicated no Escherichia coli on edible parts of carrot or eggplant irrigated with wastewater. Carrots were expected to have the poorest microbiological quality. Therefore carrot root bacterial quality must be further examined. Results on eggplant are not surprising as these vegetables are somewhat far from the ground and they receive significant solar radiation which acts like a disinfectant. Lettuce from wastewater treatment plots, however, exhibited presence of Escherichia coli, meaning that lettuce is likely to be contaminated by pathogens. However, no pathogens were detected neither on crops irrigated with fresh water nor on those irrigated with wastewater. Heavy metals results demonstrated that the crop's consumption did not involve higher risk for consumers when the vegetables were irrigated with domestic wastewater, in comparison with fresh water irrigation. Kossodo treatment plant receives mainly industrial wastewater, which are characterized by high levels of sodium and bicarbonates. The treated wastewater supplies a market garden in which space has been defined for the study of this second component. The main objective was to assess the impact of treated wastewater on soil quality during two years of irrigation. Early in the second year, the presence of black spots, suspected to be black alkali (dissolved organic matter), appeared at the surface of plots irrigated with treated wastewater. These indications led to put forward the hypothesis of alkalinisation/sodisation on soil receiving wastewater. The methodological approach used was based on in situ measurement of infiltration at the end of the second year of irrigation, supplemented by shrinkage curve modelling and chemical analysis. The hypothesis of an alkalinization/sodisation and dissolved organic matter (black alkali) presence in plots irrigated with treated wastewater were validated by the chemical analysis. Shrinkage curve modelling showed a reduction of the structural porosity on wastewater irrigated plots. The reduction was more marked in the subsurface horizons than in surface, which is probably caused by dispersed clay leached in depth. These structural changes were confirmed in situ by an infiltration capacity greatly reduced on plots irrigated with treated wastewater, compared to control plots (irrigated with fresh water) where the infiltration capacity is higher and comparable to that of non-irrigated soil. The study confirmed the fertilizing value of domestic wastewater while emphasizing the need to concentrate future investigations on sustainable effluent/fertilizers management. The sanitary assessment with different crops regarding their respective distances to the soil was very useful since it showed the strong interaction of soil microbial community on the crop microbial quality. It also revealed the importance to determine a faecal indicator for the crop, specifically related to wastewater contamination. Soil quality assessment reiterated the necessity to verify wastewater quality before its reuse in agriculture. In the case of this study, the sodic and alkaline properties of the industrial effluents make them definitively unfit for irrigation

Impacts of irrigation with industrial treated wastewater on soil properties

Wastewater reuse in agriculture is a widespread practice in developing countries, especially in urban areas where water shortage and poverty encourage people to use that marginal resource. Raw or treated wastewaters are used by farmers, but even treated wastewaters frequently do not meet WHO and FAO standards for irrigation water. Such practices may lead to health hazards, relatively well documented in the literature and to environmental damages. Adverse environmental impacts such as soil degradation and groundwater contamination are frequently associated with the use of wastewater from industrial sources. Previous studies have demonstrated that wastewater irrigation may decrease soil hydraulic conductivity and infiltration rate. Nevertheless, the effects on soil structural and chemical behaviors have been little studied so far and need further investigations. The impacts of irrigation with alkaline and sodic industrial wastewater previously treated in microphyte ponds on soil physical and chemical properties were studied downstream the sewage treatment plant of Kossodo in Ouagadougou, on plots cropped with eggplants. Plots irrigated with fresh water and non cropped, non irrigated plots were used as controls. Different soil properties were characterized: pore volumes determined by using shrinkage analysis, pH and electrical conductivity of water extracts, and major soluble and exchangeable cations (Ca, Mg, K, and Na). Organic matter characterization was performed by means of three dimensional fluorescence spectra analysis to determine its origin and evolution on irrigated soils. Plots irrigated with wastewater showed important structural damages, especially in the subsurface horizon where the soil pore network collapsed dramatically, resulting in a compact impermeable layer. Fluorescence spectra revealed that the organic matter contained in the wastewater was largely dissolved due to a sharp soil pH increase, resulting in black alkali formation at the surface; the soil became sodic, with an exchange complex dominated by sodium, whereas plots irrigated with fresh water kept properties comparable to that of non irrigated plots. Such a rapid soil sodication was seldom reported so far. The study emphasizes the need to carefully examine irrigation water quality and particularly calcite residual alkalinity and suggests that shrinkage analysis could be used to monitor the physical changes of soil properties upon sodication. Inadequate wastewater quality is likely to cause deep and irreversible damages to irrigated soils

Impacts of irrigation with industrial treated wastewater on soil properties

Wastewater reuse in agriculture is a widespread practice in developing countries, especially in urban areas where water shortage and poverty encourage people to use that marginal resource. Raw or treated wastewaters are used by farmers, but even treated wastewaters frequently do not meet WHO and FAO standards for irrigation water. Such practices may lead to health hazards, relatively well documented in the literature and to environmental damages. Adverse environmental impacts such as soil degradation and groundwater contamination are frequently associated with the use of wastewater from industrial sources. Previous studies have demonstrated that wastewater irrigation may decrease soil hydraulic conductivity and infiltration rate. Nevertheless, the effects on soil structural and chemical behaviors have been little studied so far and need further investigations. The impacts of irrigation with alkaline and sodic industrial wastewater previously treated in microphyte ponds on soil physical and chemical properties were studied downstream the sewage treatment plant of Kossodo in Ouagadougou, on plots cropped with eggplants. Plots irrigated with fresh water and non cropped, non irrigated plots were used as controls. Different soil properties were characterized: pore volumes determined by using shrinkage analysis, pH and electrical conductivity of water extracts, and major soluble and exchangeable cations (Ca, Mg, K, and Na). Organic matter characterization was performed by means of three dimensional fluorescence spectra analysis to determine its origin and evolution on irrigated soils. Plots irrigated with wastewater showed important structural damages, especially in the subsurface horizon where the soil pore network collapsed dramatically, resulting in a compact impermeable layer. Fluorescence spectra revealed that the organic matter contained in the wastewater was largely dissolved due to a sharp soil pH increase, resulting in black alkali formation at the surface: the soil became sodic, with an exchange complex dominated by sodium, whereas plots irrigated with fresh water kept properties comparable to that of non irrigated plots. Such a rapid soil sodication was seldom reported so far. The study emphasizes the need to carefully examine irrigation water quality and particularly calcite residual alkalinity and suggests that shrinkage analysis could be used to monitor the physical changes of soil properties upon sodication. Inadequate wastewater quality is likely to cause deep and irreversible damages to irrigated soils. (C) 2013 Elsevier B.V. All rights reserved

Greywater Characteristics In Rural Areas of the Sahelian Region for Reuse Purposes: The Case of Burkina Faso

The characteristics of greywater generated in two rural areas (“Barkoundba” and “Kologoudiessé”) located in the Sahelian region in Burkina Faso were assessed through observations in selected concessions, sample collection and laboratory analyses. The study aimed at characterizing the qualitative and quantitative characteristics of greywater in order to evaluate its reuse potential for gardening in rural areas. The results showed that greywater is generated from 3 to 4 main sources with average daily productions of 8 ± 1 L•capita‑1•d‑1 in “Barkoundba” and 13 ± 3 L•capita‑1•d‑1 in Kologoudiessé”. Despite these low rates, the average quantity of greywater production varied from 67 to 344 L•concession‑1•d‑1 during the dry season. This greywater can be collected to provide additional water for irrigation in home gardens of size varying from 10 to 43 m2. Shower activity is the major contributor of greywater with up to 56% in “Barkoundba” and 70% in “Kologoudiessé”. The qualitative assessment of the greywater streams showed that every source is contaminated with chemicals and microbial pollutants at levels not suitable for direct reuse in agriculture. Therefore, it is recommended to treat the greywater before its use for irrigation purposes. Based on World Health Organization (WHO) reuse guidelines, the treatment system should be able to remove bacteria by more than 2 log units and 4 log units if restricted and unrestricted irrigation are considered respectively. Since shower greywater is directly poured onto the ground, the treatment unit should be adapted to the shower room to allow shower greywater collection, in order to collect the required quantities for gardening. A slanted soil treatment system could be investigated. Hazards of a direct reuse are discussed for soils, plants and human health on the basis of the various qualitative parameters. However, an accurate risk assessment would require further investigations with the evaluation of the interannual variability of greywater quality.Les caractéristiques des eaux grises produites dans deux localités rurales (« Barkoundba » et « Kologoudiessé ») situées en zone sahélienne au Burkina Faso ont été évaluées à travers des observations dans des concessions sélectionnées, des échantillonnages et des analyses de laboratoire. L'étude visait à déterminer les caractéristiques qualitatives et quantitatives des eaux grises afin d'évaluer leur potentiel de réutilisation en agriculture en milieu rural. Les résultats ont montré que les eaux grises sont produites à partir de trois à quatre sources principales avec des productions moyennes de 8 ± 1 L•habitant‑1•j‑1 à « Barkoundba » et 13 ± 3 L•habitant‑1•j‑1 à « Kologoudiessé ». Malgré ces faibles taux, la quantité moyenne d’eaux grises produites a varié entre 67 et 344 L•concession‑1•j‑1 pendant la saison sèche. Ces eaux grises peuvent être collectées pour l'irrigation de jardins familiaux de taille variant entre 10 et 43 m2. La douche produit plus d’eaux grises avec des contributions de 56 % à « Barkoundba » et 70 % à « Kologoudiessé ». L'évaluation qualitative a montré que toutes les eaux sont contaminées par des polluants chimiques et microbiens à des niveaux ne permettant pas leur réutilisation directe en agriculture. C’est pourquoi il est recommandé de les traiter avant leur réutilisation. Sur la base des directives de l'Organisation Mondiale de la Santé (OMS), le système de traitement doit pouvoir éliminer plus de deux à quatre unités logarithmiques de bactéries selon que l’irrigation est restrictive ou non restrictive, respectivement. Comme les eaux grises des douches sont directement déversées sur le sol, l'unité de traitement devrait être reliée à la douche pour permettre la collecte et récupérer les quantités requises pour le jardinage. Un système de traitement « Slanted Soil » pourrait être envisagé. Les dangers d’une réutilisation directe pour les sols, les plantes et la santé humaine ont été discutés sur la base des multiples paramètres qualitatifs mesurés. Cependant, des mesures complémentaires, et notamment l’évaluation de la variabilité interannuelle de la qualité des eaux grises, seraient nécessaires dans la perspective d’une étude de risques

4th International Dry Toilet Conference Inactivation mechanisms of pathogenic bacteria in several matrixes during composting process in composting toilet

Abstract: This study aimed to compare the inactivation rate and the mechanisms of pathogenic bacteria in three matrixe