Qualité et essais de traitement des eaux en milieu périurbain : cas des eaux de forage des cantons Légbassito et Vakpossito (Togo)

L’objectif de ce travail est de contribuer à la potabilisation des eaux de forages dans les zones périurbaines de la ville de Lomé (Togo). L’évaluation de la qualité physicochimique et bactériologique a été réalisée sur 30 échantillons en utilisant les méthodes normalisées (AFNOR). Les essais d’élimination des nitrates par le charbon actif et de désinfection par le chlore pour la détermination du break-point ont été réalisés sur les eaux de plus forte teneur en nitrate dans chaque site étudié. Les résultats des enquêtes ont montré que les forages réalisés dans les zones périurbaines sont à 95% manuels. Les forages sont souvent implantés sans orientation technique à cause de la facilité qu’offre la formation sédimentaire. La profondeur varie de 25 à 35 m. Les résultats ont montré que les forages sont réalisés dans un environnement insalubre, dépourvu d’infrastructure d’assainissement (plus de 80%). Plus de 70% des échantillons d’eaux analysés ont des pH acide (< 6,5). Quatre-vingt-dix pour cent des échantillons d’eaux analysés ont des goûts salés, 87% deséchantillons ne sont pas conFormes à aux valeurs guides de l’OMS. La concentration des nitrates (élément toxique) et le fer (élément indésirable) sont très élevés, respectivement dans les proportions de 13% et 6% des eaux de forages analysées. La totalité des échantillons analysés est contaminée par des germes indicateurs d’origine fécale. Les échantillons d’eaux analysés ne sont pas conformes aux normes de potabilité des eaux de consommation. La contamination serait due prioritairement aux techniques de « foration » et à la maintenance périodique de la pompe. Les essais de traitement par le charbon actif et le chlore se sont révélés efficaces et constitueraient une des mesures à prendre en compte dans le traitement des eaux. Mots clés : Eau de forage, contamination, traitement, charbon actif, chlore.   English title: Quality and testing of water treatment in peri-urban areas: case of borehole water in the Légbassito and Vakpossito cantons (Togo)The target of this study is to have a part in the preservation of sinking waters of Lomé city’s suburbs areas. (Togo). The assessment of physicochemical quality and bacteriological has been carried out on 30 samples using standardized methods (AFNOR). Nitrate  elimination tests with activated charcoal and disinfecting chlorine for break-point determination have been carried out on waters of high nitrate content on each studied site. Surveys’ results have shown that sinking, carried out in the suburbs’ areas are of 95% manuals. Sinkings are often done without technical orientation due to the easy layer of sedimentary formation. The depth varies from 25 to 35 m. Results showed that sinkings are carried out (over 80%) in an unhealthy environment devoid of sanitation infrastructures. The pH is mostly acid (< 6,5). Waters are salted (about 90%) and 87% of samples are not standard to the WHO recommended values. Nitrates concentration (toxic element) and the iron (undesirable element) are very high, respectively in the proportions of 13% and 6% of tested sinking waters. The whole of tested samples are contaminated by germ indicators from faeces. Tested water samples are not standard to preservation norms of drinking water. Contamination might have resulted as a priority from « foration » techniques and periodic maintenance of the pump. Tests treatment with activated charcoal and the chlorine are effectively revealed and constitute one the measures to be taken into account in water-processing.Keywords: Water sinking, contamination, processing, activated charcoal, chlorin

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

Strengthening the knowledge base to face the impacts of climate change on water resources in Africa : a social innovation perspective

Abstract: While it is increasingly important to strengthen the existing knowledge base in Africa to adequately respond to the rising risks and impacts of climate change on water resources, a significant research gap remains to identify areas and mechanisms to cope with these societal challenges. The aim of the paper is twofold: i) to provide subject-specific insights by analyzing the current knowledge base in Africa given water-related challenges due to climate change, and ii) to offer methodological insights into how a knowledge base can be studied comprehensively. This study overcomes the limitations of existing studies by combining two different perspectives, namely a thematic focus on six societal challenges and a conceptual focus on five social innovation dimensions. It does so by undertaking an innovative qualitative analysis that combines both top-down and bottom-up perspectives. Top-down, it explores the extent to which five social innovation dimensions are included and addressed in policy agendas and action plans. Bottom-up, it explores the perception of African experts and practitioners in how these knowledge gaps should be addressed. The research identifies a strong bias in the policy arena towards water security versus other water-related societal challenges. Our research suggests that rather than focusing on traditional policy instruments, water-related societal challenges should be addressed by joint attention to all five social innovation dimensions. There is a strong call from practitioners and experts towards strengthening the existing knowledge base by engaging local realities and local stakeholders and for the involvement of business and private sector actors

寄生虫卵と病原性バクテリアのコンポスト型トイレにおける挙動に関する研究

On-site sanitation systems have gained much interest in recent years. One such system is the urine diverting composting toilet, which are promoted to sanitize human excreta for recycling them into fertilizer. A　composting toilet using waste material as bulking agent has the potential to trap pathogens that might be contained in human feces. Unfortunately, in some marginal area, composting toilet could not get specific conditions for destroy all pathogens. Several studies have reported the inactivation of pathogenic bacteria and viruses in composting toilet. However, the removal of intestinal parasites has not been so far studied since parasites tend to have stronger resistance than pathogenic bacteria and viruses. Therefore, this study aimed to investigate the fate of intestinal parasites and pathogenic bacteria in the composting toilet for sanitizing compost from composting toilet.Chapter 1 describes the background and the objectives of this research. The literature review has summarized the state of the art regarding to the removal of pathogens in composting toilet, the inactivation mechanisms of the pathogen organism cells during the composting process and the different adequate post-treatments for sanitizing compost.Chapter 2 deals with the removal of intestinal parasites (helminthes eggs and protozoan cysts) and that of pathogenic bacteria during the composting process in a composting toilet. Batch experiments were conducted by composting human feces in an aerobic composting reactor during 60 days. The results showed that among parasites, protozoan cysts (Entamoeba hystolitica) were present in humans feces collected at high concentration (854/g mean) than helminthes eggs (Ascaris lumbricoides) (204/g mean). A mesophilic temperature, desiccation and alkaline pH were obtained during the composting process. Compared to pathogenic bacteria (Salmonella sp), which were eliminated totally after 30 composting days, helminthes eggs were reduced after 35 days; while protozoan cysts were still present after 60 days. In high concentration, protozoan cysts have survived stronger than helminthes eggs in the composting toilet and may constitute a sanitary risk when used as fertilizer. Because of the persistence of intestinal parasites in composting toilet, both helminthes eggs and protozoan cysts are good indicator for the removal of intestinal parasites.Chapter 3 elucidates the inactivation mechanisms of pathogenic bacteria cells in composting toilet during the composting process. The inactivation mechanisms were evaluated by culture E. coli strain as pathogenic bacteria in 3 types of media namely Tryptic Soy Agar, Desoxycholate Agar and Compact Dry EC. By comparing, the inactivation rate constant of E. coli, the damaged components and/or functions of bacteria cell were estimated in three different composting matrixes (sawdust, rice husk and charcoal). The results showed that composting process and composting matrixes did not significantly affect inactivation rate of pathogenic bacteria; however, these differences affected damaging component or function of the bacteria cells. The composting process damaged the bacteria cell from membrane and enzyme to metabolisms while the composting matrix damaged from membrane to enzymes and metabolisms. However, the composting process, when accompanied with alkaline pH, changed the damage part of bacteria more lethally with nucleic acid damage.iiiChapter 4 evaluates the post-treatment of compost by storage treatment for a short time. Fresh composts produced in composting toilet with continuous feces supply, were stored for 2 months, in uncontrolled conditions. The microbiology analysis of fresh and stored composts, showed that, both composts contained indicator bacteria (fecal coliforms, enterococci, spores of sulphite-reducing clostridia), pathogenic bacteria (Salmonella) and intestinal parasites (helminthes eggs and protozoan cysts), at levels above suggested limits for compost quality. There was no significant difference of the microbial level in fresh and stored composts exanimated, thus the storage period tested resulted in slow reduction of microorganisms for compost quick sanitizing. However the microbial level in fresh and stored composts from a composting toilet was known and their health implications suggested further sanitizing treatments.Chapter 5 evaluates the post-treatment of compost by solar heating as thermal treatment. Fresh composts from composting toilet were inoculated with indicator microorganisms and subjected to solar heating (direct sunlight and solar box). The inactivation rate constant and the decimal decay of microorganisms in compost were estimated by using the inactivation kinetics. The result showed that the temperature regime produced by direct sunlight and solar box were categorized in mesophilic (>30°C) and pasteurization (>70°C), respectively. The log reduction of microorganisms in compost by solar box was significantly higher than that of direct sunlight. The inactivation of microorganisms was slower in compost heated by direct sunlight but fast in compost heated by solar box, thus the decimal decay occurred rapidly with solar box heating while it was prolonged with direct sunlight heating. The high and uniform temperature distribution obtained with solar box during heating proved to be an efficient option for sanitizing compost.Chapter 6 evaluates the post-treatment of compost by urea addition as alkaline treatment. Fresh composts from composting toilet were inoculated with indicator microorganisms and subjected to different urea concentrations (0.5-2% w/w) and temperatures (22, 32 and 42°C). The inactivation kinetics parameters were determined in relation to pH, ammonia content and temperature during treatment time. The results showed that urea addition to compost enhanced inactivation of microorganisms. The inactivation rate constants of all microorganisms tested were positively correlated to the increase of NH3 (aq) concentration and temperature. The relationship between inactivation rate of microorganisms and ammonia through urea concentration and temperature were established. Therefore, the best decimal decay of E. coli, enterococci and A. eggs occurred with 2% w/w urea concentration at 42°C within 0.9, 1.1 and 1.4 days, respectively. Urea treatment has proved to be an efficient option for safe use of compost from composting toilet.Chapter 7 summarizes the most important findings as conclusions of this research and future studies are listed