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Mémoires Année : 2017

Assessing wastewater and sanitation conditions and management in the Ramotswa transboundary aquifer area between South Africa and Botswana

Résumé

Since the eighties, the sanitation system has developed a lot in the Ramotswa Transboundary Aquifer Area between South Africa and Botswana. It was essential to protect the groundwater from sanitation in a region of water scarcity. At first, pit latrines were promoted in rural and urban areas. The efficien-cy of pit latrines depends on the construction quality and the soil characteristics. In the RTBAA, pit latrines can be considered as a direct source of nitrate pollution in groundwater by wastewater infiltra-tion because of the fractured rock soil and the high groundwater table of the Ramotswa Aquifer. Then, between 1985 and 2000, wastewater treatment plants were introduced in urban areas such as Gaborone, Lobatse, Ramostwa and Zeerust. But, with population increase and industrial development, wastewater treatment plants such as oxidation ponds are not efficient to treat wastewater. Discharge of wastewater treatment plant and losses from the sewerage network are indirectly affecting the groundwater quality. A vulnerability map of the aquifer to sanitation from the DRASTIC method delimits a priority area where sanitation facilities have to be improved. In fact, more than 50% of the Ramotswa aquifer is highly vulnerable to sanitation pollution during the wet season compare to 2.5% during the dry season. Climate conditions have an impact on sanitation pollution. Moreover, potential challenges of sanitation were assessed such as industrial wastewater pollutants, water balances and transboundary water pollution issues. To improve the current situation, some recommendations are given for on-site sanitation system, wastewater treatment plant management and the development of a sustainable sanitation system.
L’aquifère de Ramotswa est un aquifère transfrontalier situé entre le Botswana et l’Afrique du Sud. Le climat étant semi-aride, la ressource en eau est essentiellement souterraine dans cette région où l’activité agricole prime. Cependant, cette ressource d’eau potable est menacée par diverses pollutions. En effet, l’aquifère est particulièrement chargé en nitrate et en pollution fécale provenant majoritairement de l’assainissement. Dans cette étude, les latrines sont les installations sanitaires majoritaires. Quelques stations d’épuration du type lagunage sont également présentes. Le manque de connaissance et d’entretien de ces systèmes sont les causes de pollution de la ressource en eau. Ainsi, des axes d’amélioration sont proposés afin de diminuer les risques sanitaires. Enfin, certaines propositions sont faites afin de développer un système d’assainissement durable pour la communauté et de privilégier le recyclage et la réutilisation des eaux.
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Dates et versions

dumas-01668380 , version 1 (12-05-2020)

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  • HAL Id : dumas-01668380 , version 1

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Natacha Martin. Assessing wastewater and sanitation conditions and management in the Ramotswa transboundary aquifer area between South Africa and Botswana. Engineering Sciences [physics]. 2017. ⟨dumas-01668380⟩
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