Browsing by Author "Gwenzi, Willis"

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Application of the Kilimanjaro Concept in Reversing Seawater Intrusion and Securing Water Supply in Zanzibar, Tanzania
(MDPI, 2021-07-30) Pembe-Ali, Zuleikha; Mwamila, Tulinave; Lufingo, Mesia; Gwenzi, Willis; Marwa, Janeth; Rwiza, Mwemezi; Lugodisha, Innocent; Qi, Qinwen; Noubactep, Chicgoua
There is escalating salinity levels on small islands due to uncontrolled groundwater extraction. Conventionally, this challenge is addressed by adopting optimal groundwater pumping strategies. Currently, on Unguja Island (Zanzibar), urban freshwater is supplied by desalination, which is expensive and energy-intensive. Hence, desalinization cannot be afforded by rural communities. This study demonstrates that the innovative Kilimanjaro Concept (KC), based on rainwater harvesting (RWH) can remediate seawater intrusion in Unguja, while enabling a universal safe drinking water supply. The reasoning is rooted in the water balance of the whole island. It is shown that if rainwater is systematically harvested, quantitatively stored, and partly infiltrated, seawater intrusion will be reversed, and a universal safe drinking water supply will be secured. Water treatment with affordable technologies (e.g., filtration and adsorption) is suggested. The universality of KC and its suitability for small islands is demonstrated. Future research should focus on pilot testing of this concept on Unguja Island and other island nations.
Avoiding the Use of Exhausted DrinkingWater Filters: A Filter-Clock Based on Rusting Iron
(MDPI, 2018-05-02) Ndé-Tchoupé, Arnaud Igor; Lufingo, Mesia; Hu, Rui; Gwenzi, Willis; Ntwampe, Seteno Karabo Obed; Noubactep, Chicgoua; Njau, Karoli
Efficient but affordable water treatment technologies are currently sought to solve the prevalent shortage of safe drinking water. Adsorption-based technologies are in the front-line of these efforts. Upon proper design, universally applied materials (e.g., activated carbons, bone chars, metal oxides) are able to quantitatively remove inorganic and organic pollutants as well as pathogens from water. Each water filter has a defined removal capacity and must be replaced when this capacity is exhausted. Operational experience has shown that it may be difficult to convince some low-skilled users to buy new filters after a predicted service life. This communication describes the quest to develop a filter-clock to encourage all users to change their filters after the designed service life. A brief discussion on such a filter-clock based on rusting of metallic iron (Fe0) is presented. Integrating such filter-clocks in the design of water filters is regarded as essential for safeguarding public health.
Conceptualizing the Fe0/H2O System: A Call for Collaboration to Mark the 30th Anniversary of the Fe0-Based Permeable Reactive Barrier Technology
(MDPI, 2022-10-03) Cao, Viet; Bakari, Omari; Tchidjo, Joseline; Bandjun, Nadège; Tchoupé, Arnaud; Gwenzi, Willis; Njau, Karoli; Noubactep, Chicgoua
Science denial relates to rejecting well-established views that are no longer questioned by scientists within a given community. This expression is frequently connected with climate change and evolution. In such cases, prevailing views are built on historical facts and consensus. For water remediation using metallic iron (Fe0), also known as the remediation Fe0/H2O system, a consensus on electro-chemical contaminant reduction was established during the 1990s and still prevails. Arguments against the reductive transformation concept have been regarded for more than a decade as ‘science denial’. However, is it the prevailing concept that denies the science of aqueous iron corrosion? This article retraces the path taken by our research group to question the reductive transformation concept. It is shown that the validity of the following has been questioned: (i) analytical applications of the arsenazo III method for the determination of uranium, (ii) molecular diffusion as sole relevant mass-transport process in the vicinity of the Fe0 surface in filtration systems, and (iii) the volumetric expansive nature of iron corrosion at pH > 4.5. Item (i) questions the capability of Fe0 to serve as an electron donor for UVI reduction under environmental conditions. Items (ii) and (iii) are inter-related, as the Fe0 surface is permanently shielded by a non-conductive oxide scale acting as a diffusion barrier to dissolved species and a barrier to electrons from Fe0. The net result is that no electron transfer from Fe0 to contaminants is possible under environmental conditions. This conclusion refutes the validity of the reductive transformation concept and calls for alternative theories.
Integrated Water Management in Mountain Communities: The Case of Feutap in the Municipality of Bangangté, Cameroon
(MDPI, 2023-04-09) Nya, Esther; Mwamila, Tulinave; Komguem-Poneabo, Lydie; Njomou-Ngounou, Emma; Fangang-Fanseu, Junior; Tchoumbe, Raoul; Tepong-Tsindé, Raoul; Gwenzi, Willis; Noubactep, Chicgoua
The whole population of Feutap still collects drinking water from two protected springs, some 1 km away from this small rural agglomeration. For many generations, the only improvement has been the protection of the springs during the 1980s. The resulting high incidence of gastrointestinal infections continues to hinder the socioeconomic development of this mountain community. This dynamic wherein “poverty begets disease, and disease begets poverty” seems endless given the number of water improvement programs and other health-focused campaigns in rural areas of Cameroon since the 1960s. Fortunately, the hydrographic regime of Feutap and its geographical situation enable the implementation of the Kilimanjaro Concept (KC), wherein rainwater is quantitatively harvested, partly infiltrated, and largely stored to (i) meet the whole-year water needs of the population, (ii) create new ecosystems, and (iii) enable irrigated agriculture. This communication prepares the implementation of the KC in Feutap, including the creation of irrigation ponds for agriculture and small farm animals (e.g., goats and sheep). The view is promoted that Feutap is a potential viable space in which life and work are possible, using the existing rainfall and the few natural springs in a sustainable manner. The presented concept can be extended to other hilly small communities with similar hydraulic regimes.
Integrated water resource management: Rethinking the contribution of rainwater harvesting
(MDPI, 2021-07-26) Huang, Zhe; Nya, Esther; Rahman, Mohammad; Mwamila, Tulinave; Cao, Viet; Gwenzi, Willis; Noubactep, Chicgoua
Rainwater harvesting (RWH) is generally perceived as a promising cost-effective alternative water resource for potable and non-potable uses (water augmentation) and for reducing flood risks. The performance of RWH systems has been evaluated for various purposes over the past few decades. These systems certainly provide economic, environmental, and technological benefits of water uses. However, regarding RWH just as an effective alternative water supply to deal with the water scarcity is a mistake. The present communication advocates for a systematic RWH and partial infiltration wherever and whenever rain falls. By doing so, the detrimental effects of flooding are reduced, groundwater is recharged, water for agriculture and livestock is stored, and conventional water sources are saved. In other words, RWH should be at the heart of water management worldwide. The realization of this goal is easy even under low-resource situations, as infiltration pits and small dams can be constructed with local skills and materials.
Making Rainwater Harvesting a Key Solution for Water Management: The Universality of the Kilimanjaro Concept
(MDPI, 2019-10-11) Qi, Qinwen; Marwa, Janeth; Mwamila, Tulinave Burton; Gwenzi, Willis; Noubactep, Chicgoua
Rainwater is conventionally perceived as an alternative drinking water source, mostly needed to meet water demand under particular circumstances, including under semi-arid conditions and on small islands. More recently, rainwater has been identified as a potential source of clean drinking water in cases where groundwater sources contain high concentrations of toxic geogenic contaminants. Specifically, this approach motivated the introduction of the Kilimanjaro Concept (KC) to supply fluoride-free water to the population of the East African Rift Valley (EARV). Clean harvested rainwater can either be used directly as a source of drinking water or blended with polluted natural water to meet drinking water guidelines. Current e orts towards the implementation of the KC in the EARV are demonstrating that harvesting rainwater is a potential universal solution to cover ever-increasing water demands while limiting adverse environmental impacts such as groundwater depletion and flooding. Indeed, all surface and subsurface water resources are replenished by precipitation (dew, hail, rain, and snow), with rainfall being the main source and major component of the hydrological cycle. Thus, rainwater harvesting systems entailing carefully harvesting, storing, and transporting rainwater are suitable solutions for water supply as long as rain falls on earth. Besides its direct use, rainwater can be infiltrating into the subsurface when and where it falls, thereby increasing aquifer recharge while minimizing soil erosion and limiting floods. The present paper presents an extension of the original KC by incorporating Chinese experience to demonstrate the universal applicability of the KC for water management, including the provision of clean water for decentralized communities.
White Teeth and Healthy Skeletons for All: The Path to Universal Fluoride-Free DrinkingWater in Tanzania
(MDPI, 2019-01-12) Ndé-Tchoupé, Arnaud Igor; Tepong-Tsindé, Raoul; Lufingo, Mesia; Pembe-Ali, Zuleikha; Lugodisha, Innocent; Mureth, Risala Iddi; Nkinda, Mihayo; Marwa, Janeth; Gwenzi, Willis; Mwamila, Tulinave Burton; Rahman, Mohammad Azizur; Noubactep, Chicgoua; Njau, Karoli
Fluorosis has been prevalent in the great East African Rift Valley (EARV) since before this region was given a name. In the Tanganyika days, Germans reported elevated fluoride concentrations in natural waters. In the 1930s, the clear relationship between high fluoride level and mottling of teeth was established. Since then, the global research community has engaged in the battle to provide fluoride-free drinking water, and the battle is not yet won for low-income communities. An applicable concept for fluoride-free drinking water in the EARV was recently presented, using the Kilimanjaro as a rainwater harvesting park. The Kilimanjaro concept implies that rainwater is harvested, stored on the Kilimanjaro mountains, gravity-transported to the point of use, eventually blended with natural water and treated for distribution. This article provides a roadmap for the implementation of the Kilimanjaro concept in Tanzania. Specifically, the current paper addresses the following: (i) presents updated nationwide information on fluoride contaminated areas, (ii) discusses the quality and quantity of rainwater, and current rainwater harvesting practices in Tanzania, (iii) highlights how low-cost water filters based on Fe0/biochar can be integrating into rainwater harvesting (RWH) systems to provide clean drinking water, and (iv) discusses the need for strict regulation of RWH practices to optimize water collection and storage, while simplifying the water treatment chain, and recommends strict analytical monitoring of water quality and public education to sustain public health in the EARV. In summary, it is demonstrated that, by combining rainwater harvesting and low-cots water treatment methods, the Kilimanjaro concept has the potential to provide clean drinking water, and overcome fluorosis on a long-term basis. However, a detailed design process is required to determine: (i) institutional roles, and community contributions and participation, (ii) optimal location and sizing of conveyance and storage facilities to avoid excessive pumping costs, and (iii) project funding mechanisms, including prospects for government subsidy. By drawing attention to the Kilimanjaro concept, the article calls for African engineers and scientists to take the lead in translating this concept into reality for the benefit of public health, while simultaneously increasing their self-confidence to address other developmental challenges pervasive in Africa.