Browsing by Author "Njau, Karoli N."

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    Evaluating the performance of faecal sludge dewatering technologies in urban settings of developing African countries: a review
    (Taylor & Francis online, 2024-05-02) Mwamlima, Petro; Njau, Karoli N.; Rwiza, Mwemezi; Chacha, Nyangi
    Inadequate dewatering technologies are reported as the dominant challenge in handling faecal sludge (FS) within urban settings of most African countries. Studies have been carried out to evaluate the efficiencies of unplanted sand drying beds (USDBs), decentralized wastewater treatment systems (DEWATS), and geo-tubes. However, limited information is available on comparative capabilities in dewatering the FS. This work reviewed treatment efficiencies by assessing the reported actual waste removal capacities and ascertaining if they align with the design removal provisions. Peer-reviewed papers, books, and technical reports from trusted sources were examined. The results show that all the technologies perform best in dewatering the FS; however, USDBs are widely adopted for city-wide treatment, and the other two are suited for decentralized communities. The USDB is challenged by frequent clogging and poor quality of dewatered sludge when reused or recycled in the production of solid fuel and compost due to sticking sand after sludge harvesting. The DEWATS and geo-tubes increase operational costs when used to treat the FS at a large scale. More studies should be conducted to explore locally made, cost-effective filter media and technologies to enhance the dewatering quality and quantity of the FS and increase the quality of recycled by-products.
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    Metallic iron for safe drinking water provision: Considering a lost knowledge.
    (Elsevier Ltd., 2017-06-15) Mwakabona, Hezron T; Ndé-Tchoupé, Arnaud Igor; Njau, Karoli N.; Noubactep, Chicgoua; Wydra, Kerstin D
    Around year 1890, the technology of using metallic iron (Fe) for safe drinking water provision was already established in Europe. The science and technology to manufacture suitable Fe materials were known and further developed in this period. Scientists had then developed skills to (i) explore the suitability of individual Fe materials (e.g. iron filling, sponge iron) for selected applications, and (ii) establish treatment processes for households and water treatment plants. The recent (1990) discovery of Fe as reactive agent for environmental remediation and water treatment has not yet considered this ancient knowledge. In the present work, some key aspects of the ancient knowledge are presented together with some contemporised interpretations, in an attempt to demonstrate the scientific truth contained therein. It appears that the ancient knowledge is an independent validation of the scientific concept that in water treatment (Fe/HO system) Fe materials are generators of contaminant collectors.