Browsing by Author "Mwamlima, Petro"

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    Efficacy of waste stabilization ponds and constructed wetlands adopted for treating faecal sludge in Africa: a review
    (Taylor & Francis online, 2024-05-24) Mwamlima, Petro; Njau, Karoli; Rwiza, Mwemezi
    The generation of faecal sludge (FS) in capitals and urban settings of African countries outpaces the available storage, emptying, transportation and treatment technologies. The low technology-based treatment systems for handling FS are preferable and widely adopted in the African context due to their less associated investment and operation costs. The waste stabilization ponds and constructed wetlands were principally developed as wastewater treatment systems however they are widely adopted for treating FS in urban settings of Africa. Less information is known about the efficiency of these systems in lowering FS pollutant concentrations to meet the design specifications and the allowable discharge limits. This paper reviewed the technical efficacy of waste stabilization ponds and the constructed wetlands in treating FS by evaluating the actual treatment efficiency data against the design efficiencies and the maximum allowable discharge limits. The review results revealed that these technologies are user-friendly although they fail to lower the solids concentrations to meet the design and maximum allowable discharge limits. This failure imposes extra costs on operation and maintenance due to the fast filling of solids in the systems hence leading to short-circuiting issues. So, studies on the adequate dewatering technologies of FS before entering the systems are needed.
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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.