4 research outputs found
Performance of Subsurface Flow Constructed Wetland for Domestic Wastewater Treatment
Constructed wetlands (CW) have recently emerged as efficient technology for secondary treatment of wastewater in developing countries because of its low cost, ease operation, maintenance and generally good performance. At present there are a number of small scale units of CW for wastewater treatment in Tanzania but information on their performance is scarce. This study investigated the removal efficiency of fecal bacteria indicators, inorganic nutrients and Biochemical Oxygen Demand (BOD) from wastewater by a CW at the University of Dar es Salaam. The CW received wastewater from a primary facultative pond and was a monoculture system planted with Phragmites mauritianus (> 10 years old) with one unplanted cells as control. The results showed significantly (P < 0.001) higher removal of fecal indicator bacteria, in planted than in unplanted cells. Thus, the overall E. Coli and Fecal coliform percentage removal were 92.9±6.05% and 93.2±6.13% in planted cells as compared to unplanted cell which were 75.2±21.3% and 58.7±21.2%, respectively. The BOD5 values in influent was also significantly (P < 0.001) reduced (71 ± 6.2%) in effluent of planted cells than in unplanted cells where the average percentage removal averaged 45 ± 3.3%. Similarly, nutrients were significantly (P < 0.001) removed in planted cells compared to unplanted cells. The results of this study show that plants enhanced the removal process and that the CW are efficient in wastewater treatment, supporting the ideas put forward by several researchers on the usefulness of these systems in developing countries. The system continues to perform efficiently for long time which signifies its cost effectiveness. It is recommended that CW be promoted for sewage treatment in a strategy to reduce wastewater pollution in Tanzania
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Population dynamics of normal human blood inferred from somatic mutations.
Haematopoietic stem cells drive blood production, but their population size and lifetime dynamics have not been quantified directly in humans. Here we identified 129,582 spontaneous, genome-wide somatic mutations in 140 single-cell-derived haematopoietic stem and progenitor colonies from a healthy 59-year-old man and applied population-genetics approaches to reconstruct clonal dynamics. Cell divisions from early embryogenesis were evident in the phylogenetic tree; all blood cells were derived from a common ancestor that preceded gastrulation. The size of the stem cell population grew steadily in early life, reaching a stable plateau by adolescence. We estimate the numbers of haematopoietic stem cells that are actively making white blood cells at any one time to be in the range of 50,000-200,000. We observed adult haematopoietic stem cell clones that generate multilineage outputs, including granulocytes and B lymphocytes. Harnessing naturally occurring mutations to report the clonal architecture of an organ enables the high-resolution reconstruction of somatic cell dynamics in humans.This work was supported by the Leukemia Lymphoma Society and the Wellcome Trust. PJC is a Wellcome Trust Senior Clinical Fellow (WT088340MA). HLS is a recipient of a Wellcome Trust PhD studentship. NFO is the recipient of a Danish Lundbeck Fellowship (2016-17) and MSS is the recipient of a BBSRC CASE Industrial PhD Studentship. Work in the DGK lab is supported by a Bloodwise Bennett Fellowship (#15008), a European Research Council Starting Grant (ERC-2016-STG–715371) and a European Hematology Association Non-Clinical Advanced Research Fellowship. Work in the ARG Lab is supported by the Wellcome Trust, Bloodwise, Cancer Research UK, the Kay Kendall Leukaemia Fund, and the Leukemia and Lymphoma Society of America. Work in EL lab is supported by a Wellcome Trust Sir Henry Dale Fellowship, BBSRC and a European Haematology Association Non-Clinical Advanced Research Fellowship. The DGK, EL and ARG labs are supported by a core support grant from the Wellcome Trust and Medical Research Council to the Cambridge Stem Cell Institute. We acknowledge further assistance from the National Institute for Health Research Cambridge Biomedical Research Centre and the Cambridge Experimental Cancer Medicine Centre