Materials, Energy, Water and Environmental Sciences

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Browsing Materials, Energy, Water and Environmental Sciences by Author "Alex, Rita"

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    Assessment of groundwater pollution in Singida urban and Manyoni districts
    (NM-AIST, 2021-06) Alex, Rita
    The quality of groundwater in Tanzania has over the years remained poorly understood, hence posing risks to human health and the environment. In this study, the quality of groundwater sources used for drinking purpose in Singida Urban and Manyoni districts were investigated with a view to explore how the end users could be safeguarded from water borne diseases. Water samples from 30 boreholes and 28 shallow wells were randomly collected during dry and wet seasons. Water quality assessments were conducted following recommended guidelines by Tanzania Bureau of Standards (TBS) and international standards (WHO) for drinking water. Twelve physicochemical parameters were assessed using standard methods for water and wastewater from American Public and Health Association (APHA). Microbial water quality (TC, FC, and E.coli) were examined using membrane filtration technique while toxic metals were determined using Inductively Coupled Plasma Optical Emission Spectrometer. Nitrate source identifications were done using Elemental Analyzer/ isotope ratio mass spectrometry techniques. Results showed that shallow wells recorded significant higher turbidity (p<0.0001) compared to boreholes. The water samples collected during wet season had significantly higher microbial contamination compared to those collected during dry season. Additionally, the wells were buckets are used to draw water had significantly higher TC, FC and E.coli (n=11, p≤ 0.01), also wells without covers (n=15, p≤0.01) had significantly higher feacal coliform bacteria than those which motor or hand pump were used in both seasons. Concentration of toxic metals was significantly higher (p<0.05) during the dry season than in the wet season and 40- 66% of all samples had an elevated level of Mn, Cr, Pb, and Al above the recommended standards by World Health Organization (WHO) and Tanzania Bureau of Standards (TBS), hence unsafe for drinking. Nitrate sources identification revealed that, most nitrate contamination were originated from sewage effluents and/or organic wastes such as manure. The study recommends that water from shallow wells should be treated either by boiling, chlorination, or use of low cost technologies such as sand filter before consumption. In addition, the proper sitting of the wells based on the recommended standards by TBS has to be enforced in order to prevent further contamination from human activities.
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    Sources of Nitrate in Ground Water Aquifers of the Semiarid Region of Tanzania
    (Hindawi, 2021) Alex, Rita; Kitalika, Aldo; Mogusu, Emmanuel; Njau, Karoli
    Nitrate isotopic values are often used as a tool to identify sources of nitrate in order to effectively manage ground water quality. In this study, the concentrations of NO3−, NO2−, and NH4+ from 50 boreholes and shallow wells in the Singida and Manyoni Districts were analyzed during the dry and wet seasons, followed by identification of nitrate sources using the hydrochemical method (NO3−/Cl−) and stable isotope (δ15N and δ18O) techniques. Results showed that NO2− and NH4+ concentrations were very low in both seasons due to the nitrification process. The concentrations of NO3− ranged from 2.4 ppm to 929.6 ppm with mean values of , during the dry season and from 2.4 ppm to 1620.0 ppm with mean values of , during the wet season. The higher NO3− contamination observed in the wet season could be due to rainfall which accelerated the surface runoff that collects different materials from various settings into the ground water sources. Nitrate source identification through hydrochemical technique revealed that most nitrates originated from sewage effluents and/or organic wastes such as manure. Likewise, the mean values of δ15N-NO3− ( and ) and the mean values of δ18O-NO3−( and ) suggest that 80% of boreholes and 52% of shallow wells were dominated with nitrate from sewage effluents and/or manure as most ground water sources were situated in densely populated areas with congested and poorly constructed onsite sanitation facilities such as pit latrines and manure. Therefore, to reduce nitrate pollution in the study area, a central sewer must be constructed to treat the discharged wastes. Also, groundwater harvesting should consider the proper principles for groundwater harvesting recommended by the respective authority to minimize chances of contamination and hence prevention of health risk