The consumption of bottled and plastic-bagged drinking water in Tanzania has increased largely because of the deteriorating quality of tap water. It is uncertain whether these water products are safe for drinking. In this study, the microbiological quality of bottled and plastic-bagged drinking water sold in Dar es Salaam, Tanzania, was investigated. One hundred and thirty samples representing 13 brands of bottled water collected from shops, supermarkets and street vendors were analysed for total coliform and faecal coliform organisms as well as heterotrophic bacteria. These were compared with 61 samples of tap water. Heterotrophic bacteria were detected in 92% of the bottled water samples analysed. Total and faecal coliform bacteria were present in 4.6% and 3.6%, respectively, of samples analysed with a tendency for higher contamination rates in plastic-bagged drinking water. Microbiological quality of tap water was found to be worse compared with bottled water, with 49.2% and 26.2% of sampling points showing the presence of total coliform and faecal coliform organisms, respectively. The results suggest caution and vigilance to avert outbreaks of waterborne diseases from these types of drinking water.
Anaerobic degradation of cis-1,2-dichloroethene (cis-1,2-DCE) and 1,2-dichloroethane (1,2-DCA) was studied in
microcosms derived from a laboratory-scale upflow treatment
wetland system used to biodegrade chlorinated compounds
present in groundwater from a Superfund site. Dechlorination kinetics of cis-1,2-DCE (0.94−1.57 d-1) and 1,2-DCA (0.15−0.71 d-1) were rapid, and degradation proceeded
to completion with ethene or ethane as terminal dechlorination products. Hydrogen concentrations, measured
simultaneously during dechlorination, were significantly
different for the two compounds, approximately 2.5 nM for
cis-1,2-DCE and 38 nM for 1,2-DCA. Methanogenesis
proceeded during the degradation of 1,2-DCA when H2
concentrations were high but not during the dechlorination
of cis-1,2-DCE when H2 concentrations were below
published thresholds for methanogenesis. A 16S rRNA gene-based approach indicates that microorganisms closely
related to Dehalococcoides ethenogenes were present and
that they were distributed throughout the bottom, middle,
and top of the upflow treatment wetland system. These results
coupled with consideration of hydrogen thresholds,
degradation kinetics, daughter products, and measurements
of methanogenesis strongly suggest that halorespirers
were responsible for dechlorination of cis-1,2-DCE and that
1,2-DCA dechlorination was co-metabolic, likely mediated
by acetogens or methanogens. Rapid dechlorination
potential was distributed throughout the wetland bed,
both within and below the rhizosphere, indicating that
reductive dechlorination pathways can be active in anaerobic
environments located in close spatial proximity to aerobic
environments and plants in treatment wetland systems.
A large number of informal settlements in developing countries are located in high risk areas(low-lying lands and on river banks). This situation is caused by poverty and the inabilityof authorities to supply planned plots for building to meet demands of the growing urbanpopulations. Informal settlements have, in turn, triggered disaster risks, flooding being just oneof them. As a way of reducing impacts of flooding, residents in informal settlements have resortedto the use of structural adaptation strategies. Despite these efforts, the vulnerability of peopleand properties in informal settlements is increasing. This article aimed to provide an answer as towhy this is the case, by assessing and comparing the technical suitability of adaptation strategiesto flooding in the informal settlements of Sangkrah and Keko Machungwa and recommendingmeasures for improvement. Household interviews, physical observation (visual inspections ofsigns of damage and deterioration), measurements of height of physical adaptation strategies,mapping, photographing, and in-depth interviews were the key methods employed. Generally,in both cases, it was determined that flood mitigation and risk minimisation measures throughstructural adaptation strategies were hardly achieved at the household level, as adaptationstrategies were constructed with little or no attention to acceptable technical considerations.However, when levels of compliance to technical considerations in the construction of houseswere compared between the two cases, they were found to be slightly higher in Sangkrah thanin Keko Machungwa. Residents in Sangkrah demonstrated a slight difference, especially in theuse of reinforced concrete (4.3%) for constructing a building’s foundation, as well as in the useof ceramics (72.9%) to construct the floor. In order to deliver technically suitable adaptationstrategies, efforts need to be directed toward: regulating and controlling the construction ofstructures for adaptation, enhancing individual coping capacity, deployment of a workforcetrained in disaster risk and management and enforcement of relevant urban planning andenvironmental management laws in managing risky areas.
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