| 1. |
- Gomez Lopez, Etzar, et al.
(författare)
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Quantitative estimations of aquifer properties from resistivity in the Bolivian highlands
- 2019
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Ingår i: H2Open Journal. - : IWA Publishing. - 2616-6518. ; 2:1, s. 113-124
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Tidskriftsartikel (refereegranskat)abstract
- Resistivity data constitute the largest part of the available information to assess the hydrogeological characteristics of the aquifer system near Oruro, in the central part of the Bolivian Altiplano. Two aquifers are part of this system; top unconsolidated sediments storing fresh water in their granular voids, overlying fractured hard rock formations where saline water was detected in connection to some faults. This study proposes an indirect and cost-effective way to estimate aquifer hydraulic properties for the groundwater management in the region. Hydraulic conductivity and transmissivity in the top aquifer were estimated using an empirical linear relationship between hydraulic conductivity and resistivity. This latter parameter, as well as the aquifer thickness, were obtained from the inverted models corresponding to the geoelectrical tests performed in the study area (electrical resistivity tomography, transient electromagnetic soundings and vertical electrical soundings). The highest estimated transmissivity values are ∼4.0 × 10−2 m2/s located in the centre of the study area, the lowest values are ∼3.4 × 10−3 m2/s, located around thermal intrusions to the south and where the top of the bedrock is shallow (∼20 m depth) to the west. The methodology presented in this study makes wider use of resistivity measurements to identify promising groundwater production sites.
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| 2. |
- Johansson, Jonas, et al.
(författare)
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Solar disinfection at low costs: an experimental approach towards up-scaled continuous flow systems
- 2022
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Ingår i: H2open Journal. - : IWA Publishing. - 2616-6518. ; 5:1, s. 153-165
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Tidskriftsartikel (refereegranskat)abstract
- SOlar DISinfection (SODIS) systems have been studied with the aim of maintaining pathogen removal efficiencies and low costs. Such systems are useful for quickly improving the situation of more than 700 million people worldwide that lack access to an improved water source. Currently, SODIS is mainly used with PET-bottles that are exposed to UV-A radiation for 6 h in the sun. Up-scaled continuous flow SODIS systems could instead provide a continuous source of drinking water, whereas the use of plastic tubes, easily available on local markets, ensures a low construction cost of the systems. Such tubes (PVC) were tested and the best option showed a UV-A transparency ratio of similar to 50%, to be compared with similar to 60% for PET-bottles. By using static batches in samples of this tube, the residence time was investigated and the results show that E. coli concentrations of 0 CFU/ml are reached within less than 4 h of exposure to solar radiation, starting from an initial concentration of 10(6) CFU/ml. It can be concluded that cheap, easily available plastic tubes can be used for treating contaminated water with the SODIS technique, which is promising for future investigations towards constructing continuous flow SODIS systems at low costs.
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| 3. |
- Okwori, Emmanuel, 1988-, et al.
(författare)
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Performance assessment of Swedish sewer pipe networks using pipe blockage and other associated performance indicators
- 2020
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Ingår i: H2Open Journal. - London : IWA Publishing. - 2616-6518. ; 3:1, s. 46-57
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Tidskriftsartikel (refereegranskat)abstract
- Sewer pipe networks are expected to operate with minimal or no interruptions. The complex nature of randomlyoccurring failures in sewer networks arising from blockages significantly adds to the cost of operation and maintenance.Blockages are significant due to sewage backup or basements flooding, resulting from theiroccurrence. Therefore, continuous performance assessment of sewer pipe networks is necessary to ensurerequired levels of service at an acceptable cost. This study provides insight into the performance of the sewerpipe networks by assessing the proneness of the network to blockages. Furthermore it draws inferences at a holisticstrategic level of influential explanatory factors of blockage proneness, using data available in the SwedishWater and Wastewater Association’s benchmarking system. Results indicate that medium sized municipalitiesare prone to at least 30% more blockages per km per year compared to other municipalities. A hypothesis ofexplanatory factors includes reduced flow volumes and flow depth. Flow velocities below self-cleaning velocityin sewer pipe networks, encouraged by sluggishness of flow are responsible for increased possibility for sedimentdeposition and accumulation in sewers leading to blockages. This is also exacerbated by the deposition of nondisposables(wet wipes, baby diapers, hard paper, etc.), accumulation of fats, oils and grease in sewers andincreased water conservation measures.
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| 4. |
- Whitton, Rachel, et al.
(författare)
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Tertiary nutrient removal from wastewater by immobilised microalgae : impact of wastewater nutrient characteristics and hydraulic retention time (HRT)
- 2018
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Ingår i: H2Open Journal. - : IWA Publishing. - 2616-6518. ; 1:1, s. 12-25
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Tidskriftsartikel (refereegranskat)abstract
- Immobilising microalgal cells has been proposed as a process solution to overcome the barriers associated with the implementation of microalgae for wastewater remediation. This work evaluated the performance and remediation mechanisms of immobilised microalgae for continuous wastewater treatment under varying hydraulic retention times (HRT). Three domestic secondary wastewaters with differing concentrations of orthophosphate (PO4-P), ammonium (NH4-N) and nitrate (NO3-N) were treated by Scenedesmus obliquus immobilised within 2% calcium alginate. Trials were run in continuous operation at HRTs of 3, 6, 12 and 20 h. Removal rates for PO4-P improved with increasing HRT, with minimum residual concentrations of 0.3-3.1 mg center dot L-1 observed at 3 h and 0.01-0.2 mg center dot L-1 at 20 h. Ammonium remediation was not linked to HRT or NH4+ concentration with minimum residual concentrations of <0.001 mg center dot L-1. Reduction in NO3-N improved with increasing HRT, with minimum residual concentrations of <= 19.3 at 3 h and <= 0.4 mg center dot L-1 at 20 h. Remediation was achieved through a combination of mechanisms including biological uptake and precipitation as a by-product of photosynthesis and nutrient metabolism. As such, immobilised microalgae have been proven to be an effective alternative solution for PO43- and NH4+ remediation of wastewater effluents at HRTs of 6-12 h.
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