Water is becoming a scarce resource in many parts of South Africa and, therefore, numerous plans are being put in place to satisfy the increased urban demand for this resource. Two of the methods ...currently considered are desalination of seawater and reuse of mine-affected water based on the use of reverse osmosis (RO) membranes. Due to their high energy consumption and associated environmental impacts, these methods have been under scrutinity and, therefore, an LCA was undertaken for both methods. To allow comparison between the two, the functional unit of 1 kL of potable water was specified. Design data were collected for both the construction and operation phases of the plants while SimaPro was used as the LCA analysis software with the application of the ReCiPe Midpoint method. The results indicate that the operation phase carried a greater environmental burden than the materials required for the infrastructure. In particular, electricity production and consumption is responsible for the majority of environmental impacts that stem from the respective plants. The total energy consumption of the proposed desalination plant is 3.69 kWh/kL and 2.16 kWh/kL for the mine-water reclamation plant. This results in 4.17 kg CO2 eq/kL being emitted for the desalination plant and 2.44 kg CO2 eq/kL for the mine-affected plant. A further analysis indicated that replacing South African electricity with photovoltaic (solar) and wind power has the potential to bring significant environmental benefits. The integration of these renewable energy systems with desalination and membrane treatment of mine-affected water has been proven to reduce environmental burdens to levels associated with conventional water technologies powered by the current electricity mix.
The Engineering Field Testing Platform (EFTP) was designed to provide an opportunity for technology developers (TDs) to test non-sewered sanitation prototypes in the eThekwini Municipal Area ...(Durban), South Africa. Between 2017 and 2020, 15 sanitation systems were tested in informal settlements, peri-urban households, and other ‘real world’ settings. This paper illustrates the lessons learned from establishing and managing this testing platform. Costs and timelines for testing are dependent on several factors, including the aims of testing, the development stage of the prototype, whether testing takes place in a community or household setting and if a testing site is shared between prototypes. Timelines were routinely underestimated, particularly for community engagement and commissioning of prototypes to reach steady-state operation. Personnel accounted for more than half of the EFTP’s costs. The presence of the municipality as a platform partner was vital to the success of testing, both for gaining political support and for enabling access to testing sites. It is noted that working in communities, with test sites in public spaces, requires technical and social sensitivity to context. It was important to ensure testing supported future municipal decision-making on service provision, as well as longer-term development within communities. The high number of stakeholders, locally and internationally, raised management challenges common to any large project. However, the EFTP added value to TDs, the eThekwini Municipality, and communities requiring improved sanitation services; this was amplified through the platform approach.
We investigate the nature of CXOU\,J005440.5-374320 ( a peculiar bright ($ and soft X-ray transient in the spiral galaxy NGC\,300 with a six-hour periodic flux modulation that was detected in a 2014 ...observation. Subsequent observations with and as well as a large observational campaign of NGC\,300 and its sources performed with the Swift Neil Gehrels Observatory showed that this source exhibits recurrent flaring activity: four other outbursts were detected across sim 8 years of monitoring. Using data from the archive and from the and catalogues, we determined that the source is likely associated with a bright blue optical/ultraviolet counterpart. This prompted us to perform follow-up observations with the Southern African Large Telescope in December 2019. With the multi-wavelength information at hand, we discuss several possibilities for the nature of Although none is able to account for the full range of the observed peculiar features, we found that the two most promising scenarios are a stellar-mass compact object in a binary system with a Wolf--Rayet star companion, or the recurrent tidal stripping of a stellar object trapped in a system with an intermediate-mass (sim 1000\,M$_ black hole.
We present nearly 500 days of observations of the tidal disruption event (TDE) ASASSN-18pg, spanning from 54 days before peak light to 441 days after peak light. Our data set includes X-ray, UV, and ...optical photometry, optical spectroscopy, radio observations, and the first published spectropolarimetric observations of a TDE. ASASSN-18pg was discovered on 2018 July 11 by the All-Sky Automated Survey for Supernovae (ASAS-SN) at a distance of d = 78.6 Mpc; with a peak UV magnitude of m 14, it is both one of the nearest and brightest TDEs discovered to-date. The photometric data allow us to track both the rise to peak and the long-term evolution of the TDE. ASASSN-18pg peaked at a luminosity of L 2.4 × 1044 erg s−1, and its late-time evolution is shallower than a flux ∝t−5/3 power-law model, similar to what has been seen in other TDEs. ASASSN-18pg exhibited Balmer lines and spectroscopic features consistent with Bowen fluorescence prior to peak, which remained detectable for roughly 225 days after peak. Analysis of the two-component H profile indicates that, if they are the result of reprocessing of emission from the accretion disk, the different spectroscopic lines may be coming from regions between ∼10 and ∼60 lt-days from the black hole. No X-ray emission is detected from the TDE, and there is no evidence of a jet or strong outflow detected in the radio. Our spectropolarimetric observations indicate that the projected emission region is likely not significantly aspherical, with the projected emission region having an axis ratio of 0.65.
A review concerning the anaerobic baffled reactor (ABR) treating communal wastewater under mesophilic conditions is presented. Existing studies indicate strong resilience of the reactor towards ...loading variations and shock-loads. The compartmentalisation of the ABR is a strongly stabilising factor with feed fluctuations being evened out across reactor chambers. Significant chemical oxygen demand (COD) reduction occurs almost exclusively in the first three chambers. The hydraulic rather than the organic loading rate is treatment limiting. Laboratory-scale studies show high treatment efficiencies of above 80% COD removal. It was found that most laboratory-scale studies do not factor in important aspects of field operation, such as diurnal fluctuations of feed characteristics, adequate start-up periods and periods of constant loading and optimised chamber outlet design, and never studied the effect of loading on sludge digestion. Performance data on full-scale ABR implementations, however, are extremely scarce, and existing studies are without exception affected by site-specific treatment-limiting factors hindering the extrapolation of generally valid conclusions. In view of a large-scale roll-out, communal ABRs are not sufficiently understood. Current challenges concerning the optimisation of reactor design require numerous well-monitored long-term full-scale reactor investigations. Existing ABR investigations yield encouraging results, supporting that the ABR may be one of the solutions answering the global call for low-maintenance, robust treatment systems.
The study assessed the suitability of two effluent types, namely anaerobic filtered (AF) and horizontal flow constructed wetland (HFCW) effluent for Moistube irrigation (MTI). Secondary to this, the ...study determined the plugging coefficients (α) on MTI for the respective effluents. The feed water was supplied from a raised tank (3.5 m), and mass-flow rates were recorded at 15 min intervals using an electronic balance. The effluent feed water concentrations and experimental room temperature (25 °C ± 1 °C) were continuously monitored and kept constant. Hermia's models based on the Formula: see text coefficient was used to select the best fitting fouling mechanism model and, consequently, the plugging coefficients. In addition, microbial colony analysis and scanning electron microscopy (SEM) analysis was carried out to assess the composition of the deposited sediment (DS) and adhered bacterial film (ABF) onto the MTI lateral. The study revealed that MTI pore blocking was a complex phenomenon described by complete pore-blocking model (Formula: see text ≥ 0.50). Discharge followed an exponential decay with early fouling observed on AF effluent because of a high concentration of total suspended solids (TSS) and dissolved organic matter (DOM). Discharge declined by 50% after 20 and 10 h of intermittent operation for AF and HFCW effluent, respectively. The α for each effluent (foulant) were Formula: see text = 0.07 and Formula: see text = 0.05, respectively, for AF and HFCW. The microbial analysis revealed bacterial aggregation structures that contributed to pore blocking. SEM imaging revealed complete surface coverage by deposited sediment. It is concluded that water quality determines the operation life span of MTI, and the two effluents promote accelerated MTI pore fouling or blocking. Continuous use without flushing the MTI will promote membrane degradation and reduced discharge efficiency. Additional filtration can potentially mitigate the membrane degradation process.
We report an ethnographic study of specialist travel agents in luxury wildlife tourism. Agents consider 30 factors in 5 groups, related to client, destination, attraction, operator and agent. They ...consider the groups in sequence rapidly and intuitively. They are driven by a powerful regard for the high expectations of wealthy clients, and a sense of responsibility to the clients, but they assume authority over the decision. They rely on personal experience with each particular place and tourism product, and sell only what they know. One of their skills is to project themselves into the client's perspective so as to imagine a trip in great detail. This process contrasts strongly with the explicit deterministic approach used by retail travel agents in high-volume lower-priced subsectors, where earnings are driven by commission and incentive structures. For high-end agents, establishing long-term relationships of mutual trust with individual clients and tour operators is paramount.
•We analyse decision processes of specialist travel agents in luxury wildlife tourism.•Agents narrow down their choice by considering 5 groups of external factors sequentially.•Agents use intuitive tacit expertise relying principally on their personal experience.•Expectations are very high and agents act as powerful information brokers.•To confirm their choice, agents project themselves into their clients' perspective.
ABSTRACT
It was recently proposed that the cataclysmic variable (CV) LAMOST J024048.51+195226.9 may be a twin to the unique magnetic propeller system AE Aqr. If this is the case, two predictions are ...that it should display a short period white dwarf spin modulation, and that it should be a bright radio source. We obtained follow-up optical and radio observations of this CV, in order to see if this holds true. Our optical high-speed photometry does not reveal a white dwarf spin signal, but lacks the sensitivity to detect a modulation similar to the 33 s spin signal seen in AE Aqr. We detect the source in the radio, and measure a radio luminosity similar to that of AE Aqr and close to the highest so far reported for a CV. We also find good evidence for radio variability on a time-scale of tens of minutes. Optical polarimetric observations produce no detection of linear or circular polarization. While we are not able to provide compelling evidence, our observations are all consistent with this object being a propeller system.
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