Carbon footprint analysis for increasing water supply and sanitation in South Africa: a case study

This study investigates the environmental burdens due to the provision of potable water and sanitation in the eThekwini Municipality (Durban), South Africa. This was achieved by employing LCA studies for the individual parts of the urban water system (impoundment, water treatment, distribution, collection, sewage treatment and water recycling). Based on the results of the individual LCAs a base case was constructed.For the provision of potable water and sanitation to new customers, which have not been previously served, two different scenarios (200 000 new customers in an urban environment with waterborne sewage and in a peri-urban environment with on-site sanitation) and three different options (maximising use of existing assets, recycling water and building new infrastructure) were considered and analysed. With regard to the impact scores calculated for both scenarios (urban and peri-urban), the recycling of water is followed by maximising the use of existing assets as the most environmentally friendly options. The construction of new infrastructure carries a higher environmental burden and the use of bottled water for drinking (an additional scenario) carries the highest environmental burden.     

Dominance status influences female reproductive strategy in a territorial African rodent <Emphasis Type="Italic">Rhabdomys pumilio</Emphasis>

Dominance status influences the fitness of many mammals. Using African striped mice Rhabdomys pumilio, we tested whether (1) dominant females have greater reproductive success than subordinate females, (2) dominant females influence the reproductive output of subordinate females when they are housed in close proximity, (3) reproductive output of a female changes in response to the dominance status of her neighbours, and (4) whether prolonged association between individuals influences the variance in reproductive success between dominants and subordinates (i.e. the ‘dear enemy’ phenomenon). The size and mass of litters of dominants increased significantly when housed adjacent to subordinates than when housed apart. The litter size and mass of subordinates remained unchanged, although subordinates spent significantly more time with their pups when housed close to dominants than when housed apart; time spent with pups by dominants remained unchanged. Moreover, females modified their reproductive output and behaviour in relation to the dominance status of their neighbours. Following prolonged association, dominants still had greater reproductive success, but now, the time spent with pups decreased in subordinates. We suggest that dominants adopt a strategy to increase the reproductive value of their litter, whereas subordinates adopt a pup defence strategy. These strategies are flexible and are influenced by the dominance status and period of association between neighbours, so that females could maximize their fitness in response to varying social conditions.     

Male mate guarding in a socially monogamous mammal,the round-eared sengi: on costs and trade-offs

Mate guarding is predicted to be one of the driving forces for the evolution of monogamy, but supporting evidence in free-living mammals is rare. The goals of our study were three-pronged. First, we tested if mate guarding, measured as intrapair distance, occurs as a behavioral tactic in round-eared sengis (Macroscelides proboscideus), a socially monogamous species lacking paternal care and in which females breed asynchronously, producing 2–3 litters during an 8-month long breeding season. Second, we determined if mate guarding involves costs which we identified as changes in male body mass. Third, we investigated whether variation in individual investment in mate guarding depended on the males’ body mass and the number of neighboring males. Field data were collected in a semidesert in South Africa using radio-tracking, trapping, and direct observations during three successive breeding seasons. Mate guarding strongly depended on the females’ reproductive state, and all males started to guard their mates prior to and during estrus, as exemplified by reduced intrapair distance. Mate guarding incurred costs: overall, males lost about 5% of body mass. Male body mass loss and initial body mass were negatively related to the intensity of precopulatory mate guarding. Furthermore, during estrus intrapair distance was inversely correlated with the number of neighboring males. The results show that mate guarding is the predominant male tactic in round-eared sengis. However, since mate guarding imposed costs, males may balance benefits and costs associated with guarding by varying their effort in relation to their physical capabilities and the competitive environment.     

Assessing barriers to effective spatial planning in Mauritius. A combination of SWOT and gap surveys

This paper examines the barriers to effective spatial planning in Mauritius. With its competitive advantage, due to its strategic position into Africa, the island is experiencing rapid development. However, current land development, especially considering land scarcity, reflects a lack of integrated strategic decision-making in the spatial planning system in Mauritius. Using a PESTLE framework and two quantitative surveys, namely a SWOT analysis addressed to the planners in Mauritius, followed by a gap analysis addressed to a wider group of professionals, the barriers have been identified. The result shows that overall significant barriers exist. The contributions of the research have been: first, in the methods adopted to identify such barriers towards effective spatial planning; second, in the identification of the barriers in order of importance; and third, in the formulation of strategies to address these barriers.     

Land application of biomass residue generated from palm oil processing: its potential benefits and threats

Man’s increased demand for food and better living conditions has led to over exploitation of resources and the consequent generation of enormous amounts of liquid and solid waste materials. This is one of the global challenges for mankind. In Malaysia, palm oil mill waste (POMW) contributes the highest proportion of industrial solid wastes produced yearly. Wastes from the mills include palm oil mill effluent, decanter cake, empty fruit bunches, seed shells and the fibre from the mesocarp. Direct application of POMW into agricultural soil has resulted in a number of problems such as water pollution, leaching. However, with application rates specific for targeted plant species, land application can be employed as a permanent solution to the problem of waste from palm oil mills. This review examines the characteristics of each of the palm oil wastes and their potential for use as a future fertilizer supplement.     

Assessment of physico-chemical qualities and heavy metal concentrations of Umgeni and Umdloti Rivers in Durban,South Africa

We assessed the effects of seasonal dynamics on the physico-chemical qualities and heavy metals concentrations of the Umgeni and Umdloti Rivers in Durban, South Africa. Water samples were taken from nine different sampling points and analysed for the following parameters; temperature, pH, turbidity, electrical conductivity (EC), biological oxygen demand (BOD₅), chemical oxygen demand (COD), phosphate (PO₄ ^2?), nitrate (NO₃ ^2?), ammonium (NH₄ ⁺), sulphate (SO₄ ^2?), lead (Pb²⁺), mercury (Hg²⁺), cadmium (Cd²⁺), aluminium (Al³⁺), and copper (Cu²⁺) using standard methods. The data showed variations it terms of the seasonal fluctuations and sampling regime as follows: temperature 12–26.5 °C; pH 5.96–8.45; turbidity 0.53–18.8 NTU; EC 15.8–5180 mS m^?1; BOD₅ 0.60–7.32 mg L^?1; COD 10.5–72.9 mg L^?1; PO₄ ^2??<?500–2,460 μg L^?1; NO₃ ^2? <0.05–4.21 mg L^?1; NH₄ ⁺?<?0.5–1.22 mg L^?1; SO₄ ^2? 3.90–2,762 mg L^?1; Pb²⁺ 0.023–0.135 mg L^?1; Hg²⁺ 0.0122–0.1231 mg L^?1 Cd²⁺ 0.068–0.416 mg L^?1; Al³⁺ 0.037–1.875 mg L^?1, and Cu²⁺0.006–0.144 mg L^?1. The concentrations of most of the investigated parameters exceeded the recommended limit of the South African Guidelines and World Health Organization tolerance limits for freshwater quality. We conclude that these water bodies are potentially hazardous to public health and this highlights the need for implementation of improved management strategies of these river catchments for continued sustainability.     

Adsorptive removal of Pb2+ form aqueous solution by macrocyclic calix[4]naphthalene: kinetic, thermodynamic, and isotherm analysis

Background

The adsorption characteristics of Pb²⁺ ions from aqueous solutions onto calix[4]naphthalene have been investigated.

Method

Calix[4]naphthalene was prepared by the condensation of 1-naphthol and formaldehyde (1:2) in presence of hydrochloric acid at 80°C. The effect of various operation parameters, such as solution pH, initial metal ion concentration, contact time, and temperature, on the adsorption capacity of calix[4]naphthalene for Pb²⁺ have been investigated.

Result

Experimental results showed that the adsorption of Pb²⁺ ions increased with the increase in solution pH and temperature. Langmuir and Freundlich isotherms models were used to describe the adsorption behavior of Pb²⁺ by calix[4]naphthalene. Equilibrium data fitted well with the Langmuir isotherm model and the maximum adsorption capacity of calix[4]naphthalene for Pb²⁺ at 30°C was found to be 29.15 mg g^?1. Kinetic studies indicated that the adsorption followed pseudo-second order model and the thermodynamic studies revealed that the adsorption process was spontaneous and endothermic in nature. The obtained results demonstrated that calix[4]naphthalene can be used as an effective adsorbent for Pb²⁺ ions removal from water.     

Bacterial biosensors for rapid and effective monitoring of biodegradation of organic pollutants in wastewater effluents

Significant amounts of toxic substances which are hazardous to animals, plants, microorganisms, and other living organisms including humans are released annually into aquatic and terrestrial environments, mostly from improper wastewater discharges. Early detection of such pollutants in wastewater effluents and proper monitoring before their final release into the environment is therefore necessary. In this study, two whole-cell bacterial biosensors were constructed by transforming competent cells of Shigella flexneri and Shigella sonnei with pLUX plasmids and evaluated for their potential to monitor wastewater samples undergoing degradation by measuring bioluminescence response using a microplate luminometer. Both bacterial biosensors were found to be extremely sensitive to the wastewater samples, with different patterns, concomitant with those of the COD removals demonstrated at the different days of the degradation. Generally higher bioluminescence values were obtained at the later days of the degradation period compared to the initial values, with up to 571.76% increase in bioluminescence value obtained at day 5 for 0.1% (v/v) effluent concentration. Also, a steady decrease in bioluminescence was observed for the bacterial biosensors with increasing time of exposure to the wastewater effluent for all the sampling days. These biosensor constructs could therefore be applicable to indicate the bioavailability of pollutants in a way that chemical analysis cannot, and for in situ monitoring of biodegradation. This has great potential to offer a risk assessment strategy in predicting the level of bioremediation required during municipal wastewater treatment before their final discharge into the aquatic milieu.     

Adsorption of malachite green and chrysoidine-Y by Sn-pillared clay

The aim of this research was to pillar the bentonite clay (Bt) with polyhydroxy tin chloride. The synthesized Tin-pillared interlayer clay (Sn-PILC) was characterized using X-ray diffraction (XRD), Fourier Transform Infrared spectra (FT-IR), Brunauer-Emmer Teller (BET) analysis, Thermogravimetric analysis (TGA), and Scanning Electron Microscopy (SEM). Adsorption capacity of raw-Bt and tin pillared interlayer clay (Sn-PILC) was examined for two dyes, namely, Malachite Green (MG) and Chrysoidine-Y (CY) from their aqueous solutions. The effects of physicochemical parameters like solution pH, dose, and dye concentration were investigated. The maximum adsorption efficiency at equilibrium dye concentration for Sn-PILC was 66.229 mg g^–1 for MG and 63.792 mg g^–1 for CY. Sn-PILC obeyed Langmuir isotherm for both the dyes whereas raw-Bt followed Freundlich isotherm. On the other hand, both adsorbents followed PFO as well as PSO kinetic model, indicating physisorption assisted by chemisorption. Thermodynamic studies were performed to determine the adsorption behavior of Sn-PILC for both the dyes. Regeneration studies revealed 80% efficiency up-to five adsorption-desorption cycles.     

Elemental uptake by edible herbs and lettuce (Latuca sativa)

The total concentration of toxic elements (aluminum, cadmium, chromium and lead) and selected macro and micro elements (iron, manganese, copper and zinc) are reported in six leafy edible vegetation species, namely lettuce, spinach, cabbage, chards and green and red types of Amaranth herbs. Although spinach and chards had greater than 125 mv of iron, both the amaranthus herbs recorded > than 320 microg g(-1) dry weight. In both the spinach and chard species, the Mn and Zn levels were appreciable recording > 225 microg g(-1) and 150 microg g(-1) dry weight, respectively. Aluminum concentrations were (in microg g(-1) dry weight) lettuce (10), cabbage (11), spinach (167), chards (65), amaranthus green (293) and amaranthus red (233). All the micro and macro elements and the toxic elements (Ni, Cr, Cd and Pb) elements analyzed, were below the recommended maximum permitted levels (RMI) in vegetables. Further the elemental uptake and distribution of the nine elements, at three growth stages of the lettuce plant grown on soil bed under controlled conditions are detailed. In the soil, except for iron (16%), greater than 33% of the other cations were in exchangeable form. Generally in the lettuce plant, roots retained much of the iron (> 224 microg g(-1)) and aluminum (> 360 microg g(-1)), while leaves had less than 200 microg g(-1) of iron and 165 microg g(-1) of Al. Although the concentrations of elements marginally decreased with growth, the lettuce leaves had significant amounts of Mn (30 microg g(-1)), Zn (50 microg g(-1)) and Cu (3.6 microg g(-1)). Some presence of lead in leaves (2.0 microg g(-1)) was noticed, but all the toxic and other elements analyzed were well below the RMI values for the vegetables.