Abstract:The impact on water resources caused by municipal wastewater discharges has become a critical and ever-growing environmental and public health concern. So far, interventions have been positioned largely 'at the end of the pipe', via the introduction of high-tech and innovative wastewater treatment technologies. This approach is incomplete, inefficient and expensive, and will not be able to address the rapidly growing global wastewater challenge. In order to be able to efficiently address this problem, it is important to adopt an integrated approach such as the three-step strategic approach (3-SSA) consisting of (1) minimization and prevention, (2) treatment for reuse and (3) stimulated natural self-purification. In this study, the 3-SSA was validated by applying it to the Upper Cauca river basin, in Colombia and comparing it to a conventional strategy. The pollutant load removed was 64,805 kg/d Biochemical Oxygen Demand BOD 5 (46%) for the conventional strategy and 69,402 kg/d BOD 5 (50%) for the unconventional strategy. Cost benefit analysis results clearly favoured the 3-SSA (unconventional strategy): NPV for the conventional strategy = −276,318 × 10 3 Euros, and NPV for the unconventional strategy (3-SSA) = +338,266 × 10 3 Euros. The application of the 3-SSA resulted in avoided costs for initial investments and operation and maintenance (O&M), especially for groundwater wells and associated pumps for sugar cane irrigation. Furthermore, costs were avoided by optimization of wastewater treatment plants (WWTPs), tariffs and by replacement of fertilizers.
The organogenesis of the digestive system was described in the African lungfish (Protopterus aethiopicus) from 6 days post‐hatching (6 DPH) to 17 days post‐hatching (17 DPH) reared at 27°C. To elucidate the position of the gastrointestinal tract in relation to the neural tube, notochord and yolk sac at 6 DPH, and to the vertebral column, lungs and kidneys at 17 DPH, larvae were mapped by means of computer‐assisted 3D reconstructions starting from histological serial sections. The larvae showed a simple digestive tract, which appeared as a straight undifferentiated and closed tube at 6 DPH. Microscopical observation showed that yolk reserves were not completely depleted by 17 DPH. During the endogenous feeding period at least up to 17 DPH, the larval digestive system experienced a fast transformation with almost complete development of most digestive organs (pharyngeal teeth, intestinal vestibule, intestine and liver). Our findings suggest that, by 17 DPH, African lungfish larvae are ready to start exogenous feeding.
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