Environmental Impacts of the Emerging Digital Economy: The E-for-Environment E-Commerce?

The Internet-led digital economy is changing both the production and consumption patterns at the global scale. Although great potential exists to harness information technology in general and the Internet in particular and improve the environment, possible negative impacts of e-commerce on the environment should also be considered and dealt with. In this forum, we discuss both the potential positive and negative impacts of e-commerce. Drawing from insights gained from the complexity theory, we also delineate some broad contours for environmental policies in the information age. Given the paradoxical nature of technological innovations, we want to caution the scientific community and policymakers not to treat the Internet as the Holy Grail for environmental salvation.     

Destruction of fecal bacteria in wastewater by three photosensitizers

Agriculture in Tunisia faces acute problems of water quality and quantity caused by limited conventional water resources. One possibility to cope with low water resources is to purify wastewater for reuse. Among different methods for the disinfection of wastewater, the inactivation of fecal coliforms using a combination of a photosensitiser (Rose Bengal, Methylene Blue, cationic porphyrin) with sunlight was determined on a small scale. In parallel the sensitizer photobleaching was also followed under the same conditions. The results described in this paper show that the meso-substituted cationic porphyrin is more efficient and more photostable than Methylene Blue and Rose Bengal in wastewater. A lower cationic porphyrin concentration, 1 microM, resulted in very little cell death. Higher concentrations, 5 microM or 10 microM, produced more cell death. Nevertheless there was a small difference between concentrations 5 and 10 microM. By increasing the duration of irradiation we can improve the log reduction in bacteria and compensate for a low concentration of sensitizer or for a less efficient type of sensitizer. The same log reduction in fecal bacteria was obtained with 5 and 10 microM of cationic porphyrin during the fourth hour of treatment.     

Determining effective interfacial tension and predicting finger spacing for DNAPL penetration into water-saturated porous media

The difficulty in determining the effective interfacial tension limits the prediction of the wavelength of fingering of immiscible fluids in porous media. A method to estimate the effective interfacial tension using fractal concepts was presented by Chang et al. [Water Resour. Res. 30 (1994) 125]. We modified the method in that the macroscopic interface length was used instead of the system width. Methods to determine the macroscopic and the microscopic interface length are given. Lab experiments of dense nonaqueous phase liquid (DNAPL) penetrating into water-saturated glass beads were carried out in a two-dimensional (2-D) transparent chamber. The displacement processes were recorded using a 35-mm camera or a video camera, which was directly connected to and controlled by a computer. Unlike the method of Chang et al. (1994), the modified method used here gives a constant value of the effective interfacial tension over time. The predicted wavelengths of fingering are relatively close to those observed except for the fine beads.     

A two-dimensional water-quality model for a winding and topographically complicated river

In this paper, a two-dimensional numerical calculation algorithm for water-quality modeling is presented. The algorithm is designed specifically for river systems with complicated geometric conditions. When velocity field data of the river are not available, the numerical calculation algorithm for the water-quality modeling can be used to project river-water quality by using a topographic map of the river course and a finite element method. The calculation results of the water-quality model can show the concentration fields of various pollutants. The water-quality model was applied to a case-study in the Hengyang City section of Xiangjiang River in Hunan Province, China. The river under consideration is winding and has an isle between two branches. In 1995, Chinese government secured a World Bank loan to conduct a Waterways Project in the study region. It was expected that construction works in the river section might affect water quality. Given that the project would change the hydrological regime of the river system and discharges, and so would affect water quality, there would be a need for model results that would predict the water-quality impacts of the Waterways Project. In particular, the study intended to apply the model to identify changes in river-water quality associated with the construction of Dayuandu navigation key project. It is hoped that the numerical calculation algorithm for the water-quality modeling presented in this paper can also be applied to other shallow rivers with similar topographical conditions.     

Piggery waste treatment by anaerobic digestion and nutrient removal by ionic exchange

Piggery wastes must be treated before their disposal. The high solids content and high chemical oxygen demand of piggery wastes indicated that anaerobic biological treatment could be successfully applied as primary treatment. For that reason, a comparison between upflow anaerobic sludge bed reactor (UASB) and anaerobic fixed bed reactor (AFBR) at a similar organic volumetric loading rate of 5 kg DQO/m³ day was carried out. 60% of the piggery waste COD was removed with the AFBR compared to 40% with the UASB, thus showing a better performance of the AFBR. After 1-h sedimentation secondary process, both anaerobic effluents were treated by ionic exchange with natural zeolite due to their high values of ammoniacal nitrogen (NH⁺₄ plus free NH₃). The high removal of nutrients reported (90%) shows zeolite to be a good choice as tertiary treatment.     

Trisomy 20 mosaicism confirmed in a phenotypically normal liveborn

Prenatal diagnosis of trisomy 20 mosaicism in this case was based on cytogenetic analysis of cultured amniotic fluid cells (23/52 cells were trisomy 20 representing cells from each of four primary cultures). The pregnancy continued to term and the mosaicism was confirmed in the phenotypically normal male neonate by analysis of cultured foreskin fibroblasts (7/49 cells + 20) and placental cells 20/20 cells + 20) whereas the peripheral lymphocytes were cytogenetically normal (20/20 cells were 46,XY). This represents the first confirmation of trisomy 20 mosaicism in a phenotypically normal full-term neonate.