Application of Biological and Chemical Processes to Wastewater Treatment

Existing wastewater treatment plants (WWTPs) face huge challenges that can impede the achievement of sustainable development goals for clean water and sanitation (SDG 6) and clean energy (SDG 7), amongst others [...

Photocatalytic oxidation of natural organic matter in water

Increased concentrations of natural organic matter (NOM), a complex mixture of organic substances found in most surface waters, have recently emerged as a substantial environmental issue. NOM has a significant variety of molecular and chemical properties, which in combination with its varying concentrations both geographically and seasonally, introduce the opportunity for an array of interactions with the environment. Due to an observable increase in amounts of NOM in water treatment supply sources, an improved effort to remove naturally-occurring organics from drinking water supplies, as well as from municipal wastewater effluents, is required to continue the development of highly efficient and versatile water treatment technologies. Photocatalysis has received increasing interest from around the world, especially during the last decade, as several investigated processes have been regularly reported to be amongst the best performing water treatment technologies to remove NOM from drinking water supplies and mitigate the formation of disinfection by products. Consequently, this overview highlights recent research and developments on the application of photocatalysis to degrade NOM by means of TiO2-based heterogeneous and homogeneous photocatalysts. Analytical techniques to quantify NOM in water and hybrid photocatalytic processes are also reviewed and discussed

Improving carbon coated TiO2 films with a TiCl4 treatment for photocatalytic water purification

Using a simple thermal decomposition route, carbon-TiO2 hybrid films have been synthesized from a catechol-TiO2 surface complex. The coated films display enhanced visible region absorption, owing to the thin (~2 nm) layer of carbon encapsulating the TiO2. While photocatalytically active under visible light alone, it is demonstrated that the activity of the carbon coated films can be improved further by a hydrolytic treatment with TiCl4, leading to the introduction of small TiO2 particles (5-10nm) and doping of chlorine into the structure. The combination of the carbon layer and TiCl4 treatment gives increased photocatalytic performance for the photodegradation of dyes, phenolic pollutants and the reduction of toxic Cr(VI) to relatively benign Cr(III). In addition, the carbon coated films show improved bactericidal activity under UV irradiation, and hence have been successfully tested against the most common types of pollutant present in potential drinking waters

Environmental Impacts of Conventional versus Organic Eggplant Cultivation Systems: Influence of Electricity Mix, Yield, Over-Fertilization, and Transportation

We report a comparative environmental study of organic and conventional open-field eggplant cultivation systems under Mediterranean (northern Greece) climatic conditions. Actual life cycle inventory (LCI) data were collected from local farm systems. Using life cycle assessment (LCA), organic eggplant cultivation exhibited better environmental performance per unit area (24.15% lower total environmental footprint compared to conventional cultivation), but conventional cultivation performed better per unit of mass (28.10% lower total environmental footprint compared to organic cultivation). The conventional system attained higher scores in eutrophication (up to 37.12%) and ecotoxicity (up to 83.00%) midpoint impact categories, due to the use of chemical fertilizer and pesticide. This highlights the need for spatially explicit LCA that accounts for local environmental impacts at the local scale. For both cultivation systems, the main environmental hotspot was groundwater abstraction for irrigation owing to its infrastructure (drip irrigation pipes and pump) and electricity consumption from the fossil fuel-dependent energy mix in Greece. Excessive addition of soil fertilizer greatly affected the environmental sustainability of both systems, especially conventional cultivation, indicating an urgent need for fertilizer guidelines that enhance environmentally sustainable agricultural practice worldwide. Results were sensitive to lower marketable fruit yield, with the organic system performing better in terms of environmental relevance with respect to maximum yield. When renewable energy sources (RES) were used to drive irrigation, both systems exhibited reductions in total environmental footprint, suggesting that RES could help decarbonise the agricultural sector. Finally, eggplant transportation greatly affected the environmental sustainability of both cultivation systems, confirming that local production and consumption are important perquisites for environmental sustainability of agricultural products.</jats:p