Evaluating the sustainability of ceramic filters for point-of-use drinking water treatment.

This study evaluates the social, economic, and environmental sustainability of ceramic filters impregnated with silver nanoparticles for point-of-use (POU) drinking water treatment in developing countries. The functional unit for this analysis was the amount of water consumed by a typical household over ten years (37,960 L), as delivered by either the POU technology or a centralized water treatment and distribution system. Results indicate that the ceramic filters are 3-6 times more cost-effective than the centralized water system for reduction of waterborne diarrheal illness among the general population and children under five. The ceramic filters also exhibit better environmental performance for four of five evaluated life cycle impacts: energy use, water use, global warming potential, and particulate matter emissions (PM10). For smog formation potential, the centralized system is preferable to the ceramic filter POU technology. This convergence of social, economic, and environmental criteria offers clear indication that the ceramic filter POU technology is a more sustainable choice for drinking water treatment in developing countries than the centralized treatment systems that have been widely adopted in industrialized countries.

Retention and transport of silver nanoparticles in a ceramic porous medium used for point-of-use water treatment.

The retention and transport of silver nanoparticles (Ag-NPs) through a ceramic porous medium used for point-of-use drinking water purification is investigated. Two general types of experiments were performed: (i) pulse injections of suspensions of Ag-NPs in aqueous MgSO4 solutions were applied to the ceramic medium, and effluent silver was quantified over time; (ii) Ag-NPs were applied directly to the porous medium during fabrication using a paint-on, dipping, or fire-in method, a synthetic, moderately hard water sample with monovalent and divalent inorganic ions was applied to the ceramic medium, and effluent silver was quantified over time. These latter experiments were performed to approximate real-world use of the filter medium. For experiments with Ag-NPs suspended in the inflow solution, the percentage of applied Ag-NPs retained in the ceramic porous medium ranged from about 13 to 100%. Ag-NP mobility decreased with increasing ionic strength for all cases and to a lesser extent with increasing nanoparticle diameter. Citrate-capped particles were slightly less mobile than proteinate-capped particles. For ceramic disks fabricated with Ag-NPs by the paint-on and dipping methods (where the Ag-NPs are applied to the disks after firing), significant release of nanoparticles into the filter disk effluent was observed relative to the fire-in method (where the nanoparticles are combined with the clay, water, grog, and flour before firing). These results suggest that the fire-in method may be a new and significant improvement to ceramic filter design.

Evaluation of environmental impacts of two common restoration methodologies for pipes that convey stormwater runoff.

This study investigated the environmental impact of two commercial stormwater pipe-repair technologies (Ultraliner and Troliner). These technologies use liners believed to contain three plasticizers of potential environmental concern: bisphenol A (BPA), di-(2-ethylhexyl) phthalate (DEHP), and benzyl butyl phthalate (BBP). The release of these two products was investigated both experimentally and mathematically. Kinetic batch experiments were conducted to determine if contaminants were leaching from Ultraliner, Troliner, and the grout (used with Troliner) into water. In all cases for all incubation times up to 48 h, none of the three plasticizers were detected in water in contact with any of the pipe-repair materials. A generic GC-FID scan did not detect any unidentified compounds relative to control samples. In addition, a mathematical model of plasticizer leaching from the pipe-liner material was developed. Under various pipe geometries, simulated aqueous concentrations of the plasticizers were less than regulatory limits.

Photocatalytic degradation of Bisphenol A (BPA) using immobilized TiO2 and UV illumination in a horizontal circulating bed photocatalytic reactor (HCBPR).

Photocatalytic degradation of Bisphenol A (BPA) in the presence of titanium dioxide (TiO(2)) and ultraviolet (UV) illumination was performed in a self-designed horizontal circulating bed photocatalytic reactor (HCBPR). TiO(2) catalyst was immobilized on the surface of polyurethane foam (PF) cubes via microwave-assisted liquid phase deposition. The effects of initial BPA concentration, initial pH, TiO(2) dosage and temperature on BPA photodegradation were investigated in order to obtain the optimum operational conditions. The results reveal that the BPA degradation efficiency can be effectively improved by increasing pH from 3.4 to 12.3 or decreasing the initial BPA concentration from 50 to 10 ppm. The optimum TiO(2) carrier dosage (the ratio of the volume of PF carriers to the effective reaction volume of HCBPR) was about 1%. Besides, the effect of temperature on BPA photodegradation was found to be unremarkable in the range of 21.2-30.5 degrees C. Total organic carbon (TOC) was used to evaluate the mineralization of BPA during the photodegradation process. Under the optimum conditions, 95% removal of TOC and 97% removal of BPA can be achieved after 6h of UV radiation, which demonstrates the high photodegradation efficiency of BPA in HCBPR.