Nitrogen-doped TiO2 nanostructured membranes

I have a leading role as researcher in a European Union-funded project study aimed at developing a photocatalytic water-treatment process that harnesses UVA and visible (VIS) solar wavelengths to disinfect water and break down organic pollutants. First, the impact of water quality on the physical and operational parameters of the solar-activated N-doped TiO2 catalyst thin film coated on glass was demonstrated. Results of this study have been published in the Journal of Hazardous Materials and Chemical Engineering Journal. A sol-gel method was then developed to deposit photocatalytically active thin films of N-doped TiO2 on commercial porous α-Al2O3 ceramic membranes. This study has already advanced current knowledge by presenting an optimal low-cost and promising technology that integrates water filtration and oxidation using coated ceramic membranes in a simple treatment unit. Water flow through the photocatalytic membrane resulted in significantly higher reaction rates compared to flow on top of the membrane. In addition, N-doped TiO2-coated membranes showed enhanced activity for the UV-VIS wavelengths compared to TiO2-coated membranes. We are currently investigating the impact of this technology on inactivation of various bacteriophages and fluorescently tagged viruses, and are using additional catalysts and porous supports.

Wastewater reuse for global water scarcity

Wastewater reuse is one of the most sustainable and promising solutions for global water scarcity. As such, wastewater reuse provides a major alternative to fresh water for the growing needs of water for food production. However, there remain barriers to more widespread application of wastewater reuse, including inadequate removal of organic carbon and nitrogen compounds, micropollutants and pathogens. Soil aquifer treatment (SAT) improves water quality via the percolation of treated waste water through unsaturated soil. Nevertheless, the use of reclaimed waste water for irrigation is an important route for the introduction of organic compounds into the environment. In this study, we are implementing an innovative tertiary hybrid pilot system consisting of high-rate biofiltration, ozonation and short (short hydraulic residence time) SAT technology to replace the conventional SAT and produce similar- or better-quality reclaimed effluent for reuse (funded by a BMBF-MOST grant). During SAT, oxygen depletion was observed in the aquifer; infiltration of more oxygenated water (via synergistic hybrid ozonation treatment) enables more efficient use of an artificial recharge system and provides high-quality water originating from waste water for reuse. We are currently demonstrating the long-term application, funded by an EU grant, and analyzing the microbial communities inhabiting the biofilter and recharge borehole.

Biofuels in general and ethanol in particular may have many advantages over fossil fuels

As a consequence, there is a constant search for better methods of biomass conversion. To date, industrial production of fuels from biomass has focused on specially grown crops, but this practice carries with it a host of problematic issues. Therefore, there is increasing interest in the production of such fuels from lignocellulosic waste, such as agricultural wastes. Such wastes are very rich in cellulose that can be fermented to ethanol after proper pretreatment (i.e. saccharification). Nevertheless, one problem of using such waste is the presence of high concentrations of lignin that inhibit enzymatic conversion of the cellulose to sugars. The aim of this project is to test the use of various advanced oxidation processes (AOPs) to degrade the lignin. The effects of these catalytic processes on saccharification and fermentation are currently being evaluated.

Image analyses of particle

A topic that particularly fascinates me is image analyses of particle size and shape and further understanding the interactions between particles from various water sources and advanced-oxidation and particle-separation processes. In a recent study, the influence of effluent particles on ozone degradation of trace organic contaminants and effluent-quality parameters was examined. Secondary effluent was filtered through different pore-size filters and ozonated by various ozone doses. Degradation of both ozone-reactive and ozone-refractory contaminants improved following ozonation of effluent filtered with smaller-pore-size filters, indicating that particles in this range may adversely affect ozonation. The inhibitory effect of particles was attributed to their reaction with ozone, reducing available ozone and HO• radicals. Ozone was shown to react with particles even during the first seconds of the process, suggesting a high rate of some ozone–particle reactions, comparable to ozone reaction with highly reactive dissolved organic matter moieties. Particle image analysis revealed that particle formation/aggregation and particle disintegration occur simultaneously during wastewater ozonation. Thus particles could affect the efficiency of wastewater ozonation. This study was recently published in Environmental Science and Technology.