We conducted a field survey of periphyton cultivated on benthic mesh installations in freshwater aquatic systems, including two constructed wetlands and a pond, and also studied periphyton grown on a benthic mesh in laboratory mesocosms. The objectives of this study were to (1) determine if periphyton cultivated on benthic mesh denitrifies at higher rates than the underlying sediments and (2) determine if denitrification rates within periphyton vary with characteristics such as algal and bacterial community structure and biomass. We measured denitrification potential rates of field and laboratory periphyton by the acetylene inhibition method. We characterized algal community composition by algal identification and bacterial community composition by terminal restriction fragment length polymorphisms. Periphyton collected on benthic mesh from our field sites denitrified at significantly higher rates than the underlying sediments, regardless of sampling site or season. Results from both our field survey and laboratory studies indicated a significant, positive correlation between diatom presence and denitrification rate. In our laboratory studies, we found that periphyton with the highest diatom abundance showed the highest denitrification rates as well as a distinct bacterial community composition. These results suggest a synergistic relationship between diatoms and denitrifying bacteria that warrants further study.

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Although ozone disinfection is a well established technology for drinking water treatment, ozone disinfection mechanisms in wastewater are not well understood such that, historically, ozone wastewater disinfection has not been a feasible technology to implement. The HiPOx system is an ozone-based pressurized in-vessel system that can be used either as an advanced oxidation reactor or as a highly efficient ozone dissolution system. The pilot-scale HiPOx system was temporarily installed at the Dublin San Ramon Services District (DSRSD) Wastewater Treatment Plant in Dublin, California. Detailed bioassay testing was conducted on the pilot reactor between October and December 2007. Tests on benchtop reactors were performed in June and August 2007. Pilot tests on the HiPOx reactor located at DSRSD showed that 6.5 log removal of MS2 coliphage was observed at conservative transferred ozone doses of 5 mg/L (contact time of 93 seconds) in microfiltered water, and 7 mg/L (contact time of 50 seconds) in media filtered water. In media filtered water, minimum CT values of 1.0 mg-min/L resulted in non detect total coliform.

The removal of selected pharmaceuticals and personal care products, atrazine, and disinfection by-product precursors, was evaluated during a pilot-scale study conducted at the Bollman Water Treatment Plant in Concord, California, USA. Treatment alternatives included ozonation followed by biologically active filtration (BAF), and nanofiltration. Both technologies exhibited excellent broadspectrum removal of the spiked target contaminants. The ozone/BAF system in particular showed a high degree of effectiveness despite relatively low ozone doses corresponding to a low disinfection target (0.5-log Giardia reduction). The BAF system was observed to remove several contaminants that were relatively unreactive with ozone, demonstrating an important synergy between the ozone and BAF.

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