Aspects of waste water treatment by electrochemical method and nano-technology: Their possible application in Hong Kong

This presentation provides a brief overview of recent developments in waste water treatment using electrochemical processes and nano-Technology which can find possible applications in Hong Kong. The presence of antibiotics as micropollutants in the environment, such as in municipal wastewater, surface water, ground water, and agricultural soils, has gained much attention in recent years. Antibiotics are used not only to prevent diseases and infection, but they are also added to animal feed at sub-therapeutic levels to promote weight production. Approximately 21.9 million pounds of antibiotics were administered to animals annually from 2002 to 2004 in the United States, but only a fraction of them were absorbed in the guts of animals. Consequently, up to 90% of administered antibiotics might be excreted into the environment via animal manure or urine. In this study, electrochemical degradation of antibiotics in water was carried out to provide reference for exploring a feasible way to treat these organics. A Ce doped SnO2 anode and Ti were used as an anode and cathode set in an undivided cell. Metronidazole (MNZ) was used as model compound. Electrolysis was performed in Na2SO4 electrolyte. The results showed that the Ce doping made the structure of the SnO2-Sb electrodes compact and multi-porous, and the efficiency of the process was increased. Recently, Nano-scale zero-valent iron (NZVI) technology has also been widely used for the treatment of environmental pollutants. It has the advantage that the small particle size of the adsorbent results in a large specific surface area and hence a high density and great intrinsic reactivity of e surface sites. All of these lead to a high efficiency in the elimination of a variety of pollutants. However, the mechanism of contaminant removal by NZVI is still under debate, although several mechanisms have been proposed. In the study reported here, the mechanism for the absorption of MNZ by NZVI particles was established based on the experimental results obtained. The findings can be used for the optimization of conditions to be used for this treatment process.