A biochemical oxygen demand (BOD) monitoring system, based on electrochemically-active bacteria in combination with a microbial fuel cell, has been developed for the purpose of on-site, on-line and real-time monitoring of practical wastewater. A microbial fuel cell that had been enriched with electrochemically-active bacteria was used as the basis of the measurement system. When synthetic wastewater was fed to the system, the current generation pattern and its Coulombic yield were found to be dependent on the BOD5 of the synthetic wastewater. A linear correlation between the Coulombic yields and the BOD5 of the synthetic wastewater were established. Real wastewater obtained from a sewage treatment plant also produced a highly linear correlation between the Coulombic yield and BOD5 in the system. To examine on-site, on-line and real-time monitoring capability, the BOD monitoring system was installed at a sewage treatment plant. Over 60 days, the measurement system was successfully operated with high accuracy and good stability with the measuring period for a sample being 45 min. This application showed that the application of the measurement system was a rapid and practical way for the determination of BOD5 in water industries.

Wastewater produced in the form of an o/w emulsion is difficult to treat properly because of its complex behavior. To acquire information for the optimization of emulsion controlling processes, the interfacial features of emulsion systems have been investigated in this work. The surface tension is found to decrease as the oil content is increased, and contact angle is influenced by the hydrophobicity of the substrate. The work of adhesion for substrates with different degrees of hydrophobicity has been estimated from the contact angle and surface tension. Temperature and pH have a significant influence on the turbidity and surface tension, and it is observed that electrophoretic characteristics of oil droplets are closely related with turbidity. Also, effects of inorganic salts and surfactants on the electrokinetic properties of emulsions have been considered, and the influence of coagulant on the stability is discussed through the calculation of potential energy of interaction between oil droplets. Adsorption and electrocoagulation processes have been attempted under various conditions in order to examine the practical treatment efficiencies of emulsion in relation to its interfacial characteristics.