The graphite powder was added to a microbial fuel cell (MFC) that uses soil to decrease the internal resistance and increase the electric power and electric charge (ampere hour: Ah). The effect of adding the graphite powder to soil MFC is evaluated by experiment and simulation using mathematical models. In this experiment, the total weight of the reddish granular soil and the graphite powder was 1000 g, and ratios of the graphite were set to five values between 0% and 20% by weight. The grain size of the soil was between 3 and 8 mm. The diameter of electrode was 9 cm. The initial chemical oxygen demand (COD) of synthetic wastewater was 1400 mg/L. As a result, the amount of Ah was maximized when 10% of the graphite was mixed. When the amount of the graphite increased, the internal resistance decreased; however, consumption of COD decreased and the microbial reaction decreased. This might be because the graphite covers the surface of the soil, and it disturbs the adsorption of the soil and decreases the biofilms. Therefore, a suitable proportion of the graphite exists, and it was approximately 10% in this experiment.
Oseltamivir and zanamivir are the two most prescribed antiviral drugs against influenza in Japan. Oseltamivir and its metabolite are frequently detected in surface water bodies in Japan during the last few years particularly in seasonal influenza period posing a potential threat of emergence of drug-resistant genes in human pathogens. Despite the second largest use of zanamivir as an antiviral drug in Japan, its presence and fate in environmental waters is unknown until now. Accurate assessment on the presence and fates of these drugs in environmental waters is the very first step in countering the potential negative impact on human health. We have recently developed a novel solid-phase extraction (SPE) method for simultaneous recovery of oseltamivir and zanamivir in environmental waters. These antiviral drugs were quantified in Neya River water and a nearby conventional sewage treatment plant (STP) during the 2010/2011 seasonal influenza using the SPE method in this investigation. Oseltamivir and zanamivir concentrations in the river water and STP water samples are discussed and compared with those of the 2009/2010 pandemic influenza in this article. This successful simultaneous quantitation of zanamivir in wastewater and river water with high recovery ratios paves the way for its monitoring in environmental waters.
As a method for raising the electric power of microbial fuel cells (MFC), we have noticed that repeat of discharge (closed circuit: CC) and charge (open circuit: OC) produces higher electric power than continuous CC. We tried to find the best interval time for the electric power generation of MFC using compost by experiments and model simulations. As a result of the experiment, the interval time of CC and OC, which was less than 60 seconds, produced about 1.2 times-higher electric power output than the continuous CC. In addition, as for the fixed interval time of CC, which was 30 s, the longer time of OC produced higher power. It is difficult to keep the same condition on the MFC, because each experiment uses the power of the MFC, and then the voltage decreases. Therefore, we simulated the experiments by making a mathematical model for estimating the electric power. The model was based on variation of the concentration of organic compounds, which are consumed by electric current and supplied by diffusion. As a result of the calculation, the effective interval time of CC and OC is less than 15 s. As for the fixed time of CC, the model shows the longer time of OC generates the higher power; however, as the time efficiency, the shorter time of OC is preferable. Therefore, the time efficiency should be considered for practical use of the MFC.
