Microbial fuel cells (MFCs) can generate electricity from organic compounds present in wastewater; however, the resulting small electric power is insufficient for practical applications. This issue occurs because of the high internal resistance of MFCs, which can be addressed by first precisely measuring these internal resistances. However, a standard method for measuring the internal resistance, which depends on the conditions of the MFCs, does not exist. Therefore, five measurement methods in the open-circuit (OC) mode were evaluated in this study. In addition, the internal resistances in the closed-circuit (CC) mode were measured using a one-resistance method and electrochemical impedance spectroscopy (EIS). The values obtained by the linear sweep intensity of current potentiometry (LSIP) method were different from those measured by the other four methods. This was presumably because LSIP involved forcibly flowing electric current in the MFCs. The one-resistance method yielded similar internal resistances to those of the other methods in the OC mode. In addition, this method was applicable in the CC mode. Therefore, the one-resistance method can be used during discharging and for developing MFCs based on discharging.

A polar organic chemical integrative sampler (POCIS) was developed for the detection of linear alkylbenzene sulfonates (LASs), which are one of the most widely used chemicals globally and represent a type of surfactant agent. In the present study, the LASs were significantly sorbed onto the polyethersulfonate (PES) membrane, suggesting that the less sorptive polytetrafluoroethylene (PTFE) membrane is suitable for application in the POCIS device. Calibration experiments showed that the POCIS device with Oasis WAX as the sorbent and PTFE as the membrane filter had linear ranges > 28 d and sampling rates ranging from 0.035 ± 0.007 (tetradecylbenzenesulfonate) to 0.139 ± 0.024 (dodecylbenzenesulfonate) L d^–1. Furthermore, this POCIS device was validated under non-steady-state conditions via both field and chamber tests. The time-weighted average concentrations of dodecylbenzenesulfonate measured using the POCIS agreed well with those obtained via grab sampling within 21% over the sampling period of 14 d in both the field and chamber tests. Therefore, the POCIS can be successfully applied in the detection of LASs in LAS-contaminated aquatic environments.

In recent years, Japanese water utilities are facing pressing problems like staff shortage and climate-induced water quality deterioration. Utilization of online water quality monitoring data have received increasing attention to address these problems. A questionnaire survey was carried out for 32 water utilities to comprehend current situation of online water quality monitors (OWQMs), including installation of OWQMs and critical obstacles, water quality items monitored, utilization of water quality dataset, and future challenges. Turbidity, pH, and chlorine were mostly monitored using OWQMs from source to tap, for determining operating conditions of water purification process. Turbidity, pH, toxic substance, musty-odor substance, and residual chlorine were regarded as highly significant for both operational management and risk management. Initial/operational costs, measurement accuracy, and maintenance work volume were typical obstacles of OWQM installation. Nineteen out of the 32 water utilities have utilized water quality dataset obtained by OWQMs for predicting residual chlorine/bromate concentration, and for determining injection ratio of chemical coagulant and powdered activate carbon. Further OWQM installation and data utilization would be the key to strengthen the basis of water supply systems in Japan.