The indophenol reaction or the phenate method for ammonia-nitrogen determination described in standard analytical methods does not refer to aliphatic amine interference. However, the production of the blue color from a primary aliphatic amine was confirmed during the indophenol reaction by the procedure in Standard Methods of Analysis for Hygienic Chemist. Also, sodium nitroprusside used as a catalyst in the reaction was revealed to promote blue color formation. Formaldehyde and acetaldehyde were detected in color formation from methylamine and ethylamine, respectively; therefore, the production of ammonia and aldehyde via imine and/or iminium ions from a primary aliphatic amine was proposed as the mechanism of the color formation. Linear relationships between the concentrations of primary aliphatic amines and chitosan and their absorbances after the reaction indicated that the indophenol reaction using sodium nitroprusside would be an effective quantitative method for determining primary aliphatic amines and chitosan concentrations.

In mountainous areas where depopulation and aging are progressing, some communities have no access to public waterworks and thus rely on their own community water supplies. Mindful of the large burden of operation on, we proposed the use of low-power wide-area (LPWA) network technologies to support the residents. We fabricated simple radio communication modules and conducted experiments in woods, resulting in the observation that the radio waves in the 920 MHz band attenuated inversely proportionally to approximately fifth power of the propagation distance. From this observation, we predicted the path gain of radio wave propagations around a water supply facility and observed an agreement of the predicted and measured values with the coefficient of determination R² = 0.95 (p < 0.01, N = 20) . An attempt to monitor the water level in the treated water storage tank in real time was successful in minimizing the frequent visit and checking by the resident in charge, reducing the burden on the resident. In addition, the water level can now be recorded as data, which may enable us to develop precautionary measures against water shortage by issuing early notice to the residents in the future. This study shows the practicality of LPWA network technologies in the management of water supply facilities in small communities in mountainous areas.

We compared the water quality level in "the ISO guidelines for treated wastewater irrigation" with that of wastewater treated by the intermittent-aeration activated-sludge process widely adopted in rural sewerage treatment plants, and we examined the operation management necessary to achieve the required water quality level in each category. The study revealed that the BOD and SS concentrations of treated wastewater were likely to meet the water quality levels of category A in the ISO guidelines under the condition that the DO in the aeration tank is managed to be 1–2 mg L^-1 at the end of the aeration period. The water quality after the intermittent-aeration activated-sludge process was higher than that after the anaerobic filter-aerobic submerged biofilter process with a flow equalization tank in rural sewerage treatment plants. Since the response of the DO concentration in the aeration tanks varied greatly depending on the diffuser system used, the importance of the management of the degree of aeration in accordance with the diffuser system was clarified. The number of coliform groups in the treated wastewater was likely to meet the quality levels of categories B and A in the case where residual chlorine is more than 0.15 mg L^-1. From the perspective of using treated wastewater in irrigation, the monitoring of the residual chlorine concentration is important.