Chlorine disinfection is commonly used in household Johkasou because the equipment is simple, and the disinfecting effect is maintained for a long time due to residual chlorine. However, it is necessary to consider new disinfection methods to improve maintenance and management efficiency. In recent years, with the development of LEDs capable of emitting near-ultraviolet (near－UV) rays, it has become possible to introduce UV disinfection, which was previously only possible at medium-sized Johkasou or larger sewage treatment plants, into the small Johkasou of ordinary households. In small Johkasou, the water quality and flow rate are likely to fluctuate over time depending on the lifestyle of each household, which is predicted to affect the UV disinfection efficiency. Research on this issue has yet to be conducted. In this study, an LED near－UV disinfection unit was installed in an actual household Johkasou, and the effects of water quality and flow rate on UV disinfection efficiency were examined. The results showed that UV disinfection can sufficiently inactivate coliform bacteria and Escherichia coli in advanced treatment type Johkasou (target water quality, BOD: 10 mg･L－¹ or less, SS: 10 mg･L－¹ or less). However, it was confirmed that decreased UV irradiation time due to increased flow rate reduces the UV disinfection efficiency. Therefore, UV disinfection units are considered more effective when combined with higher-functioning flow equalization.

 Tidal flow constructed wetlands (TFCWs) with a rhythmic sequential cycle of filled/wet and drained/dry phases can enhance nitrogen removal in wastewater treatment. However, the performance and mechanisms of nitrogen removal by TFCWs in the treatment of actual wastewater have not been investigated. In this study, a pilot-scale TFCW with common reed plants was established at a sewage treatment plant and operated with a 6－h filled/wet and 2－h drained/dry cycle for 11 months. Efficient substrates (pumice and zeolite materials)-to-sewage oxygen supply and organic compound removal were observed during the filled/wet period, and then the sewage was changed from aerobic to anaerobic conditions. Efficient nitrification and denitrification were also observed during the filled/wet period. Owing to efficient nitrification and denitrification, the pilot-scale TFCW showed higher nitrogen removal performance (37.9 g total-dissolved inorganic nitrogen/m²/d) than previous conventional CWs. The nitrogen mass balance analysis revealed that microbial reactions (82.97%), plant uptake (0.98%), substrate adsorption (0.05%), and discharge in effluent (15.99%) were the main factors affecting total inorganic nitrogen inflow in the TFCW over 11 months of treating actual sewage (26.11 kg), indicating that microbial nitrification and denitrification reactions play a major role in nitrogen removal.