In recent years, pharmaceuticals and their metabolites have been detected in aquatic environments, and their risk management has become an emergent concern about the environment, water supply and sewerage. In particular, pharmaceuticals for external use may be discharged in large amounts into aquatic environments. In this study, we monitored three pharmaceuticals for external use, namely, crotamiton, lidocaine and diethyltoluamide (DEET), in water samples (i.e., river water, effluent of wastewater treatment plants (WWTPs), and groundwater) from the Tama river basin in Japan. The calculated loads of the target compounds in effluent samples from WWTPs in the Tama river basin were comparable to those in the river water samples, indicating that the major source of the compounds is wastewater effluent. The loads in the WWTP effluent samples varied seasonally depending on their application. The removal efficiency of groundwater recharge varied among the target compounds. Lidocaine and DEET were removed more efficiently than crotamiton. The removal efficiency of chlorination also varied among the target compounds. Although negligible amounts of crotamiton and DEET were removed, lidocaine was almost completely removed within 1 hour.

View full abstract

The effect of salinity on nitritation in a Down-flow Hanging Sponge (DHS) reactor was evaluated through a long-term continuous experiment for 700 days. The DHS reactor was fed with artificial wastewater containing 100 mg-N·L^-1 ammonium nitrogen (HRT = 2 h, 20-25°C). The salinity of the influent was controlled by adding NaCl at concentrations of 5 to 18 g-Cl^-·L^-1. The effluent nitrite concentration increased with increasing of salinity, i.e., the nitrite concentration increased up to approximately 60% of the total nitrogen in the effluent at 18 g-Cl^-·L^-1. The nitrifying bacterial community in the DHS markedly changed at the species level. For example, the dominant nitrite-oxidizing bacteria changed from Nitrospira-sublineage I at 0 g-Cl^-·L^-1 to Nitrobacter spp. at 18 g-Cl^-·L^-1.

View full abstract

In the previous paper, the loading rates of TN and TP were measured in Aburahi-S Experimental Forested Watershed (AsEFW; 3.34 ha), and the specific loads (L_ss) were evaluated to be 9.95 and 0.168 kg·ha^-1·y^-1, respectively. The L_s values should be verified to converge within AsEFW in order to be appreciable as parameters characterizing AsEFW. However, it is difficult to install a sufficient number of weirs in such a small watershed to prove directly such convergence. In this paper, water samples of the baseflow were taken up monthly at twelve sites (R0-R7 and L1-L4) located upstream of the weir (R0) of AsEFW for one year. The average concentrations of the nutrients at R0 did not significantly differ (p<0.01) from those at R1-R4 within a distance of 130 m. During two rainfall events (58.5 and 151 mm), the concentrations were observed at R0, R1 and R3. The concentration levels and changing patterns were similar between R0 and these upstream sites. It was concluded, from these results, that the L_s values converge within AsEFW. Since springs may affect significantly L_s values, especially in small watersheds, their existence and effect should be checked. A small spring (L5) was found in AsEFW, and its influence on the L_s values of the nutrients was confirmed to be negligible.

View full abstract