This study aimed to collect fundamental information on environmental risks posed by Class 1 chemicals under the Japanese Pollutant Release and Transfer Register (PRTR) system. The concentration of the substances in treated wastewater was estimated using the publicly available information in the PRTR system. Initial ecological and human health risk assessments were performed by comparing the estimated concentration and existing toxicity indexes on the basis of a hazard quotient (HQ). The results showed that linear alkylbenzene sulfonate (LAS) and its salts had the highest concentrations (166 μg/L). Thirty-six (e.g., hydrazine) and 11 chemicals (e.g., glutaraldehyde) had high HQ values (≥ 0.1) in initial ecological and human health risk assessments, respectively. Using comparisons between a previous study and this study, an interannual variability of high HQ value chemicals revealed that the composition of chemicals for ecological risk was similar for the different periods; however, it was different for human health risk. Further monitoring and development of countermeasures against the chemicals are required to avoid ecological and health risks.
Groundwater level is a major parameter in quantifying groundwater resource. Application of simple tools to simulate and predict groundwater levels is an important issue in groundwater hydrology. Tank model is a simple and useful conceptual hydrological model which is capable to simulate different system states without considering complex hydrological structure. The Shuffled Complex Evolution-University of Arizona (SCE-UA) algorithm is an efficient automatic calibration algorithm in searching the global optimum of objective function. This paper investigated the capability of mixed-tank model for consideration of mixed hydrological structure to simulate the groundwater level fluctuation with precipitation in four observation wells in Kumamoto City. The SCE-UA algorithm was introduced and modified to minimize the root-mean-square error (RMSE) between simulation and observation data for parameter calibration. The simulation accuracy was also assessed by Nash-Sutcliffe efficiency (NSE) coefficient. The results indicate that the mixed-tank model is highly effective for the simulation of groundwater levels showing different behaviors in their fluctuation situations.
Tetracycline is named by its four special benzene rings in molecular structure, which has been proven as a strong inhibition chemical for many kinds of bacterial. To solve the problem of residual tetracycline containing in municipal and medicine industrial wastewater effluents, this study tried to combine the ultrasound with transition metals (including Co2+, Ag+ and Fe2+) and oxidizing agents (persulphate ions, S2O82- and hydrogen peroxide, H2O2) with a continuous dosing mode as an innovative "Enhanced sonolysis" for degrading the tetracycline. Experimental results indicated that the addition of Fe2+ and H2O2 with ultrasound showed the better performance than other combinations by Co2+, Ag+ and S2O82-. As the ultrasound coupled with 0.2 mM Fe2+ and 2 mM H2O2, more than 90.7% and 45.9% of tetracycline were degraded and mineralized. In addition, the toxicity was significantly reduced while the cell viability increased from 53.1% (un-treated) to 87.5% (treated). Effect of pH on the degradation of tetracycline in this study was insignificant but pH 3 showed the better efficiency. It was concluded that the enhanced sonolysis was effective on the degradation, mineralization and detoxicity of tetracycline solution.