To generate information for better understanding of the occurrence and transportation of particulate organic matter (POM) in forested rivers, POM in both water and riverbed sediment phases of a forested river was collected from Oct. 2010 to Oct. 2011, and the composition and origin of POM were investigated. In addition, based on the concentration of POM and the discharge, the flux of the water phase POM was also computed. Particulate organic matter in both water and sediment phases was classified into three size fractions: large POM (> 16 mm), coarse POM (1 - 16 mm) and fine POM (1 μm - 1 mm). The composition of these three fractions was further classified into allochthonous (leaves, twigs, herbs and soil organic matter) and autochthonous (green algae and biofilm). For the fine POM fraction that was too small to be classified by the eyes, analysis with a multi-source model enabled the clarification of its origin based on measurement of the carbon isotope ratio for both samples and end members. The obtained results revealed spatial and time variances in the concentration and the composition of all three POM fractions, with the fine POM being found to be the dominant constituent of the water phase POM. Less significant concentration differences among all three POM fractions in the sediment phase than in the water phase were also revealed. Large and coarse POM was found mainly consisted of such allochthonous species as fallen leaves and branches. For many fine POM samples, however, the percentages of the autochthonous species of green algae and biofilm were relatively larger.

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Nitrogen (N) effluent loading discharged from paddy fields has a large impact on water quality in downstream areas. Cyclic irrigation, which reuses drainage water for irrigation purposes, is considered an effective water pollution prevention measure in paddy fields. In this study, we evaluated the effectiveness of cyclic irrigation in the reduction of N loading from a paddy-field district. We measured temporal variations in N concentration in drainage water and estimated the N mass balance for the study district for three consecutive years since 2007. We found that cyclic irrigation reduced N loadings. Mean N effluent loadings during the cyclic irrigation were 4.4 kg/ha and were smaller compared to lake water irrigation (non-cyclic irrigation). The hydrological structure and effect of a cyclic irrigation system can be characterized by using three parameters: ratio of the N concentration in drainage water to that in irrigation water; intensity at which drainage water is reused; and ratio of surplus irrigation water to the total amount of irrigation water. We conclude that the efficient use of irrigation water is important for reducing N effluent loadings from the paddy-field district because N in drainage water may not be qualitatively purified.

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Eight effluent samples were collected from four conventional activated sludge wastewater treatment plants (WWTPs) to determine the complexation of Zn, Cu, Cd and Ni by dissolved organic matter (DOM) in WWTP effluent. The collected effluents were subjected to determine the labile Zn, Cu, Cd and Ni concentrations using Empore^TM chelating disk cartridge. It was observed that more than 55% of the dissolved metals were strongly complexed by ligands in the effluents. In addition, the Zn, Cu and Cd titration data obtained by square wave anodic stripping voltammetry were interpreted with Scatchard linearization to determine the conditional stability constant and the total binding site concentrations of DOM in three of the WWTP effluents. The titration data for Zn and Cu fitted to a two-ligand system while Cd data represented a one-ligand system. The conditional stability constant for Cu was greater than that for Zn with DOM in WWTP effluents. Zinc complexation parameters in natural organic matter (river water DOM and Suwanee River humic substances) were also compared with those of DOM in WWTP effluents. The results demonstrated higher stability constant and higher binding site concentrations for the DOM in WWTP effluents than the natural organic matter.

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Small-scale field research was conducted in an agriculture-dominated alluvial fan in Kofu, Japan, where nitrate contamination was found in groundwater. The aim of this study was to examine the seasonal differences in nitrate contamination and to quantify the relative contribution of pollutant sources in groundwater. Proportions of δ¹⁸O-NO₃^-/δ¹⁸O-H₂O were evaluated to identify the seasonal differences in N leaching during transport from soil to groundwater. This indicated a significant difference in the ranges of nitrate concentrations between seasons. Three major nitrate source end-members (manure, soil, and upland groundwater) were identified based on isotopic (δ¹⁸O-NO₃^- and δ¹⁵N-NO₃^-) and major ion compositions. The contribution of each nitrate source was quantified using a method of multivariate mixing and mass balance calculation. In this method, the assumption is made that the groundwater chemistry is a result of mixing as well as water-soil interaction. Results showed that soil was the major source of NO₃^- (45%), followed by upland groundwater (30%) and manure (25%).

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This paper presented a potential use of zero-valent iron (ZVI) powder for the reduction and retardation of nitrate in soil columns under saturated and unsaturated flow conditions. Uniform mixture ratios of ZVI powder with soil were of concern in the range of 30% by weight of soil in order to investigate the change of mobility and reduction of nitrate. As a comparison, layered formations of ZVI powder within soils were also comprised with a certain height, which corresponded to a prescribed weight of ZVI powder. Temporal moment approaches allowed to identify the degradation rate constant and retardation factor based on experimental breakthrough curves of nitrate leachate and to quantify mass recovery fractions associated with NO₃-N and NH₄-N. The results showed that the increase of the amount of ZVI powder resulted in the increase of the degradation rate constant and retardation factor values up to 1.3 per hour and 1.7, respectively. The decrease of NO₃-N and the increase of NH₄-N were observed and were significant under saturated conditions due to the corrosion. Moreover, there was a slight difference between two repacked formations of ZVI powder in soil columns in terms of mobility and reduction of nitrate.

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The effectiveness of chitosan as a coagulant/flocculant in tunnel construction wastewater treatment has been studied. Chitosan is a biodegradable cationic polymer. The objective of this study is to develop an integrated desander and flocculator with inclined settler (IDFIS) system using chitosan coagulant. As a result of jar test, a chitosan optimum dosage of 5 mg/L for tunneling wastewater sediment, leave a residual turbidity of less than 5 NTU with this condition. Because the effectiveness of chitosan in removing turbidity was independent of pH, the operation of IDFIS system would be simple. The synthesized turbidity was made with clay particles, stream sediments, stream suspended sediment, and tunneling wastewater sediments. Results indicate that the overall removal efficiencies for turbidity, SS, COD and TP were 98%, 99%, 85% and 95%, respectively. The IDFIS system is possible to operate with compact design, because the increase of floc size favours the increase of settling speed and reduces the settling time.

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Cyclic irrigation, which is the reuse of drainage water as irrigation water, is practiced in paddy-field districts near Lake Biwa to conserve water quality. The water purification thus achieved, such as denitrification and adsorption of phosphorus to the sediment, is considered to depend significantly on storage capacity and water temperature of drainage canals. A paddy-field district where cyclic irrigation was being implemented was investigated and temporal variations in the vertical profiles of water temperature in the main drainage canal were measured during the period 2006 - 2008. In addition, a water temperature model for drainage canals was developed. Measurements confirmed that under cyclic irrigation, the temperature of drainage water was 2°C greater than that of the water in Lake Biwa, which is the original source of irrigation water. Although cyclic irrigation increased the suspended solids (SS) in the drainage canal, no significant relationship between water temperature and SS was observed. The results of simulation of water temperature in the drainage canal were improved by considering surplus irrigation water flowing into the drainage canal. It is suggested that operation of the irrigation pump and the inflow of surplus irrigation water has a more pronounced effect on water temperature than SS during the irrigation period.

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The yearly risk of Campylobacter infection was estimated for a treatment plant in the Netherlands. The median and mean values for the overall removal efficacy of the four treatment steps at the plant were estimated to be 7.46 log₁₀ and 6.22 log₁₀, respectively. The mean yearly risk of infection was estimated to be 1.68 × 10^-3 infection/person/yr. The uncertainty analysis demonstrated that the following items had large impacts on the yearly risk of infection: the ratio of Campylobacter to E. coli in the source water, the method of pairing the concentration data before and after treatment, and the variation in the removal efficacy of slow sand filtration depending on the water temperature. Based on these results, the important components that are required to improve the accuracy of the estimates were identified. Disability Adjusted Life Years (DALYs) and costs-of-illness in the distribution area were estimated. The uncertainty analyses of DALYs showed that the ratio of illness to infection is the most important factor that affects the DALYs. It should be noted that it is important to estimate the ratio of illness to infection to decrease the uncertainty of the DALYs.

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In this study, GA (granulated aluminum oxyhydroxide) was prepared from aluminum oxyhydroxide without a binder, and its phosphate adsorption capacity was investigated. Scanning electron microscopy images, specific surface area, pore volume, mean pore diameter, and solution pH of GA were analyzed. The amount of phosphate adsorbed was studied using batch techniques, and was shown to increase at higher temperatures. Moreover, adsorption isotherms were fitted to both the Freundlich equation (correlation coefficient: 0.866 - 0.972) and the Langmuir equation (correlation coefficient: 0.993 - 0.999). Adsorption equilibrium was reached within 24 h. The kinetic data for adsorption was best described by a pseudo-first-order rate equation. A pH of about 3 was the most suitable for phosphate adsorption. Moreover, the adsorption mechanism of phosphate onto GA could be related to the specific surface area and surface hydroxyl groups on GA. Both adsorption and desorption could be performed on GA using NaOH at different concentrations. These results suggest that the GA prepared in this work is appropriate for practical applications.

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This study was carried out to develop a technique for treatments of acidified river water using waste concrete aggregates for sustainable protection of the water environment. In this study, the water quality in the Matsukawa River, Japan, which receives acidic mine drainage, were investigated as a model field of an acidic water environment. Additionally, chemical component analyses of the waste concrete aggregates and neutralization testing in batch mode were carried out to use of waste concrete aggregates to neutralize acidified rivers. The results of the field investigation suggested that dissolved Al acts as a buffer substance, inhibiting rises in pH in acidified water environments. The results of the neutralization tests confirmed that it was possible to neutralize acidified river water by using concrete aggregates; dissolved Al in the acidified river water was settling removed effectively by these neutralization treatments. Additionally, increases in pH could be accelerated by adding aeration to the neutralization process. Aeration decreased the requirement for neutralization aggregates by approximately 30%. These results suggested that use of waste concrete aggregates effectively neutralizes water that has been acidified by high concentrations of Al acting as a buffer inhibiting pH rise.

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Freshwater green algae Scenedesmus acutus and ostracod Heterocypris incongruens were used to evaluate sediment toxicity. They were exposed to a series of copper and zinc concentrations for 6 days. Effects of different food (algae and TetraMin^®) and modifications of photoperiod in the toxicity test were also determined. TetraMin^® met the validity criteria, though it cannot be a complete substitute of algal food in the toxicity test. Modification of photoperiod has significant influenced on the ostracod toxicity test. The median lethal concentrations (LC50) of copper when fed with TetraMin^® were 270 μgCu/L and 571 μgCu/L under 24-h dark and light/dark conditions, respectively. Almost no significant effect on ostracod sensitivity to zinc when exposed under light (470 to 423 μgZn/L). On the other hand, light condition has similar effects on ostracod sensitivity to copper and zinc when fed with S. acutus. The preliminary results of the ostracod toxicity tests seem to show complex phenomena of multi exposure pathways and further investigation of the interrelationship between ostracod and food organisms is necessary.

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