Some researchers suggest that Zostera japonica has important roles as primary producers in tidal flat ecosystem. Recently, it is known that the methods involving tracers in stable isotope ratio analysis and fatty acid structures stand up to clarify the origin of organic matter. If these methods can be used, it would be possible to clarify the role of organic matter derived from Z. japonica. However, these methods cannot be used yet because the characteristics of stable isotope ratios and fatty acid structures in Z. japonica are not clear. The objectives of this research are the clarification of the characteristics of stable isotope ratio and fatty acid structure in Z. japonica. Moreover, the availability as tracer of organic matter origin was explored; and the characteristics of stable isotope and fatty acid structure of Z. japonica were compared with other primary producers in tidal flat. Results showed that Z. japonica contained large amounts of 18:2n6 and 18:3n3 and they were used as biomarkers of other seagrass-derived organic matter. In addition, Z. japonica also contained LCFAs, which is used as biomarker of terrestrial plants. These results show that LCFAs are not the only biomarkers that can be used to trace the organic matter in terrestrial plants.

View full abstract

Matsuyama region, located in Shikoku Island, Japan faces the Seto Inland Sea on the west, where the annual rainfall is relatively less than in the other areas in Japan. In such favorable condition, the cultivation of citrus fruits is popular, and there are a large number of small reservoirs for irrigation purposes. The citrus groves are distributed in hilly areas surrounding the paddy fields and residential areas so there are higher chances for the nearby water environment to get affected by leachate from the groves. This paper investigates the water quality characteristics of the leachate from the groves, and studies the changes of the leachate quality near the collecting reservoirs. It was found that the grove soils are highly acidic and the leachate contains metals and nutrients in high concentration. On the other hand, the water quality of the leachate changed after it flowed into the reservoirs, and the concentrations became lower. It is understood that chemical and biological reactions help remove the contaminants in the reservoir, and from the standpoint of self-purification, reservoirs play an important role. This paper also discusses the kinetics of the self-purification and the quantitative estimation based on the experimental results.

View full abstract

Giant reed has high biomass productivity, and is a promising plant to be used for a constructed wetland system in which energy/material production and water purification are achieved simultaneously (multi-functional wetland). In this study, the cadmium removal by hydroponically cultured giant reed was observed, and its concentration in the plant body was measured to clarify the applicability of the wetland for cadmium treatment. The results suggested that the hydroponic culture of giant reed has high potential for cadmium removal. In addition, the inhibitory effect of cadmium on phosphorus removal, that is also important for water purification, was not observed under a concentration lower than 1 mg-Cd/L for 7 days. After about 2 months of hydroponic culture the absorbed cadmium was highly concentrated in the rhizome. Furthermore, the positive correlation between glutathione (GSH) in the rhizome and cadmium removal rate was observed, indicating that the production of GSH was controlled by the cadmium assimilated in the giant reed.

View full abstract

This study aims to obtain the knowledge necessary for constructing an urban water recycling system in Beijing City. A macro-scale water balance model was constructed for Beijing City according to statistical data, and domestic water demand structure in the city was analyzed through a survey of 124 families living in the Haidian district in 2006. Annual per capita water use in Beijing City was 220 L, and about 75% of it was used for cooking, washing, showering, and toilet flushing. The use of reclaimed wastewater for toilet flushing and room cleaning, which was estimated as 22% of domestic water demand, was deemed acceptable by most of households questioned. Finally, we estimated the effect of supplying reclaimed wastewater for municipal use by macro-scale water balance estimation based on the structure of municipal water demand. Assuming that 60% of treated sewage is reclaimed from 41% of the current total, this would result in a saving of 122 million m³ of the groundwater required. Moreover, with the useful ratio of reclaimed wastewater set to 80% and 100%, 250 million m³ and 377 million m³ of groundwater, respectively, can be saved.

View full abstract

The water quality of six rivers in Hadano basin was investigated and its relationship with nonpoint sources of pollution was analyzed. This study was undertaken to spatially examine the present status of the river water quality of Hadano basin. Ground water circulation influenced both the water quality and quantity. In the downstream basins of Muro and Kuzuha Rivers, COD and TP were diluted by the ground water inflow. In Mizunashi River and the upstream of Kuzuha River, water infiltrated to the subsurface due to the higher permeability of the river bed. Chemical oxygen demand (COD), total phosphorus (TP) and total dissolved solids (TDS) showed good correlation with unsewered population and agriculture area. While total nitrogen (TN) had good correlation with atmospheric nitrogen (N) deposition loads. Multiple regression analysis between water quality pollution loads and influencing factors revealed that unsewered population had higher impact on the river water quality; nonetheless, agriculture also had some effects. For TN, atmospheric N deposition load was taking effect, implying that it plays a significant role on the water quality and cannot be denied for proper water quality management. Development of sewerage system could be considered as the decisive factor to maintain the river water quality in the Hadano basin.

View full abstract

In order to assess the stability of nitrogen removal systems utilizing anaerobic ammonium oxidation (anammox), it is necessary to study effects of influent dissolved oxygen (DO) on anammox activity since effluent from nitritation process feed to anammox process. In this study, the effects of influent DO on anammox bacteria entrapped in gel carriers were investigated using continuous feeding tests. The tests were performed in duplicate to confirm the reproducibility and anammox activities were evaluated under different DO concentration of 0 from 5 mg/L in influent. These results suggested that the DO concentration in influent to anammox reactor must be less than 2.5 mg/L. In addition, it was shown that the effect of influent DO on the anammox reaction is reversible because fallen anammox activity by influent DO of 5 mg/L recovered when the influent DO concentration was decreased to less than 1 mg/L.

View full abstract

In major cities, rapid urbanization due to population and economic growth generally cause increase in water demand. Furthermore, lifestyle change encourages per capita water consumption to increase. The government tends to have policies that support increasing capacity to response to rising demand but this requires huge funding and several other problems such as opposition by environmentalist. To overcome these problems, water demand should decrease especially by reducing per capita water consumption through water conservation. On such basis, this paper focuses on the evaluation of 'Water Conservation Plan' (WCP) implemented by Tokyo Metropolitan Government (TMG). Tokyo faced tight water resources problem during the high economic growth period around 1960s. However, by incorporating both supply and demand side control measures in WCP, Tokyo became advanced in water resources management and now has excess water supply to meet the demands. Tokyo managed to reduce the per capita water consumption to about 171 L/p/d or more in 30 years. But due to pushing-up factors, which contributed 89.5 L/p/d of increment, the actual reduction was equivalent to 81 L/p/d or 19% reduction rate. Total supply side measures are almost equal to demand side measures where the weightage is 44:56 respectively. Hence, the authors analyze the effects of WCP from the viewpoint of supply and demand side control.

View full abstract

Freshwater shortage and energy crisis are the two major challenges in the 21^st century. The coupling of wastewater treatment and energy production to supply reclaimed water and sustainable energy is a very promising approach to handle these two challenges. A novel process of domestic wastewater reclamation coupled with biofuel/biomass production based on microalgae is proposed in this paper. The organic pollutants in wastewater are separated and concentrated by flocculation and filtration, and nitrogen and phosphorus are used as nutrients for microalgal cultivation. The organics separated and microalgal biomass harvested can be further processed to produce biofuel. The novel process proposed in this paper will bring about innovation in wastewater treatment, and the conventional wastewater treatment process will be transformed from a mere "treatment process" to a "production process" using wastes as raw materials and thereby can produce biofuel and other valuable by-products. At present, this novel process is in the conceptual stage, and some key techniques necessary to be further studied are also discussed in this paper.

View full abstract

Three reaction media (zero valent iron, activated carbon and modified bentonite) were used to design four kinds of permeable reactive barriers (PRB) and study the feasibility and the efficiency of the PRB technology in the remediation of landfill leachate. The results indicated that PRB is highly effective for the treatment of landfill leachate. The ammonium removal rates in the two reaction media with zero valent iron and modified bentonite was 97.58% at maximum, the removal rate of COD in reactors with zero valent iron and activated carbon was 84.87% at maximum, and the removal rate of total phosphorus in PRB reactors was 80% at maximum.

View full abstract

The influence of phosphorus concentration on the biodegradation of dissolved organic matter (DOM) was discussed as a possible cause of the accumulation of chemical oxygen demand by acidic permanganate method (COD_Mn) in Lake Biwa. Enhancement of oxygen consumption in the biodegradation test by dissolved phosphorus (DP) was observed in Lake Biwa water with the natural bacterial community. The response-curve of the oxygen consumption on DP was expressed by a modified Michaelis-Menten type equation with a threshold. The threshold of DP for oxygen consumption was in the range of 0.0031 to 0.0040 mgP/L. The pseudo first-order biodegradation rate constant of DOM was estimated to be 0.0022 d^-1 in 1980s and 0.0014 d^-1 in 2000s based on DP in the northern basin of Lake Biwa. Consequently, DOM in 2000s was expected to be 1.6 times higher than that in 1980s from mass balance analysis. Since the ratio of COD_Mn observed in 2000s to that in 1980s in the northern basin of Lake Biwa was 1.3, it was likely that the deterioration of bioactivity for DOM degradation contributed to the accumulation of COD_Mn in Lake Biwa.

View full abstract

A quantitative survey was performed to understand the annual and diurnal profiles of Cryptosporidium and Giardia, representative waterborne infectious protozoans, in river water which is used for drinking water sources in Japan. To investigate the annual profiles, 84 river water samples were collected at 7 sites in the tributary rivers of the Tone River basin in Japan from June 2008 to February 2010. Cryptosporidium and Giardia were detected in 59 (70%) and 64 (76%) out of the 84 samples (10 liters each), showing the highest concentration of 344 oocysts/10 L and 144 cysts/10 L, respectively. Annual variation of the concentrations of Cryptosporidium and Giardia was high. The ratio of the maximum concentration to the mean value at each sampling site ranged from 2-8 except for one sampling site in which the frequency of detection was extremely low. To investigate diurnal profiles, 15 river water samples were collected at 3 sites in the tributary rivers of the Tone River on October 9^th, 2008. The maximum concentrations of Cryptosporidium and Giardia in some sampling sites were approximately 10-fold higher than the lowest value. The correlation between the anaerobic spore-forming bacteria and these infectious protozoans was stronger than other microbial indicators (total coliforms, Escherichia coli and heterotrophic bacteria).

View full abstract