Drainage water from dumping site of waste soil from tunnel excavation work for transportation network building some time contains higher concentration of arsenic than its environmental standard. For arsenic removal from the contaminated water, technologies such as ion-exchange and flocculation precipitation treatment have been developed and applied, but the high cost of the treatment and production of secondary waste still cause problems to be solved. In this research, a low cost arsenic purification method by using arsenic hyperaccumulator plant Pteris vittata was developed. Hydroponic purification pilot plant experiment by using P. vittata for removing arsenic from drainage was set in the tunnel excavation soil landfill site in Sendai, Japan. Drainage from this landfill site contained 20~30 μg/L arsenic and its pH was alkaline (around pH 9). After 3 months P. vittata hydroponics treatment of the drainage water from the soil dumping site, arsenic concentration of the treated drainage water was lowered to below 10 μg/L and pH also was lowered to 8.3 that clears its environmental standard. From these results, we concluded that hydroponics purification technology by using arsenic hyperaccumulator plants for arsenic removal is effectively applicable as a lowcost purification of arsenic contaminated drainage water from soil dumping sites.

View full abstract

 The objective of this study was to clarify the effect of temperature change on dissolution characteristics and chemical forms of boron and arsenic in four sediments (obtained from 50 m length boring core) from the middle part of the Arakawa Lowland located north of the Tokyo metropolitan area, Japan. Dissolution experiment (fractionated as water-soluble (dissolved) fraction) of these four sediments was carried out under anaerobic and different temperature (15°C, 25°C, and 40°C) conditions. For the sediments after the dissolution experiment, sequential extraction method that selectively fractionates five chemical forms (exchangeable fraction, bound to carbonates, bound to iron and manganese oxides, bound to organic matter, and residual fraction) was applied. Especially for some sediments which were significantly affected by temperature change in the dissolution experiment, maximum dissolution amount, i.e., total amount of water-soluble and exchangeable fractions and bound to carbonates increased with increase in temperature. On the other hand, bound to iron and manganese oxides showed a decreasing trend with increasing temperature. These results suggested that bound to iron and manganese oxides containing boron and arsenic changed to relatively soluble fractions of boron and arsenic such as water-soluble and exchangeable fractions and bound to carbonates with temperature increase.

View full abstract

 This study developed novel loop-mediated isothermal amplification (LAMP) methods for specific and quantitative monitoring of Dehalococcoides spp. using 16S rRNA gene and dehalogenase genes bvcA and vcrA as the target genes. The quantification limit for the developed LAMP methods was 1 × 10³ copies per microliter-DNA sample, and the quantification results of the developed methods correlated positively with those of real-time PCR, which has been commonly applied for monitoring Dehalococcoides spp. Application of the developed LAMP methods to the practical anaerobic biostimulation of groundwater contaminated with chlorinated ethenes, in addition to the measurements of conventional physical and chemical indicators, demonstrated that the penetration of injected nutritional materials, change to a strong anaerobic condition, increase of Dehalococcoides spp., decomposition of chlorinated ethenes occurred in sequence. These results indicated that the LAMP methods developed here enable simple and reliable monitoring of Dehalococcoides spp. and are helpful in the management of in situ bioremediation.

View full abstract

 Initial health and ecological risk assessments of chemicals in treated wastewater in Okinawa Prefecture, Japan under the Japanese Pollutant Release and Transfer Register (PRTR) system were carried out. In the initial health risk assessment, the intake of root vegetables cultured using treated wastewater, the exposure to sprinkle of treated wastewater and so on were assumed. Direct exposure of aquatic organisms to treated wastewater was assumed in the initial ecological risk assessment. As a result, polyoxyethylene alkyl ether may cause health risk in case of the intake of the root vegetables. No chemical seemed to have a bad effect on human health in case of the sprinkle of treated wastewater and so on. In the initial ecological risk assessment, it was suggested that a detail survey like the measurement of the concentration of eight kinds of chemicals in treated wastewater such as hydrazine be conducted.

View full abstract

 Material dynamics in urban areas with developed water supply and sewerage systems are determined not only by the natural hydrological circulation system but also by the artificial water circulation system. In this study, we used data collection and field survey to quantitatively analyze the dynamics of nitrogen, phosphorus, and silicon in the artificial water circulation system in Osaka City. The impact of scenarios that the future policies may change the water and material flow in the system was also evaluated.
 This study revealed that the loading amounts of total nitrogen and total phosphorus added by domestic drainage were the most dominant factors that affect material flow in the system. Additionally, the dissolved silicon (DSi) input by uptake from the purified water sources and infiltration of the water from unknown sources into sewerage pipes also had considerable influence on the flow. In addition, DSi was not removed by water purification and sewerage treatment process, and it was transported conservatively within the system. Moreover, the results indicated that, in the future, when the use of groundwater for industrial purposes is promoted or also when the intrusion of water form unknown sources into sewerage pipes is prevented, the proportion of N, P, and Si discharged from the sewerage treatment plants will change greatly; this change could result in affecting the water quality and the ecosystem of rivers.

View full abstract