Focusing on the property of Volatile Organic Compounds (VOC) that tend to be adsorbed on organic substances in soil, we studied the capability of lumber residuals to treat water polluted by VOC. Batch experiments to investigate the capability of lumber residuals for adsorbing DCM (Dichloromethane) in static water were performed to exame if the relationship between the amount of adsorption and the concentration of DCM in liquid-phase can be expressed by a non-equilibrium adsorption isotherm. We then performed column treatment experiments using sawdust as an adsorbent while 1,2-DCA (1,2-Dichloroethane) dissolved in water migrates in the column under the influence of adsorption, desorption, advection and dispersion. We measured the capacity of sawdust as the adsorbent of VOC in flowing water. In addition, we applied an advective-dispersive equation with non-equilibrium adsorption-desorption isotherm to the experiments, and solved the equation numerically with the use of the method of characteristics linked with finite elements, and then inversely identified parameters. We satisfactorily analyzed the mass transport with adsorption of VOC in a column packed with sawdust.

View full abstract

  Hydrogenotrophic denitrification utilizing hydrogen produced from Solid-Polymer-Electrolyte (SPE) membrane electrode was developed for high-rate treatment of groundwater. In this study, continuous experiment was conducted using synthetic groundwater under different pH and electric current conditions, where denitrification rate of about 2400g-N/(m³·d) was achieved at pH7.0. A combined biological and electrochemical model could explain satisfactorily the performance and indicated an advantage of high-rate treatment. It was also indicated that the SPE denitrification process could be a feasible alternative to former groundwater treatment processes.

View full abstract

  Wastewater management options for improving the amenity value of riverfront were compared. Construction and maintenance costs were compared with the benefit of water environment obtained by a conjoint analysis. River Water quality, quantity and the change of energy consumption by each option were used as parameters. The results of benefit-cost analysis supported the scenarios combining centralized sewerage system with on-site treatment or satellite sewerage systems because these scenarios can improve both of river water quality and quantity. Implementation of centralized sewage system alone and the combination with the advanced on-site treatment were not supported by the residents due to the decrease of water quantity and large energy consumption, respectively.

View full abstract

  A long-term on-site experiment was conducted to investigate process performance and possibility of self-supplement of alkalinity of a thermophilic MS-UASB reactor for the treatment of seasonal campaign alcohol distillery (shochu) wastewater. A pilot-scale MS-UASB reactor having a working volume of 2.5 m³ was operaterd at 55°C for a period of over 1,400 days. The reactor steadily withstood an OLR of 60 kgCOD·m^-3·d^-1. To curtail the cost for external alkalinity supplement, two different feeding modes, i.e. sequential multi-feeding mode (SqMF) and effluent recycle mode (ER) were proposed. During SqMF feed-mode with barley and sweet potato wastewater, alkali supply could be curtailed by 69% and 78% respectively. The ER feed-mode gave better results proving 100% needlessness of external alkali supplement.

View full abstract

  It is presently anticipated for reusing drinking water sludge which is discharged during water purification as geotechnical material. However, drinking water sludge contains flocculating agent, poly-aluminum chloride, and it is expected that aluminum leaches and influences to plant growth. Therefore, this study assessed the environmental impact of drinking water sludge, focusing on aluminum leaching. Japanese leaching test, column leaching test, pH-dependant test, and serial batch test were executed, and aluminum leaching characteristics and the applicability to geotechnical works were discussed. Finally, this study showed the flowchart of environmental impact assessment of drinking water sludge.

View full abstract

  In this paper, an in-situ permeability control (reduction / renature) method is proposed for soil contaminated sites, and its efficiency is assessed in a series of laboratory tests including cultivation tests and permeability tests. The main outcomes of this research were: (1) The carbon source concentration is most effective item for the in-situ permeability control (reduction / renatute) method using microbial function. (2) The reduction process can enhance the calcium carbonate precipitation and can reduce soil permeability. (3) The renature process can enhance the decalcify and can increase soil permeability. (4) Permeable (reduction / renature) process based on microbial function can be controled on the bordering on pH=5.5. An in-situ permeability control method can be utilized to control of contaminated groundwater.

View full abstract