Microbial removal of cadmium from a waste tissue (hepatopancreas) of a scallop was examined. During a sequential and mixed cultivation of soil microbes and a strain of sulfate-reducing bacteria in an extract of the tissue, cadmium was removed completely from the extract as the metal-sulfide precipitated. Whereas a significant amount of cadmium remained in the extract after the cultivation of soil microbes or the sulfate-reducing bacterium alone.
These results suggested that protein-bound cadmium in the tissue extract would be transformed to a free-state by enzymes like proteases secreted by soil microbes, and then, metal sulfide could be formed with the free-cadmium and hydrogen sulfide produced by the sulfate-reducing bacterium. Availability of the cadmium-free preparation as feed was also discussed.

View full abstract

A new and practical dehydration technology and system have been developed for aerobic fermentation and composting garbage with high moisture.
Dehydrability tests were carried out using garbage with a moisture content of about 80-88%. It was found that the sample was dehydrated efficiently when it was pressed with a load of 2 kg/cm²after being shredded to 5 mm and pretreated under facultative anaerobic conditions for several days. A certain degree of the facultative anaerobic degradation of cellular tissue of the garbage seems to cause easy dehydrating. After that, this pretreating technology was applied to a NEDO verification test plant which composts 500 kg of garbage a day, it was observed that the system consisted of a shear-type shredder, paddle-type facultative anaerobic pretreating container, screw press-type dehydrator and scoop-type fermentor which were effective in composting.
It was confirmed that dehydration efficiency improved very much when the shredded garbage was simply left under facultative anaerobic conditions for several days and it was able to compost without adding any materials for moisture control, energy for drying and so on, which are necessary in conventional technology.

View full abstract

This study presents the three diagrams for the design of gas vents, in order to control gas flux through final cover soil, and the maximum pressure under final cover soil. Each of the three diagrams corresponds to one of the following cases; 1) a gas vent of independent vertical type, 2) a vertical gas vent connected to a leachate collection pipe network, and 3) the surface of a landfill site finally covered by impermeable geomembrance. By using the diagrams, K_s and L_xare designed when G, L_z and K_x was given as the landfill conditions and η and ΔP_maxas the control conditions, where, K_s=permeability of final cover soil [m²], L_x=half-distance between two vents [m], G [s^-1] =gas generation rate, L_z=depth of refuse layer [m], K_x=permeability of refuse [m²], η=landfill gas collection efficiency [-], and ΔP_max=the maximum pressure under final cover soil [Pa] .

View full abstract

Viscosity and glass forming tendency have been studied in the glass and melt prepared from chrysotile, portland cement and waste glass, in order to use waste asbestos as a raw material of glass wool. The addition of the waste glass to the chrysotile and portland cement decreased liquidus temperature, crystallization temperature and degree of supercooling. Viscosity at the liquidus temperature and the forming temperature increased with increasing proportion of the waste glass. From these effects, the addition of the waste glass to the chrysotile and portland cement suppresses the crystallization from the melt and reaches the value suitable for drawing glass wool.

View full abstract

An experimental study using both laboratory permeability testing apparatus and permeating soft groundwater contaminated by sexivalent chromium (Cr⁶⁺groundwater) was carried out to develop a measure on groundwater pollution prevention (caused by Cr⁶⁺compound leached from chromium containing wastes such as scoriae dumped out from smelting works in the past), by providing cut-off barriers which were made from a mixture of blast furnace slag cement and a sodium type bentonite (CB) cut-off barrier.
From the laboratory tests, it was necessary to maintain the permeability coefficient of 2×10^-9m/s or less, as soon as possible after the barrier provision.
Through Test I, in which MgCl₂270 mg/l and some amounts of Ca (OH) ₂for pH adjustment were added to the permeating Cr⁶⁺groundwater, it was found that adjusting the pH within a range of 9.0 to 9.5 was an appropriate approach. Through Test II, in which MgCl₂270 mg/l and some amounts of either Poly-aluminum chloride (PAC) or Al₂ (SO₄) ₃were added to the permeating Cr⁶⁺groundwater, it was also found that the addition of PAC brings a good result due to the reduction of permeability and no breakthrough of T-Cr containing leachate. It was confirmed from Test III that the minimum requirement of PAC was 30 mg/l approximately as Al₂O₃.
No ettringite existed in CB test pieces which had had PAC added, while much ettringite was found in inlet and outlet sides of the test piece which had had Al₂ (SO₄) ₃added. The ettringite generated in the test piece did not exert a favorable influence upon the reduction of permeability coefficient.

View full abstract

The effect of extraction conditions (S/L and pH) on the toxicity evaluation of a municipal waste incinerator's (MWI) fly ash was examined by quantitative analysis and the Daphnia acute toxicity test.
Regarding S/L, the toxicity of MWI fly ash per unit amount of fly ash, which was determined with the leachate prepared with S/L=1 w/v%, was larger than that which was determined with the leachate prepared with 10 w/v%.
Regarding pH, the leachate prepared with pH=4 showed higher toxicity than that prepared with pH=7 or 12. The leaching condition with pH=12, however, was considered preferable in order to evaluate the release of lead, because the release of lead under this pH condition was higher than that of other pH conditions.
Considering the relationship of pH dependency to the toxicity of leachate, the major toxic constituent in the leachate prepared with pH=4 was copper, and that prepared with pH=12 was lead.

View full abstract