In batch system for the catalytic decomposition of contaminants in wast water, the recovery of the catalytic particles is of great concern. One of the possible recovery means is to utilize magnetic separation. In the present work, in order to recover non-magnetic MnO₂ catalytic particles, fine Fe₃O₄ particles were added into the solution and the coagulates were collected magnetically. The recovery efficiency was as high as 99%. Furthermore, the influence of Fe₃O₄ particles on the catalytic decomposition of H₂O₂ by MnO₂ was investigated because H₂O₂ causes various problems in maintainning stable operation of wast water treatment system. The experimental results showed that the addition of Fe₃O₄ enhances the decomposition rate of H₂O₂ because MnO₂ particles were well dispersed by Fe₃O₄. These results suggests that the introduction of fine Fe₃O₄ particles is effective for the decomposition of H₂O₂ as well as the recover of MnO₂ catalytic particles.

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cis-1,2-Dichloroethylene (cis-DCE) is frequently found as a groundwater contaminant. cis-DCE can be biotransformed via reductive dechlorination to ethylene under anaerobic conditions. We have recently reported a high-rate transformation of cis-DCE to ethylene by anaerobic enrichment cultures. A small part of ethylene was further reduced to ethane. Hydrogen appeared to be the actual electron donor for reductive transformation of cis-DCE in these cultures. In this study, batch experiments were conducted for investigating the mechanism of cis-DCE transformation by these anaerobic enrichment cultures. Hydrogen was used as an electron donor. Addition of 2-bromoethanesulfonate (BES), a specific inhibitor of methanogenesis, did not inhibit reductive dechlorination of cis-DCE. The major organisms utilizing hydrogen were not methanogens but homoacetogens. These results suggest that the dechlorinating organisms were homoacetogens. On the other hand, reduction of ethylene to ethane was inhibited in the presence of BES, suggesting a role of methanogens in this transformation.
Batch experiments examining the biodegradability of tetrachloroethylene (PCE) by these cultures were also conducted and it was found that the cultures were able to transform PCE to ethylene at high rates.

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A commercial calcinated sand, Cleansand-205 (abbr. Kls-205 : a silica sand coated by a special procedure with a mixtutre of the oxides of Si, Al, Ti, and Ag), was tested for its ability to inhibit the growth of algae in a laboratory (batch-system) experiment. The growth of algae in water taken from a domestic gold fish basin was inhibited almost completely by about 5%(w/v) of Kls-205, under the conditions where fairly amounts of both nitrogen and phosphorus were present. However. Kls-205 (5 %) showed little inhibition on algae which had already abundantly grown, and did not suppress further growth. The abilities of Kls-205 to adsorb nitrogen, phosphorus and carbon dioxide required for the growth and photosynthesis of algae were weak. The amounts of beta- and gamma-radiation and harmful heavy metal ions were the same levels as those from non-treated natural water. The dissolution of any antialgal substances and the generation of active oxygens were not observed. The possible role of Ag and/or its oxide with oligodynamie in inhibiting the growth of algae by Kls-205 was discussed.

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The significance of Calorie/Water (C/W) ratio was investigated in the treatment of highly concentrated organic wastes by the Thermophilic Oxic Process (TOP). Shochu processing wastewater was used in this study. When C/W ratio was 2.18, most of carbon in influent was converted to CO₂ and all water was evaporated. Organic matter was not completely converted to carbon dioxide (CO₂) when the C/W ratio was less than 1.85. It is because that the biological activity was low due to the increase of moisture. The mixture in the reactor was dried when C/W ratio was 4.13 because excess energy was provied. Considering these results, it is concluded that the optimum C/W ratio is 2.18. The thermophilic oxic process is included in the high energy combustion, in other word this process was defined as “Biocombustion”.

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