We studied phosphorus removal for small-scale wastewater treatment systems using the electrochemical elution of iron.
The efficiency of this method to remove phosphorus is better than chemical precipitation of ferric chloride, and is affected by the Fe:P ratio and the influence of calcium ion and magnesium ion concentrations. In laboratory tests combining an electrolytic bath and biofilter, we succeeded in removing over 90% of the phosphorus while maintaining the Fe:P ratio at 1.5.
This method can control the iron elution concentration easily, and is available to remove phosphorus from small-scale wastewater treatment systems.

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Decolorization of an anthraquinone dye (Mitui Nylon Fast Sky Blue B, SBB) by white-rot fungi, Trametes versicolor and Phanerochaete chrysosporium, was investigated in a low-nitrogen and high-carbon liquid culture. Over 90% of the dye was decolorized after the 12h-incubation with T. versicolor. On the contrary, the decolorization by P. chrysosporium occurred mainly due to biological adsorption of the dye. The production of ligninolytic enzymes, laccase and manganese peroxidase (MnP), was observed during decolorization by T. versicolor, suggesting that the decolorization of SBB is related to ligninolytic activity of white-rot fungi. Four kinds of anthraquinone dyes were treated with partially purified laccase and MnP. Decolorization of each dye by laccase was reached to more than 80%, but two dyes were not decolorized by MnP at all. These results demonstrate that laccase is the most important enzyme in decolorization and degradation of anthraquinone dyes by white-rot fungi. Toxicities of SBB before and after laccase treatment were evaluated by algal growth inhibition test using Selenastrum capricornutum. Although the dye itself showed toxicity at low concentration (2.4mg·l^-1 as ErC₅₀), the dye treated with laccase was found to be nontoxic. These findings indicate that the treatment of anthraquinone dyes with laccase is effective in decolorization and detoxification of the dyes.

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We surveyed THM (trihalomethanes) and TOX (total organic halides) concentrations in the chlorinated effluents from 55 domestic wastewater treatment facilities ; 53 middle or large scale gappei-shori johkasous (wastewater purifying facilities) and 2 rural sewerage systems, and examined whether operation and maintenance of the facilities had an influence on the formation of THM and TOX.
The THM concentrations ranged from 0 to 56.1 μg·l^-1, but it was lower than 2 μg·l^-1 at 65% of the facilities, while the TOX concenrations ranged from 55 to 612 μg·l^-1. Both the THM and TOX concentration correlated with free residual chlorine. More than 20 μg·l^-1 of THM was detected in 3 facilities where free residual chlorine was higher than 2.5mg·l^-1. The facilities with high concenration of THM showed the following features : (1) BOD and NH₄-N were low, that is, water qualities were good, or (2) the water amounts of influent were extremely small.
Since a small amount of free residual chlorine may result in insufficient disinfection performance while more than 2mg·l^-1 causes high concenration of THM or TOX, it was proved that the maintenance of facilities and the improvement of disinfection equipment should be performed accoding to volume and quality of the biologically treated wastewater.

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Degradation of tetrachloroethene (PCE) and trichloroethene (TCE) by combining an anaerobic consortium with an aerobic bacterium was investigated. The anaerobic enrichment culture that dechlorinated high concentration of PCE to cis-1, 2-dichloroethene (cDCE) without methane production and sulfate reduction, was obtained from TCE contaminated soil. The aerobic phenol-oxidizing bacterium that degraded TCE and cDCE was isolated from leachate of a waste landfill site. Each culture retained chloroethene degrading activities after immobilization in κ-carrageenan gel beads. In a batch bioreactor containing the immobilized cells, PCE and TCE were converted to cDCE and chloride ion under anaerobic condition. After addition of phenol and oxygen (or hydrogen peroxide) to the reactor, cDCE was degraded. PCE and TCE (40-50mg·l^-1) were degraded in 3 days with the bioreactor. The immobilized cells retained the degrading activities in repeated use.

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Degradation of tetrachloroethene (PCE) by using a two-stage anaerobic/aerobic bioreactor system was investigated. A PCE-dechlorinating anaerobic consortium was immobilized on the surface of crushed scallop shells. The maximum rate of PCE dechlorination to cis-1, 2-dichloroethene (cDCE) with an anaerobic fixed-bed upflow reactor containing the biofilm on the shell was 30μmol PCE·l^-1 reactor volume·h^-1. A phenol-oxidizing bacterium, capable of co-metabolic degradation of cDCE was immobilized in κ-carrageenan gel beads. Gaseous cDCE purged from effluent of the anaerobic reactor was degraded with an air-lift aerobic reactor containing the immobilized cells. To degrade PCE continuously, yeast extract was added to the anaerobic reactor feed, and phenol was added to the aerobic reactor feed. The life of the two-stage anaerobic/aerobic bioreactor had been tested for one month at a PCE supply rate of 17μmol PCE·l^-1 reactor volume·h^-1. The activity of the aerobic reactor decreased gradually, although the activity of the anaerobic reactor was stable during the experimental period.

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Photocatalytic treatment process using titanium dioxide for waste water generated by chelatometric titration for determination of water hardness has been studied. Zinc-ethylenediaminetetraacetic acid (EDTA), magnesium-EDTA, and calcium-EDTA complexes in the waste water could be readily degraded with irradiation of high-pressure mercury lamp, black light, and the sunlight, accompanying a decrease of the concentrations of total organic carbon (TOC) and total zinc. As degradation products, iminodiacetate, oxalate, nitrite, and nitrate ions and inorganic carbon were detected. In this process, the separation of the titanium dioxide particles used for the treatment was easy, because the particles sedimented almost completely by standing for a few days after the irradiation. This method proposed here is simple and does not require any special equipments.

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Molasses wastewater has been disposed by ocean dumping because of the dark brown color. However, ocean dumping will banned near future according to London dumping treaty. Many fermentation and sugar industries using molasses require the suitable decolorization treatment. Electrolysis for decolorization was applied for molasses wastewater, mainly wastewater from alcohol distillery, and high decolorization efficiency more than 99% was obtained. The optimal initial condition of color by dilution was 200,000U without NaCl addition. NaCl addition was effective to raise decolorization efficiency which shows the decolorization by unit electron quantity The voltage and initial pH did not effect the efficiency. The experiments using wastewater from glutamate processing industry, sugar processing industry and sugar refinery industry also showed the effectiveness of electrolysis for decolorization.

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In order to solve the eutrophication problem in closed water area, it is well-known fact that to reduce the nitrogen and phosphorus is one of the important ways. However, such nutrients in present sewege systems are not sufficiently removed. The objective of this study is to propose a treatment system for secondary effluent by using reed bed treatment system with different packed media. The effect of por osity of packed media on nitrogen and phosphorus removal was discussed.
The results indicated that the removal rate of nitrogen in reed bed treatment system packed with gravel was higher (1.54 gN·m^-2·d^-2) than those packed with sand and net material. According to numeral analysis 50 percent of nitrogen in the sand system was removed due to adsorption on sand, whereas in the gravel and net material systems 60 percent of it was removed by biological denitrification at the root zoon of reed. It was found that nitrification- denitrification at the root zoos of reed was important way for nitrogen removal, and the nitrogen removal at the root zoon was effectively carried out as the porosity of packed media increased. On the other hands 80 percent of phosphorus in the sand and gravel systems was adsorbed on packed media.

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Alcaligenes faecalis, a typical heterotrophic nitrifying and denitrifying bacterium, was added into activated sludge and was made to be a dominant species in the activated sludge ecosystem under anoxic conditions. Influent COD to total nitrogen ratios (C:N) and quantities of the inoculated A. faecalis were changed to test the responses of the systems. The systems' behaviors of N₂O emission and wastewater treatment were evaluated. On the other hand, a batch experiment was also conducted in which Helium (He) was used to bubble an activated sludge system. Characteristics of N₂O emission from the system were tested. Experimental results showed that N₂O production of the systems containing A. faecalis was generally about 50% less than those of the control reactors containing only activated sludge. In addition, the former systems had a higher total nitrogen removal capability, and their average total nitrogen removal efficiencies were about 7-56% higher than those of the control activated sludge systems. Moreover, TOC removal efficiencies of the systems containing A. faecalis were a little higher than those of the control systems. On the other hand, more alien A. faecalis addition and higher influent C:N ratio led to lower N₂O emission and better effluent water qualities. Therefore, increasing A. faecalis' population in activated sludge should be encouraged for controlling N₂O emission and upgrading wastewater treatment capability under anoxic conditions. Batch experiments showed that bubbling led to higher N₂O production. A critical He flowrate existed corresponding to the highest N₂O production yield.

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