Ion-selective electrodes (ISE) are widely utilized for the determination of fluoride in water. For the determination of trace amounts of fluoride in groundwater, a pre-concentration process is required because of lack of sensitivity of ISE to fluoride. Calcium hydrogenphosphate dihydrate (DCPD) efficiently reacts with fluoride ion in a solution to form fluorapatite (FAp). The aim of this study was to develop a simplified method of determination of trace amounts of fluoride in groundwater using DCPD. In this paper, a suitable pH range for measuring fluoride using ISE was assessed on the basis of chemical equilibrium. It was found that the suitable pH for fluoride determination by ISE is 5.5-7.0, and FAp can be dissolved in this pH range by the complex-forming reaction of CyDTA. From the obtained results, a simple method for determining trace amounts of fluoride in groundwater has been established. Fluoride in a 100 ml water sample is quantitatively fixed as FAp using 0.10 g of DCPD at 60°C for 1hr. The fluoride that separated as FAp is dissolved in a 10 ml solution containing NaCl, CyDTA and HEPES. The amount of fluoride ion in the solution is easiliy measured by using ISE.

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To evaluate the effectiveness of various reactor types for anaerobic ammonium oxidation (anammox), four types of reactor, a sequencing-batch reactor, a fixed-bed reactor with nonwoven carriers, a fluidized-bed reactor with tube-shaped attachment carriers, and a fluidized-bed reactor with methanogenic granules as carriers, were examined. While activity in the sequencing-batch reactor occasionally decreased markedly, a stable nitrogen removal was maintained for 200 days in the fixed-bed and fluidized-bed reactors. It appeared that the biofilm mode was not inhibited by oxygen due to the high biomass density and the existence of oxygen-consuming microorganisms on the biofilm surface. However, overgrowth on the nonwoven and tube-shaped carriers sometimes resulted in gas entrapment and the floatation of carriers. After 173 days of operation, the maximum nitrogen removal rate of the fluidized-bed reactor using methanogenic granules as carriers was 2.87 kg N·m^-3·d^-1, which was the highest among these four reactors. Considering biomass attachment and hydrodynamic mixing characteristics in addition to treatment efficiency, the use of methanogenic granules as attachment carriers in a fluidized-bed reactor appeared to be the most effective for the anammox process.

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Phosphorus recovery from wastewater has been a growing concern. Since human urine is one of the main sources of phosphorus in the environment, several studies have been undertaken to recover phosphorus from human urine diverted from feces. Phosphorus in human urine can be recovered as a precipitate of MAP (i.e., struvite, MgNH₄PO₄·6H₂O) by adding magnesium salt under alkaline conditions. However, little is known about the chemical reaction of MAP formation in human urine, which is essential for the practical application of the reaction. In this study, we established an equilibrium model to understand such a chemical phenomenon and to predict MAP formation in human urine. In addition, MAP precipitates were formed experimentally from synthesized and diverted human urine for the validation of the model. As a result, there was a considerable validity of the model of MAP formation. Using this model, we predicted MAP formation in diverted human urine at different pHs and amounts of magnesium salt added. We concluded that the addition of at least 10 mM MgCl₂ is necessary in MAP formation in urine in a urine-diversion toilet and in achieving a PO₄-P concentration of 0.1 mg·l^-1 in the supernatant. In such a case, the optimal pH is 9.7.

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Chlorinated organic compounds formed in activated sludge by the addition of hypochlorite solution were analyzed. Although many types of chlorinated organic compound were detected, their concentrations were high particularly those of chloroform (CHCl₃), chloral hydrate, dichloroacetonitrile (DCAN) and trichloroacetic acid. The mixed liquor of activated sludge was fractioned into supernatant, extracellular and intracellular fractions and the by-products (CHCl₃ and DCAN) of each fraction was also investigated. CHCl₃ and DCAN were related to the extracellular and intracellular fractions, respectively. To determine the precursor of DCAN, 23 N compounds were mixed with hypochlorite solution and the amount of DCAN formed was measured. DCAN was formed only from polypeptide and amino acid-containing cyclic N compounds. From this result, it was concluded that DCAN is formed mainly from cyclic N compounds in proteins in activated sludge. Clogged membrane modules in the laboratory experiments were cleaned using hypochlorite solution. The formation of CHCl₃ and DCAN was detected in both cases: cleaning directly in the mixed liquor and cleaning in pure water. The amount of the by-product formed seems to be decreased by cleaning in pure water. The trihalomethane (THM) formed by membrane cleaning in existing wastewater treatment facilities was also analyzed. THM was detected in the penetrate of membrane after the cleaning.

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Around the western part of Teshima Island in Kagawa Prefecture, various types of industrial waste were dumped illegally for about 20 years. The dumped wastes amount to a total of approximately 500,000 tons. The biological monitoring of coastal seawater was carried out using the sea urchin embryo development test to elucidate the influence of polluted seawater on marine organisms. The monitoring was conducted while the seaside restoration was in progress from March 1999 to February 2003. The results of March 2001 showed that the pluteus formation stage decreased from level one to three, and similar results were observed in July, 2001. The decrease coincided with the time after work on seaside restoration had been completed. On the basis of these results, the Apollo-like deformation of sea urchin embryos was considered to be mainly due to an increase in the zinc concentration of seawater.

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The removal of pharmaceuticals in the membrane separation bioreactor process was examined. The deposition of activated sludge on the microfiltration membrane surface provided an additional barrier for the permeation of target substances, although the additional effect of the deposition on the removal was lower than 25% for hydrophilic compounds with log Kow between 2 and 3. The additional effect increased with time and log Kow, and reached 65% after 44 days of operation for a solute with a log Kow of 4.8.

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The removal rate of 1,4-dioxane in a sewage treatment plant with an activated sludge system was examined. We estimated the removal rate of 1,4-dioxane by comparing 1,4-dioxane inflow into and outflow from the plant, in relation to the sewage retention time of the treatment system. The estimated removal rate (8.5%) was low. Volatilization by aeration tanks and transfer with dehydrated cake negligibly contributed to the removal of 1,4-dioxane. These findings indicate that almost all of the removal can be attributed to biodegradation in the aeration tank.

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Water samples were collected from 24 monitoring points in three rivers, Sasagase, Kurashiki and Kamo Rivers, flowing into L. Kojima, Japan bimonthly, from February 2001 to December 2002. Chemical oxygen demand (COD_Mn) was measured in each sample and/or filtrate. The COD_Mn of the sample (t-COD) was used as an index of total organic matter and that of the filtrate (d-COD) was used as an index for dissolved organic matter (DOM). The difference (p-COD) between t-COD and d-COD was used for determining particulate organic matter. Approximately 80 % of t-COD was d-COD as an average of the entire monitoring point. Each d-COD was closely related to the intensity of the fluorescence peak that appeared at EX 300-350 nm/EM 400-450 nm in the fluorescence excitation matrix (EEM). Therefore, the main component of DOM seemed to be fulvic. However, it was suggested that the EEM spectra of the point affected by domestic wastewater was associated with fluorescence whitening agents. On the other hand, p-COD was related to the concentration of chlorophyll a, and was higher at the point having occasionally long residence time. Therefore, each monitoring point had its particular factor for an enhancing t-COD.

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