The Influence of volatile fatty acids on hydrogen fermentation from an organic waste by a mixed microflora was investigated in a batch experiment. The batch reactor with a working volume of 1.0 liter was operated at 35°C and a constant p H (5.5 or 6.5) for each experimental run. Dog food was used as the substrate. The seed microflora was a mixed culture obtained by acclimatizing a thermophilic digested sludge by treating the organic fraction of municipal solids waste using glucose as the substrate. The experiments were conducted by changing the initial concentrations of acetic acid and butyric acid from 0 to 50,000mg·l^-1 at the substrate concentrations of TS2% to evaluate the substrate decomposition, gas production and metabolic production under each condition. Hydrogen production potential, gas production rate and hydrogen content in the biogas decreased with the increase in the initial concentration of volatile fatty acid. The inhibition effect at a pH of 5.5 was much stronger than that at a pH of 6.5 for a same fatty acid concentration. It was also found that the inhibition caused by fatty acids depends on not only the concentration, but also the type of fatty acid. Butyric acid exerted a stronger inhibition effect than acetic acid. In addition, it was found that an un-ionized fatty acid is a more powerful inhibitor and that hydrogen fermentation is significantly inhibited at an un-ionized fatty acid concentration higher than 200mg·l^-1.

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In an evaluation of health and environmental effect in wastewater reuse, one of the important parameters is the toxicity of reclaimed wastewater. We applied bioassay using cultured human cell lines to the samples from three experiments: 1) decay process of activated sludge, 2) ultrasonication of activated sludge, 3) aerobic degradation process of ultrasonicated activated sludge. The bioassay results showed that 1) aerated activated sludge increased the toxicity of the filtrate of sludge, 2) the dose-response relationships of hydrophilic organic matter obtained during activated sludge decay process were almost identical and they had approximately same 50% Effective Concentration (EC₅₀). The comparison of dose-response relationships obtained from several samples in this research showed that 1) the hydrophobic organic matter detached from activated sludge showed toxicity in 30hours and they were degraded biologically, 2) the toxicity in decay process of activated sludge depended mainly on the hydrophilic organic matter released from activated sludge cells. We examined the toxicity of Lipopolysaccharide(LPS) and the mixture of LPS and activated sludge before and after aeration. The mixture after the aeration showed more intensive toxicity than before aeration.

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Hot-spring water and mine effluent flow into the Toyohira River, which runs through the center of Sapporo, Japan. In the river, the concentrations of components from hot-spring water and mine effluent change according to the flow regime. This phenomenon must be addressed in water quality management. We found that when the water level is low, the arsenic originating from hot-spring water is washed out as a point-source (dilution) pollutant or together with polluted water with a constant arsenic concentration. In the region downstream of the dam, the arsenic washed out during flood is a non-point-source (diffuse) pollutant. The flow-regime-dependent difference in the washout component is attributed to arsenic accumulation in the bottom mud during low water levels. The arsenic concentration in the bottom mud is high in the region downstream of Jozankei, a hot-spring resort. The arsenic accumulated in large amounts in the dam is stably supplied to the river. During flood, however, the agitation of the bottom mud enhances the washout of suspended arsenic, and the concentration of suspended arsenic washed out is high.

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Hot-spring water and mine effluent flow into the Toyohira River, which runs through the center of Sapporo, Japan. In the river, the concentrations of components from hot-spring water and mine effluent change according to the flow regime. This phenomenon must be addressed in water quality management. The authors focused on arsenic supplied to the Toyohira River. Arsenic washout load was quantitatively assessed, and the flow-regime-dependent characteristics of the washout load were studied. We found that the washout load of dissolved arsenic increases during snowmelt and fall flood, phenomena that increase the inflow of hot-spring water. The highest washout load of suspended arsenic occurs during flood. The estimated annual arsenic washout load is 10,763 kg·year^-1 (2002), 43% of which is washout during flood (snowmelt or rainfall). According to the arsenic washout load balance of the river basin as a whole, approximately 20% of arsenic supplied to the Toyohira River is suspended and sediment there. Also, approximately 40% of suspended arsenic washed into the Toyohira River by flood comes directly from hot-spring water.

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A signal processing algorithm for the real-time monitoring of nitrate ions using UV absorption spectrophotometry was developed and applied to the on-site monitoring of nitrate ions in effluent from a sewage treatment plant and influent to a gravel filtration plant for a few months. The algorithm developed can detect a change in the absorption spectrum by interfering substances at UV absorbances of 225,230 and 235nm and correct it in real time by a sequential processing. As the results of the on-site monitoring, this algorithm achieved reliable real-time monitoring of nitrate ions without any additional pretreatment and cleansing of the flow cell. The prediction error during the on-site monitoring was about 1.4 - 4.6 times smaller than that of the conventional method. Turbidity and cloudiness of the optical cell can be apparently regarded as absorption substances. Accordingly, the effects of turbidity and cloudiness of the cell are cancelled by the algorithm developed. Thus, the algorithm developed was considered to be applicable to the real-time monitoring of nitrate ions in terms of high accuracy and easy maintenance.

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The iron electrolysis process was applied to an existing domestic wastewater treatment plant that used the contact aeration process. The wastewater in the second contact aeration tank was pumped up into the iron electrolysis tank that contained iron electrodes and flowed back to the first sedimentation/ separation tank. The removal efficiencies for phosphorus and nitrogen were improved by introducing the iron electrolysis process and were 75% and 50%, respectively, when it was operated at an Fe:P ratio or 1.5, a polarity reversal of 24 hours, and a recycle ratio of 1.0 Iron electrolysis did not inhibit biochemical oxygen demand removal. The voltage between the electrodes were stable during 90 days operation and then increased. The amount of eluted iron that was controlled by electric current was almost equal to the theoretical amount. The cost of electrolysis was estimated and was shown to be less expensive than the poly aluminium chloride coagulation process.

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A basic study of the rate and mechanisms of phosphorus removal from water in batch reactor was conducted. The material of the adsorbent used enhanced phosphorus removal capacity after iron (II) sulfate pretreatment, maybe due to the formation and precipitation of iron (II) phosphate. To clarify the mechanisms, adsorption and precipitation were separately measured and analyzed. Results showed that the adsorption of phosphorus onto an adsorbent is expressed by the second-order reaction kinetics, while the precipitation of iron (II) phosphate is expressed by the first-order reaction kinetics. After pretreatment with iron (II) sulfate, the conditions for the iron (II) ion residue onto the material affected the removal capacity. The use of an efficiently washed sample increased the removal capacity without iron (II) ion release. To increase the removal capacity, the adsorbent must have a larger microsurface area that has affinity to iron (II) ions.

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The monitoring of 1,4-dioxane in groundwater and river water was conducted by solid-phase extraction and GC/MS determination. 1,4-Dioxane in groundwater was investigated at 338 wells of the Tama district in Tokyo and was detected in 74.1% of shallow wells and 79.3% of deep wells. The concentrations detected ranged from 0.05 to 113μg·l^-1, and the averages were 2.23μg·l^-1 (shallow wells) and 4.69μg·l^-1 (deep wells). The 1,4-dioxane concentration in the groundwater containing more than 50 μg·l^-1 of 1,4-dioxane negligibly changed in more than 6 months. In the case of the Tama River water, 1,4-dioxane was detected at concentrations from 0.06 to 2.15 μg·l^-1 at downstream sites, but was not detected at upstream site. This could be due to the inflow of effluent from sewage plants. The amount of 1,4-dioxane loaded from sewage plants ranged from 28 to 269 g·day^-1.

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