Tsuno Hiroshi

A biologically activated carbon anaerobic reactor was applied for treatment of two types of food industry wastewater : low soluble COD concentration wastewater of 1000-1500㎎/L with high suspended solid of 300㎎/L, and bean paste production process wastewater. Mean total COD removal efficiency of 86% and 89% were obtained for both wastewaters under the fluidized-bed-volume organic loading rate of 0.5-33㎏ COD/(m³・d) and 1.6-29㎏ COD/(m³・d) respectively. It was indicated that conversion efficiency of removed soluble COD to solid COD was 0.12㎏ COD/㎏ COD-removed and the solubilization ratio of solid-COD was 95% for the low soluble COD concentration wastewater.

Batch and semi-continuous thermophilic l-lactate fermentation experiments were performed using Bacillus coagulans and glucose as a substrate. Reactor performance and biomass concentrations were assessed using two methods: turbidity as a traditional biomass index and real-time polymerase chain reaction (PCR) quantification of 16S rRNA genes. In the batch experiment, although the relationship between turbidity and real-time PCR assay differed depending on the growth phase, a correlation was observed between both assay methods. In the semi-continuous experiment, real-time PCR measurement was well suited for use as an index for evaluating bacterial mass under different organic loading conditions. A mathematical model was applied to evaluate the real-time PCR quantification to long-term, semi-continuous lactate fermentation. Lactate fermentation was well suited since only B. coagulans was involved in the reactions. The results obtained revealed a fundamental relationship between real-time PCR and traditional biomass analyses.

Batch and semi-continuous thermophilic l-lactate fermentation experiments were performed using Bacillus coagulans and glucose as a substrate. Reactor performance and biomass concentrations were assessed using two methods: turbidity as a traditional biomass index and real-time polymerase chain reaction (PCR) quantification of 16S rRNA genes. In the batch experiment, although the relationship between turbidity and real-time PCR assay differed depending on the growth phase, a correlation was observed between both assay methods. In the semi-continuous experiment, real-time PCR measurement was well suited for use as an index for evaluating bacterial mass under different organic loading conditions. A mathematical model was applied to evaluate the real-time PCR quantification to long-term, semi-continuous lactate fermentation. Lactate fermentation was well suited since only B. coagulans was involved in the reactions. The results obtained revealed a fundamental relationship between real-time PCR and traditional biomass analyses.

The effect of biological hyperthermal (80°C) hydrolysis treatment on anaerobic digestion residue was evaluated using thermal digestion residue samples of kitchen waste and paper. Residues of continuous thermal anaerobic digestion were hydrolyzed at 80°C C for a day and their biogas production volumes were measured by batch analysis. One day of hydrolysis converted 8 to 14% of solid COD to soluble COD, and 6.5, 5.1, and 3.5m³ of biogas were produced from one-ton samples of anaerobic digestion residue from kitchen waste, a kitchen waste and paper mixture, and paper, respectively. Assuming a continuous semi-dry treatment process, a hyperthermal hydrolysis treatment will make biogas production 17%, 17 and 16% in the cases of kitchen waste, a kitchen waste and paper mixture, and paper, respectively.

Attached growth reactors were developed separately for solids retention time (SRT)-controlled partial nitrification and for anaerobic ammonia oxidation (Anammox) treatment, and a new nitrogen removal process is proposed for wastewater containing highly concentrated ammonia. For partial nitrification, an attached growth medium of polyurethane foam was used. Partial nitrification was achieved stably under a SRT of 4 days, and the abundance ratio of NO2--N to the sum of NH4+-N, NO2--N and NO3--N was approximately 0.8 after 10 days. Under a SRT of 4 days, the amoA gene concentrations of ammonia-oxidizing bacteria increased from 1 x 10(8) to 7 x 10(8) copies/l, whereas the 16S ribosomal RNA (16S rRNA) gene concentrations of nitrite-oxidizing bacteria did not increase. These results indicate that SRT-controlled operation is a promising technology for achieving partial nitrification. For the Anammox treatment, an attached growth medium of non-woven fabric was used. Inorganic nitrogen removal of approximately 80-90% was observed at an inorganic nitrogen loading rate of over 10 kgN/(m(3)-medium.d) and an influent nitrogen concentration of 400 mgN/l. Our non-woven fabric reactor showed similar or superior Anammox performance to that reported previously. By using a combination of these two rectors, we can develop a method that combines partial nitrification and Anammox treatment for effective and stable nitrogen removal.

The authors evaluated the energy efficiency of a novel oxidation ditch (OD) system with dual dissolved oxygen (DO) control technology through clean water tests and continuous treatment of domestic wastewater in a full-scale OD. The system maintained a constant DO gradient in the loop channel by independently controlling the aeration intensity and the circulation flow rate. Clean water tests demonstrated that a standard aeration efficiency of 1.4 - 2.1 kgO₂/kWh was obtained in the OD equipped with membrane diffusers, blowers and vertical flow boosters, and these values were relatively higher than the previously reported values. The calculated standard aeration efficiency varied depending on the airflow rate and rotational speed of the flow boosters. Continuous treatment revealed that the power consumption was reduced by 67% when compared with the existing OD system. Reducing endogenous respiration, improving the standard aeration efficiency, and applying dual DO control were estimated to contribute 15%, 28% and 23%, respectively, to the total reduction of power consumption. Overall, this novel OD system showed extraordinary nitrogen removal performance with very low energy consumption.

 Ozone-added activated sludge process is one of the modified processes for reduction of excess sludge production. Although ozone-added activated sludge system was originally developed in order to reduce excess sludge production, it is expected that its direct ozonation to activated sludge can also remove some biorefractory compounds by chemical oxidation, and the treatment efficiency and stability can be increased as results. In this study, phenol was used as a biorefractory compound in wastewaters and behaviors of EDCs at sludge ozonation were also investigated in order to evaluate several functions of ozone-added activated sludge process. The treatment characteristics were investigated with lab scale experimental setups. It is made clear that direct ozonation to activated sludge within a range of 15 mgO₃/gSS does not inhibit biological activities and biorefractory compound(phenol) is promptly removed chemically. On the other hand, the experimental case without ozonation can not remove phenol quickly and biological activity is inhibited by existence of phenol. These results suggest that the system can treat wastewaters which contain biorefractory compounds effectively and stably besides both bulking control and low excess sludge production.

Field surveys on persistent organic pollutant (POP) bioaccumulation were conducted with oysters, clams and scallops whose consumption amount accounted for large shares in the total consumption of shellfish in Japan. There was no numerical difference in bioaccumulation characteristics between oysters, clams, scallops, Corbicula and Mytilus galloprovincialis. Therefore, it was clear that the bioaccumulation characteristics in oysters, clams and scallops, which are important for food, could be ascertained by using the monitoring results with Corbicula and M. galloprovincialis which are easily sampled in various water areas in the world. Non-cancer risk (hazard quotient, HQ) and cancer risk (excess cancer risk, Delta R) via shellfish ranged from 10(-8) to 10(-4) and from 10(-11) to 10(-7), respectively, at sampling points, which showed the risks of POP exposure via shellfish to be low enough. However, concerning the intake of other food, the importance of dieldrin monitoring should be suggested in Japan. Based on these results, the effectiveness of primary risk assessment could be suggested for screening chemicals whose preferential monitoring is needed.

Attached growth reactors were developed separately for solids retention time (SRT)-controlled partial nitrification and for anaerobic ammonia oxidation (Anammox) treatment, and a new nitrogen removal process is proposed for wastewater containing highly concentrated ammonia. For partial nitrification, an attached growth medium of polyurethane foam was used. Partial nitrification was achieved stably under a SRT of 4 days, and the abundance ratio of NO2--N to the sum of NH4+-N, NO2--N and NO3--N was approximately 0.8 after 10 days. Under a SRT of 4 days, the amoA gene concentrations of ammonia-oxidizing bacteria increased from 1 x 10(8) to 7 x 10(8) copies/l, whereas the 16S ribosomal RNA (16S rRNA) gene concentrations of nitrite-oxidizing bacteria did not increase. These results indicate that SRT-controlled operation is a promising technology for achieving partial nitrification. For the Anammox treatment, an attached growth medium of non-woven fabric was used. Inorganic nitrogen removal of approximately 80-90% was observed at an inorganic nitrogen loading rate of over 10 kgN/(m(3)-medium.d) and an influent nitrogen concentration of 400 mgN/l. Our non-woven fabric reactor showed similar or superior Anammox performance to that reported previously. By using a combination of these two rectors, we can develop a method that combines partial nitrification and Anammox treatment for effective and stable nitrogen removal.

The authors evaluated the energy efficiency of a novel oxidation ditch (OD) system with dual dissolved oxygen (DO) control technology through clean water tests and continuous treatment of domestic wastewater in a full-scale OD. The system maintained a constant DO gradient in the loop channel by independently controlling the aeration intensity and the circulation flow rate. Clean water tests demonstrated that a standard aeration efficiency of 1.4 - 2.1 kgO₂/kWh was obtained in the OD equipped with membrane diffusers, blowers and vertical flow boosters, and these values were relatively higher than the previously reported values. The calculated standard aeration efficiency varied depending on the airflow rate and rotational speed of the flow boosters. Continuous treatment revealed that the power consumption was reduced by 67% when compared with the existing OD system. Reducing endogenous respiration, improving the standard aeration efficiency, and applying dual DO control were estimated to contribute 15%, 28% and 23%, respectively, to the total reduction of power consumption. Overall, this novel OD system showed extraordinary nitrogen removal performance with very low energy consumption.

Field surveys on persistent organic pollutant (POP) bioaccumulation were conducted with oysters, clams and scallops whose consumption amount accounted for large shares in the total consumption of shellfish in Japan. There was no numerical difference in bioaccumulation characteristics between oysters, clams, scallops, Corbicula and Mytilus galloprovincialis. Therefore, it was clear that the bioaccumulation characteristics in oysters, clams and scallops, which are important for food, could be ascertained by using the monitoring results with Corbicula and M. galloprovincialis which are easily sampled in various water areas in the world. Non-cancer risk (hazard quotient, HQ) and cancer risk (excess cancer risk, Delta R) via shellfish ranged from 10(-8) to 10(-4) and from 10(-11) to 10(-7), respectively, at sampling points, which showed the risks of POP exposure via shellfish to be low enough. However, concerning the intake of other food, the importance of dieldrin monitoring should be suggested in Japan. Based on these results, the effectiveness of primary risk assessment could be suggested for screening chemicals whose preferential monitoring is needed.

An advanced sewage treatment process has been developed, in which excess sludge reduction by ozonation and phosphorus recovery by crystallization process are incorporated to a conventional anaerobic/oxic (A/O) phosphorus removal process. The mathematical model was developed to describe the mass balance principal at a steady state of this process. Sludge ozonation experiments were carried out to investigate solubilization characteristics of sludge and change in microbial activity by using sludge cultured with feed of synthetic sewage under A/O process. Phosphorus was solubilized by ozonation as well as organics, and acid-hydrolyzable phosphorus (AHP) was the most part of solubilized phosphorus for phosphorus accumulating organisms (PAOs) containing sludge. At solubilization of 30%, around 70% of sludge was inactivated by ozonation. The results based on these studies indicated that the proposed process configuration has potential to reduce the excess sludge production as well as to recover phosphorus in usable forms. The system performance results show that this system is practical, in which 30% of solubilization degree was achieved by ozonation. In this study, 30% of solubilization was achieved at 30 mg O-3/gSS of ozone consumption. (c) 2005 Elsevier Ltd. All rights reserved.

An advanced sewage treatment process has been developed, in which excess sludge reduction by ozonation and phosphorus recovery by crystallization process are incorporated to a conventional anaerobic/oxic (A/O) phosphorus removal process. The mathematical model was developed to describe the mass balance principal at a steady state of this process. Sludge ozonation experiments were carried out to investigate solubilization characteristics of sludge and change in microbial activity by using sludge cultured with feed of synthetic sewage under A/O process. Phosphorus was solubilized by ozonation as well as organics, and acid-hydrolyzable phosphorus (AHP) was the most part of solubilized phosphorus for phosphorus accumulating organisms (PAOs) containing sludge. At solubilization of 30%, around 70% of sludge was inactivated by ozonation. The results based on these studies indicated that the proposed process configuration has potential to reduce the excess sludge production as well as to recover phosphorus in usable forms. The system performance results show that this system is practical, in which 30% of solubilization degree was achieved by ozonation. In this study, 30% of solubilization was achieved at 30 mg O-3/gSS of ozone consumption. (c) 2005 Elsevier Ltd. All rights reserved.

The mathematical model of biofiltration which was developed for the treatment of precoagulated sewage from a grid chamber is applied to explain the experimental performance of a biofilter used for tertiary treatment of secondary effluent. Its applicability is discussed by comparing the results simulated using the model with the experimental data. This model can favorably estimate the 525-day treatment performance, biomass concentrations and details of water-quality profiles through the filter bed in continuous treatment without changing any parameters of the proposed model, including rate constants, half-saturation concentrations and yield coefficients. Then some design and operational parameters are discussed referring to this model. Under large fluctuation of nitrate concentration in the filter, McCarty's equation can be used to determine the appropriate amount of methanol to be added. The maximum ammonium nitrogen loading rate in the nitrification filter is shown to be 0.55 kgN·m-3·d-1 in winter. Also, the maximum nitrate nitrogen loading rate in the denitrification part of the polishing filter is shown to be 5 kgN·m-3·d-1 in winter. The developed model is proved to be a promising tool for discussing the design and operational parameters of full plants.

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.

The contribution of ozone and hydroxyl radical to the formation of bromate ion was investigated in a continuous flow reactor. Experiments were conducted under a wide range of ozone dose (0.7 similar to 3.8 mg/L), pH (6.5 similar to 8.5), and t-butanol concentration (0 similar to 0.5 mM). The formation of bromate ion was found to depend on radical reaction pathway, because the amount of bromate ion formed increased with pH and decreased with t-butanol, a radical scavenger, even when dissolved ozone concentrations were almost the same. In fact, the amount of bromate ion formed was reduced by 90% in the presence of t-butanol. Furthermore, the formation of bromate ion occurred even when dissolved ozone was not significantly detected in the presence of organic matter (TOC of 1 mgC/L). The second-order reaction rate constant of hydroxyl radical with bromide ion, (HO)-H-k,Br- of 1.7 x 10(9) (M(-1)s(-1)), was obtained on the assumption that the reactions of bromide ion and t-butanol with hydroxyl radical were competitive with each other in the presence of t-butanol and that the formation of bromate ion depended on the reaction of bromide ion with hydroxyl radical. Therefore, it is concluded that the reaction of bromide ion with hydroxyl radical dominated in the overall reaction from bromide ion to bromate ion in the continuous flow reactor.

The contribution of ozone and hydroxyl radical to the formation of bromate ion was investigated in a continuous flow reactor. Experiments were conducted under a wide range of ozone dose (0.7 similar to 3.8 mg/L), pH (6.5 similar to 8.5), and t-butanol concentration (0 similar to 0.5 mM). The formation of bromate ion was found to depend on radical reaction pathway, because the amount of bromate ion formed increased with pH and decreased with t-butanol, a radical scavenger, even when dissolved ozone concentrations were almost the same. In fact, the amount of bromate ion formed was reduced by 90% in the presence of t-butanol. Furthermore, the formation of bromate ion occurred even when dissolved ozone was not significantly detected in the presence of organic matter (TOC of 1 mgC/L). The second-order reaction rate constant of hydroxyl radical with bromide ion, (HO)-H-k,Br- of 1.7 x 10(9) (M(-1)s(-1)), was obtained on the assumption that the reactions of bromide ion and t-butanol with hydroxyl radical were competitive with each other in the presence of t-butanol and that the formation of bromate ion depended on the reaction of bromide ion with hydroxyl radical. Therefore, it is concluded that the reaction of bromide ion with hydroxyl radical dominated in the overall reaction from bromide ion to bromate ion in the continuous flow reactor.

The simulation model to predict dissolved ozone concentration in a real ozone contactor was developed. The hydrodynamic behavior in the contactor was investigated by CFD (Computational Fluid Dynamics) technique before developing the reaction model. The ozone contactor was divided into small compartments and interaction between compartments was evaluated based on the result of CFD. Mass balance equations were established in each divided compartment with reaction terms. As state variables, organic compounds, odor compounds, bacteria groups, bromide ion, bromate ion as well as dissolved ozone were selected. Organic compounds were classified into only two groups in this model. The concentration of dissolved ozone was favorably evaluated and reasonable results were obtained for other items. From these, we conclude that dissolved ozone concentration as well as organic compounds, bacteria groups, bromate ion can be predicted in this model.

Thermophilic methane fermentation at 55°C was applied to garbage treatment. Continuous feed-and-draw operation was conducted in a complete-mixing type reactor with artificially prepared garbage. Based on calculations of COD, more than 80% of the garbage was transformed to methane, with 0.4 to 0.5 L of methane gas being produced from 1 g VS of garbage. Inhibition of methanogenesis by ammonium nitrogen was initiated when its concentration exceeded 2, 000 mgN/L. Total nitrogen concentration in the garbage treated should be less than 4, 000 mgN/L, as about half of the total nitrogen was transformed to ammonium nitrogen by anaerobic methane production processes.

A mathematical model of biological filtration process is developed in this paper. A biological filtration process has advantages that filtration action and biological activities are combined in a single reactor with aid of filter media. Both physical and biological functions are incorporated in this developed model to simulate both mechanisms. Backwashing is expressed by the assumption that a mean captured solids concentration is input as data, and a captured solids concentration is kept at that value during each filtration run. The developed model is applied to explain the experimental performance with biological filtration reactors, in which batch cultivation of autotrophic bacteria and continuous treatment of actual sewage are carried out. Its applicability is discussed by comparing the simulated results with the experimental data. This model can favourably estimate maximum accumulation of autotrophic bacteria on the medium in batch cultivation, long-term treatment performance in continuous treatment, details of water quality profiles through the filter bed, and biomass. Required hydraulic retention time for nitrification and an appropriate recirculation ratio in a winter season are discussed with this model. This model predicts that a HRT of 1.1 h or above is required to achieve nitrification with remaining NH4+-N of less than I mgN/L and that an appropriate recirculation ratio is 2-3. (C) 2003 Elsevier Ltd. All rights reserved.

A mathematical model of biological filtration process is developed in this paper. A biological filtration process has advantages that filtration action and biological activities are combined in a single reactor with aid of filter media. Both physical and biological functions are incorporated in this developed model to simulate both mechanisms. Backwashing is expressed by the assumption that a mean captured solids concentration is input as data, and a captured solids concentration is kept at that value during each filtration run. The developed model is applied to explain the experimental performance with biological filtration reactors, in which batch cultivation of autotrophic bacteria and continuous treatment of actual sewage are carried out. Its applicability is discussed by comparing the simulated results with the experimental data. This model can favourably estimate maximum accumulation of autotrophic bacteria on the medium in batch cultivation, long-term treatment performance in continuous treatment, details of water quality profiles through the filter bed, and biomass. Required hydraulic retention time for nitrification and an appropriate recirculation ratio in a winter season are discussed with this model. This model predicts that a HRT of 1.1 h or above is required to achieve nitrification with remaining NH4+-N of less than I mgN/L and that an appropriate recirculation ratio is 2-3. (C) 2003 Elsevier Ltd. All rights reserved.

A pre-coagulation and bio-filtration process for advanced treatment of sewage was developed and experimentally discussed with a pilot plant. The bio-filtration unit consists of a denitrification filter, a nitrification filter with side stream to the denitrification filter, and a polishing filter with anoxic and aerobic parts. Concentrations of SS, T-CODSCr, T-carbonaceous BOD, T-N and T-P in the effluent were stably kept at less than 3, 20, 5 mg/L, 2 mg N/L and 0.2 mg P/L, respectively, and transparency at higher than 100 cm, under total hydraulic retention time of 3.2h in the bio-filtration parts (filter-bed). ORP in an anoxic tank before a nitrification tank should be at a low level of less than -120 mV to keep remaining NOx--N less than 1 mg N/L, but must be maintained at a level higher than -150 mV. The maximum nitrogen-loading rate under a water temperature of 18 degreesC should be less than 0.25 kg N/(m(3)-filter-bed (.) d). Concentrations of microorganisms kept in the reactors were as high as 4000-5000 mg COD/L-filter-bed. Denitrification activity of 0.4 or 0.7 kg N/(m(3)-filter-bed (.) d), and nitrification activity of 0.3 kg N/(m3-filter-bed (.) d) were obtained, respectively, under a water temperature of about 18 degreesC. Backwashing in each tank as well as methanol addition and aeration in the polishing filter were operated successfully by the automatic control systems. These results proved that this process is applicable to advanced treatment of sewage with easy maintenance. (C) 2003 Elsevier Ltd. All rights reserved.

A pre-coagulation and bio-filtration process for advanced treatment of sewage was developed and experimentally discussed with a pilot plant. The bio-filtration unit consists of a denitrification filter, a nitrification filter with side stream to the denitrification filter, and a polishing filter with anoxic and aerobic parts. Concentrations of SS, T-CODSCr, T-carbonaceous BOD, T-N and T-P in the effluent were stably kept at less than 3, 20, 5 mg/L, 2 mg N/L and 0.2 mg P/L, respectively, and transparency at higher than 100 cm, under total hydraulic retention time of 3.2h in the bio-filtration parts (filter-bed). ORP in an anoxic tank before a nitrification tank should be at a low level of less than -120 mV to keep remaining NOx--N less than 1 mg N/L, but must be maintained at a level higher than -150 mV. The maximum nitrogen-loading rate under a water temperature of 18 degreesC should be less than 0.25 kg N/(m(3)-filter-bed (.) d). Concentrations of microorganisms kept in the reactors were as high as 4000-5000 mg COD/L-filter-bed. Denitrification activity of 0.4 or 0.7 kg N/(m(3)-filter-bed (.) d), and nitrification activity of 0.3 kg N/(m3-filter-bed (.) d) were obtained, respectively, under a water temperature of about 18 degreesC. Backwashing in each tank as well as methanol addition and aeration in the polishing filter were operated successfully by the automatic control systems. These results proved that this process is applicable to advanced treatment of sewage with easy maintenance. (C) 2003 Elsevier Ltd. All rights reserved.

The applicability and operation factors of thermophilic methane fermentation for garbage treatment in high concentration under once-a-day feeding condition were investigated by using a semi-continuous flow completely-mixed reactor. The experiment were conducted by changing the HRT from 158 to 9 days and the CODcr volumetric loading rate from 1.75 to 25.6 Kg/(m³·d) under the conditions of a temperature of 55°C and a constant feeding TS of 15%. Some reactors were operated with returning solids materials for keeping the microorganism in the reactor at high concentration. The methane fermentation system could respond successfully, when CODcr volumetric loading rate were increased up to 25.6Kg/(m³·d) under the condition of returning solids materials. It is suggested that the appropriate CODcr volumetric loading rate would be 20KgCODcr/(m³·d), corresponding to the HRT of 11 days, for the reactor with returning solids materials, and 6-10KgCODcr/(m³·d) for the reactor without returning solids materials. More than 80% of garbage was transformed to methane gas as calculated on COD base. The stable ammonia concentrations under the conditions of each organic loading rate decreased from 2680 to 1500mgN/L with increasing CODcr volumetric loading rate. Methane fermentation activity was obtained to be 2.2g COD-CH₄/(gVSS·d).

Bromate ion, an anion with carcinogenic properties, may be formed when bromide-containing water is ozonated during treatment. Investigation showed that bromide and bromate level in sewage effluents were in a range of 44-447μg/L and 1.2-15μg/L, respectively. In this study it is showed that bromate ion is a principal disinfection by-product during ozonation in sewage effluents. Formation amount of the bromate ion is affected by coexistence matters like nitrite ion and organic groups, which have high absorbance at 254nm. To control the formation of bromate ion, it is good to apply ozone at consumption amount in the range of 1.0-2.0mgO₃/mgC. Bromate ion in sewage was reduced to bromide in biological filtration for denitrification after nitrate was denitrified.

Reaction rate constants of di-n-butyl phthalate (DBP) and 17β-estradiol (E2) with ozone and hydroxyl redical (HO·) were measured in water. The rate constants of DBP with ozone and HO· were <0.2 and 5.3X109 M-1·s-1, respectively (DBP-d4 was used for the measurement of the rate constant of DBP with HO·), thus, it was found that DBP was decomposed only by HO· during ozonation. Reaction rate constants of undissociated and dissociated forms of E2 with ozone were 7.1(±2.5)X104 and 1.3(±0.2)X109 M-1·s-1, respectively, and the reaction rate constant of the undissociated form of E2 with HO· was 5.3(±0.4)X109 M-1·s-1. The order of the apparent rate constants of E2 with ozone was from 105 to 107 M-1·s-1 in the case that the pH of the solution was in the range of 6-8. Therefore, it was shown that E2 reacted mainly with ozone molecules and was rapidly decomposed during practical ozonation. The relationship among the residuals of the compounds decomposed mainly by HO· during ozonation in the absence of co-existing substances was not affected by the dissolved organic matter (DOM) when the dissolved organic carbon (DOC) was less than several mg·l-1.