津野 洋

都市下水を対象として, 好気性ろ床を組み込んだ前凝集・生物膜プロセスの処理特性および設計操作因子の検討を, パイロットプラント規模実験により試みた. 水温20℃を下回る低水温期においても生物反応器の水理学的滞留時間8hで, 流出SS濃度は5mg/L以下を, 流出のT-ATU-BOD濃度は5mg/L以下を, 流出T-N濃度は3mgN/L以下を, そして流出T-P濃度は1mgP/L以下を安定して保つことができた. 生物処理の最終部に組み込んだ好気性ろ床は, 目的とした残存有機物およびSS成分の除去, ならびにDO濃度の回復の機能を十分に果たした. 最終沈殿池を省略することで建設費および処理時間を削減でき, 本プロセスは既存の施設を活用した都市下水の高度処理に適用可能であることが示された.

Soil samples were collected from A and A0 horizons at 38 points in Shiga Prefecture under consideration of geological feature, soil type and vegetation. The samples were analyzed and used in artificial acid rain added experiments to clear soil characteristics and effects of acid rain. Ca, Mg and Al included in the extracted solution with buffer solution of 0.5M acetic acid and ammonium acetate (pH4.7) are shown to be available as indices for discussion on effects of acid rain on soil. According to these indices, forests with broad-leafed trees are shown to be stronger against acid rain than those with red pine, Japanese cypress and Japanese cedar. It is also shown that Al is afraid to be eluted from granite soil and that dune soil is typically weak against acid rain.

Soil samples were collected from A and A0 horizons at 38 points in Shiga Prefecture under consideration of geological feature, soil type and vegetation. The samples were analyzed and used in artificial acid rain added experiments to clear soil characteristics and effects of acid rain. Ca, Mg and Al included in the extracted solution with buffer solution of 0.5M acetic acid and ammonium acetate (pH4.7) are shown to be available as indices for discussion on effects of acid rain on soil. According to these indices, forests with broad-leafed trees are shown to be stronger against acid rain than those with red pine, Japanese cypress and Japanese cedar. It is also shown that Al is afraid to be eluted from granite soil and that dune soil is typically weak against acid rain.

Effect of effective depth of the reactor on nitrogen removal from domestic sewage by a draft tube type reactor is discussed with the data from continuous-treatment experiments. More than 2 minutes of the circulating time in the annulus partis required to obtain more than 70% of TN removal efficiency. As effective depth affects on circulating time, the range of D_i/D_o (the ratio of draft tube diameter to diameter of the reactor), in which high TN removal efficiency can be obtained, increases as effective depth increases. More than 70% of TN removal efficiency can be obtained in the reactor with depth of 6m under D_i/D_o conditions of both 0.19 and 0.26, while it can be obtained only when D_i/D_o is 0.19 in the reactor with depth of 4m.

本研究では, 反応器断面積あたりの空気流量 (U_go) が少なくかつ内管径の反応器径に対する比 (D_i/D_o) が低い条件下において運転される二重管縦型下水処理反応器の液流動に関して理論的および実験的検討を行った. その結果, 本反応器の液循環流速に関する経験式を提示し, 各種装置条件および各種U_go条件における液循環流速の予測を可能にした. また, 実測値および経験式による予測値に基づき考察した結果, 液循環流量 (Q_L) は曝気を行う内管部の断面積の反応器断面積に対する比 (A_i/A_o) にほぼ比例することを明らかにした. さらに, UU_go=0.0005～0.005m³/(m²・s), A_i/A_o=0.02～0.14の範囲では外管部下降時間は外管部断面積の内管部断面積に対する比 (A_a/A_i) にほぼ比例することを明らかにした.

Effect of effective depth of the reactor on nitrogen removal from domestic sewage by a draft tube type reactor is discussed with the data from continuous-treatment experiments. More than 2 minutes of the circulating time in the annulus partis required to obtain more than 70% of TN removal efficiency. As effective depth affects on circulating time, the range of D_i/D_o (the ratio of draft tube diameter to diameter of the reactor), in which high TN removal efficiency can be obtained, increases as effective depth increases. More than 70% of TN removal efficiency can be obtained in the reactor with depth of 6m under D_i/D_o conditions of both 0.19 and 0.26, while it can be obtained only when D_i/D_o is 0.19 in the reactor with depth of 4m.

The effect of the ratio of draft tube diameter to reactor diameter (D-i/D-o) on the efficiency of nitrogen removal from domestic sewage is discussed based on liquid-circulating flow rate and continuous treatment data More than 2.5 minutes of circulation time in the annulus part, which is required to create an anoxic zone, could be maintained under operating conditions in which air flow rate per reactor volume was 2 m(3)/(m(3).hr) and D-i/D-o was 0.19. When D-i/D-o was set at 0.19, the average total organic carbon (TOC), total nitrogen (TN) and dissolved nitrogen (DN) removal efficiencies were 83.2%, 72.1% and 71.6%, respectively, which were higher than those when D-i/D-o was at 0.26 or 0.36. From these results, it is concluded that 0.19 is the best D-i/D-o for nitrogen removal in a draft-tube type reactor with an effective depth of 4.0m under the treatment condition in which the BOD volumetric loading rate is in the range 0.22 to 0.46 kgBOD/(m(3).day). More than 80% nitrification and denitrification efficiencies can be achieved simultaneously when the both conditions, the aerobic zone ratio being more than 0.2, and the anoxic zone ratio being more than 0.3, are satisfied. (C) 1998 Published by Elsevier Science Ltd. All rights reserved

Effect of effective depth of the reactor on nitrogen removal from domestic sewage by a draft tube type reactor is discussed with the data from continuous-treatment experiments. More than 2 minutes of the circulating time in the annulus partis required to obtain more than 70% of TN removal efficiency. As effective depth affects on circulating time, the range of D_i/D_o (the ratio of draft tube diameter to diameter of the reactor), in which high TN removal efficiency can be obtained, increases as effective depth increases. More than 70% of TN removal efficiency can be obtained in the reactor with depth of 6m under D_i/D_o conditions of both 0.19 and 0.26, while it can be obtained only when D_i/D_o is 0.19 in the reactor with depth of 4m.

The effect of the ratio of draft tube diameter to reactor diameter (D-i/D-o) on the efficiency of nitrogen removal from domestic sewage is discussed based on liquid-circulating flow rate and continuous treatment data More than 2.5 minutes of circulation time in the annulus part, which is required to create an anoxic zone, could be maintained under operating conditions in which air flow rate per reactor volume was 2 m(3)/(m(3).hr) and D-i/D-o was 0.19. When D-i/D-o was set at 0.19, the average total organic carbon (TOC), total nitrogen (TN) and dissolved nitrogen (DN) removal efficiencies were 83.2%, 72.1% and 71.6%, respectively, which were higher than those when D-i/D-o was at 0.26 or 0.36. From these results, it is concluded that 0.19 is the best D-i/D-o for nitrogen removal in a draft-tube type reactor with an effective depth of 4.0m under the treatment condition in which the BOD volumetric loading rate is in the range 0.22 to 0.46 kgBOD/(m(3).day). More than 80% nitrification and denitrification efficiencies can be achieved simultaneously when the both conditions, the aerobic zone ratio being more than 0.2, and the anoxic zone ratio being more than 0.3, are satisfied. (C) 1998 Published by Elsevier Science Ltd. All rights reserved

The low pH of acid precipitation is buffered by soil to some extent, but the pH-buffering mechanism also releases variety of materials, which may cause wide effect on the aquatic environment. So in this research, we have permeated artificial acid rain through soil to examine the quality of soil leachates. As a result, we have found that some soils around Lake Biwa have reached the aluminium buffer range which has possibilities of deteriorating the aquatic ecosystem. We have also found that phosphorus included in the leachate causes great effect on algal growth potential under low pH condition as 4.0.

The low pH of acid precipitation is buffered by soil to some extent, but the pH-buffering mechanism also releases variety of materials, which may cause wide effect on the aquatic environment. So in this research, we have permeated artificial acid rain through soil to examine the quality of soil leachates. As a result, we have found that some soils around Lake Biwa have reached the aluminium buffer range which has possibilities of deteriorating the aquatic ecosystem. We have also found that phosphorus included in the leachate causes great effect on algal growth potential under low pH condition as 4.0.

Wastewater from sludge drying process in sludge melting system contains both ammonium trogen and dissolved organic compomds in high concentrations.It also contains inhibitory organic cnoimpounds to nitrification, which are biodegradable and absorbable to granulated activated carbon (GAC). The inhibition is transitory as nitrification acdvity recovers immediately after the inhibitory compounds are removed. With combination of several pretreatment methods for concentration and extraction such as Sep-Pak C₁₈ concentration, GACex action, vacuum evaporration and liquid-liquid extracdon, and GC-MS analysis, paramethylphenol (p-cresol) is determined as a main inhibitory organic compound to nitrificahon in the wastewater. From the inhibition test with standard reagent of p-cresol, the 90% inhihibitory concentration is detennined to be 10 mg·L^-1. P-cresol is also shown to be biodegradable and absorbable to GAC, that indicates the availability of treatment with biological activated carbon (BAC).

A combined biological activated carbon (BAG) and biological zeolite (BZ) reactor is under development to remove organics and nitrogen from wastewater which contains both inhibitory organics to nitrification and high concentration of ammonium nitrogen. In this study, the combined BAC and BZ reactor was applied to treatment of scrubber-washed wastewater from sludge drying process. Successful treatment performance was accomplished by decreases in concentrations of the inhibitory organics (in BAC tank) and ammonium nitrogen (in BZ tank) occurred by both adsorption to the mediums and biological reaction. Appropriate nitrogen loading rate for fine and stable treatment was shown to be less than 7 mgNOx(.)-N .(gGAC . d)(-1) for denitrification in BAC tank and less than 4 mgNH(4)(+)-N-(gZeolite . d)(-1) for nitrification in BZ tank. DOC/NOx(-)-N loading ratio to BAC tank is required to be more than 2.0 mgDOC .(mgNOx(-)-N)(-1) for successful denitrification. Copyright (C) 1996 IAWQ.

In this study, anaerobic degradation of PCP was discussed in an expanded-bed GAC anaerobic reactor which was applied to treatment of wastewater containing high concentration of PCP-Na as well as acetate. Total-COD concentration in effluent was kept less than 100 mg/L except for the start-up duration and PCP-Na concentration was kept less than 0.50 mg/L under the experimental conditions (HRT of 5 days, influent PCP-Na concentration of 100 and 400 mg/L, and influent Total-GOD concentration of 480 and 1600 mg/L). It was indicated by methane production rate and material balance of PCP-Na that about 60% of PCP-Na loaded into the reactor was transformed to methane and CO2 for 375 days. GC/MS analysis of extracts of the GAG medium and effluent indicated that reductive dechlorination of PCP occurred and dechlorinated phenols were adsorbed on the GAC in the reactor. Microorganisms collected from the reactor degraded PCP-Na and 2-GP anaerobically and addition of acetate in culture accelerated anaerobic degradation of PCP-Na in batch experiments. Copyright (C) 1996 IAWQ.

A mathematical model was developed to predict the effect of vertical water circulation caused by air-lift on water quality restoration in a lake. In this model, several ecosystem paths such as Algal growth, predation by zooplankton, degradation of organics and so on were combined with completely-mixing series tank model, in which a water body was divided vertically to two districts, epilimnion and hypolimnion. This model was applied to Lake Yogo, where two sets of the vertical water circulation unit were set, and verified by comparing the simulated results with observed data. The vertical circulation effects on lake restoration were discussed with this model from the viewpoints of concentrations of dissolved oxygen in hypolimnion, phytoplankton, total nitrogen and total phosphorus.

Wastewater from sludge drying process in sludge melting system contains both ammonium trogen and dissolved organic compomds in high concentrations.It also contains inhibitory organic cnoimpounds to nitrification, which are biodegradable and absorbable to granulated activated carbon (GAC). The inhibition is transitory as nitrification acdvity recovers immediately after the inhibitory compounds are removed. With combination of several pretreatment methods for concentration and extraction such as Sep-Pak C₁₈ concentration, GACex action, vacuum evaporration and liquid-liquid extracdon, and GC-MS analysis, paramethylphenol (p-cresol) is determined as a main inhibitory organic compound to nitrificahon in the wastewater. From the inhibition test with standard reagent of p-cresol, the 90% inhihibitory concentration is detennined to be 10 mg·L^-1. P-cresol is also shown to be biodegradable and absorbable to GAC, that indicates the availability of treatment with biological activated carbon (BAC).