Tsuno Hiroshi

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.

Fluid mechanism in an air-lift draft tube type sewage treatment reactor, which is operated under the conditions of low gas flow rate based on cross sectional area of the reactor (U_go) and low ratio of draft tube diameter to reactor diameter (D_i/D_o), was studied theoretically and experimentally. Empirical equations of gas hold up, pressure losses and liquid velocity in the draft tube were developed. It was found that liquid flow rate (Q_L) is almost proportional to the ratio of cross sectional area of the draft tube to that of the reactor (A_i/A_o). It was also found that under the conditions of U_go from 0.0005 to 0.005m³/(m²·s) and of A_i/A_o from 0.02 to 0.14 circulating time in the annulus is almost proportional to the ratio of the cross sectional area of the annulus to that of the draft tube (A_a/A_i).

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.

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 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.

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).

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.

Scrubber-washed wastewater of Sludge drying process in sludge melting system contains both ammonium nitrogen and dissolved organic carbon (DOC) in high concentrations, and is also found to contain compounds which show inhibition to nitrification. In batch experiments, the inhibitory compounds are found to be biodegradable and also absorbable to activated carbon. Nitrification activity can be recovered immediately after the inhibition compounds are removed.<br>Therefore in this study, biological treatment process using a expanded-bed activated carbon reactor is applied to accomplish nitrification as well as removal of organic compounds from the wastewater. Under the condition where DO is more than 1mg&middot;l^-1, TKN loading rate can be raised till 5mgN&middot;(gGAC)^-1&middot;d^-1 to attain more than 90% nitrification of influent nitrogen. DOC concentration in the bio-reactor should be maintained less than 40mgC&middot;l^-1 for avoiding inhibition and assuring nitrification.

Single high-loaded denitrification reactor has been developed and applied to treatment of night soil. Degradation of organic compounds, nitrification and denitrification occur concurrently in the reactor by the creation of both aerobic and anoxic zones and circulation of mixed liquor. In this study, a mathematical model is developed, in which the reactor consists of 3 zones (2 are aerobic and 1 is anoxic) and degradation of organics, nitrification, denitrification and growth of bacteria associated with each process are incorporated. The model is verified by the comparison of the simulated results with the tracer experiment and the performance results of the reactor operated in practice to treat night soil. The optimum operational conditions of the reactor for night soil treatment is discussed by the model. It is shown that the hydraulic retention time of 4.5 days in the reactor and DO concentration of 1mg/l in the middle zone between anoxic zone and higher DO zone are optimum for both fine and stable treatment.