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Ebara Engineering Review No.192

Study on Sludge Reduction and Other Factors by Use of an Ozonation Process in Activated Sludge Treatment

by ARAKAWA, Yousei KATSU, Toshihiro TANAKA,& Takuya KOBAYASHI

Continuous tests were conducted to study sludge reduction and other factors by the use of ozonation in activated sludge treatment, in particular the relationship between sludge liquefaction and sludge reduction. Furthermore, batch tests were conducted to study the characteristics of organic and inorganic constituents in ozone treated sludge, as well as changes in viability of nitrifying bacteria. The amount of liquefied sludge increased almost in proportion to the increase in the ozone injection rate, and the amount of sludge decreased in line with this. The viability of nitrifying bacteria rapidly decreased when the ozone injection rate became higher than 20 mg-O3/g-MLVSS. All in all, test results indicated that the amount of sludge liquefied by ozonation was an important parameter in activated sludge treatment which uses ozonation.

Keywords
Ozonation, Acidic ozonation, Activated sludge process, Sludge liquefaction, Sludge reduction, Viability of nitrifying bacteria, Liquefied ratio of potasium, Specific sludge production ratio, Synthesized sewage

Longitudinal Diffusion by Passing Vehicles in Road Tunnels - Investigation of Experimental Formula for Longitudinal Diffusion Coefficient in Road Tunnels -

by Hideo OHASHI, Takashi YAMADA, & Kohzo KOMATSU

A study was made on the use of longitudinal diffusion coefficients for predicting the concentration and emission of exhaust gas of vehicles in road tunnels. Study results have clarified the heretofore unclear effects by the direction of traffic or the number of lanes. Experimental equations have been established for calculating longitudinal diffusion coefficients. It was found that longitudinal diffusion coefficients could be established through the vehicular equivalent resistance area ratio alone, regardless of whether there was a one-way or two-way traffic in a tunnel. The knowledge attained has made it possible to estimate the longitudinal diffusion coefficient D for all types of vehicular road tunnels as well as for all traffic conditions. It is the wish of the authors that the attained knowledge be enthusiastically applied in the calculation of ventilation in road tunnels.

Keywords
Turbulence, Diffusion, Vehicle, Tunnel ventilation, Concentration, Diffusion coefficient, Drag coefficient, Vehicular equivalent resistance area, Longitudinal diffusion coefficient in tunnel, Reynolds number

Assessment of Creep Damage in 2.25Cr-1Mo Steel by Electromagnetic Acoustic Resonance

by Toshihiro OHTANI, Hirotsugu OGI, Tomohiro MORISHITA, & Masahiko HIRAO

A study was made on the performance of a novel EMAR (Electromagnetic Acoustic Resonance) technique for assessing creep damage in 2.25Cr-1Mo steel. The steel was exposed to a temperature of 923K and put under various stress. The EMAR technique featured the use of two non-contacting electromagnetic acoustic transducers (EMAT) for test samples with different configurations. Ultrasonic velocity was obtained from resonant frequency and attenuation coefficient from ring down curves at resonance. One EMAT was a bulk wave type for measuring the frequency dependence of shear-wave attenuation of sample plates. The other was an axial-shear-wave type for detecting attenuation changes of shear waves traveling in the circumferential direction of cylindrical samples. It was found that attenuation was more sensitive to damage accumulation than was resonant frequency, reaching a ten-fold value (as compared to the initial attenuation value) when approaching a rupture. The frequency dependence of the attenuation also showed a remarkable increase with damage. All in all, research results indicated that the EMAR technique had a great potential of being used for practical non-destructive/non-contact damage monitoring. The EMAR technique was proven to be capable of sensing the evolution of attenuation, as well as providing diagnostic data on damage for predicting the creep life of 2.25Cr-1Mo steel.

Keywords
Creep damage, Electromagnetic acoustic resonance (EMAR), Steel, Ultrasonic attenuation, Non-contacting evaluation

Treatment of Toluene Containing Exhaust Gas by a Packed-Bed Biofiltration System

by Shigeki YAMASHITA, & Masami KITAGAWA

An experimental packed-bed biofiltration system, featuring the use of polyurethane filtration media, was tested to evaluate the feasibility and performance of treating exhaust gas containing volatile organic compounds (VOCs). Continuous test results indicated a maximum VOC removal rate of Vm = 1.5 g/(m3¥day) and a saturation coefficient of K2 = 0.043 g/m3. Converting these figures to the case of a full-scale system indicated that this method could be practicalized in such a full-scale system. It was also found that further improvement was possible in terms of treatment rate and stability. Once practicalized, widespread use of this system is expected for treating VOC containing exhaust gases. The packed-bed biofiltration system will surely contribute to the betterment of the environment.

Keywords
Packed bed biofilter, Volatile organic compound (VOC), Toluene, Maximum elimination rate, Saturation constant, Toluene degrading bacteria, Space velocity, Packing media, Polyurethane form, Exhaust gas

Bearingless Motor

by Tadashi SATOH, Satoshi MORI, & Masaru OHSAWA

A bearingless motor, featuring a motor and a magnetic bearing built into one unit, has been developed. Lubrication oil is unnecessary for this motor unit, as magnetic levitation prevents friction and wear. Combining the motor and the magnetic bearing has enabled compactness, shortened shaft length, and high speed operation. A saving in manufacturing costs can be realized by the use of marketable motor parts and inverters, as compared to using a rotating machine whose motor and magnetic bearing are separate.

Keywords
Bearingless motor, Magnetic levitation, Magnetic bearing, Maintenance free, Canned pump, High speed rotation

The "Gaikaku Housuiro" Drainage Pump Station - Third Report: Downsizing a Large-scale Drainage Pump -

by Shinya HIBINO, Shoichi KUME, Takashi ENOMOTO, Hiroyuki KUBOTA, Tetsuo TAKABE, & Shinjiro MAE

The downsizing of large-scale drainage pumps is becoming an important issue today in line with the minimization of capital investment for drainage pump stations. Computational fluid analysis was applied to design the performance of a newly designed vertical-shaft, volute type, mixed-flow pump. Pump model test results indicated that the design factors for this pump, which were high efficiency, high suction performance, and compactness, were satisfactory. A highly reliability was achieved by the use of leading edge technology for the bearing and seal units of this pump.

Keywords
Drainage pump station, Drainage system, Underground at great depth, Volute type mixed flow pump, Volute casing, Suction liner, Bearing unit, PEEK bearing, Seal unit

Pumps and Auxiliary Equipment for The Ohbagawa Jyoryu Drainage Pump Station

by Kenji WADA

EBARA pumps and auxiliary equipment had been delivered to and installed at the Ohbagawa Jyoryu Drainage Pump Station, Saitama Prefecture. The drainage capacity of this large-scale pump station, currently 40 m3/second, will be extended to 60 m3/second when this pumping station will be fully completed. This pump station has been planned and is run by Saitama Prefecture as a measure against floods in the low plateau area around Misato City, Eastern Saitama. The main pumps comprisefÓ3000 (1 set) andfÓ2000 (2 sets) pumps and these are driven by diesel engines. The monitoring and control of pump operation is done semi-automatically to reduce the work load on operators.

Keywords
Drainage pump station, Vertical shaft mixed-flow pump, Adjustable-vane, Combined gear reducer

Large-scale Wind Turbine Power Generating System installed in Akita Araya Wind Farm

Hiroshi ISHII, Nobuyori BESSHO, Youichi IDE, & Hirotoshi MONMA

A total of eight wind turbine power generators (750 kW, NM 750 models) have been installed by EBARA at the Akita Araya Wind Farm, Akita Prefecture. This wind farm, which had previously been equipped with two other wind turbine generators (400 kW, NM 400 models), also by EBARA, has now a total power generation capacity of 6800 kW. This farm is contributing to environmental protection as a clean, natural energy source, with no CO2 emission.

Keywords
Wind farm, Wind turbine generating system, Wind turbine generator, Clean energy, New energy