Yamaoka Masaru




Researcher Number(JSPS Kakenhi)


Current Affiliation Organization 【 display / non-display

  • Duty   University of the Ryukyus   Faculty of Agriculture   Regional Agricultural Engineering   Professor  

University 【 display / non-display

  • 1980.04

    Mie University   Faculty of Agriculture   Graduated

External Career 【 display / non-display

  • 1984.04


  • 1992.04


  • 1996.11


  • 2005.04


Research Interests 【 display / non-display

  • 資源循環

  • バイオマス

  • 集落排水

  • 汚泥

  • メタン発酵

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Research Areas 【 display / non-display

  • Environmental Science/Agriculture Science / Rural environmental engineering and planning

Acquisition of a qualification 【 display / non-display

  • Consultant Engineer (agriculture)

  • Pollution Prevention Manager

  • Septic Tank Management Person

  • Septic Tank Technological Manager

Thesis 【 display / non-display

  • 回分式活性汚泥方式における窒素・リン除去性能の向上に関する研究


Published Papers 【 display / non-display

  • Prototype of Radio-Controlled Mowing Machine for Aquatic Plants in Irrigation Canals ― Survey of navigation performance and aquatic plant mowing ―

      89 ( 2 ) II_97 - II_103   2021.12 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

  • A Study on Characteristics and Management of Treated Wastewater in Rural Sewerage with Submerged Biological Filters for Irrigation Use

    NAKANO Takuji, HARUTA Shinsuke, YAMAOKA Masaru

    Transactions of The Japanese Society of Irrigation, Drainage and Rural Engineering ( The Japanese Society of Irrigation, Drainage and Rural Engineering )  88 ( 2 ) I_203 - I_212   2020.12 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

     View Summary

    <p>This study examined the achievement situation and desirable management method of treated wastewater from rural sewerage with submerged biological filters by the ISO guidelines for irrigation use. The study found that the BOD concentrations and SS concentrations of treated wastewater had close relation to influent concentrations, hydraulic loading, and aeration rate in the contact aeration tank. The study also found that the BOD concentrations of treated wastewater in normal operation has mostly satisfied the quality of category C. There was a high probability that the BOD concentrations of treated wastewater achieved the quality of category B under the operating condition in which the aeration rate in the contact aeration tank was around 3 m<sup>3</sup>∙m<sup>‐3</sup>∙h<sup>‐1</sup>, and the influent BOD concentrations in the contact aeration was managed with around 30 mg∙L<sup>-1</sup>. In order to achieve the quality of category A, it was thought that the operation required an increasing frequency of cleaning of the sedimented sludge and high aeration-rate operation of the contact aeration tank. The number of coliform groups in the treated wastewater could satisfy the quality of category B in the case where residual chlorine was more than 0.1 mg∙L<sup>-1</sup>. From the perspective of the irrigation use of treated wastewater, it was considered that monitoring residual chlorine concentration was important.</p>

  • Optimum Mechanical Treatment Month for Aquatic Plant Control in the Ninoseki Irrigation Channel


      88 ( 2 ) II_59 - II_63   2020.12 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

     View Summary

    Growth of aquatic plants to physically large sizes can cause a decline in waterway areas and negatively impact scenic views. We determined optimum mechanical treatment month for aquatic plant control, of a colony consisting mainly of Elodea nuttallii, in an irrigation channel located in the Tohoku region of northern Japan. We removed aquatic plants using an engine-powered water jet in early August and mid-September and observed aquatic plant colony heights and surface aquatic plant varieties. We set up 4 test blocks, each of which consisted 48 monitoring stations and analyzed by comparing test blocks. Early August treatments did not show significant effects, since treated colony heights were similar to those of untreated blocks. However, colony heights did not reach the water surface and thus did not cause scenery deterioration. If aquatic plants do not grow rapidly enough to reach the water surface, mid-September treatments could be skipped. Conversely, mid-September treatments could effectively reduce October colony heights.

  • Development of a Simple Autonomous Navigation Method for a Mowing Machine for Aquatic Plants in Irrigation Canals ― Verification by model experiment ―

    YAMAOKA Masaru*, TAKANO Kiyoshi, MINETA Takuya, YOSHINAGA Ikuo, WATABE Keiji

    IDRE Journal   88 ( 2 ) 323 - 331   2020.12 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

     View Summary

    A simple automatic control method was envisioned for the autonomous navigation of a radio-controlled mower based on a commercial bush cutter that was developed for aquatic plants in irrigation canals and was verified by a model experiment. The method aimed to zigzag between the right and left canal walls when flowing down from upstream to downstream. The experimental hull model was approximately 33 cm in length and 25 cm in width and had one rudder. An Arduino-compatible control board controlled the servomotor to steer the hull by signals from sensors on the hull. A thread with a weight was attached to the back of the hull. The hull dragged the weight and flowed down. As a result of the model experiment, zigzag navigation was realized by steering the rudder by detecting the right and left canal walls using an infrared photo reflector and/or the distance from the canal wall using an ultrasonic distance sensor.

  • Improvement of Device Measuring Biogas Volume in Laboratory-Scale Methane Fermentation Experiments - Experiments for countermeasures against CO2 dissolution in water by simulated biogas -

    YAMAOKA Masaru, NAKAMURA Masato, ORITATE Fumiko

    IDRE Journal   88 ( 1 ) II_1 - II_9   2020.06 [ Peer Review Accepted ]

    Type of publication: Research paper (scientific journal)

     View Summary

    The authors, using the prototype biogas volume measuring device they developed, observed the dissolution of carbon dioxide (CO2) in water; however, using the prototype, based on downward displacement of water, CO2 dissolution lowered the height of the water column in the device and destabilized gas volume measurement. Therefore, the authors improved the device to avoid the influence of CO2 dissolution on biogas volume measurement. The accuracy and precision of the improved device was verified by injecting simulated biogas into the device using syringes. The simulated biogases, CO2 mixed with methane gas to 30, 50, 75 and 100% of the CO2 concentration, were applied to the verification of the device. The results were a difference of -2.8 to 4.7 mL and a standard deviation of 0 to 3.0 mL. Lowering of the rates of water-column height were also measured and indicated correlative relationship with the CO2 concentration, depending on Henry's law. The correlative relationship would be useful for monitoring biogas production. In addition, 3 mol/L of sodium hydroxide solution was added to the water in the device after simulated biogas volume measurement. After the sodium hydroxide solution absorbed all the CO2 in the simulated biogas, the gas volume was remeasured. The CO2 concentrations calculated with volumes before and after sodium hydroxide solution addition were approximately 2% smaller than the accurate concentrations. The addition of a sodium hydroxide solution to the device gives approximate CO2 concentrations for convenience of measurements and supports making a relational expression between CO2 concentration and the lowering rates of water-column height.

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Other Papers 【 display / non-display

Presentations 【 display / non-display

  • Study on Starting Up Dry Methane Fermentation for Agricultural Residues

    Masaru YAMAOKA, Masato NAKAMURA, Fumiko ORITATE

    2017 International environmental engineering conference  2017.11  -  2017.11