Iori Mishima

Ritsumeikan University, Kioto, Kyōto, Japan

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Publications (12)4.16 Total impact

  • Iori Mishima · Jun Nakajima
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    ABSTRACT: Addition of coagulant to the activated sludge process is an effective method to remove phosphorus from wastewater. Recently, iron electrolysis method has been developed as a new methodology of addition of coagulant into the activated sludge process. Although this process has been applied to industrial wastewater treatment plants or small-scale domestic wastewater treatment plants, the phosphorus removal performance by iron electrolysis combined with full-scale activated sludge process has not been clear yet. The objective of this study is to investigate the phosphorus removal efficiency by iron electrolysis combined with the activated sludge process. The enhanced biological phosphorus removal took place and phosphorus removal efficiency was increased without iron addition because of the occurrence of anaerobic condition in the surveyed wastewater treatment plant. Phosphorus removal performance in the investigated wastewater treatment plant was improved by the iron electrolysis. Effluent phosphorus concentration was decreased below 1.0 mg/L with additional iron of Fe/P molar ratio 0.4. The theoretical weight of iron release agreed with the actual weight decrease of iron electrodes. The introduction of iron electrolysis to the activated sludge process could enhance the phosphorus removal efficiency without any effects on substrate removal performance and make the phosphorus removal to be stable and sustainable.
    No preview · Article · Jan 2011 · Journal of Water and Environment Technology
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    Full-text · Article · Jan 2011 · Journal of Water and Environment Technology
  • Iori Mishima · Jun Nakajima

    No preview · Article · Jan 2010 · Journal of Water and Environment Technology
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    ABSTRACT: Technical and social performances of an arsenic-removal technology--the sono arsenic filter--in rural areas of Bangladesh were investigated. Results of arsenic field-test showed that filtered water met the Bangladesh standard (< 50 microg/L) after two years of continuous use. A questionnaire was administrated among 198 sono arsenic filter-user and 230 non-user families. Seventy-two percent of filters (n = 198) were working at the time of the survey. Another 28% of the filters were abandoned due to breakage. The abandonment percentage (28%) was lower than other mitigation options currently implemented in Bangladesh. Households were reluctant to repair the broken filters on their own. High cost, problems with maintenance of filters, weak sludge-disposal guidance, and slow flow rate were the other demerits of the filter. These results indicate that the implementation approaches of the sono arsenic filter suffered from lack of ownership and long-term sustainability. Continuous use of arsenic-contaminated tubewells by the non-user households demonstrated the lack of alternative water supply in the survey area. Willingness of households to pay (about 30%) and preference of household filter (50%) suggest the need to develop a low-cost household arsenic filter. Development of community-based organization would be also necessary to implement a long-term, sustainable plan for household-based technology.
    Full-text · Article · Oct 2009 · Journal of Health Population and Nutrition
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    M. S. Azam · M. Shafiquzzaman · Iori Mishima · Jun Nakajima
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    ABSTRACT: Leaching experiment was conducted to understand the mechanism of arsenic release from soil in the natural field conditions. Two types of column were run, one with de-ionized water (DW) and another with synthetic Bangladesh groundwater (GW) as influent which simulated rainfall and groundwater conditions, respectively. As the primary mechanism for the arsenic release from soil it was identified that the redox potential (Eh) was major importance. In highly reducing conditions both arsenic and iron release was high. Released mass of arsenic was higher in DW column than GW column. The difference was caused by the presence of calcium and magnesium ion in the synthetic groundwater. Comparing to the acid-alkali sequential extraction it was found that calcium and magnesium prohibited the release of arsenic bound with iron. The effect of calcium and magnesium was clarified in the batch experiment performed in the study.
    Full-text · Article · Apr 2009 · Journal of Scientific Research
  • I Mishima · J Nakajima
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    ABSTRACT: The control of membrane fouling is an essential issue in membrane bioreactor (MBR) process. It has been recognized that the most important factors that affect membrane fouling are presence of soluble microbial products (SMP) and extracellular polymeric substances (EPS) in a reactor. The objective of this study was to examine the effect of the coagulant addition on the membrane fouling in the MBR process. Accordingly, laboratory scale batch experiments and MBR experiments were conducted using coagulant. In batch experiments, effective SMP removal and control of EPS release were observed by coagulant addition. Fe coagulant was slightly more effective than Al coagulant in the addition of same mole amount. Therefore, Fe was used as coagulant in MBR experiments. In MBR experiments, Fe solutions of 0 mg/L, 2,260 mg/L and 4,520 mg/L were added into the tanks (Run1, Run2 and Run3, respectively) with the flow rate of 200 mL/d. COD removal efficiencies of 97% and phosphorus removal efficiencies of 92% were observed by Fe addition in the MBR experiment. Membrane fouling occurred more often in Run1 than in the other two Runs. Membrane was cleaned 18, 9 and 5 times in Run1, Run2 and Run3, respectively during 40 days runs. This suggested that the membrane fouling was reduced by the coagulant addition. The protein and carbohydrate concentrations of the SMP in the fraction of 1 microm-0.4 microm in Run2 and Run3 were significantly lower than that in Run1 and the particle size of the activated sludge was obviously increased in Run2 and Run3. These results suggested that the coagulant addition is effective to control the membrane fouling.
    No preview · Article · Feb 2009 · Water Science & Technology
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    Mohammad Shafiul Azam · Iori Mishima · Jun Nakajima

    Preview · Article · Dec 2008 · Journal of Scientific Research
  • Jun Nakajima · Iori Mishima
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    ABSTRACT: MBR (membrane bioreactor) process has been applied to wastewater treatment plants recently. It is well known that the most important point of the optimum maintenance is control of membrane clogging in the process. Suitable indices for operation and maintenance in MBR are desired to predict the timely cleaning period and carry out the effective cleaning of the membrane. A large amount of foam is sometimes produced in MBR facilities. Some foam seems to be produced by extracellular protein that is known to cause the membrane clogging. Therefore measurement methodology of foam quality produced by activated sludge in MBR process and characteristics of its extracellular polymer substances (EPS) were studied. The conclusions were: (1) EPS was able to be extracted by steaming treatment on the optimum condition at 105 degrees C for 30 minutes. (2) Bingham viscosity and yield stress of activated sludge were measured. The yield stress was contributed by EPS and this suggested that EPS was one important factor for foaming. (3) The measurement of foam quality using a video camera showed good performance. The foaming power and the foam stability increased proportionally with the concentration of protein in EPS. It was clear that the protein concentration in EPS was strongly related to the foam quality and quantity. (4) The foaming power decreased by addition of MLSS. This decrease was caused by adsorption of EPS to MILSS. Foaming in an aeration tank will be an index CL for membrane cleaning requirement.
    No preview · Article · Jul 2005 · Acta Hydrochimica et Hydrobiologica
  • J Nakajima · I Mishima
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    ABSTRACT: Adding coagulant to the activated sludge process is effective in maintaining the stability of phosphorus removal. However, the precise mechanisms of the reaction and behavior of coagulants and phosphorus are not well known. By introducing a new phosphorus removal model (PRM), the behavior of coagulant and phosphorus in the process could be described. The experimental data of the effluent phosphorus concentration and Fe content in the activated sludge agreed with the values calculated by PRM. The amount of coagulant addition to the activated sludge process for phosphorus removal is reduced with the enhanced biological phosphorus removal process. It is suggested that the amount of reduction is determined by using PRM.
    No preview · Article · Feb 2004 · Water Science & Technology
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    ABSTRACT: We have studied and determined the most suitable electrolytic conditions and applied them to the biological filtration process by the electrochemical elution of iron, but have not made it clear whether to apply them to the activated sludge process.In this study, we examined phosphorus removal, dehydrogenase activity and oxygen uptake rate using an experimental activated sludge system for the electrochemical elution of iron in the laboratory. This method was successful in more than 70% phosphorus removal while maintaining an Fe:P ratio of more than 0.75, a current density 0.25mA·cm-2 and an intermittent operation of electrolysis. Phosphorus removal technologies based on the electrochemical elution of iron usually require an Fe:P ratio of 1.5. Our results were achieved by combining our system with a biological process that maintains phosphorus. This combined method offers high stability and provides more than two months of phosphorus removal. The electrochemical elution of iron does not negatively affect the performance of the biological treatment. The effluent BOD and nitrogen concentrations were not increased by introducing this method.Moreover, the unit features a compact design and a low operating cost. In view of this, we consider that phosphorus removal technologies that incorporate electrochemical elution of iron can be provided for any wastewater treatment systems.
    No preview · Article · Jan 2003 · Journal of Japan Society on Water Environment
  • Iori MISHIMA · Jun NAKAJIMA
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    ABSTRACT: In order to remove phosphorus from domestic wastewater, enhanced biological phosphorus removal (EBPR) and the activated sludge process with coagulant addition have been widely used. According to the performance of phosphorus removal in actual existing facilities, it is considered possible to reduce the amount of coagulant added to the aeration tank by combining of the two processes. Therefore the dynamics of phosphorus and coagulants were investigated by examining three existing domestic wastewater treatment facilities. EBPR took place unintentionally in these facilities because of their denitrification operations. The unintentional EBPR was unstable and its performance was poor when denitrification was incomplete. An addition of coagulants to the unintentional EBPR facilities stabilized the performance. The coagulants moved to the activated sludge immediately after their addition. The content of the coagulants in the activated sludge decreased exponentially with a constant rate of 1/SRT after the ceasing of addition. The performacne of phosphorus removal continued to be high and stable while the coagulant content was remained high. Maintaining a high coagulant content of the sludge is effective to keep the performance of phosphorus removal. This indicated a new method of reducing the amount of coagulant addition.
    No preview · Article · Jan 2003 · Journal of Japan Society on Water Environment
  • Iori Mishima · Jun Nakajima

    No preview · Article · Jan 2003