All issues
Volume 53 (2017)
- Issue 4 Pages 95-
- Issue 3 Pages 81-
- Issue 2 Pages 33-
- Issue 1 Pages 1-
Volume 53, Issue 4
Displaying 1-4 of 4 articles from this issue
- |<
- <
- 1
- >
- >|
ORIGINALS
-
YUZURU KIMOCHI, HITOSHI TANAKAArticle type: ORIGINALS
2017 Volume 53 Issue 4 Pages 95-109
Published: 2017
Released on J-STAGE: March 10, 2018
JOURNAL FREE ACCESSWe proposed a method to estimate previous levels of dissolved oxygen (DO) in aquatic environments ranging from hours to an entire day, based on measured values of dissolved methane (DCH4) and nitrous oxide (DN2O). The most important aspect of our method is that it can be used to estimate previous DO levels without the need for continuous monitoring. We assumed the theoretical behavior of DCH4 and DN2O and how they would influence increases and decrease in DO, based on microbial metabolic reactions under various environmental conditions. The patterns we made corresponded reasonably well with the data obtained from an in situ wastewater treatment experiment: and we set the threshold at 0.025 mg C/L for DCH4 and 0.003 mg N/L for DN2O in order to determine the previous DO condition. From the verification of the threshold by continuous monitoring in actual ponds, at least the DCH4 threshold appeared to reflect previous anaerobic condition, and to be useful in order to determine and screen the required minute investigation site. We also made the test decision of lake environment on the data in previous reports based on the method with the threshold of DCH4, DN2O: the results were reasonable. Finally, we proposed how to examine and improve the new method form the viewpoint of such as inaccuracy of the thresholds.View full abstractDownload PDF (1824K) -
YOKO FUJIMURA, KOICHI KIUCHI, YOSHIMASA AMANO, MOTOI MACHIDAArticle type: ORIGINALS
2017 Volume 53 Issue 4 Pages 111-118
Published: 2017
Released on J-STAGE: March 10, 2018
JOURNAL FREE ACCESSIn this study, the performance of on-site treatment system for domestic wastewater (Johkasou) was evaluated. The qualities of effluent from actual nitrogen removal type Johkasou which has begun to become popular recently and removal efficiencies were examined. The nitrogen removal type Johkasou showed better performance for BOD and nitrogen removal than the conventional type Johkasou. Both BOD and total nitrogen (T－N) concentrations were 15 mg/L or less in 75－80% of effluent water samples investigated. The high performance of the treatments system was attributed to a mixed liquor recycle system for denitrification. The reduction of BOD concentration in the effluent water was also observed accompanied by the high efficiency of nitrogen removal. Recycling of treated water would result in improving reduction of not only NO3－N but also dissolved Kjeldahl nitrogen (DKN) reduction, and the decrease in DKN led to a decrease in both N－BOD and BOD as well. The denitrification activity was declined when circulation ratio drop to 1 Q or less where Q is the influent flow quantity. The effluent T－N seemed to be controlled below 20 mg/L with the recycle ratio of 2 Q－15 Q. The average removal rates of T－N and total phosphorus (T－P) of the surveyed Johkasous were 67% and 58%, respectively.View full abstractDownload PDF (1013K) -
TAKAMARU NAGATA, TAKAYUKI HANAZATOArticle type: ORIGINALS
2017 Volume 53 Issue 4 Pages 119-128
Published: 2017
Released on J-STAGE: March 10, 2018
JOURNAL FREE ACCESSWe assessed the combined impacts on the community of small-sized herbivorous zooplankton using mesocosms, in which their populations were exposed to copepod Mesocyclops pehpeiensis predation and/or food shortage. The densities of the small-sized zooplankton were depressed in the tanks with M. pehpeiensis and a low algal density, probably because the prey populations were unable to compensate for the population loss by copepod predation. In contrast, most of the herbivorous zooplankton, especially rotifers, established large populations, despite their exposure to predation in the tanks with high algal density. This might be due to their high reproductivity under the conditions. In addition, the release from competitive pressure by cladocerans, whose populations were suppressed by intensive predation by M. pehpeiensis, would be favorable for the rotifers. Our experimental findings may explain the herbivorous zooplankton community structure in the shallow eutrophic lakes inhabited by abundant copepods. The results may become valuable information for reducing biological interference with rotifers within zooplankton assemblages, leading to effective use of the animals for water treatment systems.View full abstractDownload PDF (918K)
TECHNICAL NOTES
-
NOBUYUKI AIKO, HIROTAKA NAKANISHI, DAISUKE HIRAArticle type: TECHNICAL NOTES
2017 Volume 53 Issue 4 Pages 129-137
Published: 2017
Released on J-STAGE: March 10, 2018
JOURNAL FREE ACCESSLandfill leachate is a typical large source of nitrogenous wastewater. We have revealed that nitrification reaction occurs in the leachate lagoons at two sea landfill sites, “Sakai 7－3” and “Izumiotsuoki”, located in Osaka Bay. By using nitrifying bacteria which are thought to be present in the lagoon sludge, it was expected that efficient nitrogen treatment could be performed in the leachate lagoon. In sea landfill sites, it is common that the salt concentration of leachate changes with the passage of time. In this study, a continuous nitrification test using synthetic leachate with a swim-bed reactor was conducted on the sludge samples of “Sakai 7－3” and “Izumiotsuoki” lagoons, and the effect of salinity on the treatment efficiency was investigated. It was confirmed that the ammonia oxidation occurred promptly in the synthetic leachate containing 0.5% or 3.0% sodium chloride. In contrast, the inhibition of nitrite oxidation was remarkable in the Izumiotsuoki sludge under high salinity of 3.0%. Then, the microbial community during continuous nitrification test, especially ammonia oxidizing bacteria and nitrite oxidizing bacteria were investigated. From these results, the nitrogen cycle in the lagoons was discussed.View full abstractDownload PDF (1203K)
- |<
- <
- 1
- >
- >|