Japanese Journal of Water Treatment Biology
Online ISSN : 1881-0438
Print ISSN : 0910-6758
ISSN-L : 0910-6758
Volume 57, Issue 3
Displaying 1-2 of 2 articles from this issue
ORIGINALS
  • SATOSHI SODA, MANAMI MAEKAWA, RYOMA KAJI, REINA MATSUYAMA, TOMOHIRO AK ...
    Article type: ORIGINALS
    2021 Volume 57 Issue 3 Pages 43-53
    Published: 2021
    Released on J-STAGE: September 15, 2021
    JOURNAL FREE ACCESS

     To assess the performance of an Excess Sludge reduction system using Carriers based on Acrylic PilE fabrics (ESCAPE) process, synthetic wastewater was treated using lab-scale continuous-flow activated sludge reactors. Bacteria and oligochaetes were presumed to settle on the pile carriers, thereby reducing excess sludge in the food chain. Each reactor consisted of an aeration tank (5L) equipped with the pile carrier (3cm pile length, 35/cm2 density, 7.5 × 25.5cm) and a settling tank (2L). A control reactor and a test reactor were, respectively, uninoculated and inoculated with oligochaetes (50g-wet). A 14-day operation period was repeated 13 times in all to evaluate the mass balance in the reactors. In eight operation runs at a low loading rate of 140 mgTOC/L・d, the net sludge reduction occurred with observed yield of -1.50 to -0.28 gVS/gTOC for the control reactor and -2.45 to -1.45 gVS/gTOC for the test reactor. In five operation runs at a high loading rate of 420 mgTOC/L・d, low excess sludge production occurred with observed yield of 0.31-0.62 gVS/gTOC for the control reactor and 0.07-0.56 gVS/gTOC for the test reactor, which were only 4-42% of the typical theoretical sludge yield of 1.46 gVS/gTOC. The test reactor removed organic matter from synthetic wastewater effectively with no negative influence on the effluent quality by introduction of the oligochaetes. Monophyephorus rubroniveus, a predominant oligochaete species, survived for 190 days, maintaining its reproductive ability on the pile carrier. The oligochaete recovered from the carrier laid cocoons on plate media, hatching 5-9 juveniles per cocoon. The oligochaete needed 9-18 days for hatching and 32-60 days for growth to 15 mm length. Providing efficient and stable operation conditions, the ESCAPE process will contribute to resolution of sewage sludge treatment difficulties.

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  • RYOKO SEKIFUJI, LE VAN CHIEU, MASAFUMI TATEDA, HIROSHI TAKIMOTO
    Article type: ORIGINALS
    2021 Volume 57 Issue 3 Pages 55-65
    Published: 2021
    Released on J-STAGE: September 15, 2021
    JOURNAL FREE ACCESS

     Extremely lightweight of rice husks due to low specific gravity is disadvantageous for accelerating its usage. To overcome this disadvantage, rice husks are sometimes compacted, that is, pelletized or solidified to assist easy and cheap collection and hauling. However, the compaction process may negatively affect the properties of silica in the husk. In this study, the influence of the compaction process was studied through the solubility and physical properties of silica. Two types of fuels, pellet and stick fuels, were synthesized and their influence on the properties of the fuel ash was evaluated. Consequently, stick fuels were better than pellet fuels in terms of fertilizer use of the ash during their use in residential stoves and small commercial heaters. Contrastingly, rice husks in the existing form were better than stick fuels under washing conditions; however, rice husks had disadvantages in terms of cost and handling during collection and hauling. Selection of rice husks in their existing form or compacted rice husks must be carefully considered based on the business approaches of the rice production stakeholders.

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