Elucidation of the clarification mechanism of the zero emission oriented toilet system by analysis of bacterial flora

• Project/Area Number: 15580300
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Boundary agriculture
• Research Institution: Tokyo University of Science
• Principal Investigator: SUZUKI Tomonori Tokyo University of Science, Faculty of Science and Technology, Research Associate, 理工学部, 助手 (50256666)
• Project Period (FY): 2003 – 2004
• Project Status: Completed (Fiscal Year 2004)
• Budget Amount: ¥3,200,000 (Direct Cost: ¥3,200,000); Fiscal Year 2004: ¥900,000 (Direct Cost: ¥900,000); Fiscal Year 2003: ¥2,300,000 (Direct Cost: ¥2,300,000)
• Keywords: zero emission / toilet / septic tank / bacterial flora / PCR-DGGE / 16S rRNA gene / 16S rRNA遺伝子

Research Abstract

In the zero emission oriented toilet system, the human excrement is oxidized in the aeration tank and is led into the wood chip tank. It is thought that biological treatments are being done there, however its mechanism is not clarified. To settle this issue, this research project aimed to determine the bacterial flora of the actually operating toilet system and of the laboratory-scale model septic tank system by molecular phylogenetic analysis.
The bacterial flora of the actually operating toilet system was comprised of a large share of Cytophaga-Flavobacterium-Bacteroides(CFB) group bacteria, Eubacterium tenue relative, genus Ochrobactrum relative and Gram-positive low GC group bacterium.
The laboratory-scale model septic tank system was constructed and analyzed the water quality and the bacterial flora successively. The removal of phosphorus, nitrogen, BOD and COD was confirmed for a while. About two months later, the salt concentration had increased and the removal of BOD had decreased. The result of analysis of bacterial flora in the laboratory-scale model septic tank was similar to the case of the actually operating toilet system. The flora were represented by CFB group bacteria, and following bacterial genera were recognized; Ctytophaga, Clostridium, Chitinophaga, Leuconostoc, Microbulbifer, Oxalophagus, Planctomyces, Ruminobacter, Thermoanaerobacter, Vibrio and order Sphingobacteriales.
Taken together, these results suggest that major bacteria in the wood chip tank are CFB group bacteria. It is thought that CFB group bacteria and the other bacteria digest the human excrement in the zero emission oriented toilet system. It has been suggested that the decline of the clarification function associated with the rise of the salt concentration. It is, therefore, important to consider the measures not to decrease the removal of BOD.