By rethinking the design from the ground up, and positioning two carrier flow chambers in series, treatment performance has been dramatically improved. An intermittent metering pump has also been adopted for the circulation transfer pump in order to increase nitrogen removal performance. In addition, up to now biofiltration-type units required two blower pipes for aeration and backwashing, however NIKKO has succeeded in the unification of this piping in the Johkaou through a patented backwash system. Workability has also been greatly improved.