Updated: July 2002

1. Overview and Advantages

Kurabo film-type wastewater treatment system is configured by incorporating an immersed type film (hollow fiber type) separator into a biochemical wastewater treatment tank in order to directly achieve solid-liquid separation.
Using an osmotic film membrane with a mean fiber bore diameter of 0.15µm, out film-type wastewater treatment system produces safe effluent by undergoing not only SS separation but also elimination of pathogenic microorganisms (for example, crypto-sporidium). A solid-liquid separation process in a reaction tank means deletion of sedimentation tank, suggesting a reduction in sludge disposal cost. Also, no management procedure is needed for precipitation behavior of active sludge. Furthermore, since the concentration of MLSS in the reaction tank can be kept at a higher level, the necessary capacity of reaction tank can be smaller. At the same time, the SRT can be maintained for a longer duration. Consequently, our system configuration is suited as a denitrification system as it can maintain nitrification bacteria etc. A longer SRT causes decomposing bacteria, for substances previously considered to be difficult to decompose with conventional active sludge techniques, to survive, leading to better water quality of the resultant effluent.

2. Performance

We have introduced Kurabo film-type wastewater treatment system (schematic is given below) into an active sludge treatment system of an anonymous manufacturer, and compared the resultant performance with that of the old system.
BOD removal ratio 85% -> 92% (active sludge process -> film-type treatment)
COD removal ratio 62% -> 72% (active sludge process -> film-type treatment)
Total nitrogen removal ratio 35% -> 55% (active sludge process -> film-type treatment)
Amount of excess sludge generated 0% (relative to active sludge process)
Amount of chemically precipitated sludge 35% (relative to active sludge process)
Tank capacity 50% (relative to active sludge process)

3. Applications and Substance Being Treated

This system can be applied to industrial wastewater from food processing plants, chemical plants and dyeing plants, as well as to sewage water, night soil treatment water and refuse leachate. The system is applicable to every wastewater type that can be biochemically treated. It may successfully precondition a particular wastewater type (which was previously considered to be hard to treat biochemically) into a biochemically treatable liquid (feasibility of this scheme must be determined by a preliminary test).