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TITLE Development of waste water treatment technology using oligotrophic bacterium
(Joint Program to Promote Technological Development with the Private Sectors)
AUTHOR qhsd|ATSUGI LABARATORY in Showa Shell Sekiyu K.K.

Waste water treatment using active sludge is an environmentally acceptable method because this method used microorganisms as the catalysts to degrade pollutants.

The waste water from oil refineries or chemical plants usually contain xenobiotics and small amount of nutrients, especially phosphate and nitrogen.

It is necessary to add nutrient salts during the waste water in order to maintain enough biological activity. However the addition of nutrient salts increases the handling cost of the treatment and increases the possibility of the eutriphication of the aquatic environment in case of excessive addition of nutrients.

In our laboratory, we confirmed that Burkholderia cepacia strain 1A which was isolated by Showa Shell Sekiyu K.K. can grow at the concentration of under 1 ppm of phosphate and nitrogen using phenol as sole carbon source. This condition is 500 ~ 1,000 times less phosphate and nitrogen demanding than existing phenol utilizers. It will be useful to use strain 1A for the treatment of waste water from refineries and chemical plants without having to add nutrient salts.

We found that polystyrene beads remarkably promotes the cell growth of strain 1A, and the effect was enhanced by shaking polystyrene beads. It was thought that good growth was shown by absorbing on the surface of polystyrene beads.

We carried out the study for scale up conditions using 4l airlift bioreactors. We made a draft tube out of stainless wire net coverd by polyethylene-polypropylene nonwoven fabric and put many rods inside the draft tube. And also we set another polyethylenepolypropylene nonwoven fabric in the bioreactor.

In the reactor the bacterial cells were immobilized on the polyethylene-polypropylene nonwoven fabric.

Using this modified bioreactor, the phenol degrading activity was increased about 4 fold (40 mg/hr/l) as compared with the control reactor. We made a large scale bioreactor (200l) based on the data from the modified 4l airlift bioreactor. The large scale bioreactor showed about 1.5 fold higher activity as compared with the 4l reactor.

The phenol degrating activity of the large scale bioreactor was 61 mg/hr/l.

This study will provide low cost waste water treatment technology and prevent secondary pollution by addition of phosphate or nitrogen.