RITE - TSUKUBA NO.２ LABORATORY in KUBOTA Corp. 

The conventional waste water-treating technique mainly represented by activated sludge processes has advantages that it can be adapted to a wide range of waste water, treatment thereof is simple, and the like. On the other hand, however, in this technique, most of organic carbons contained in waste water are discharged as CO2. Further, when CO2 discharged from fossil fuels burnt to obtain electric power for conducting aeration is combined, it is recognized that enormous amount of CO2 is discharged.

In this study, there has been developed a system to recover organic substances in waste water as asset compounds, vitamin B12 and 5-aminolevulinic acid by utilizing methane fermentation as base means, and feasibility study was conducted from the view points of the material balance and the amount of carbon dioxide discharged into environment.

As study concerning a cultivation method, there were conducted the development of defusing technique for chloride based harmful substances included in waste water, the identification of trace elements required for the production of vitamin B12 and 5-aminolevulinic acid, and the like. Further, sludge was collected from 238 places in the whole country, and there were conducted the screening of a strain having high producing ability, isolation, the typing basis of 16S-rRNA gene sequence similarities and differences of the strain obtained in this way, the purification of 5-aminolevulinic acid dehydratase which is a catabolic enzyme of 5-aminolevulinic acid and one of vitamin synthetic pathway enzymes, and the like.

As a result, in an experiment using artificial waste water containing methanol, it was confirmed that vitamin B12 can be produced in a concentration not less than 40 mg/L and 5-aminolevulinic acid can be produced in a concentration not less than 100 mg/L. Further, regarding vitamin B12, continuous culture for vitamin production for not less than 100 days was succeeded.

Based on the total a mount of carbon dioxide directly discharged from waste water treating plants and carbon dioxide discharged from thermal power stations for supplying electric power, the amount to be discharged of a carbonic acid gas per unit organic substance in discharged water was evaluated. Then, it was clarified that the carbonic acid gas discharged in the treating method developed by the instant study was approximately 20 % of that of the activated sludge processes.