Many of AMD （acid mine drainage） treatment of abandoned mines in Japan are being conducted under governmental support as non-profit enterprises. Because the conventional system which uses alkaline chemicals, produces a large amount of precipitation to be treated as waste, more economical processes are strongly desired. We have proposed "the bacterial oxidation and two step neutralization processes" for the low pH and high Fe content AMD, and conducted the operation tests using a 1/100 scale plant. As a result, it was shown clearly that the amount of the neutralizer used can be reduced by 20％ and that the amount of neutralized sediment can be lowered by 37％ compared with the conventional system. Furthermore, we tried to reuse this neutralized sediment as interior tile. While the tiles produced have sufficient performance to be used, the cost of production should be improved.