STUDIES ON CONCRETE CORROSION BY SULFUR-OXIDIZING BACTERIA

从污水处理厂腐蚀混凝土中分离到嗜酸硫氧化菌NB1-3，鉴定为硫氧化硫杆菌。菌株NB1-3在硫介质中的生长不仅受到镍的强烈抑制，而且受到钨的强烈抑制。研究发现，镍和钨结合在菌株NB1-3的质膜上，抑制了产能酶、硫双加氧酶和亚硫酸盐氧化酶，从而抑制了细胞的生长。从腐蚀混凝土中分离到可在碱性条件下生长的硫氧化菌RO-1，鉴定为硫杆菌。由于应变RO-1从加入pH为9.0的硫代硫酸盐介质的混凝土块中渗出Ca^<2+>，说明由于刚建成的混凝土结构中含有氢氧化钙，pH值为12-13，因此应变RO-1参与了混凝土腐蚀的早期阶段。从日本8个污水处理厂获得的腐蚀混凝土样品中分离出36株铁氧化细菌。由于T.thiooxidans和T.ferrooxidans都能氧化还原性硫化合物并产生硫酸，因此作者首次提出T.ferrooxidans和T.thiooxidans都参与混凝土腐蚀。制备含镍和钨的硅酸盐水泥棒（4×4×16 cm），悬挂在污泥池人孔盖上，暴露于5 ~ 80 ppm硫化氢大气中1 ~ 5.5年。结果表明，含镍、钨的硅酸盐水泥表面光滑，不含镍、钨的硅酸盐水泥表面易碎、粗糙。根据研究结果，作者首次提出镍和钨可以作为抗腐蚀剂保护混凝土的腐蚀。

Acidophilic sulfur-oxidizing bacterium strain NB1-3 was isolated from corroded concrete of sewage treatment plant and identified as Thiobacillus thiooxidans. The growth of strain NB1-3 in a sulfur medium was strongly inhibited by not only nickel but also tungsten. It was found that nickel and tungsten bind to the plasma membrane of strain NB1-3 and inhibit the enzymes involved in energy generation, sulfur dioxygenase and sulfite oxidase, and as a result, inhibit cell growth. Sulfur-oxidizing bacterium strain RO-1 that can grow under alkaline pH was also isolated from corroded concrete and identified as Thiobacillus versultus. Since strain RO-1 exuded Ca^<2+> from concrete blocks added to thiosulfate medium with pH 9.0, suggesting that strain RO-1 is involved in the early stage of concrete corrosion because concrete structures just after construction contain calcium hydroxide and have a pH of 12-13. Thirty-six strains of iron-oxidizing bacteria were isolated from corroded concrete samples obtained at eight sewage treatment plants in Japan. Since not only T.thiooxidans but also T.ferrooxidans can oxidize reduced sulfur compunds and produce sulfuric acid, author first suggested that T.ferrooxidans as well as T.thiooxidans is involved in concrete corrosion. Portland cement bars (4×4×16 cm) containing nickel and tungsten were prepared and these bars were hung from the lid of the a sludge tank manhole and exposed to 5〜80 ppm hydrogen sulfide atmosphere for 1〜5.5 years. It was found that the surface of the portland cement containing nickel and tungsten was especially smooth, while that without these heavy metals was brittle and rough. From the results, author first suggested that nickel and tungsten are useful as antimicrobial reagents to protect concrete corrosion.