Bacteria sulphite-reducing

In case of bad smell troubles, count of anaerobes and sulphite-reducing bacteria are useful as well as measures in lab of VFA (Volatile Fatty Acid). 

General corrosion damage was the cause of failure of an A1 alloy welded pipe assembly in an aircraft bowser which was attacked by a deicing-fluid — water mixture at small weld defects . Selective attack has been reported in welded cupro-nickel subjected to estuarine and seawater environments . It was the consequence of the combination of alloy element segregation in the weld metal and the action of sulphate reducing bacteria (SRB). Sulphide-coated Cu-enriched areas were cathodic relative to the adjacent Ni-rich areas where, in the latter, the sulphides were being continuously removed by the turbulence. Sulphite ions seemed to act as a mild inhibitor. 

The cultures are examined after 2 days and 4-5 days incubation. In the case of a negative result, the incubation time should be extended to 10 to 14 days in order to be quite certain. The sulphate-reducing bacteria appear as black colonies as a result of the formation of ferrous sulphite. 

Nitrite has an inhibitory effect on SRB, mainly because (a) nitrite is toxic to SRB, and with their nitrite reductase, the bacteria will produce a detoxifying reaction. The end result is that while the bacteria are still aUve, no growth happens and their sulphate reduction activity will be inhibited, (b) Nitrite can directly affect the enzyme required for reducing sulphite to sulphide see [63]. 

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