Microbes Used In Water Treatment

Different microbes are used for elimination of different contaminants from water. Bacterial microbe, Kuenenia stuttgartiensis, a protype of anammox group, is that microbe which is capable of directly converting the amonia into nitrogen gas.

The following treatment is intended to reproduce in the purification plant, the different stages of nitrogen cycle are run to yield the final transformation of all the nitrogen contents present in water into gaseous form (N2), which then released into the atmosphere. Elimination of nitrogen which is in the form of amonia is obtained through biological treatment “nitrification-denitrification”. The first phase of this treatment is nitrification transformation, in this transformation aerobic ammonium oxidizer such as Nitrosomonas eutropha, convert ammonia nitrogen into the nitrite or nitrate (NO3) as an electron acceptor, in the presence of oxygen. Second phase is dinitrification, in which conversion is carried out by denitrifying bacteria in the absence of oxygen.

Mode of action

In the first step of “nitfification-denitrification” amonia biologically oxidizes with hydroxylamine, which is most likely derived from the nitrite, as the probable electron acceptor. Conversion of hydrazine to dinitrogen gas is that reaction which generate electrons which are equivalents for the reduction of nitrite to hydroxylamine. Two possible mechanisms of this reaction are proposed, membrane bound enzyme complex convert ammonia and hydroxyl amine into hydrazine, which is followed by the oxidation of hydrazine to dinitrogen gas in periplasm. At the same time nitrite is reduced to hydroxylamine at the cytoplasmic site of the same particular enzyme complex which is responsible for hydrazine oxidation with an internal electron transporter. Another possible mechanism for anammox processs is that in which amonium and hydroxylamine are converted to hydrazine by a membrane bound enzyme complex, hydrazine is oxidized in periplasm to dinitrogen oxide, and the generated electrons are transferred by an electron transport chain to nitrite reducing enzyme which is present in the cytoplasm where nitrite is reduced to NH2OH.

Whether the reduction of nitrite and oxidation of hydrazine occur at different sites of the same enzyme complex or the reactions are catalyzed by different enzyme systems which are connected with each other through an electron transport chain. The formed hydrazine and imino are converted by enzyme named hydroxylamine oxidoreductase to dinitrogen gas, and the reducing equivalents produced as a result are required to combine NO or HNO and ammonium or to reduce nitrite to NO.

Important specie that is most widely used to treat the water through this mechanism is candidatus Kuenenia stuttgartiensis. Removal of noitrogen by this mechanism require design of two separate besins in which the optimal conditions for both phases(basins) are generated. The use of anammox for waste water treatment is advantageous because of two reasons, first is that it reduces the cost through single step processing seconderily it produces less biomass, which reduces the mass of sludge for disposal at the end of treatment.