Acidobasic balances in the course of heterotrophic denitrification

Acidobasic balances are discussed to define the influence of organic substrate composition on CO2, HCO−3, CO2−3 production and pH value changes in the course of heterotrophic denitrification. The decisive parameter for these balances for undissociated substrates is average oxidation number of carbon (AONC). For dissociated substrates the balances are influenced by the composition of organic compounds (the number of C, H, O atoms and the oxidation number). The rules for determination of pH value changes according to substrate composition are discussed both for dissimilative and assimilative reactions. The theoretical conclusions are verified in kinetic denitrification tests with selected organic compounds (glucose, glycerine, ethanol, methanol, acetate, endogenous substrate). Furthermore, indication of nitrates and nitrites removal (the end of denitrification) by continuously measured pH is described (when denitrification has been finished, pH value begins to decrease).