capacities of different sub phases. By dividing the total dry biomass
generated with the total VOC eliminated, yield coefficients were
estimated for different sub-phases (Table S1). The yield coefficient
(YT) obtained for MEK in batch studies conducted with the same
acclimatized culture, in our earlier work was 0.51 [40]. Though
the YT value varied between different sub-phases (Table S1), the
overall YT value obtained for the M phase was 0.48.
The sole nitrogen source in the MSM being ammonium sulfate,
monitoring the ammonium ion concentration of the reactor effluent
provides a good idea of nitrogen utilization. The ammonium
ion concentration at the inlet was found to be 210.8 mg/L consistently
throughout the study. Nitrification process involves conversion
of ammonium–nitrogen to nitrate–nitrogen by autotrophic
micro-organisms. The presence of increasing inlet loading of MEK
was found to inhibit nitrification of ammonia to nitrate represented
by a higher residual ammonium ion concentration at higher
ILRs at the effluent. Removal of ammonium ion concentration was
complemented with a simultaneous increase in nitrate ion concentration.
In general, heterotrophs which feed on organic carbon [41]
grow faster than the nitrifiers, and thus nitrification will be inhibited
by heterotrophic processes provided that organic carbon is
available (Table S2). Gomez et al., found that presence of VOCs such
as ethanol, acetate, propionate, and butyrate inhibits the growth of
ammonia oxidizing bacteria, however, the degree of inhibition varied
for different compounds [42]. For an MEK inlet loading rate of
90 g/m3/h, a higher degree of nitrification was observed with the
residual ammonium ion concentration being 68.2 mg/L. However,
for higher ILRs the nitrification rate was inhibited and for the