two periods, respectively. The very low utilization ratio for Period
2 potentially indicated relatively more of the N removal was due to
autotrophic vs. heterotrophic denitrification compared to Period 1.
The absence of measureable cBOD5 reductions was likely due to the
extremely short HRTs. While itis likely that heterotrophic denitrifi-
cation did account for some of the nitrate removal, internal cycling
of solids may have complicated the COD balances.