Page 451 - Industrial Wastewater Treatment, Recycling and Reuse

422 Industrial Wastewater Treatment, Recycling, and Reuse

12
11

10

8 7
BOD 5 (mg/L) 6 < 5 < 5

4

2

0
15 12 10 7
HRT (hours)
Permeate BOD
Figure 10.12 Concentrations of BOD 5 in the permeate as a function of HRT.

during the run of 10 and 7 h HRT, respectively. Figure 10.12 shows the evo-
lution of BOD 5 concentrations in permeate as a function of HRT.

10.4.3.1.2 The Effect of OLR on Biogas Generation and Yield
The biogas generation was monitored on a daily basis, and the average biogas
generation during each period of specific OLR is presented in Figure 10.13.
The average biogas generation was increased from 159 to 193 L/day with
3
the increase in OLR from 0.62 to 0.77 kg COD/m /day, respectively.
The average biogas generations were 219 and 289 L/day with OLRs of
3
0.92 and 1.32 kg COD/m /day, respectively. Even though the average bio-
gas generation was increased with an increase in OLR, the biogas yield was
3
continuously decreased from 0.48 m biogas/kg COD removed to 0.42 m 3
biogas/kg COD removed with an increase in OLR from 0.62 to 1.32 kg
3
COD/m /day. This is due to a better food-to-microbe ratio (0.08 kg
COD/kg MLVSS/day) at a lower OLR. At a higher OLR, although the
gas generation is increased, the organic degradation efficiency is compara-
tively lower due to a high food-to-microbe ratio (0.17 kg COD/kg
MLVSS/day). Higher concentration of the microbial population can be
maintained in the bioreactor for reducing the food-to-microbe ratio at a