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Table 1

Summary of the results obtained during the operation of the Control and Test reactors (30 °C, HRT 10 h)

Parameter1st phase – 226 d without EE
2nd phase – 132 d
TestControlTest with EEControl
pH influent 7.7 ± 0.4 7.7 ± 0.4 7.6 ± 0.3 7.8 ± 0.4 
pH effluent 7.8 ± 0.3 7.9 ± 0.3 8.0 ± 0.2 8.1 ± 0.2 
COD influent (mg/L) 724 ± 177 724 ± 177 696 ± 196 660 ± 189 
COD effluent (mg/L) 76 ± 47 75 ± 44 80 ± 37 63 ± 25 
COD removal (%) 89.1 ± 7.2 89.1 ± 7.4 88.7 ± 3.5 90.9 ± 2.9 
VFA influent (mg/L) 38 ± 10 38 ± 10 72 ± 21 52 ± 18 
VFA effluent (mg/L) 16 ± 4 19 ± 7 32 ± 12 24 ± 10 
TA influent (mg/L) 182 ± 43 182 ± 43 219 ± 49 200 ± 51 
TA effluent (mg/L) 258 ± 64 277 ± 64 329 ± 32 314 ± 36 
VFA/TA effluent 0.07 ± 0.04 0.07 ± 0.03 0.10 ± 0.03 0.08 ± 0.05 
O&G scum (mg/L) – 1st sample (69 days after cleaning) 1,321 ± 371 2,496 ± 738 
O&G scum (mg/L) – 2nd sample (63 days after cleaning) 877 ± 429 1,527 ± 92 
Scum formation rate (mg O&G/d) – 1st sample 26.8 ± 7.5 50.6 ± 15.0 
Scum formation rate (mg O&G/d) – 2nd sample 19.5 ± 9.5 33.9 ± 2.0 
Average scum formation rate (mg O&G/d) 23.1 ± 5.2 42.3 ± 11.8 
Parameter1st phase – 226 d without EE
2nd phase – 132 d
TestControlTest with EEControl
pH influent 7.7 ± 0.4 7.7 ± 0.4 7.6 ± 0.3 7.8 ± 0.4 
pH effluent 7.8 ± 0.3 7.9 ± 0.3 8.0 ± 0.2 8.1 ± 0.2 
COD influent (mg/L) 724 ± 177 724 ± 177 696 ± 196 660 ± 189 
COD effluent (mg/L) 76 ± 47 75 ± 44 80 ± 37 63 ± 25 
COD removal (%) 89.1 ± 7.2 89.1 ± 7.4 88.7 ± 3.5 90.9 ± 2.9 
VFA influent (mg/L) 38 ± 10 38 ± 10 72 ± 21 52 ± 18 
VFA effluent (mg/L) 16 ± 4 19 ± 7 32 ± 12 24 ± 10 
TA influent (mg/L) 182 ± 43 182 ± 43 219 ± 49 200 ± 51 
TA effluent (mg/L) 258 ± 64 277 ± 64 329 ± 32 314 ± 36 
VFA/TA effluent 0.07 ± 0.04 0.07 ± 0.03 0.10 ± 0.03 0.08 ± 0.05 
O&G scum (mg/L) – 1st sample (69 days after cleaning) 1,321 ± 371 2,496 ± 738 
O&G scum (mg/L) – 2nd sample (63 days after cleaning) 877 ± 429 1,527 ± 92 
Scum formation rate (mg O&G/d) – 1st sample 26.8 ± 7.5 50.6 ± 15.0 
Scum formation rate (mg O&G/d) – 2nd sample 19.5 ± 9.5 33.9 ± 2.0 
Average scum formation rate (mg O&G/d) 23.1 ± 5.2 42.3 ± 11.8 

EE, with addition of enzyme extract for a lipase activity of 24 U/L; COD, chemical oxygen demand; VFA, volatile fatty acids; TA, total alkalinity; O&G, oil and grease.

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