Table 1: Operational physicochemical conditions of the anaerobic sludge digesters.

Digester Feed 60% Raw Sludge, 40% Activated Sludge
Digester Number 1 3 5
Parameters
Digester capacity (m3) 7433 7433 7433
pH 7.13 -7.5 7.27-7.55 7.36
Temperature(0C) 34 34 34
Digester feeding per day (m3) 2248 2148 2552
Solid retention time (days) 16 16 14
Up flow velocity (m3/hr) 120 120 120
Hydraulic Retention Time (HRT) (days) 3.3 3 2.91
Organic loading rate (kg. oDS / m3.d) 6.84 5.84 6.61
Dry solid (%) 2.91-3.34 2.56-5.74 2.79-3.54
Volatile solids (%) 70.27-70.95 43.75-70.15 54.54-67.49
Volatile fatty acid 165-195 168-205 145.5-195
Alkalinity 3014-3451 2992-3512 2893-3190
Dissolved sulfide (mg/L) 37.2-38 32.4-37.2 26.4-27.6