Type of sludge Type of sludge Type of sludge Type of sludge Type of sludge
Parameter Untreated primary sludge Digested primary sludge Digested primary sludge Digested primary sludge Secondary sludge
Poor Moderate Good
pH 5.0-7.0 6.5-7.0 6.8-7.3 7.3-7.8 6.5-8.0
Total dry solids-TS (%) 2.0-8.0 4-12 4-12 4-12 0.8-1.2
Volatile solids (% of TS) 60-80 55-80 55-80 30-55 55-80
Volatile fatty acids (mgCH3COOH/dm3) 1800-3600 2500-4000 1000-2500 3000-4000 1800-3600
Nitrogen (% of TS) 2-7 1-5 1-3.5 0.5-2.5 3-10
Phosphorus (% of TS) 0.4-3 0.9-1.5 0.8-2.6 0.8-2.6 0.9-1.5
Potassium (% of TS) 0.1-0.7 0.1-0.3 0.1-0.3 0.1-0.3 0.1-0.8
Filtration option (m/Kg) 1011-1013 51.011-5.1013 1011-1012 1011-1012 1010-1011
Heating value (kJ/g) 16-20 15-18 12.5-16 8-11 15-21