Organic Farm Waste and Municipal Sludge - Bioenergy Crop Plants - page 781

taBle 32.15
typical chemical composition of untreated sludge

untreated Primary sludge untreated activated sludge

Item range range

Total dry solids (TS), % 5-9 0.8-1.2

Volatile solids (% of TS) 60-80 60-90

Grease and fats (% of TS) 13-35 5-12

Protein (% of TS) 20-30 32-41

Nitrogen (N, % of TS) 1.5-4.0 2.4-5.0

Phosphorous (P 2 O 5 , % of TS) 0.8-2.8 2.8-11

Potassium (K 2 O, % of TS) 0-1 0.5-0.7

Cellulose (% of TS) 8-15 -

Iron (not as sulfide) 2.0-4.0 -

Silica (SiO 2 , % of TS) 15-20 5-20

pH 5.0-8.0 6.5-8.5

Alkalinity (mg/l as CaCO 3 ) 500-1500 580-1100

Organic acids (mg/l as HAc) 200-2000 1100-1700

Energy content (kJ/kg TS) 23000-29000 19000-23000

taBle 32.16
heavy metal content in Wastewater sludge

dry solids (mg/kg)

metal range median

Arsenic 1.1-230 10

Cadmium 1-3410 10

Chromium 10-99,000 500

Cobalt 11.3-2490 30

Copper 84-17,000 800

Iron 1000-154,000 17,000

Lead 13-26,000 500

Manganese 32-9870 260

Mercury 0.6-56 6

Molybdenum 0.1-214 4

Nickel 2-5300 80

Selenium 1.7-17.2 5

Tin 2.6-329 14

Zinc 101-49,000 1700

g PE -1 /day for primary sludge (thickened with solids content of 5 mass %) and secondary sludge
of 25 g PE -1 /day at trickling filters (solids content of 4 mass %) or 35 g PE -1 /day at activated sludge
process (solids content of 0.7 mass %) (Novotny et al. 1989). In Europe, the contribution of raw
municipal wastewater is 200 L PE -1 /day with BOD 5 value of 60 g BOD 5 PE -1 /day. These numbers
add up to sludge quantity of 45 g PE -1 /day for primary sludge (thickened with solids content of 5
mass %) and secondary sludge of 25 g PE -1 /day at trickling filters (solids content of 4 mass %) or 35 g
PE -1 /day at activated sludge process (solids content of 0.7 mass %) (Novotny et al. 1989). Thickened
mixed primary and secondary sludge quantity (in both U.S and Europe) amounts 80 g PE -1 /day
(solids content of 4 mass %). The typical sludge concentrations are presented in Table 32.18.