Table 3: Average results of physicochemical analyses of sewage sludge in winter cycles.

Average results for winter cycles (replications number = 3)
ParameterUnitSampling terms for the research (days)
07142128

Sludge dry matter after centrifuge%13.86 (±0.62)*
Sludge dry matter in the pile%18.90 (±3.21)21.43 (±4.33)25.12 (±3.93)24.54 (±4.84)
Organic substance% D.M.64.20 (±2.17)65.50 (±2.04)64.20 (±2.65)63.40 (±2.87)62.40 (±3.50)
pH6.90 (±0.06)6.90 (±0.06)7.00 (±0.11)6.98 (±0.10)6.90 (±0.06)
Total nitrogen content% D.M.2.10 (±0.15)2.12 (±0.17)2.00 (±0.06)2.12 (±0.17)2.09 (±0.23)
Ammonium nitrogen content% D.M.0.10 (±0.06)0.10 (±0.06)0.11 (±0.04)0.09 (±0.03)0.15 (±0.01)
Total phosphorus% D.M.2.20 (±0.12)2.22 (±0.13)2.21 (±0.11)2.20 (±0.12)2.20 (±0.12)
Calcium content (Ca)% D.M.1.15 (±0.03)1.13 (±0.03)1.12 (±0.02)1.15 (±0.03)1.15 (±0.03)
Magnesium content (Mg)% D.M.0.23 (±0.04)0.23 (±0.04)0.23 (±0.04)0.34 (±0.05)0.23 (±0.03)

Heavy metals
 Lead (Pb)mg/kg D.M.22.23 (±2.79)22.20 (±2.76)22.20 (±2.76)22.20 (±2.76)22.20 (±2.76)
 Cadmium (Cd)mg/kg D.M.1.98 (±0.26)1.97 (±0.21)1.89 (±0.20)1.89 (±0.20)1.87 (±0.18)
 Mercury (Hg)mg/kg D.M.0.05 (±0.03)0.05 (±0.03)0.05 (±0.03)0.00 (–-)0.05 (±0.03)
 Nickel (Ni)mg/kg D.M.19.50 (±1.94)19.50 (±2.12)19.50 (±1.94)19.50 (±1.94)19.50 (±1.94)
 Zinc (Zn)mg/kg D.M.1248.00 (±131.15)1248.00 (±131.15)1248.00 (±131.15)1249.00 (±125.87)1250.00 (±126.26)
 Copper (Cu)mg/kg D.M.220.70 (±17.43)220.70 (±17.43)220.70 (±17.43)220.70 (±17.50)220.70 (±17.43)
 Chromium (Cr)mg/kg D.M.27.64 (±2.08)27.64 (±2.08)27.64 (±2.08)27.64 (±2.08)27.64 (±2.08)

*Standard deviation.