Table 1 Working parameters and digested sludge parameters of the wastewater treatment plant in Saxony

Temperature

30–35 °C

Solids retention time (SRT)

16.5 days

pH

7.6

Total solid content (TS)

2.8%

Volatile solids (VS)

57.9%

Ammonium content (NH₄-N)

1109 mg/l

Total organic carbon (TOC)

336.7 mg/g

Soluble chemical oxygen demand (COD)

1220 mg/l

Dissolved organic carbon (DOC)

329.9 mg/l

C:N ratio*

0.2 mg/l

Total volatile fatty acids (TVFA)

27.1 mg/l

 Lactic acid (C₃H₆O₃)

–

 Formic acid (CH₂O₂)

4.5 mg/l

 Acetic acid (CH₃COOH)

16.4 mg/l

 Propionic acid (C₃H₆O₂)

1.9 mg/l

 Iso-butyric acid (C₄H₈O₂)

0.8 mg/l

 Butyric acid (C₄H₈O₂)

3.5 mg/l

 Valeric acid (C₅H₁₀O₂)

–

Calcium (Ca)

118.5 mg/l

Magnesium (Mg)

33.7 mg/l

Potassium (K)

178.3 mg/l

Sodium (Na)

16.5 mg/l

Copper (Cu)

–

Zinc (Zn)

160.3 mg/l

Nickel (Ni)

53 mg/l

Molybdenum (Mo)

–

Manganese (Mn)

54.5 mg/l