TABLE 1.
Physical and chemical properties of the fresh and mature sludges
| Parameter | Result for sludgea
|
|
|---|---|---|
| Fresh | Mature | |
| Total solids (%) | 29.1 (1.0) | 27.1 (1.8) |
| Volatile solids (%) | 57.3 (2.2) | 54.8 (2.2) |
| pH at 1:5 (wt/vol) | 7.93 (0.05) | 8.65 (0.03)* |
| Electrical conductivity at 1:10 wt/vol (mS cm−1) | 3.97 (0.05)* | 3.75 (0.10) |
| C (%) | 30.07 (2.50)* | 24.72 (1.50) |
| N (%) | 2.00 (0.08) | 1.92 (0.11) |
| C/N ratio | 15.0 (0.5)* | 12.9 (0.2) |
| Acetate (mM) | 10.02 (1.01)* | 1.01 (0.20) |
| Propionate (mM) | 7.16 (0.73) | 6.69 (0.49) |
| Butyrate (mM) | 3.31 (0.40)* | 0.06 (0.04) |
| i-Valeriate (mM) | 1.03 (0.11)* | 0.52 (0.10) |
| i-Butyrate (mM) | 0.57 (0.03)* | 0.28 (0.03) |
| Valeriate (mM) | 0.37 (0.05) | 0.35 (0.24) |
a
Standard deviations are given in parentheses (n = 5). Asterisks indicate significant differences at P < 0.001 after Student's t test or multivariate one-way analysis of variance (for VFAs) with SPSS 15.0.