To measure the decomposition rate of sludges from ANC, MW, and SLP as a function of waste type, soil type, temperature, and rates/frequency of application.
- 3 sludges (ANC, MW, SLP)
- 3 temperatures (5°C,15°C and 25°C)
- 6 rates/frequencies of sludge additions (once at 0, 2.5, 5, and 10 cm; and twice at 2.5 and 5 cm)
- 6 sampling times (0, 1, 3, 6, 12, and 24 weeks)
- 2 soils (coarse and medium texture)
- 3 replicates
- CO2 evolved and O2 consumed (every week)
- Soil C, and N (every sampling event)
- Soil pH, CEC, oil and grease (first and last sampling times)
- GC-MS of oil and grease extract and Microtox (first and last sampling times)
- Higher degradation rates were observed for the coarse textured soil.
- Degradation (for all 3 sludges) increased with both temperature and rate of application.
- Rates of degradation (24 weeks incubation) ranged from 10 to 40% of added sludge, and increased with temperature.
- Differences were observed for sludge source (SLPC>MW>=ANC).
- Soil pH and oil and grease content increased with sludge additions; the increase depended on sludge rate, type and incubation temperature.
- Microtox (EC50) of the soil water soluble fraction increased with time of incubation, indicating a detoxification of the sludge material through degradation
- GC-MS analysis of oil and grease fraction from the 3 sludges showed the presence of fatty acids, plant sterols, and phthalate (a likely industrial contaminant)
- Sludge incubation (24 weeks) led to a significant decrease in the above organic compounds for all sludges