Total Petroleum Hydrocarbon (TPH) Remaining
Group/ Treatment  C (mg/kg) C + E5 (mg/kg) C + E10 (mg/kg) C+E20 (mg/kg)
Day 0 15056.86 ± 92.11 15056.86 ± 92.11 15056.86 ± 92.11 15056.86 ± 92.11
Day 14 12275.36 ± 28.03 13167.91 ±108.82 9237.21 ± 65.49 11031.86 ± 31.94
Day 28 7590.88 ± 1050.4 7241.36 ± 86.3 6554.89 ± 61.11 4162.53. ± 54.49
Key:
C = Contaminated soil (control)
C + E5 = Contaminated soil incubated with 5 earthworms
C + E10 = Contaminated soil incubated with 10 earthworms
C + E20 = Contaminated soil incubated with 20 earthworms
Table 2: Effect of earthworms’ numbers on TPH degradation in crude oil contaminated soil.