Table 2.

The proposed composition of the sludge

Water (%)	Sediments and undissolved materials (%)	Oil (%)	Ref.
30–90	3–7	5–60	da Silva et al. (2012)
30–50	10–12	30–50	Saikia et al. (2003)
30–70	2–15	30–90	Long et al. (2013b)
10–56	30–85	1–46	Egazar’yants et al. (2015)