Table 6.

Common sludge disposal protocols

Methodology	Description	Remarks	Ref.
Incineration	Waste sludge is completely burned outside with additional fuel. The rotary kiln and fluidized bed incinerator types were the two most commonly used. While combustion temperatures in fluidized beds varied from 730 to 760 °C and required days to complete, combustion temperatures in rotary kiln incinerators ranged from 980 to 1200 °C and required only 30 min.	Sludge with a high-water content needs to be pre-treated to lessen its viscosity before being charged into the incinerator. Due to its high mixing efficiency, fuel variety, low pollutant productions, and high combustion efficiency, fluidized beds are used in the treatment of low-quality sludge.	Scala and Chirone (2004)
Stabilization/solidification	It includes encasing or sealing waste with an adhesive in order to stop the waste from leaking into the surrounding environment.	Changes to the chemical pollutants are made through chemical overlapping between the cement's products of hydration and the impurities themselves.	EPA (1993); Zain et al. (2010)
Oxidation treatment	Utilizing chemical and other oxidation agents, oxidation treatment is the process of degrading organic pollutants found in the disposal outcome of sludge.	When the oily sludge is exposed to the reactive agents, organic substances will oxidize to produce carbon dioxide and water or non-hazardous materials. Fenton’s reagent, hypochlorite, ozone, ultrasonic irradiation, permanganate, and persulfate are a few examples of the several oxidation reagents that can be used.	Cui et al. (2009); Ferrarese et al. (2008)
Bioremediation	In land treatment, bio pile/composting, and biological-slurry, microorganisms have been used to biodegrade and remove environmental toxins.	Time-consuming and less efficient	Wang et al. (2012)