Leather tanning has been ranked as one of the most polluting activities compared to other manufacturing sector. Wastewater from tannery contains high levels of organic matter, nitrogenous compounds, sulfides and other pollutants. These pollutants must be eliminated/reduced to the acceptable limits during wastewater treatment. Otherwise, they can cause undesirable effect on the ecosystem and public health. Biological treatment methods are both cost effective and environmentally sound alternative for the treatments of tannery wastewater than any other methods. Specially, sequencing...