Activated sludge and chemical treatment process for Chemi-Thermo-Mechanical Pulping black liquors

Characterisation and treatment of the black liquor coming from Chemi-thermo-mechanical pulping (CTMP) of wheat straw was evaluated in this research. Toxicity of the liquor was evaluated and it was found high in Biological Oxygen Demand (BOD) 0.45%, Chemical Oxygen Demand (COD) 1.85%, dissolved solids 1.04%, suspended solids 0.33%, total sulphur contents 2.42% and silica contents 0.45%. Activated sludge and chemical treatments were employed to make it environment-friendly. Activated sludge removed 63% total solids, suspended solids 90%, BOD 67% and COD up to 60%. Chemical treatment of this liquor involved use of anionic and cationic polymers together with alum to remove soluble COD and suspended solids from the liquor. Effluent thrown out after combined treatment was below 200 ppm in total solids, 300 FAU in turbidity, 700 ppm in BOD and 800 ppm in COD.