Physico-chemical treatment of pulping effluent: Characterization of flocs and sludge generated after treatment

<p>The present study deals with the treatment of simulated pulping effluent (pH = 11, and total organic carbon (TOC) = 1900 mg/L) by acid precipitation and coagulation-flocculation processes. The maximum TOC removal (= 4845 mg/g Al³⁺) from the effluent was found with Al₂(SO₄)₃ coagulant. Addition of sufloc (a flocculant) improved the sludge settling significantly. Hydrolyzed mono- and polynuclear species generated from Fe and Al coagulants could have resulted in TOC removal. Thermal analysis of sludge showed release of gases like CO, CO₂, HCHO, CH₃SH and SO₂ during combustion. Afterwards, the dissolved metal species in treated wastewater samples should be removed.