The pulp and paper industry produces a significant amount of wastewater with toxic and recalcitrant compounds. Pulp and paper wastewater (PPW) requires a special treatment method that is diverse enough to deal with the complexities of this type of wastewater. The present study was aimed primarily at the removal of tannin/lignin from PPW using aerobic granular sludge (AGS) technology. Aerobic granules were cultivated in a sequencing batch reactor (SBR) with tannin/lignin present in the range of 50-200 mg/L. Granules were cultivated within 9 days of operation of the sequencing batch reactor (SBR), with SVI30 of 51.6 mL/g, achieving steady-state within the first three weeks of operation. On average, the COD removal efficiency for synthetic PPW was 90%. Tannin/lignin were removed up to 80% during the initial stages, but slowly decreased to an average removal of 70%. The mature granules were then transferred to a real PPW wastewater system containing tannin/lignin concentration up to 500 mg/L. Biodegradation and biosorption were observed to be the two pathways for the removal tannin/lignin. Biosorption was a primary form of removal at lower concentrations, achieving 74% removal at 50 mg/L. The biosorption ability reduced to 58% removal at 200 mg/L. This reveals that biodegradation prevails at these higher concentrations. The Haldane kinetic parameters were: Vmax = 0.93 (g tannin/lignin/g VSS· day), Ks = 1910 mg/L, and Ki = 27 mg/L. Various adsorption kinetic models and isotherms were fitted to the system. The Langmuir isotherm coefficients were: (x/m) max = 21.5 (mg tannin/lignin/g SS), b = 0.00386 L/mg. The Freundlich isotherm had coefficients of n = 1.172, K = 0.1174. COD removal of 79% and a tannin/lignin removal of 56% were achieved with real PPW. Furthermore, experimental runs in warmer and more humid temperature conditions revealed higher removal efficiencies, achieving about 80% tannin/lignin degradation at a concentration of 130 mg/L. The most prominent species responsible for the degradation of these toxic substances were Pseudomonas, Corynebacteriaceae and Flavobacterium.