Refinery wastewater was treated with activated carbon from rice husk (ARH) and corn cob (ACC) using batch method. Agrowastes were carbonized at 600oC and chemically activated, using phosphoric acid (H3PO4) and used as adsorbents. Titrimetric and spectrophotometeric methods were adopted for the determination of phenol, and some anions (Phosphate, Nitrate-Nitrogen, Sulphate and pH) of refinery wastewater. Readings after treatment with the adsorbents were also recorded and the efficiencies of the adsorbents compared, to ascertain the dose at which purification was best achieved. Initial phenol concentration of 315.9 mg/l was reduced to 159.0±48.0-276.5±46.0 mg/l (ARH), 154.7±50,0-260.2±53.0 mg/l (ACC) and 132.5±21.0-201.9±1.0 mg/l (ARH + ACC). The efficiencies of the activated carbon were of the order: Rice husk + corn cob > rice husk > corn cob, while the corresponding dose efficiencies was: 15g >10g > 5g. The highest adsorption efficiency observed for anions were COD (49.15% by corn cob), BOD, (49.4% by corn cob), phosphate, (68.18% by Rice husk + corn cob), nitrate (70.68% by rice husk) and sulphate (56.68% by corn cob). Efficiency removal was in this order: Rice husk + corn cob > corn cob > rice husk and 15g >10g > 5g for the dosage. There was significant difference (p≤0.05) between the untreated and the treated refinery wastewater samples and a significant difference also exists between the adsorbents. Findings herein showed that activated rice husks and corn cobs are effective in adsorbing phenol and selected anions in refinery wastewater.