NOVELTY - A process for treating palm oil wastewater comprises adopting pre-treatment unit that adopts precipitation or air-float process; primary anaerobic process unit that treats the wastewater with hydrolysis acidic anaerobic bacteria; aeration and precipitation treatment unit, where the primary anaerobic effluent adopts precipitation or air-float process after aeration and degasification; secondary anaerobic process unit that uses methanogen to remove most part of chemical oxygen demand in wastewater; and aerobic process unit that removes chemical oxygen demand and ammonia in the wastewater.    USE - The process is useful for fine treatment of high suspended substance, high oil palm oil wastewater with fine biochemical treatability, and analogous wastewater comprising production waste water of bioethanol, wine making, monosodium glutamate, starch; food production wastewater, dairy production wastewater, and animal culture industry wastewater. Moreover, the process is useful for fine digestion on the surplus sludge in the wastewater treatment plant especially in the municipal wastewater treatment plant (claimed).    ADVANTAGE - The process has characteristics of high load, small area, fine treatment effect, and high treatment efficiency; where most part of the organism in the wastewater can be converted into biogas that can be used as new energy after centralized. Moreover, the primary anaerobic process is controlled at hydrolysis-acidification stage that not only reduces content of suspended substance and oil in wastewater but also improves treatment effect and gas production of secondary methanogenic anaerobic reactor.    DETAILED DESCRIPTION - A process for treating palm oil wastewater comprises adopting PASAO combined process to treat the palm oil wastewater; where the P stage represents pre-treatment unit that adopts precipitation or air-float process; the first A stage represents primary anaerobic process unit that treats the wastewater with hydrolysis acidic anaerobic bacteria; the S stage represents aeration and precipitation treatment unit, where the primary anaerobic effluent adopts precipitation or air-float process after aeration and degasification; the second A stage represents secondary anaerobic process unit that uses methanogen to remove most part of chemical oxygen demand (COD) in wastewater; and the O stage represents aerobic process unit that further removes COD and ammonia in the wastewater to ensure that the effluent reach the standard.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow process of treating palm oil wastewater (Drawing includes non-English language text).