A holistic treatment system for palm oil mill effluent by incorporating the anaerobic-aerobic-wetland sequential system and a convective sludge dryer

•Hybrid treatment of palm oil mill effluent (POME) treatment was performed.•Anaerobic-aerobic-wetland sequential system and drum drying treatment is proposed.•Stepwise feeding of POME at 0.2 m3 day−1 resulted in >80% removal of contaminant.•After 360 days, the organic removals have sustained, demonstrating the plant’s fitness.•The treated effluent met Standard-A by Malaysia Environmental Quality Regulation.