Ultrasound cavitation (US), coagulation treatment (natural coagulant chitosan and synthetic coagulant ferric chloride (FeCl3)) and activated carbon as adsorbent were applied for treatment of raw palm oil mill effluent (POME). The findings showed that for US alone, increasing pH >11 COD removal increased due to more hydroxyl radical (OH·) present in alkali solution phase. The COD, colour and TSS removal at pH 11 were 26.3%, 52.7% and 58.2%, respectively after 60 min. Application of coagulants (Chitosan and FeCl3) required acidic medium for coagulation (i.e. between pH 4.5 and 5) to be effective. A dosage of 100 mg/L chitosan at pH 4.5 removed 15.4% COD, 85.8% colour and 97% TSS from POME. A dosage of 450 mg/L FeCl3 at pH 5 removed 38.54% COD, 88.6% colour and 91.5% TSS. It was observed that FeCl3 removed COD better than chitosan. Adsorption studies indicated that 800 mg/L of activated carbon removed 64.3% COD, 99.16% colour and 99.5% TSS. The dosage needed for adsorption was much higher compared to chitosan and FeCl3 coagulants required. However, activated carbon could be recycled and reused. The hybrid treatment of ultrasound cavitation and coagulation (US-FeCl3) removed 56.3% COD, 92.4% colour and 96% TSS. The US-Chitosan removed 35.1% COD, 86.8% colour and TSS 89.2%. The eventual hybrid treatment of ultrasound cavitation, FeCl3 coagulation and activated carbon adsorption in series removed BOD5 89.7%, COD 88.1%, colour 99.9% and TSS 99.5% cumulatively. The final effluent concentration of the treated POME was in the accepted range set by Department of Environment (DOE) Malaysia. The study showed that a combination of ultrasound cavitation, adsorption and coagulation (Chitosan and FeCl3) treatments were effective for removal of BOD5, COD, colour and TSS in POME wastewater. In addition, the efficiency of the treatment will further improve when these treatment technologies are combined.