Palm oil liquid waste is rich in BOD5 and COD and thus need to be processed before being flown to environment. A study aims to reduce the BOD5 and COD in that waste by using the biofilter that was added with EM4 has been conducted in April-May 2019. There were 3 treatments applied, namely the addition of 12 ml, 15 ml and 18 ml EM4 in the anaerob and aerob tanks, 3 replications. The waste was se…