Abstract Palm oil liquid waste is rich in TSS and ammonia and thus need to be processed before being flown to environment. A study aims to reduce the TSS and ammonia in that waste by using a biofilter that was added with EM4 has been conducted in March-April 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.…