2.2. Palm oil mill effluent
The UASFF reactor was fed with POME pre-settled for 1 h. The characteristics of POME are summarized in Table 1. POME samples were collected weekly from a near by palm oil mill and stored in a cold room at 4 °C before use. Different dilutions of POME were prepared using tap water. The pH of the feed was adjusted to 6.8, using a 6N sodium hydroxide solution. The alkalinity was adjusted to 1500–1700 mg CaCO3/l using sodium bicarbonate. Supplementary nutrients such as nitrogen (NH4Cl) and phosphorous (KH2PO4) were added to yield a COD:N:P ratio of 250:5:1.