Nutrient recovery from anaerobic palm oil mill effluent with thermally regenerated spent bleaching earth using response surface methodolog y

Abstract

Palm oil mill effluent (POM E) and thermally oxidised de-oiled spent bleaching earth (TDS BE) are reusable by-products. This study examined recovery of plant nutrients and biodegradable matter from anaerobically treated POM E using TDS BE. Response swface method ology was used for designing the jar test experiment and optimising the nutrient and colour recovery as afunction of TDS BE d osage and mixing time. Phosphorus (P) and ammonia (NH 3 ) were determined colorimetrically while P, copper (Cu), zinc (Zn), manganese (Mn) and iron (Fe) by atomic absorption spectroscopy. Original, spent, de-oiled (DS BE) and TDS BE were subjected to cation exchange capacity (CEC), Fourier transform infrared-Attenuated total reflectance (FTIR-ATR) and Brunauer-Emmett-Teller (BET) (N 2) analysis to determine their adsorption-relevant characteristics. TDS BE (50 g litre-1 120 min) could recover 3.7% NH 31 80% P, 7.3% Zn, 30% M n and 13.6 % Fe from POM E, but none for colour. Dosage and mixing time had a significant effect on recovery of all five nutrients (p 0.0.5) with interaction occurring only for NH 3 and Zn. Relatively poor pe1formance of TDS BE was due to lack of functional groups, low CEC and BET swface area. However, the recovery of plant nutrients from POM E using industrial by-products such as original or modified DS BE is of great importance towards a circular oil palm industry and opens up new avenues for future research.