Nutrient recovery from anaerobic palm oil mill effluent with thermally regenerated spent bleaching earth using response surface methodology
2020
Foo, N. S. | Loh, S. K. | Ismail K. | Bachmann R. T.
Palm oil mill effluent (POME) and thermally oxidised de-oiled spent bleaching earth (TDSBE) are reusable by-products. This study examined recovery of plant nutrients and biodegradable matter from anaerobically- treated POME using TDSBE. Response surface methodology was used for designing the jar test experiment and optimising the nutrient and colour recovery as a function of TDSBE dosage and mixing time. Phosphorus (P) and ammonia (NH3 ) were determined colorimetrically while P, copper (Cu), zinc (Zn), manganese (Mn) and iron (Fe) by atomic absorption spectroscopy. Original, spent, de-oiled (DSBE) and TDSBE were subjected to cation exchange capacity (CEC), Fourier transform infrared -attenuated total reflectance (FTIR-ATR) and Brunauer-Emmett-Teller (BET) (N₂) analysis to determine their adsorption-relevant characteristics. TDSBE (50 g litre-¹, 120 min) could recover 3.7% NH3, 80% P, 7.3% Zn, 30% Mn and 13.6% Fe from POME, 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 NH₃ and Zn. Relatively poor performance of TDSBE was due to lack of functional groups, low CEC and BET surface area. However, the recovery of plant nutrients from POME using industrial by-products such as original or modified DSBE is of great importance towards a circular oil palm industry and opens up new avenues for future research.
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