Biodegradation of Palm Oil Mill Effluent

Abstract

Aims: The aim of this study was to investigate the biodegradation capacity of selected indigenous fungal isolates and optimization of their degradation ability using various environmental factors such as pH, incubation temperature, nutrient concentration and inoculums size in reducing pollution effect of palm oil mill effluent (POME) in the environment. Place and Duration of Study: Two fungal isolates Candida rugosa and Geotrichum        candidum used in this work were previously isolated from POME sample collected from Starline palm oil mill industries, Umukalika, Obingwa LGA, Abia state Nigeria in previous work of  authors. The study was carried out from March to August, 2013. Methodology: Spore suspension was prepared by adding 10 ml of 0.1% Tween 80 onto PDA slant of 5 days old culture of Candida rugosa and Geotrichum candidum respectively. Biodegradation of POME was carried out by inoculating 0.1ml (106spores/ml) of respective fungal isolates into different 500 ml Erlenmeyer flasks containing 100ml each of raw POME. They were incubated at 30ºC on a rotary shaker (200rpm). Samples were taken every 24hrs for 144hrs to determine BOD, COD, oil & grease. Similarly, optimization of biodegradation was carried out by studying the effect of different environmental conditions such as different initial pH levels (4.0-8.0), incubation temperature (25-50ºC), concentrations of soy bean (1.5-4.5% w/v) and inoculum size (0.1-0.5 v/v). The experiments were done in triplicates. Results: Biodegradation studies with selected indigenous fungi showed that C. rugosa was able to remove (44.6%) BOD, (13.9%) COD , (50.7%) oil and grease (O&G) while G. candidum reduced BOD, COD, O&G by 46.9%,16.9% and 64,9% respectively after 144hrs. Optimization of degradation in POME using various environmental and nutrients conditions revealed that at pH 8, C. rugosa showed best degradation of COD (48.6%), BOD (74.5%), O&G (41.8%) removal while COD (59.1%),  BOD (75.7%) , O&G (59.1%) removal  was observed with G. candidum  treatment. The optimal incubation temperature for degradation using each of  fugal isolates was  at 35ºC with 85.2% BOD , 71.8% COD and 67.3% O&G removal for C. rugosa , 87.3% BOD and 63.4% COD for G. candidum  .The best degradation ability for C. rugosa and G. candidum  were demonstrated at 3.5w/v and 2.5w/v soybean concentrations respectively.  The result also showed that increase in inoculum size could not completely reduce oil and grease during degradation process possibly because no single culture supports degradation optimally due to presence of  complex sugars Conclusion: The selected fungal isolates exhibited high efficiency for removal of oil and grease as well as organic matter from POME but required control of environmental conditions and nutrient expansion for the effective biodegradation of POME.