Accumulation And Extraction Of Polyhydroxyalkanoate From Aerobic Granules Treating Palm Oil Mill Effluent

• Main Author: Kanadasan, Gobi
• Format: Thesis
• Language: English
• Published: 2015
• Subjects: T Technology; TP155-156 Chemical engineering
• Online Access: http://eprints.usm.my/46935/1/Accumulation%20And%20Extraction%20Of%20Polyhydroxyalkanoate%20From%20Aerobic%20Granules%20Treating%20Palm%20Oil%20Mill%20Effluent.pdf; http://eprints.usm.my/46935/
• Institution: Universiti Sains Malaysia

Polyhydroxyalkanoate (PHA) is a biodegradable polymer which has attracted a lot of interests among researchers lately. In tandem with that, PHA synthesis in microorganisms treating palm oil mill effluent (POME) is an interesting prospect. Aerobic granules developed using POME are totally unexplored till date for PHA synthesis. POME (acidogenically digested) used in this study was collected from an existing anaerobic pond of palm oil mill wastewater treatment plant. The findings of this study showed that aerobic granules were successfully developed using acidogenically digested POME within 9 days and 85 % of the influent COD was removed on average. The developed aerobic granules had an average sludge volume index (SVI) of 48 mL/g. The extracellular polymeric substance (EPS) in aerobic granules contained higher proportion of protein than carbohydrate. Besides that, 16S rRNA analysis indicated that Bacillus and Bordetella genera were the dominating group of bacteria in aerobic granules developed using acidogenically digested POME. The ensuing analysis reveals that aerobic granules were able to accumulate PHA during the treatment of acidogenically digested POME. The average PHA content was 0.68 g PHA/g CDW and the PHA accumulated was co-polymer of poly-3-hydroxybutyrate-co-hydroxyvalerate (P3(HB-co-HV)). The subsequent study reveals that at the cycle time of 6 hrs, the aerobic dynamic feeding (ADF) strategy accumulates the highest PHA (0.651 g PHA/g CDW) of all other strategies. Meanwhile, the PHA recovery study reveals that the sodium hypochlorite-chloroform dispersion method is the best choice compared to other three methods used. The key element in recovering PHA from aerobic granules found to be nearly complete removal of EPS layer in the aerobic granules. The PHA recovery yield was 0.89 g PHA/g CDW in the sodium hypochlorite-chloroform dispersion method. On the other hand, the growth-disintegration processes found to influence the amount of PHA accumulating capability. Granules in between 0.35 and 0.50 mm accumulated 0.68 g PHA/g CDW compared to 0.60 g PHA/g CDW in granules larger than 2 mm. Substrate and oxygen diffusion into the aerobic granules found to be the reason for this difference. Increase of organic loading rate (OLR) from 0.91 to 3.64 kg COD/m3.day has increased the PHA content from 0.66 to 0.87 g PHA/g CDW, respectively. Meanwhile, increase of aeration rate from 1 to 4 L/min has accelerated the formation of PHA only, whereas the PHA content in aerobic granules remained constant. The residual oil was found to attach on the surface of aerobic granules and subsequently limits the substrate diffusion which in turn decreased the PHA content. The inhibition constant was 5.61 g/L residual oil. The overall outcome of this study converges towards the successful PHA accumulation in aerobic granules.