Enhancement Of Volatile Fatty Acid Production From Anaerobic Treatment Of Palm Oil Mill Effluent
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Date
2019-06-01
Authors
Lim, Jing Xiang
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Biological treatment unit is widely used to treat high organic content
wastewater such as palm oil mill effluent (POME). A treatment that can salvage the
useful nutrient from the wastewater is needed to enhance the sustainability of the
wastewater treatment process. Volatile fatty acid (VFA) has high potential to be
applied on many application such as production of biogas or biodegradable plastic.
The recovery of nutrient in the form of methane gas (end-product of anaerobic
digestion) was well researched but the study on the enhancement of volatile fatty acid
(VFA) (intermediate-product of anaerobic digestion) was still limited. VFA production
is preferred over biogas production because VFA can be used to produce more valuable
product such as polyhydroxyalkanoate (PHA) (a type of biodegradable plastic). The
enhancement of VFA production was achieved through the elimination of
methanogenesis process. In this study, a sequencing batch reactor was used to enrich
the biomass in partial anaerobic treatment of POME to enhance the VFA production.
The SBR has a working volume of 8 L and hydraulic retention time of 5 days. The
influent concentration of POME contains about 33400 mgCOD/L. The anaerobic
reactor managed to increase the VFA accumulation to about 10500 mg/L total VFA
(about 43.8 % of VFA accumulation in the feed). The microbial population analysis
had revealed that the growth of methanogen was suppressed and no methane gas was
release during the treatment process. Further, it was discovered that the increase of
ammoniacal nitrogen has increased the total VFA production. About 105.7 % VFA
accumulation was achieved at COD:N ratio of about 40:5. However, inhibition on the
VFA production occurred at ammoniacal nitrogen content of more than 4000 mg/L
shock loading. Furthermore, the effluent from the VFA enhancement reactor was used
as the feed to produce PHA. The aerobic reactor accumulating PHA using VFA
enriched POME (AE1) has achieved output PHA concentration of about 3773
mgPHA/L (specific production of about 0.32 mgPHA/mgVSS). The results shows that
the recovery of the VFA has high potential to produce biodegradable plastic (PHA).
Additionally, the microbial growth kinetics was evaluated for the microorganism in
VFA enhancement reactor and PHA production reactor. The result of the growth
kinetics studies was used to simulate the VFA accumulation and the PHA production
by using MATLAB software.