Effect of high temperature toward microalgal organic matter
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Date
2019-06
Authors
Harsimran Kaur Kler A/P Lakbir Singh
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Abstract
Algal blooms can seriously affect the operation of water treatment especially
membrane treatment processes mainly due to accumulation of algal organic matter
(AOM). Studies have shown that AOM is capable of causing severe fouling in low
pressure membrane processes. In the recent years, membrane distillation (MD) has gained
significant regard in the industry for water treatment purpose. However, fouling in MD
differs from pressure-driven membrane processes mainly due to the higher temperature
used in MD process. In this study, the different components of AOM, which are soluble
extracellular polymeric substance (EPS), bounded EPS and internal organic matter (IOM)
were extracted from three common species of benthic algae (Amphora coffeaeformis,
Cylindrotheca closterium and Navicula salinarum) and they were characterized for the
concentration of carbohydrate, the molecular weight (MW) distribution of carbohydrate
and the concentration of protein. These characterization was done by employing
colorimetric analysis, such as phenol-sulphuric acid method to measure the carbohydrate
concentration and bicinchoninic acid (BCA) method to determine the protein
concentration. The characterization of the AOM was done after the algal were harvested
at room temperature, and also after they were exposed to higher temperature at 60oC,
70oC and 80oC for 1 hour. This is to compare the characteristics of the AOM at normal
conditions and also at higher temperature during MD process. The EPS produced by the
three algal species comprised of higher concentration of carbohydrate compared to
protein, where there is 93.04 % of carbohydrate for A. coffeaeformis diatoms, 78.35 %
for N. salinarum diatoms and 82.83 % of carbohydrate for C. closterium diatoms. On the other hand, the protein percentage in A. coffeaeformis diatoms was 51.77 %, for C.
closterium diatoms was 40.97%, and for N. salinarum diatoms was 72.25%. Hence, the
carbohydrate and protein content varies in different species, and cannot be generalized
for every algal species. When the temperature exposed to the algal cells were increased,
it was seen that the concentration of carbohydrate and protein in EPS increases, while the
concentration of carbohydrate and protein in IOM decreases. Apart from that, it was found
that the composition of higher MW of carbohydrate in AOM decreases at higher
temperature, while the composition of lower MW of carbohydrate in AOM increases at
higher temperature. Overall, the compositions of carbohydrate, protein and the MW
distributions in the soluble EPS, bounded EPS and IOM at different temperatures will
likely dictate the severity of fouling in MD during algal blooms.