Comparison of Alcian blue and total carbohydrate assays for quantitation of transparent exopolymer particles (TEP) in biofouling studies

Xu Li, Lucy Skillman, Dan Li, Wendell P Ela

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Transparent exopolymer particles (TEP) and their precursors are gel-like acidic polysaccharide particles. Both TEP precursors and TEP have been identified as causal factors in fouling of desalination and water treatment systems. For comparison between studies, it is important to accurately measure the amount and fouling capacity of both components. However, the accuracy and recovery of the currently used Alcian blue based TEP measurement of different surrogates and different size fractions are not well understood. In this study, we compared Alcian blue based TEP measurements with a total carbohydrate assay method. Three surrogates; xanthan gum, pectin and alginic acid; were evaluated at different salinities. Total carbohydrate concentrations of particulates (>0.4 μm) and their precursors (<0.4 μm, >10 kDa) varied depending on water salinity and method of recovery. As xanthan gum is the most frequently used surrogate in fouling studies, TEP concentration is expressed as xanthan gum equivalents (mg XGeq/L) in this study. At a salinity of 35 mg/L sea salt, total carbohydrate assays showed a much higher particulate TEP fraction for alginic acid (38%) compared to xanthan gum (9%) and pectin (12%). The concentrations of particulate TEP therefore may only represent ∼10% of the total mass; while precursor TEP represents ∼80% of the total TEP. This highlights the importance of reporting both particulate and precursor TEP for membrane biofouling studies. The calculated concentrations of TEP and their precursors in seawater samples are also highly dependent on type of surrogate and resulting calibration factor. A linear correlation between TEP recovery and calibration factor was demonstrated in this study for all three surrogates. The relative importance and accuracy of measurement method, particulate size, surrogate type, and recovery are described in detail in this study.

Original languageEnglish (US)
Pages (from-to)60-68
Number of pages9
JournalWater Research
Volume133
DOIs
StatePublished - Apr 15 2018
Externally publishedYes

Fingerprint

transparent exopolymer particle
Xanthan gum
Biofouling
biofouling
Carbohydrates
carbohydrate
Assays
Fouling
assay
Recovery
Alginate
Particles (particulate matter)
Calibration
Desalination
Polysaccharides
Water treatment
Seawater
fouling
Gels
Salts

Keywords

  • Alcian blue
  • Biofouling
  • Membrane fouling
  • Precursor TEP
  • Total carbohydrate assay
  • Transparent exopolymer particles (TEP)

ASJC Scopus subject areas

  • Ecological Modeling
  • Water Science and Technology
  • Waste Management and Disposal
  • Pollution

Cite this

Comparison of Alcian blue and total carbohydrate assays for quantitation of transparent exopolymer particles (TEP) in biofouling studies. / Li, Xu; Skillman, Lucy; Li, Dan; Ela, Wendell P.

In: Water Research, Vol. 133, 15.04.2018, p. 60-68.

Research output: Contribution to journalArticle

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abstract = "Transparent exopolymer particles (TEP) and their precursors are gel-like acidic polysaccharide particles. Both TEP precursors and TEP have been identified as causal factors in fouling of desalination and water treatment systems. For comparison between studies, it is important to accurately measure the amount and fouling capacity of both components. However, the accuracy and recovery of the currently used Alcian blue based TEP measurement of different surrogates and different size fractions are not well understood. In this study, we compared Alcian blue based TEP measurements with a total carbohydrate assay method. Three surrogates; xanthan gum, pectin and alginic acid; were evaluated at different salinities. Total carbohydrate concentrations of particulates (>0.4 μm) and their precursors (<0.4 μm, >10 kDa) varied depending on water salinity and method of recovery. As xanthan gum is the most frequently used surrogate in fouling studies, TEP concentration is expressed as xanthan gum equivalents (mg XGeq/L) in this study. At a salinity of 35 mg/L sea salt, total carbohydrate assays showed a much higher particulate TEP fraction for alginic acid (38{\%}) compared to xanthan gum (9{\%}) and pectin (12{\%}). The concentrations of particulate TEP therefore may only represent ∼10{\%} of the total mass; while precursor TEP represents ∼80{\%} of the total TEP. This highlights the importance of reporting both particulate and precursor TEP for membrane biofouling studies. The calculated concentrations of TEP and their precursors in seawater samples are also highly dependent on type of surrogate and resulting calibration factor. A linear correlation between TEP recovery and calibration factor was demonstrated in this study for all three surrogates. The relative importance and accuracy of measurement method, particulate size, surrogate type, and recovery are described in detail in this study.",
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