Development of in-situ detection method of TEP as an early warning system for algae blooms
Lee, Darren Yong Shern
Date of Issue2017-05-16
School of Civil and Environmental Engineering
Nanyang Environment and Water Research Institute
Over the past two decades, many methods have been developed to quantify and determine transparent exopolymer particles (TEP), a transparent and sticky organic substances that found abundantly in oceans. TEP was originally quantified by light microscopy, a slow yet labour-intensive method. This lead to the development of the first semi-quantitative method proposed by (U. Passow & A. Alldredge, 1995) and subsequently many other quantitative methods. Even though the methods were diverse, the similarity was the use of alcian blue solution (AB) as a staining agent to quantify TEP. The limitations of these methods were, being unable to be used for on-line monitoring of TEP, time consumed and implementation of several steps, that could increase the likelihood of human errors happening, possibly rendering the results unsuitable for use. Previously prominent common findings from studies have shown that peak concentrations with TEP were associated with phytoplankton blooms (Alldredge et al., 1998; Grossart et al., 1997; Mari & Kiørboe, 1996; U. Passow et al., 2001; Riebesell et al., 1995; Xavier & Adrian, 1998), and that increased release of TEP may occur during or after algae blooms. In this study, a simple on-line monitoring method is proposed for the measurement of TEP in various water sources accurately, yet quickly, to correlate the TEP concentration measured by the proposed method with algae concentrations. This method uses the Commission Internationale de l’Eclairage (CIE) 1976 colour expressions L* a* b* and alcian blue (0.02% alcian blue and 0.06% acetic acid, pH 2.5) solution as a staining agent. Cross flow ultrafiltration was the main mode to facilitate this method using a regenerated cellulose membrane of 30 kDa. The normalised b* value was then determined after the end of each filtration (90 minutes), first staining the membrane with alcian blue then using a fibre-optic spectrometer and light source emitter to detect the variation in colour. Calibration of this new method was first done with Xanthan Gum (XG), a model for TEP, with concentrations from 0 – 100 ppm (mg/L), and this calibration was then correlated against the conventional method proposed by (U. Passow & A. Alldredge, 1995). Further validation of this method was then carried out using several water samples such as a model foulant (alginic acid), natural sources (seawater, aquaculture and pond water) and cultivated algae seawater. The linear relationship, good correlation and increased sensitivity obtained from the results of this method shows the possible potential of an on-line quantification of TEP and its precursors that could possibly serve as an early warning system for algae bloom.
Final Year Project (FYP)
Nanyang Technological University