Evaluation of cyanobacterial cells removal and lysis by ultrafiltration

Abstract

The aim of this study was to evaluate the ultrafiltration (UF) performance for removing Microcystis aeruginosa cells under different growth ages (1, 2, 3 and 4 months old). Special attention was given to cell damaging and subsequent release of microcystins to permeate. Experiments were performed with a hollow-fibre cellulose acetate membrane (100 kDa). UF achieved an absolute removal of M. aeruginosa single cells, producing chlorophyll-a free water and with a turbidity below 0.1 NTU. Cell lysis occurred at all cell growth phases although greater damage was observed for older cultures. However, the permeate quality was never deteriorated and its microcystin concentration was always identical or lower than the dissolved concentration in the feed water. The hydrophilic UF membrane presented low adsorption of microcystins but the microcystin rejection increased in the presence of algogenic organic matter (AOM). The type rather than the overall concentration of salts and organics ruled the membrane fouling, the 1-month-old suspension (polysaccharide-rich AOM with scaling multivalent ions) presenting higher fouling potential than the 3-month-old suspension (protein-rich AOM with much lower content of multivalent ions).

PAC/UF for Removing Cyanobacterial Cells and Toxins from Drinking Water

“…Figure 4 shows the occurrence of cell lysis in both cultures, with a stronger impact in the older culture and at the end of the filtration cycle. Chlorophyll-a concentration is not shown but was less sensitive to cell lysis than the intra-microcystins concentration (Campinas & Rosa, 2010a). On the other hand, Figure 5 reveals a cycle-averaged rejection of total microcystins of 60% with the 2 months old culture and of 80% with the 4 months old cells, which indicates the importance of the adsorption phenomenon for this older culture.…”

“…aeruginosa culture (Pasteur Culture Collection, PCC 7820) was grown in the laboratory, in BG11 medium, at 23-24ºC, under a light regimen of 12 h fluorescent light, 12 h dark. Depending on the experiment, cultures were harvested at different growth ages, namely 1, 2-3 and 4 months, corresponding to exponential phase, late exponential phase and stationary phase, respectively (Campinas & Rosa, 2010a), and used to simulate cyanobacterial blooms. Cyanotoxins are produced at all stages of cyanobacterial growth and usually stay inside the cell (intracellular) until age or stress-driven cell lysis causes their release into the water (extracellular) (Sivonen & Jones, 1999).…”

“…Preliminary UF runs with model solutions of microcystins revealed a low adsorption of microcystins by the cellulose acetate membrane (4% average rejection (Campinas & Rosa, 2010a)). It was thus decided to indirectly assess cell lysis through the evolution of the dissolved microcystin concentration in the feed and permeate during the filtration cycle.…”

Fouling control of PAC/UF process for treating algal-rich water

“…It can be seen that the chlorophyll-a content in raw water was about 4-5.5 μg·L − 1 , and the average content was 4.67 ± 0.39 μg·L −1 during the experiment. The chlorophyll-a was almost completely removed and only a minute trace could be detected in the effluent of UF and PAC/UF processes, because of the bigger size of M. aeruginosa cells (3-7 μm) as compared with the pore size of membrane (0.01 μm) [24]. The results indicated that both PAC/UF and UF process could achieve almost complete removal of algal cells for the sieving function of UF membrane.…”

Investigation of Algal Biotoxin Removal during SWRO Desalination through a Materials Flow Analysis

“…For MF/UF systems, the range in algal cell removal efficiencies was also summarized from pilot and full-scale SWRO plant studies [38,[43][44][45][46]. Uniform probability distributions were used in the pMFA model for MF/UF systems considering the small number of reported observations from the literature ( Table 2).…”