The presence of microcystins (MC) in drinking water reservoirs, even at low
concentrations, is a problem for all involved in management and water treatment. This
cyclic peptide hepatotoxin, produced by several species of toxic cyanobacteria as
secondary metabolites, cause liver damage and is considered tumor promoter
(Matsushima et al., 1992), representing a potential hazard to human health (Carmichael,
1994). Therefore, it is necessary to ensure their removal in water treatment plants
(WTP) by innovative and effective treatments. In recent years, nanofiltration (NF) has
become an attractive alternative technology to conventional water treatment due to the
capacity to remove inorganic and organic compounds (disinfection by-products (DBP)
precursors) with low molecular weight cut-offs and low operating pressures (Her et al.,
2000; Costa and Pinho, 2006). However, the application of NF to drinking water
treatment is affected by natural organic matter (NOM) fouling (Hong and Elimelech,
1997). Membrane fouling refers to plugging and external pore blocking (Gwon et al.,
2003) which causes low performance and reduction of membrane time life, because of
flux decline and/or transmembrane pressure increase (Her et al., 2000). In addition,
good results were obtained with NF to remove cyanotoxins present in water for human
consumption. According to some authors (Ribau Teixeira and Rosa, 2005; Gijsbertsen-
Abrahamse et al., 2006; Ribau Teixeira and Rosa, 2006), NF removed cyanobacterial
toxins from water, with removal rates greater than 99% at laboratory scale. However,
pilot scale experiments in real context are missing. The aim of this work is to study NF
performance to remove microcystins from natural water, at a pilot scale in a real context
of WTP

Lucas, Helena

Ribau Teixeira, Margarida

Serrão Sousa, Vânia

Universidade do Algarve

Nanofiltration Performance to Remove Microcystins from Water for 
Human Consumption at a Pilot Scale 
 
 
V. Serrão Sousa*(1), H. Lucas**, M. Ribau Teixeira*(2) 
 
 
* CENSE, Center for Environmental and Sustainability Research, and University of Algarve, Faculty of 
Sciences and Technology, building 7, Campus de Gambelas, 8005-139 Faro, Portugal, 
(1)vssousa@ualg.pt, (2)mribau@ualg.pt  
** Águas do Algarve, Rua do Repouso, nº10, 8000-302 Faro, Portugal, h.lucas@aguasdoalgarve.pt  
 
 
Keywords Nanofiltration, microcystins, natural organic matter, pilot scale. 
 
 
INTRODUCTION 
The presence of microcystins (MC) in drinking water reservoirs, even at low 
concentrations, is a problem for all involved in management and water treatment. This 
cyclic peptide hepatotoxin, produced by several species of toxic cyanobacteria as 
secondary metabolites, cause liver damage and is considered tumor promoter 
(Matsushima et al., 1992), representing a potential hazard to human health (Carmichael, 
1994). Therefore, it is necessary to ensure their removal in water treatment plants 
(WTP) by innovative and effective treatments. In recent years, nanofiltration (NF) has 
become an attractive alternative technology to conventional water treatment due to the 
capacity to remove inorganic and organic compounds (disinfection by-products (DBP) 
precursors) with low molecular weight cut-offs and low operating pressures (Her et al., 
2000; Costa and Pinho, 2006). However, the application of NF to drinking water 
treatment is affected by natural organic matter (NOM) fouling (Hong and Elimelech, 
1997). Membrane fouling refers to plugging and external pore blocking (Gwon et al., 
2003) which causes low performance and reduction of membrane time life, because of 
flux decline and/or transmembrane pressure increase (Her et al., 2000). In addition, 
good results were obtained with NF to remove cyanotoxins present in water for human 
consumption. According to some authors (Ribau Teixeira and Rosa, 2005; Gijsbertsen-
Abrahamse et al., 2006; Ribau Teixeira and Rosa, 2006), NF removed cyanobacterial 
toxins from water, with removal rates greater than 99% at laboratory scale. However, 
pilot scale experiments in real context are missing. The aim of this work is to study NF 
performance to remove microcystins from natural water, at a pilot scale in a real context 
of WTP. 
 
METHODS 
NF experiments were performed in a commercial pilot-scale unit M20 (maximum 
pressure 80 bar; maximum flow 18 L/min and constant temperature maintained by a 
heat exchanger) using a spiral wound element (M20-2.5”) and a polypiperazine amide 
membrane (1.1 m2, 153 g/mol of molecular cut-off). This unit was installed at 
Alcantarilha Water Treatment Plant (WTP), in Algarve, Portugal, in a parallel line after 
preoxidation, coagulation/flocculation and sedimentation processes as presented in 
Figure 1. Alcantarilha WTP supplies water to ca. half million people in southern 
Portugal and was designed to treat up to 3 m3/s since 2000, with surface water from 
Funcho Dam reservoir (2 km2 and 43.4 hm3) and after 2005, mixing with ground-water 
from  Qurença- Silves aquifer.  
 
Raw 
Water
Preoxidation
(Ozonation)
Coagulation / 
Floculation
Sedimentation
Treated
Water
(Permeate)
Nanofiltration
Microcystins
addition Concentrate
DW
 
Figure 1. Experimental water treatment sequence in Alcantarilha WTP (DW - Decanted Water). 
 
Long time operation experiments (ca. 120 h) were made at 10 bar, 21ºC, at a stipulated 
concentration and during the normal operation of the WTP. Experimental procedure 
consisted of a first step of permeating deionised water until achieving the steady 
permeate flux and then the permeation of the natural water started in recirculation mode, 
during ca. 100 h. Since no bloom of cyanobacteria occurred during experiments, 
microcystins were periodically added to DW. Permeate flux was continuously 
measured, as well as pH and conductivity. Feed and permeate samples were periodically 
collected to determine dissolved organic carbon (DOC), UV absorbance at 254 nm 
(UV) and microcystin concentration. Removal efficiencies were calculated based on 
feed and permeate concentrations.  
 
Analyses were performed on a TOC-5000 analyser (Shimadzu) for DOC, a Beckman 
DU 640B spectrophotometer for UV, a HACH HQ30D conductimeter for conductivity 
and a WTW pH340 for pH. Specific UV (SUVA) was determined (defined as the ratio 
UV/DOC), since it represents an index of NOM aromaticity. Microcystins were 
extracted from a culture of Microcystis aeruginosa supplied by Pasteur Culture 
Collection (PCC7820) and maintained in laboratory. After one and an half months of 
growth (corresponding approximately to the maximum of M. aeruginosa growth 
obtained in the laboratory), stock solutions of microcystins were prepared as already 
presented elsewhere (Ribau Teixeira and Rosa, 2005). Microcystins were analysed by 
liquid chromatography with photodiode-array detection (HPLC-PDA). The standard 
operation procedures developed by Meriluoto and Spoof (2005a, b) for the 
concentration of microcystins in water samples and microcystins analysis were used 
with the adaptations described in Ribau Teixeira and Rosa (2006). A HPLC-PDA 
Dionex Summit system was used with a C18 column (Merck Purospher STAR RP-18 
endcapped, 3 µm particles, LiChroCART 55x4 mm).  
 
RESULTS AND DISCUSSION 
Figure 2 presents the variation of permeate flux, MC concentration, DOC and UV 
during operation time. MC concentration in the feed varied over the experiment, 
because of feed concentration with operation time. This concentration increased MC in 
the feed (Figure 2b1 first 5 h) to values higher than the natural occurring in surface 
waters (Rosa et al., 2004). To avoid this, MC were added periodically to DW and, as a 
result, a decrease (due to dilution) in the feed MC concentrations over time is observed. 
These variations are also reflected in the other studied parameters.  
 
 
 
 
 
a)  
 
 
b1) c1) 
 
b2)  
  
b3)  
 
Figure 2 - a) Permeate flux, and MC, DOC and UV variation: b) feed, c) permeate quality. 
Wash 
The permeate flux (Figure 2a) decreases during the experiment due to an accumulation 
of MC and NOM near the membrane surface. The microcystin variant studied, MC-LR, 
is hydrophobic, weekly negatively charged (Maagd et al., 1999) and with a molecular 
weight much higher than the membrane cut-off (991 vs. 153 g/mol). As already reported 
by some authors (Nilson and DiGiano, 1996; Jucker and Clark, 1994) hydrophobic 
compounds adsorb onto membrane surface, therefore the flux decrease may be due to 
the fouling or adsorption of the MC onto membrane surface (Ribau Teixeira and Rosa, 
2005). In addition, NOM is one of the main membrane foulants (Hong and Elimelech, 
1997). In this water, NOM is hydrophilic (based on SUVA values) with low molecular 
weight and DOC largely composed of non-humic substances (Edzwald and Benschoten, 
1990), which should have little influence on the permeate flux according to Nilson and 
DiGiano (1996). However, other researches reported recently that hydrophilic NOM 
(non-humics) might also be an important foulant of the membranes (Fan et al., 2001; 
Lee et al., 2004). These findings are reflected in the results obtained for flux with this 
organic matter (Figure 2a). The major decrease in permeate flux was observed in the 
initial hours of experiment corresponding to the highest concentration of MC in feed. 
When the MC concentration decrease in feed, the permeate flux continues to decrease 
but in a less pronounced way. This decrease is due to the effect of NOM in the 
membrane surface.  
 
The results present in Figure 2b1 show that NF at pilot-scale has ability to remove MC 
regardless its concentration in feed and during more than 100 h of operation. The 
removal rates were always higher than 98% and MC concentration in permeate (Figure 
2c1) below 1 µg/L (WHO drinking water guideline value). These high MC removals are 
due size exclusion effects, since MC present a higher molecular size than membrane 
pore and are negatively charged (Ribau Teixeira and Rosa, 2005).  
 
Removals of NOM are high, 94-98% for UV and 82-94% for DOC, and good permeate 
quality was obtained (Figure 2c2 and 2c3). Removals of DOC are lower than UV since 
the UV absorbance at 254 nm is mainly due to the adsorption by aromatic/hydrophobic 
compounds, whereas DOC measures the dissolved concentration of carbon containing 
molecules (Schafer and Fane, 2000). During the 120 h of operation, no significant 
variation is observed in permeate quality and the highest concentrations are obtained in 
the first 10 h of operation due to the highest influent concentrations. One of the main 
result from this study is that the permeate quality for DOC, UV and SUVA show low 
values (≤2mg C/L, ≤0.004 cm−1 and 0.38 L/(m mg), Figure 2c2 and 2c3), despite the 
time of operation.  
 
As far as conductivity removals are concerned (Figure 3a), the variations observed with 
time are related with the addition of MC, as already mentioned. As the membrane is 
slight negatively charge at this pH (Figure 3b), the anions are rejected and with them the 
cations, as referred by Ribau Teixeira and Rosa (2005). 
 
 
 
 
 
 
 
a) b) 
  
Figure 3 - a) Conductivity removal and b) pH variation. 
 
CONCLUSIONS 
This study shows that NF membranes are effective in MC removal in drinking water 
treatment during ca. 120 h of operation at a pilot-scale. NF has demonstrated its ability 
to remove MC regardless of the concentration variations in the feed without loss of 
efficiency (always higher than 98%). The decrease observed in the permeate flux during 
the experiment was due to the fouling or adsorption of the MC onto membrane surface, 
as well as the NOM hydrophilic character. The main conclusion from this work is good 
permeate quality is obtained in the treatment of natural hydrophilic waters with 
microcystins using NF membranes and during at least 120 h of operation. 
 
ACKNOWLEDGMENT 
This research was funded by Portuguese Science and Technology Foundation (FCT), project nº 
PTDC/ECM/68323/2006.  
 
REFERENCES 
Carmichael, W.W. (1994) Sci. Am. 270(1), 78–89. 
Costa, A. and Pinho, M. (2006) Desalination 196, 55-65. 
Edzwald, J. and Benschoten, J. (1990) in: H.H. Hahn, R. Klute (Eds.), Chemical Water and Wastewater 
Treatment, Springer–Verlag, Berlin. 
Fan, L., Harris, J.L., Roddick, F.A. and Booker, N.A. (2001) Wat. Res. 35(18), 4455-4463. 
Gijsbertsen-Abrahamse, A., Schimdt, W., Chorus, I. and Heijman, S. (2006) J. Memb. Sci. 276, 252-259.  
Gwon, E., Yu, M., Oh, H. and Yong-hun Y. (2003) Wat. Res. 37, 2989–2997. 
Her, N., Amy G. and Jarusutthirak, C. (2000) Desalination 132, 143-160. 
Hong, S. and Elimelech, M. (1997) J. Memb. Sci. 132, 159-181. 
Jucker, C. and Clark, M.M. (1994). J. Memb. Sci. 97, 37-52. 
Lee, N., Amy, G., Croue, J.-P. and Buisson, H. (2004) Wat. Res. 38, 4511–4523. 
Maagd, P.G.J., Hendriks, A.A.J., Seinen, W. Sijm, D.T.H. (1999) Water Res.33 (3) 677. 
Matsushima, N.R., Ohta, T., Nishiwaki, S., Suganuma, M., Kohyama, K., Carmichael, W.W. and Fujiki, 
H. (1992) J. Cancer Res. Clin. Oncol. 118, 420–424. 
Meriluoto J., Spoof L. (2005a). SOP: Analysis of microcystins by high-performance liquid 
chromatography with photodiode-array detection. In: J. Meriluoto, G. Codd (Eds.), Toxic 
Cyanobacterial Monitoring and Cyanotoxin Analysis, Abo Akademi University Press, Finland.  
Meriluoto J., Spoof L. (2005b). SOP: Solid phase extraction of microcystins in water samples. 
SOP_TOXIC_AAU_05F. In: J. Meriluoto, G. Codd (Eds.), Toxic Cyanobacterial Monitoring and 
Cyanotoxin Analysis, Abo Akademi University Press, Finland. 
Nilson, J. and DiGianno, F. (1996). J. Am. Wat. Works Assoc. 88(5), 53-66.  
Ribau Teixeira, M. and Rosa, M.J. (2005) Sep. Purif. Technol. 46, 192-201. 
Ribau Teixeira, M. and Rosa, M.J. (2006) Wat. Res. 40, 2837-2846. 
Rosa, M.J.; Cecílio, T.; Costa, H.; Baptista, R. Lourenço, D. (2004) 4th World Water Congress. IWA. 
Marrakech, Morocco, 19-24 September. 
Schafer, A.I, Fane, A.G., Waite, T.D. (2000) Desalination 131


Nanofiltration performance to remove microcystins from water for human consumption at a pilot scale

Sapientia

Nanofiltration Performance to Remove Microcystins from Water for Human Consumption at a Pilot Scale   V. Serrão Sousa*(1), H. Lucas**, M. Ribau Teixeira*(2)   * CENSE, Center for Environmental and Sustainability Research, and University of Algarve, Faculty of Sciences and Technology, building 7, Campus de Gambelas, 8005-139 Faro, Portugal, (1)vssousa@ualg.pt, (2)mribau@ualg.pt  ** Águas do Algarve, Rua do Repouso, nº10, 8000-302 Faro, Portugal, h.lucas@aguasdoalgarve.pt    Keywords Nanofiltration, microcystins, natural organic matter, pilot scale.   INTRODUCTION The presence of microcystins (MC) in drinking water reservoirs, even at low concentrations, is a problem for all involved in management and water treatment. This cyclic peptide hepatotoxin, produced by several species of toxic cyanobacteria as secondary metabolites, cause liver damage and is considered tumor promoter (Matsushima et al., 1992), representing a potential hazard to human health (Carmichael, 1994). Therefore, it is necessary to ensure their removal in water treatment plants (WTP) by innovative and effective treatments. In recent years, nanofiltration (NF) has become an attractive alternative technology to conventional water treatment due to the capacity to remove inorganic and organic compounds (disinfection by-products (DBP) precursors) with low molecular weight cut-offs and low operating pressures (Her et al., 2000; Costa and Pinho, 2006). However, the application of NF to drinking water treatment is affected by natural organic matter (NOM) fouling (Hong and Elimelech, 1997). Membrane fouling refers to plugging and external pore blocking (Gwon et al., 2003) which causes low performance and reduction of membrane time life, because of flux decline and/or transmembrane pressure increase (Her et al., 2000). In addition, good results were obtained with NF to remove cyanotoxins present in water for human consumption. According to some authors (Ribau Teixeira and Rosa, 2005; Gijsbertsen-Abrahamse et al., 2006; Ribau Teixeira and Rosa, 2006), NF removed cyanobacterial toxins from water, with removal rates greater than 99% at laboratory scale. However, pilot scale experiments in real context are missing. The aim of this work is to study NF performance to remove microcystins from natural water, at a pilot scale in a real context of WTP.  METHODS NF experiments were performed in a commercial pilot-scale unit M20 (maximum pressure 80 bar; maximum flow 18 L/min and constant temperature maintained by a heat exchanger) using a spiral wound element (M20-2.5”) and a polypiperazine amide membrane (1.1 m2, 153 g/mol of molecular cut-off). This unit was installed at Alcantarilha Water Treatment Plant (WTP), in Algarve, Portugal, in a parallel line after preoxidation, coagulation/flocculation and sedimentation processes as presented in Figure 1. Alcantarilha WTP supplies water to ca. half million people in southern Portugal and was designed to treat up to 3 m3/s since 2000, with surface water from Funcho Dam reservoir (2 km2 and 43.4 hm3) and after 2005, mixing with ground-water from  Qurença- Silves aquifer.   Raw WaterPreoxidation(Ozonation)Coagulation / FloculationSedimentationTreatedWater(Permeate)NanofiltrationMicrocystinsaddition ConcentrateDW Figure 1. Experimental water treatment sequence in Alcantarilha WTP (DW - Decanted Water).  Long time operation experiments (ca. 120 h) were made at 10 bar, 21ºC, at a stipulated concentration and during the normal operation of the WTP. Experimental procedure consisted of a first step of permeating deionised water until achieving the steady permeate flux and then the permeation of the natural water started in recirculation mode, during ca. 100 h. Since no bloom of cyanobacteria occurred during experiments, microcystins were periodically added to DW. Permeate flux was continuously measured, as well as pH and conductivity. Feed and permeate samples were periodically collected to determine dissolved organic carbon (DOC), UV absorbance at 254 nm (UV) and microcystin concentration. Removal efficiencies were calculated based on feed and permeate concentrations.   Analyses were performed on a TOC-5000 analyser (Shimadzu) for DOC, a Beckman DU 640B spectrophotometer for UV, a HACH HQ30D conductimeter for conductivity and a WTW pH340 for pH. Specific UV (SUVA) was determined (defined as the ratio UV/DOC), since it represents an index of NOM aromaticity. Microcystins were extracted from a culture of Microcystis aeruginosa supplied by Pasteur Culture Collection (PCC7820) and maintained in laboratory. After one and an half months of growth (corresponding approximately to the maximum of M. aeruginosa growth obtained in the laboratory), stock solutions of microcystins were prepared as already presented elsewhere (Ribau Teixeira and Rosa, 2005). Microcystins were analysed by liquid chromatography with photodiode-array detection (HPLC-PDA). The standard operation procedures developed by Meriluoto and Spoof (2005a, b) for the concentration of microcystins in water samples and microcystins analysis were used with the adaptations described in Ribau Teixeira and Rosa (2006). A HPLC-PDA Dionex Summit system was used with a C18 column (Merck Purospher STAR RP-18 endcapped, 3 µm particles, LiChroCART 55x4 mm).   RESULTS AND DISCUSSION Figure 2 presents the variation of permeate flux, MC concentration, DOC and UV during operation time. MC concentration in the feed varied over the experiment, because of feed concentration with operation time. This concentration increased MC in the feed (Figure 2b1 first 5 h) to values higher than the natural occurring in surface waters (Rosa et al., 2004). To avoid this, MC were added periodically to DW and, as a result, a decrease (due to dilution) in the feed MC concentrations over time is observed. These variations are also reflected in the other studied parameters.       a)    b1) c1)  b2)    b3)   Figure 2 - a) Permeate flux, and MC, DOC and UV variation: b) feed, c) permeate quality. Wash The permeate flux (Figure 2a) decreases during the experiment due to an accumulation of MC and NOM near the membrane surface. The microcystin variant studied, MC-LR, is hydrophobic, weekly negatively charged (Maagd et al., 1999) and with a molecular weight much higher than the membrane cut-off (991 vs. 153 g/mol). As already reported by some authors (Nilson and DiGiano, 1996; Jucker and Clark, 1994) hydrophobic compounds adsorb onto membrane surface, therefore the flux decrease may be due to the fouling or adsorption of the MC onto membrane surface (Ribau Teixeira and Rosa, 2005). In addition, NOM is one of the main membrane foulants (Hong and Elimelech, 1997). In this water, NOM is hydrophilic (based on SUVA values) with low molecular weight and DOC largely composed of non-humic substances (Edzwald and Benschoten, 1990), which should have little influence on the permeate flux according to Nilson and DiGiano (1996). However, other researches reported recently that hydrophilic NOM (non-humics) might also be an important foulant of the membranes (Fan et al., 2001; Lee et al., 2004). These findings are reflected in the results obtained for flux with this organic matter (Figure 2a). The major decrease in permeate flux was observed in the initial hours of experiment corresponding to the highest concentration of MC in feed. When the MC concentration decrease in feed, the permeate flux continues to decrease but in a less pronounced way. This decrease is due to the effect of NOM in the membrane surface.   The results present in Figure 2b1 show that NF at pilot-scale has ability to remove MC regardless its concentration in feed and during more than 100 h of operation. The removal rates were always higher than 98% and MC concentration in permeate (Figure 2c1) below 1 µg/L (WHO drinking water guideline value). These high MC removals are due size exclusion effects, since MC present a higher molecular size than membrane pore and are negatively charged (Ribau Teixeira and Rosa, 2005).   Removals of NOM are high, 94-98% for UV and 82-94% for DOC, and good permeate quality was obtained (Figure 2c2 and 2c3). Removals of DOC are lower than UV since the UV absorbance at 254 nm is mainly due to the adsorption by aromatic/hydrophobic compounds, whereas DOC measures the dissolved concentration of carbon containing molecules (Schafer and Fane, 2000). During the 120 h of operation, no significant variation is observed in permeate quality and the highest concentrations are obtained in the first 10 h of operation due to the highest influent concentrations. One of the main result from this study is that the permeate quality for DOC, UV and SUVA show low values (≤2mg C/L, ≤0.004 cm−1 and 0.38 L/(m mg), Figure 2c2 and 2c3), despite the time of operation.   As far as conductivity removals are concerned (Figure 3a), the variations observed with time are related with the addition of MC, as already mentioned. As the membrane is slight negatively charge at this pH (Figure 3b), the anions are rejected and with them the cations, as referred by Ribau Teixeira and Rosa (2005).        a) b)   Figure 3 - a) Conductivity removal and b) pH variation.  CONCLUSIONS This study shows that NF membranes are effective in MC removal in drinking water treatment during ca. 120 h of operation at a pilot-scale. NF has demonstrated its ability to remove MC regardless of the concentration variations in the feed without loss of efficiency (always higher than 98%). The decrease observed in the permeate flux during the experiment was due to the fouling or adsorption of the MC onto membrane surface, as well as the NOM hydrophilic character. The main conclusion from this work is good permeate quality is obtained in the treatment of natural hydrophilic waters with microcystins using NF membranes and during at least 120 h of operation.  ACKNOWLEDGMENT This research was funded by Portuguese Science and Technology Foundation (FCT), project nº PTDC/ECM/68323/2006.   REFERENCES Carmichael, W.W. (1994) Sci. Am. 270(1), 78–89. Costa, A. and Pinho, M. (2006) Desalination 196, 55-65. Edzwald, J. and Benschoten, J. (1990) in: H.H. Hahn, R. Klute (Eds.), Chemical Water and Wastewater Treatment, Springer–Verlag, Berlin. Fan, L., Harris, J.L., Roddick, F.A. and Booker, N.A. (2001) Wat. Res. 35(18), 4455-4463. Gijsbertsen-Abrahamse, A., Schimdt, W., Chorus, I. and Heijman, S. (2006) J. Memb. Sci. 276, 252-259.  Gwon, E., Yu, M., Oh, H. and Yong-hun Y. (2003) Wat. Res. 37, 2989–2997. Her, N., Amy G. and Jarusutthirak, C. (2000) Desalination 132, 143-160. Hong, S. and Elimelech, M. (1997) J. Memb. Sci. 132, 159-181. Jucker, C. and Clark, M.M. (1994). J. Memb. Sci. 97, 37-52. Lee, N., Amy, G., Croue, J.-P. and Buisson, H. (2004) Wat. Res. 38, 4511–4523. Maagd, P.G.J., Hendriks, A.A.J., Seinen, W. Sijm, D.T.H. (1999) Water Res.33 (3) 677. Matsushima, N.R., Ohta, T., Nishiwaki, S., Suganuma, M., Kohyama, K., Carmichael, W.W. and Fujiki, H. (1992) J. Cancer Res. Clin. Oncol. 118, 420–424. Meriluoto J., Spoof L. (2005a). SOP: Analysis of microcystins by high-performance liquid chromatography with photodiode-array detection. In: J. Meriluoto, G. Codd (Eds.), Toxic Cyanobacterial Monitoring and Cyanotoxin Analysis, Abo Akademi University Press, Finland.  Meriluoto J., Spoof L. (2005b). SOP: Solid phase extraction of microcystins in water samples. SOP_TOXIC_AAU_05F. In: J. Meriluoto, G. Codd (Eds.), Toxic Cyanobacterial Monitoring and Cyanotoxin Analysis, Abo Akademi University Press, Finland. Nilson, J. and DiGianno, F. (1996). J. Am. Wat. Works Assoc. 88(5), 53-66.  Ribau Teixeira, M. and Rosa, M.J. (2005) Sep. Purif. Technol. 46, 192-201. Ribau Teixeira, M. and Rosa, M.J. (2006) Wat. Res. 40, 2837-2846. Rosa, M.J.; Cecílio, T.; Costa, H.; Baptista, R. Lourenço, D. (2004) 4th World Water Congress. IWA. Marrakech, Morocco, 19-24 September. Schafer, A.I, Fane, A.G., Waite, T.D. (2000) Desalination 131

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Nanofiltration performance to remove microcystins from water for human consumption at a pilot scale

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