CONTROLLING BIOFOULING IN SEAWATER
REVERSE OSMOSIS MEMBRANE SYSTEMS
DISSERTATION
Submitted in fulfillment of the requirements of the Board for Doctorates of Delft University of Technology and of the Academic Board of the UNESCO‐IHE Institute for Water Education for the Degree of DOCTOR to be defended in public on Thursday 30 November 2017 at 15:00 hours in Delft, the Netherlands
by
Nirajan DHAKAL
Master of Science in Water Supply Engineering UNESCO‐IHE, Institute for Water Education
born in Gorkha, Nepal
This dissertation has been approved by the Promotor: Prof. dr. M.D. Kennedy and Copromotor: Dr. ir. S.G. Salinas Rodriguez
Composition of Doctoral Committee:
Chairman Rector Magnificus TU Delft Vice‐Chairman Rector IHE‐Delft
Prof. dr. M.D. Kennedy IHE‐Delft/TU Delft, promotor Dr. ir. S.G. Salinas Rodriguez IHE‐Delft, copromotor
Independent members:
Prof. dr. ir. W.G. J. van der Meer University of Twente
Prof. dr. ir. J. Miguel Veza Universidad de Las Palmas, Gran Canaria Prof. dr. ir. L. C. Rietveld TU Delft
Dr. ir. B. Blankert Oasen, the Netherlands
Prof. dr. ir. M.E. McClain TU Delft/IHE‐Delft, reserve member
CRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business
© 2017, Nirajan Dhakal
Although all care is taken to ensure the integrity and the quality of this publication and the information herein, no responsibility is assumed by the publishers, the author nor UNESCO‐IHE for any damage to the property or persons as a result of the operation or use of this publication and/or the information contained herein.
A pdf version of this work will be made available as Open Access via http://repository.tudelft.nl/ihe This version is licensed under the Creative Commons Attribution‐Non Commercial 4.0 International License, http://creativecommons.org/licenses/by‐nc/4.0/
Published by:
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Acknowledgement
This research presented in this thesis was carried out at UNESCO‐IHE Institute for Water Education with financial support from Wetsus, European Centre of Excellence for Sustainable Water Technology.
I wish to express my sincere gratitude to my promotor, Prof. Maria D. Kennedy, Prof. Jan C. Schippers and Sergio Salinas Rodríguez for their strong support, guidance and encouragement during my PhD research project. Their critical thinking and probing discussions throughout the project were valuable in shaping the research. It was a privilege to work with you!
I would like to thank all the participants of the Wetsus research theme “Biofouling” for the productive interaction with both academia and the water industry (Ania, Antoine, Arie, Bas, Bastiaan, Bert, Caroline, Charu, Fons, Georg, Hilde, Joop, Koen, Leo, Marcel, Mark, Mieke, Natascha, Paula, Remon, Rik). It has been a learning experience interacting with both academics and practitioners in the biofouling research theme, and this provided an opportunity to see how scientific research is applied in practice. In addition, I am indebted to the laboratory staff at wetsus, especially Mieke Kersaan for all her support and patience with the LC‐OCD analyses. I sincerely apologize to those who are not mentioned in this acknowledgment.
This work involved pilot testing in Jacobahaven, the Netherlands. This would never have been possible without the commitment and effective coordination from the R&D group of Pentair X‐Flow (Remon Dekker, Leo Vredenbregt, Tom Spanjer, Henry Hamberg, and Sander Brinks). Likewise, the support and commitment from de Zeeschelp B.V. (Marco Dubbeldam, Bernd van Broekhoven, and Hanno), Biaqua (Lute Broens, Sandie Chauveau and Monica Paravidino) and UNESCO‐IHE (Fred Kruis) were valuable for the success of the project.
Besides, I was lucky to supervise four hard‐working master students who directly contributed to this research, namely: Alaa Samir Ouda, Joshua Ampah, Mohamed Ismail Nazeer, and Nizordinah Sithole, who have performed the most challenging experiments in this project.
A doctoral degree is not achieved on one’s own. The technical and non‐technical support of my colleagues was crucial for the completion of this thesis. My gratitude goes to all friends
and colleagues (in alphabetic order): Abdulai Salifu, Ahmed Mahmoud, Almotasembellah Abushaban, Assiyeh Tabatabai, Bianca Wassenaar, Chol Abel, Chris Metzker, Emmanuelle Prest, Ferdi Battes, Ferry Horváth, Fiona Zakarika, Frank Wiegman, Frans Knops, Fred Kruis, Iosif Skoullos, Jolanda Boots, Jeroen Lodeweeg, Lea Tan, Loreen Ople Villacorte, Lute Broens, Lyzette Robbemont, Madapura Eregowda, Mariëlle van Erven, Mariska Ronteltap, Matt Luna, Mohanasundar Radhakrishnan, Mohaned Sousi, Mohaned Abunada, Muhammad Dikman Maheng, Muhammad Nasir Mangal, Peter Heerings, Peter Mawioo, Rinnert Schurer, Shreedhar Maskey, Shrutika Wadgaonkar, Sylvia van Opdorp Stijlen, Taha Al Washali, Vanessa Temminck, Water supply chair group of IHE Delft (Branislave Petrusevski, Giuliana Ferrero, Nemaja Trifunovic, Saroj Sharma and Yness March Slokar) and Yuli Ekowati. I sincerely apologize to those who are not mentioned in this acknowledgment.
I am very grateful to my family in Nepal for their never‐ending support, encouragement, and love during my stay abroad. My special gratitude goes to my mother and father who sacrificed a lot in their life. I would not be in this stage without their never‐ending support. I will always be very grateful my dear mother who passed away during my Ph.D. research period; you will be in my heart forever. My wife Anita Dhamala and my little daughter Angila Dhakal, this work would have been tough without you. I am so blessed to be surrounded by you.
Last but not the least, I thank God for giving me the opportunity, strength, and determination to complete this Ph.D. thesis.
29 October 2017
Delft, the Netherlands
Nirajan Dhakal,
To my late mother, Usha Kumari Dhakal
Summary
Seawater reverse osmosis (SWRO) is the preferred technology of choice for seawater desalination. However, membrane fouling is a major challenge for the cost‐effective operation of membrane based desalination systems. An emerging threat to SWRO is the occurrence of algal blooms and the associated high concentration of algal cells and algal organic matter (AOM) in seawater. To help minimize membrane fouling, SWRO systems are equipped with pre‐treatment systems. However, current pre‐treatment systems are not capable of removing all AOM from SWRO feed water. The AOM that passes from pre‐treatment systems accumulates on the SWRO membrane surfaces and acts as a “conditioning layer” and can initiate biofilm development in the presence of available nutrients (C, P) in RO feed water.
One notable example was the severe red tide algal bloom in the Middle East in 2008‐2009. During this period pre‐treatment processes such as granular media filter (GMF) with coagulation suffered from rapid clogging and produced poor quality water for the downstream SWRO system (SDI >5). As a result, some SWRO desalination plants in the coastal areas of the region were forced to shut down to avoid irreversible fouling of their RO membranes. After this event, the application of low‐pressure membranes such as microfiltration and ultra‐filtration (MF/UF) have been considered as a more reliable pre‐treatment during algal blooms. Previous studies have shown that conventional UF membranes are also not capable of removing all organic matter (AOM) from SWRO feed water, and thus organic/biofouling in downstream SWRO could occur. Therefore, new pre‐treatment technologies that can remove AOM, as well as other nutrients (C, P) from SWRO feed water are needed to delay the onset of organic and/or biofouling in SWRO systems. Furthermore, better methods/tools are required to assess and improve pre‐treatment processes in terms of their ability to reduce re‐growth potential prior to SWRO membranes.
The overall goal of this research was to assess the ability of conventional UF (150 kDa) and tight UF (10 kDa) either alone or in combination with phosphate removal technology (PRTTM) to delay the onset of organic/biological fouling in SWRO feed water during algal blooms. The three main objectives of the research were; i) to better understand ultrafiltration membrane fouling and the root causes of poor backwashability of organic matter generated by different marine algal species, ii) to develop an improved method to
viii
measure bacterial regrowth potential (BRP) prior to SWRO membrane systems, and iii) to apply the improved BRP method at laboratory, pilot and full scale to assess the ability of conventional UF (150 kDa) and tight UF (10 kDa) alone and in combination with a phosphate adsorbent to reduce regrowth potential and delay the onset of organic/biological fouling in SWRO feed water during algal blooms.
The study developed an improved method to measure bacterial regrowth potential (BRP) in seawater samples. During the method development, flow cytometry combined with fluorescence staining (SYBR® Green I and Propidium Iodide) was used with a natural consortium of marine bacteria as inoculum. The Level of Detection (LOD) of the method was lowered by developing a standard protocol to prepare blank seawater. The two aspects considered were i) minimize the level of contamination that might originate from sample bottles, chemicals, pipettes and the laboratory environment during blank seawater preparation and ii) minimize leaching of carbon from filters and all surfaces during BRP measurements.
The limit of detection of BRP method was lowered to 43 x 103 ± 12 x 103 cells/mL, which is equivalent to 9.3 ± 2.6 µg‐Cglucose/L assuming a yield factor of 4.6 x 106 cells/µg‐C for marine bacteria. Calibration of the method was performed with glucose as a standard substrate in artificial and natural seawater. The BRP method was applied in full‐scale seawater desalination plants in the Middle East to assess the biofouling potential of SWRO feed water, as well as to assess the performance of the pre‐treatment systems.
The next phase of the study was to investigate the fouling potential and fouling behavior of algae and algal released organic matter in ultrafiltration membranes. For this purpose, four marine algae were cultivated namely: Chaetoceros affinis (Ch), Rhodomonas balthica (Rb), Tetraselmis suecica (Te), and Phaeocystis globulosa (Ph). During the growth and stationary/decline phase, the algal cell density, chlorophyll‐a, biopolymer, transparent exopolymer particles (TEP) concentration and MFI‐UF10kDa (membrane fouling potential) were measured. Fouling experiments were executed with capillary ultrafiltration, filtration inside to outside, and backwashable and non‐ backwashable fouling was monitored.
During the growth, stationary/decline phase of the algal species remarkable differences were observed in the production of biopolymers, TEP and MFI‐UF10kDa . Membrane fouling potential (MFI‐UF10kDa) was linearly related to algal cell density and chlorophyll‐a concentration, biopolymer concentration, TEP, during the growth phase of the algal species.
After the growth phase, the relationship between MFI‐UF10kDa and algal cell density and chlorophyll‐a concentration did not continue. In experiments with capillary ultrafiltration, membranes (150 kDa) fed with water having 0.5 mg‐biopolymer ‐ C/L back washable fouling coincided with the MFI‐UF150kDa and TEP for Rh, Te, and Ph. Back washable fouling for Ch deviated and was substantially higher. The non‐back washable fouling of the ultrafiltration membranes varied strongly with the type of algal species and coincided with MFI‐UF150kDa and TEP concentration. Rh demonstrated the highest and Ph the lowest non‐back washable fouling (at a level of 0.5 mg‐biopolymer‐C/L) in the feed water. This non‐backwashable fouling is attributed to polysaccharides (stretching ‐ OH) and sugar ester group (stretching S=O) present in the AOM. Furthermore, the characterization of permeate quality of UF showed biopolymer rejection of 60 % to 80 % depending upon on the algal species. This indicates that biopolymers having a size smaller than the pores of the ultrafiltration membranes may also contribute to non‐backwashable fouling in UF/RO systems. Therefore, a more robust pre‐treatment is needed with enhanced removal of AOM from RO feed water in order to delay the onset of organic/biological fouling in SWRO systems.
The next phase of the study was to apply the improved BRP method and other analytical tools such as transparent exopolymer particles (TEP), modified fouling index (MFI‐UF), liquid chromatography organic carbon detection (LC‐OCD) to assess the biofouling reduction potential of tight ultrafiltration (10 kDa) pre‐treatment. The tests were performed at laboratory and pilot scale and were performed using MF and UF membranes with a wide range of MWCO and algal organic matter (AOM) produced by Chaetoceros affinis as a feed solution. The AOM rejection experiments performed with MF and UF membranes showed 3‐4 times lower biopolymer and TEP concentration as well as MFI‐UF10kDa with tight UF (10 kDa) compared with the permeates of high MWCO MF and UF membranes. The measured bacterial regrowth potential (BRP) of tight UF permeate was ca. 2‐3 times lower than the permeate of high MWCO MF and UF membranes. However, it should be noted that no remarkable difference was observed in bacterial regrowth potential of tight UF (10 kDa) and high molecular weight cut off (150 kDa) UF in pilot‐scale experiments.
Biofouling experiments performed at pilot‐scale using the permeate of tight UF (10 kDa) and conventional UF (150 kDa) showed no substantial head loss development in the membrane fouling simulator (MFS) monitors in short‐term (15 days) experiments. The measured biomass accumulated in the MFS monitor fed with 10 kDa UF permeate was ca. 860 pg ATP/cm2, which was 2 and 5 times lower than measured in MFS monitors fed with 150 kDa
x UF permeate and UF feed, respectively. In terms of hydraulic operation, the tight UF showed 1.5 times higher non‐backwashable fouling rate development compared with a 150 kDa UF. This could be attributed to the lower surface porosity of the 10 kDa UF membrane, which resulted in lower backwashing and chemical enhanced backwashing (CEB) efficiency compared to the 150 kDa UF. Improving the surface porosity of the 10 kDa UF may lower non‐backwashable fouling rate development. In general, the results from the laboratory and pilot‐scale demonstrated the potential for tight UF (10 kDa) as a pretreatment for SWRO during algal blooms, but validation in long‐term experiments is still necessary.
The role of phosphate removal technology (PRTTM) combined with tight ultrafiltration (10 kDa) in delaying the onset of biofouling in SWRO systems was also investigated. Laboratory‐scale experiments showed that the application of PRTTM resulted in improved removal of biopolymers as well as dissolved phosphate from SWRO feed water, compared with ultrafiltration alone. Furthermore, the application of PRTTM substantially lowered the bacterial regrowth potential (BRP) of UF permeate sample independent of the pore size of the UF membrane. The addition (spiking experiment) of 10 µg PO4 – P/L to the permeate of UF‐PRTTM resulted in a significantly higher (by factor 2) bacterial regrowth potential, suggesting that the removal of phosphate limited bacterial regrowth.
Finally, biofouling experiments using membrane fouling simulator (MFS), showed no increase in feed channel pressure drop in MFS units fed with permeate of tight UF (10 kDa) followed by a phosphate adsorbent (PRTTM) for at least 21 days when operated at a cross flow velocity of 0.2 m/s. Moreover, a pressure drop of approximately 500 mbar was observed in MFS units fed with permeate of tight UF (10 kDa) alone when operated for the same period and with similar conditions and thus illustrates the role of the phosphate adsorbent (PRTTM) in delaying the occurrence of biofouling.
Membrane autopsies also showed that the biomass accumulation in the MFS fed with permeates of UF+PRTTM was below the detection limit. While the measured ATP was 6,000 pg ATP/cm2 in the MFS fed with permeate of tight UF alone. The higher biomass accumulation in the MFS fed with the permeate of the tight UF (10 kDa) alone could be attributed to the passage of low molecular weight (LMW) organic and dissolved phosphate through the 10 kDa UF. The possible contribution of LMW organics (tested using EDTA) showed a linear regrowth (R2=0.65) between EDTA concentration and the net bacterial regrowth. Overall, the proof of principle experiments demonstrated that the removal of phosphate by the application of PRTTM combined with UF (10 kDa) restricted biomass
growth and may thus delay the onset of biofouling in SWRO membranes. Moreover, a more extended period of testing is needed for further verification of both technologies.
Overall, this study demonstrated that an improved bacterial regrowth potential (BRP) method can be used to (i) assess pre‐treatment technology in terms of BRP reduction, (ii) monitor the performance of pre‐treatment systems and (iii) develop essential strategies to mitigate membrane fouling in SWRO systems. This study also demonstrated that the removal of algal organic matter (AOM), and dissolved phosphate from SWRO feed water is a potential strategy to delay the onset of organic and biofouling in SWRO systems during algal blooms. Tight UF (10 kDa) coupled with an adsorbent to remove phosphate showed higher potential compared to UF alone (10 kDa) with respect to AOM and nutrient (C, P) removal.
Finally, it is still necessary to further develop existing and new methods that can detect low concentrations of nutrients e.g. carbon and phosphate in seawater, to support the development of improved membrane fouling prevention strategies
General introduction
Contents
1.1 Background ........................................................................................................................................... 2
1.2 Algal blooms and seawater reverse osmosis operation .................................................... 4
1.3 Pre‐treatment for seawater reverse osmosis ......................................................................... 6
1.4 Future generation of pre‐treatment in SWRO ....................................................................... 8
1.5 Goal and objectives .......................................................................................................................... 10
1.6 Outline of the thesis ......................................................................................................................... 10
1.7 References ........................................................................................................................................... 11
1.1 Background
The global demand for water has increased over the past decades due mainly to i) population growth, ii) increase in per capita water demand, iii) expanded irrigation schemes, and iv) economic development (Curmi et al., 2013, de Graaf et al., 2014).
Furthermore, uneven rainfall distribution, uneven population distribution, and unequal water use distribution have increased the regional water scarcity. The 2015 UN report on the Millennium Development Goals stated, “Water scarcity affects more than 40 % of the population.” As projected by the International Water Management Institute, more than half of the world population will suffer from water scarcity by the year 2025 (Figure 1.1). Thus, it is imperative to locate other water resources such as wastewater, water reuse, and seawater desalination to increase freshwater production in working to alleviate the global water crisis.
Freshwater comprises about 2.5 % of the total amount of water on the planet, and the rest (97.5 %) is salt water. The available freshwater is not evenly distributed around the world, with variations over geographical regions and time. Only a small part of available freshwater resources is a naturally renewable source of freshwater (Miller, 2003).
Today, desalination is one of the solutions that are increasingly applied to solve freshwater scarcity problems in many regions of the world. Although desalination is the best known to produce freshwater from seawater, it can also be used to treat slightly salty (brackish) water, low‐grade surface, and groundwater. Of the various desalination technologies,
Figure 1.1: Projected global water scarcity in 2025 (IWMI, 2006)
reverse osmosis (RO) is the most widely used desalination system for brackish and seawater. The expansion of RO globally has been relatively rapid since the year 2000 and is expected to reach the cumulative capacity of about 60 Mm3/day by the year 2018 (Figure 1.2). Almost half (47 %) of RO‐desalinated water is from seawater, and the rest is mainly from brackish, freshwater and treated wastewater (DesalData, 2016).
Thermal desalination
1.2:
reverse osmosis plant capacity from 1970‐2018 (DesalData, 2016)
Membrane‐based seawater desalination is currently dominating the market mainly because of its reduction in the power consumption and per unit production cost. As illustrated in Figure 1.3 b, the power consumption reduced from 16 kWh/m3 in 1970 to 2 kWh/m3 in 2008. Likewise, the cost per cubic meter has also decreased from $ 1.6/m3 to $ 0.6/m3 from 1982 to 2010 (Figure 1.3 a).
Figure 1.3: Trends of a) cost in $/m3 (WaterReuseAssociation, 2012) and b) power consumption in kWh/m3 (Elimelech, 2012) in Seawater reverse osmosis plants
Figure
Seawater
1.2 Algal blooms and seawater reverse osmosis operation
Many seawater reverse osmosis (SWRO) desalination plants are located in and treat seawater from coastal zones where algal blooms frequently occur (Caron et al., 2010). Even as SWRO plants are rapidly increasing throughout the world, their operations is affected by the occurrence of algal blooms, which cause problems including membrane fouling. One example is the severe “red tide” bloom that occurred in the Middle East Gulf region (2008 ‐ 2009), caused by the dinoflagellate Cochlodinium polykrikoides (Richlen et al., 2010). This bloom forced the stoppage of operations in at least five seawater desalination plants located in that region mainly due to: i) clogging of granular media filters and ii) higher silt density index (SDI >5) in the RO feed water (Pankratz, 2008, Reddy, 2009). This incident exposed the vulnerability of seawater RO plants during severe algal blooms situations. Therefore, efficient removal of algae and algal organic matter (AOM) by pretreatment systems is crucial to minimize such operational problem in SWRO systems.
Algal blooms are unpredictable events and can last from a few days to several months, depending on the life cycles of causative species, environmental conditions and nutrient availability (Villacorte, 2014). Some of the common bloom‐forming algal species are illustrated in Figure 1.4. The size of which ranges from 2 µm to 2 mm, and the cell concentration range from 1,000 to 600,000 cells/mL (Villacorte et al., 2015b).
Figure 1.4: Common species of bloom‐forming algae in fresh and marine environments (adapted from Villacorte et al., 2014)
The two most important current indicators for monitoring the occurrence of algal blooms are algal cell concentration ( >1million cells/L) and chlorophyll‐a concentration (>10µg/L)(http://www.waterman.hku.hk, 2016). Figure 1.5 shows the level of average chlorophyll‐a concentration, measured in 2009, in surface water bodies worldwide. The red color in the map shows the chlorophyll‐a concentration > 10µg/L measured in all coastal regions. This illustrates that desalination plants located in coastal zones are vulnerable to algal blooms.
Figure 1.5: Typical average annual distribution of chlorophyll‐a in surface water bodies on Earth (adapted from Villacorte et al., 2014)
Algal blooms increase the suspended solids concentration as well as the organic substances responsible for membrane fouling (Caron et al., 2010). During algal blooms, algae release algal organic matter (AOM) which has been shown to be the leading cause of membrane fouling, rather than the algae themselves (Ladner et al., 2010, Qu et al., 2012, Schurer et al., 2012, Villacorte et al., 2015a). The AOM mainly consists of polysaccharides, proteins, lipids, nucleic acids, and other dissolved organic substances (Fogg, 1983, Myklestad, 1995). A significant fraction of AOM is the transparent exopolymer particles (TEP) (Villacorte et al., 2013) which are highly sticky polysaccharides and glycoproteins (Passow et al., 1995). The presence of TEP‐like materials thus causes or initiates organic fouling in ultrafiltration (UF) and biological fouling in UF/RO membranes (Berman et al., 2005, Berman et al., 2011, Kennedy et al., 2009). The consequences of membrane fouling in reverse osmosis lead to:
Increase in head loss across the feed spacer of spiral wound elements
Controlling biofouling in seawater reverse osmosis membrane systems
Higher energy consumption to maintain the constant flux operation
Higher chemical cleaning frequency
Increase in the replacement of membranes due to irreversible membrane fouling
Decrease in the rate of water production due to longer downtime during chemical cleaning and membrane replacement
Increase in salt passage and a resulting deterioration of permeate quality
To help prevent membrane fouling, SWRO plants install pre‐treatment systems (e.g., media filters with coagulation or MF/UF). The particulate and colloidal fouling in SWRO is mostly controlled with such existing pre‐treatment; however, the occurrences of organic and biological fouling are still a significant issue in SWRO membranes.
1.3 Pre‐treatment for seawater reverse osmosis
Seawater reverses osmosis plants are equipped with pre‐treatment systems to ensure consistent performance of the SWRO membranes, and to reduce cleaning frequency. Pre‐treatment consists of the intake and screening systems, processes for particulate matter removal and control of biological growth (Huehmer et al., 2006). However, inadequate pre‐treatment is still the leading cause of SWRO system failure (Gallego et al., 2007). Pre‐treatment for SWRO systems can be i) conventional or ii) advanced or iii) a combination of both, depending upon the raw water quality. Conventional treatment systems typically consist of coagulation and (dual) media filtration using a variety of filtration media such as combinations of single and two‐stage, gravity, and pressurized media filters. However, media filters demonstrated operational problem during the 2008 ‐ 2009 algal blooms in the Gulf of Oman. The associated problems were clogging of media filters and poor effluent water quality (SDI > 5), which forced SWRO plants to shut down (Richlen et al., 2010). Furthermore, these systems are also characterized by high coagulant consumption.
Dissolved air flotation (DAF) has recently gained attention as a promising pre‐treatment option during algal blooms. DAF is a clarification process that is typically applied before media filters and MF/UF with the aim of removing particles (Cleveland et al., 2002). It has been reported that the algal cell removal efficiency of DAF is better (90 – 99 %) than sedimentation (60 – 90 %) (Gregory and Edzwald (2010), cited by (Villacorte, 2014). However, a high coagulant dose of up to 20 mg/L as FeCl3 is needed to achieve adequate removal of algae by DAF units (Rovel, 2003).
Recently, application of low‐pressure membrane systems (MF/UF) is increasing as pre‐treatment to treat seawater during algal blooms (Villacorte et al., 2015a, Voutchkov, 2010). MF/UF pre‐treatment has numerous advantages compared to conventional pre‐treatment: mainly lower footprint, higher permeate quality, higher rejection of organics, and lower chemical consumption (Pearce, 2007, Wilf et al., 2001). Furthermore, UF operated with inline coagulant dosing, with low concentration, during algal blooms has demonstrated stable hydraulic operation (Schurer et al., 2013).
Moreover, several studies have shown that existing pre‐treatment systems are often useful in removing algae itself. However, the systems allow the passage 30 – 80 % of algal released organic matter (AOM), measured as biopolymer concentration as shown in Figure 1.6 (Guastalli et al., 2013, Salinas ‐ Rodriguez et al., 2009, Tabatabai et al., 2014). The wide range of removal efficiency of pre‐treatment depends on the amount of coagulant applied during operation. As illustrated in Figure 1.6, pre‐treatment by beach wells showed the highest biopolymer rejection (> 80 %) compared to other pretreatment processes. However, beach wells are not feasible for large desalination plants.
Overall, the passage of 30 – 80 % of algal biopolymer from the existing pre‐treatment systems may accumulate on downstream SWRO membranes. The deposited biopolymers on a SWRO membrane may act as a conditioning layer, where bacteria can grow and multiply to form a biofilm in the presence of available nutrients from feed water. Therefore, SWRO operations with current pre‐treatment systems are still vulnerable mainly due to possible organic and biological fouling during algal blooms.
Despite the fact that existing pre‐treatment technologies cannot protect RO operation during algal blooms, an increasing number of large‐scale RO plants (> 500,000 m3/day) will be installed in the coming years (Kurihara et al., 2013). Such large‐scale plants may be threatened by algal blooms and thus demand a robust pretreatment technology to minimize problems of organic/biofouling occurrence in SWRO membranes.
80 A = GMF (Single)
B = GMF (Dual)
C = MF (0.1µm)
D = DAF + DMF
E = DAF + UF
F = UF (150 kDa)
G = Beach well
Figure 1.6: Biopolymer removal by various SWRO pre‐treatment systems tested with various water source i) Western Mediterranean Sea (B, C, G), ii) with Eastern Mediterranean Sea (A) (Salinas ‐ Rodriguez et al., 2009), iii) Western Mediterranean Sea (D, E) (Guastalli et al., 2013) and iv) laboratory cultured AOM from "Chaetoceros affinis” (F) (Alizadeh Tabatabai et al., 2014).
1.4 Future generation of pre‐treatment in SWRO
Membrane fouling (organic and biological) remains a major limitation of SWRO desalination operation, despite improvements in pre‐treatment systems. A new generation of pre‐treatment technology is needed to further protect the performance of SWRO operation, showing better removal of algal biopolymers as well as the ability to limit the concentration of nutrients (C, P) so that downstream SWRO will not suffer from organic and biofouling. Removal of biopolymers from the feed water in itself can substantially delay biofouling, as there is no “conditioning layer” to initiate biofilm development. On the other hand, limiting essential nutrients from the SWRO feed water may delay the onset of biological growth in the system.
The application of tight ultrafiltration (10 kDa) may eliminate fouling caused by algal‐derived biopolymers in RO systems. Although tight UF is expected to remove particulate and colloidal material from the feed water efficiently, it is not capable of removing dissolved nutrients such as carbon and phosphate as UF membranes are not designed to remove dissolved carbon and phosphate. However, the removal of such dissolved nutrients from SWRO feed water might contribute to delaying onset of biofouling in SWRO systems.
It has been demonstrated that limiting phosphate in SWRO feed water can control biofouling (Jacobson et al., 2009). It was also reported that phosphate limitation can prevent the occurrence of biofouling in RO systems even in the presence of high concentrations of other nutrients (Vrouwenvelder et al., 2010). Various technologies or methods are available that can remove phosphate from water but are reported not sustainable (Sevcenco et al., 2015). This provided an opportunity to look for alternative phosphate removal technology or methods which will are sustainable and environmentally friendly.
In this study, the application of pre‐treatment systems that can remove substantial amounts of AOM and nutrients such as carbon and phosphate and eventually delay the onset of organic and biofouling in SWRO systems were investigated. The potential of tight UF and a newly developed phosphate adsorbent were tested to verify the following hypotheses;
Tight ultrafiltration (10 kDa) having a lower molecular weight cut off than the conventional UF (150 kDa) is expected to be more effective in removing organic matter and thus delay the onset of biofouling in SWRO
A phosphate adsorbent is capable of reducing the phosphate in SWRO feed water to such a level that it can limit bacterial regrowth.
It is expected that the integration of the two technologies as pre‐treatment can be a promising solution to control organic and biofouling in SWRO systems as illustrated in Figure 1.7
Figure 1.7: Research concept
1.5 Goal and objectives
The overall aim of this study was to assess the ability of conventional and tight UF either alone or in combination with phosphate removal technology (PRTTM) to delay the onset of organic/biological fouling in SWRO feed water during algal blooms.
This specific objectives are the following:
To understanding ultrafiltration membrane fouling and the root causes of poor backwashability of organic matter generated by four different marine algal species.
To develop an improved method to measure bacterial regrowth potential (BRP) prior to SWRO membrane systems
To apply the improved BRP method at laboratory, pilot and full scale to assess the ability of conventional UF (150 kDa) and tight UF (10 kDa) alone and in combination with a phosphate adsorbent to reduce regrowth potential and delay the onset of organic/biological fouling in SWRO feed water during algal blooms.
1.6 Outline of the thesis
This thesis has been structured into seven chapters as described below:
Chapter 1 is a general introduction on the background of the study, research problems, and the needs of the future generation of advanced pre‐treatment systems to eliminate or delay the onset of biofouling in seawater reverse osmosis during algal blooms. This chapter also includes research concept, goal, and objectives of the study.
Chapter 2 is a review of the perspective and challenges for the global desalination market.
Chapter 3 describes the development of improved method to measure bacterial regrowth potential (BRP) in seawater using a natural bacterial consortium as inoculum in combination with flow cytometry.
Chapter 4 describes the fouling of ultrafiltration membranes by organic matter generated by four marine algal species
Chapter 5 describes the role of tight ultrafiltration (UF) (with a molecular weight cut off of 10 kDa) in reducing the biofouling potential of SWRO feed water during algal blooms. The proof of principle was performed at laboratory and pilot scales using various pore size MF/UF membranes.
Chapter 6 describes the role of phosphate removal technology (PRTTM) combined with tight UF in reducing biofouling potential of SWRO feed water during algal blooms. The proof of principle was performed at laboratory and pilot scale.
Chapter 7 provides a summary of conclusions and outlook.
1.7 References
Alizadeh Tabatabai, S.A., Schippers, J.C. and Kennedy, M.D. (2014) Effect of coagulation on fouling potential and removal of algal organic matter in ultrafiltration pretreatment to seawater reverse osmosis. Water Research 59, 283‐294.
Berman, T. and Holenberg, M. (2005) Don't fall foul of biofilm through high TEP levels. Filtration & Separation 42(4), 30‐32.
Berman, T., Mizrahi, R. and Dosoretz, C.G. (2011) Transparent exopolymer particles (TEP): A critical factor in aquatic biofilm initiation and fouling on filtration membranes. Desalination 276(1–3), 184‐190.
Caron, D.A., Garneau, M.‐È., Seubert, E., Howard, M.D.A., Darjany, L., Schnetzer, A., Cetinić, I., Filteau, G., Lauri, P., Jones, B. and Trussell, S. (2010) Harmful algae and their potential impacts on desalination operations off southern California. Water Research 44(2), 385‐416.
Cleveland, C., Hugaboom, D., Raczko, B. and Moughamian, W. (2002) DAF pretreatment for ultrafiltration: cost and water quality implications.
Curmi, E., Richards, K., Fenner, R., Allwood, J.M., Kopec, G.M. and Bajželj, B. (2013) An integrated representation of the services provided by global water resources. Journal of Environmental Management 129(0), 456‐462.
de Graaf, I.E.M., van Beek, L.P.H., Wada, Y. and Bierkens, M.F.P. (2014) Dynamic attribution of global water demand to surface water and groundwater resources: Effects of abstractions and return flows on river discharges. Advances in Water Resources 64(0), 21‐33.
DesalData (2016) Worldwide desalination inventory (MS Excel format), Available from www. DesalData.com on June 2016.
Elimelech, M. (2012) Seawater Desalination, 2012 NWRI Clarke prize conference, Newport Beach, California.
Controlling biofouling in seawater reverse osmosis membrane systems
Fogg, G. (1983) The ecological significance of extracellular products of phytoplankton photosynthesis. Botanica Marina 26 (1), 1‐43.
Gallego, S. and Darton, E. (2007) Simple laboratory techniques improve the operation of RO pre‐treatment systems, Maspalomas, Gran Canaria.
Guastalli, A.R., Simon, F.X., Penru, Y., de Kerchove, A., Llorens, J. and Baig, S. (2013) Comparison of DMF and UF pre‐treatments for particulate material and dissolved organic matter removal in SWRO desalination. Desalination 322, 144‐150.
http://www.waterman.hku.hk (2016) Assessing the occurrence of an algal bloom ‐ Chlorophyll‐a concentration.
Huehmer, R. and Henthorne, L. (2006) Advance in RO pretreatment techniques, Haifa, Israel.
Jacobson, J.D., Kennedy, M.D., Amy, G. and Schippers, J.C. (2009) Phosphate limitation in reverse osmosis: An option to control biofouling? Desalination and Water Treatment 5, 198‐206.
Kennedy, M.D., Muñoz ‐ Tobar, F.P., Amy, G.L. and Schippers, J.C. (2009) Transparent exopolymer particles (TEP) fouling of ultrafiltration membrane systems. Desalination and Water Treatment 6 (1‐3), 169 ‐ 176.
Kurihara, M. and Hanakawa, M. (2013) Mega‐ton Water System: Japanese national research and development project on seawater desalination and wastewater reclamation. Desalination 308(0), 131‐137.
Ladner, D.A., Vardon, D.R. and Clark, M.M. (2010) Effects of shear on microfiltration and ultrafiltration fouling by marine bloom‐forming algae. Journal of Membrane Science 356(1–2), 33‐43.
Myklestad, S.M. (1995) Release of extracellular products by phytoplankton with special emphasis on polysaccharides. The Science of The Total Environment 165(1–3), 155‐164.
Pankratz, T. (2008) Red tides close desal plants. Water Desalination Report 44 (1).
Passow, U. and Alldredge, A.L. (1995) A dye‐binding assay for the spectrophotometric measurement of transparent exopolymer particles (TEP). Limnology Oceanography 40(7), 1326‐1335.
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“Fear not a constraining measure! Yielding to the gentle spell, Lucida! from domes of pleasure, Or from cottage-sprinkled dell, Comes to regions solitary, Where the eagle builds her aery, Above the hermit’s long-forsaken cell! She comes! behold That figure, like a ship with silver sail! Nearer she draws; a breeze uplifts her veil; Upon her coming wait
As pure a sunshine, and as soft a gale, As e’er, on herbage-covering earthly mold, Tempted the bird of Juno to unfold His richest splendour, when his veering gait, And every motion of his starry train, Seem governed by a strain Of music, audible to him alone.”
And then we have a picture of the lady:—
“worthy of earth’s proudest throne!
Nor less, by excellence of nature, fit
Beside an unambitious hearth to sit Domestic queen, where grandeur is unknown; What living man could fear
The worst of fortune’s malice, wer’t thou near, Humbling that lily stem, thy sceptre meek, That its fair flowers may brush from off his cheek
The too, too, happy tear?
Queen, and handmaid lowly!
Whose skill can speed the day with lively cares, And banish melancholy
By all that mind invents, or hand prepares;
O thou, against whose lip, without its smile
And in its silence even, no heart is proof; Whose goodness, sinking deep, would reconcile
The softest nursling of a gorgeous palace,
To the bare life beneath the hawthorn roof
Of Sherwood’s archer, or in caves of Wallace
Who that hath seen thy beauty could content
His soul with but a glimpse of heavenly day?
Who that hath loved thee, but would lay
His strong hand on the wind, if it were bent
To take thee in thy majesty away?
Pass onward (even the glancing deer
Till we depart intrude not here;)
That mossy slope, o’er which the woodbine throws
A canopy, is smooth’d for thy repose!”
The next lady that he invokes before the astonished youth is his own daughter—sweet Dora—the previous one was Miss Southey.
“Come, if the notes thine ear may pierce, Come, youngest of the lovely three, Submissive to the mighty verse
And the dear voice of harmony, By none more deeply felt than thee! I sang; and lo! from pastures virginal
She hastens to the haunts
Of Nature, and the lonely elements
Air sparkles round her with a dazzling sheen; And mark, her glowing cheek, her vesture green!
And, as if wishful to disarm
Or to repay the potent charm,
She bears the stringed lute of old romance, That cheered the trellissed arbour’s privacy, And soothed war-wearied knights in raftered hall.
How vivid, yet how delicate, her glee!
So tripped the muse, inventress of the dance; So, truant in waste woods, the blithe Euphrosyne!”
But the ringlets of that head, Why are they ungarlanded?
Why bedeck her temples less Than the simplest shepherdess?
Is it not a brow inviting Choicest flowers that ever breathed, Which the myrtle would delight in, With Idalian rose enwreathed?
But her humility is well content
With one wild floweret (call it not forlorn), F W beneath her bosom worn
Yet more for love than ornament ”
Then follows that beautiful description of her moral graces, already quoted in these pages, beginning—
“Open ye thickets! let her fly, Swift as a Thracian nymph, o’er field and height;”
the whole picture being as fine a conception, and as rich an embodyment, of this sweet Dora,—judging from her portrait in the second volume of the “Memoirs,” and from numerous written and spoken reports of her person
and character,—as the highest genius and the highest art combined, could possibly have produced. And now for Miss Coleridge:—
“Last of the three, tho’ eldest born, Reveal thyself, like pensive morn Touched by the skylark’s earliest note, E’er humble-gladness be afloat. But whether in the semblance drest Of dawn, or eve, fair vision of the west, Come, with each anxious hope subdued By woman’s gentle fortitude, Each grief, thro’ meekness, settling into rest. Or I would hail thee when some high-wrought page Of a closed volume, lingering in thine hand, Has raised thy spirit to a peaceful stand Among the glories of a happy age.”
And, behold! she is here:—
“Her brow hath opened on me see it there, Brightening the umbrage of her hair; So gleams the crescent moon, that loves To be descried thro’ shady groves. Tenderest bloom is on her cheek; Wish not for a richer streak; Nor dread the depth of meditative eye; But let thy love, upon that azure field Of thoughtfulness and beauty, yield Its homage offered up in purity What would’st thou more? In sunny glade, Or under leaves of thickest shade, Was such a stillness e’er diffused Since earth grew calm while angels mused? Softly she treads, as if her foot were loth To crush the mountain dew-drop soon to melt, On the flower’s breast; as if she felt That flowers themselves, whate’er their hue, With all their fragrance, all their glistening, Call to the heart for inward listening And tho’ for bridal wreaths and tokens true Welcomed wisely; tho’ a growth Which the careless shepherd sleeps on, As fitly spring from turf the mourner weeps on And without wrong are cropped the marble tomb to strew
And now the charm is over;
“the mute phantom’s gone, Nor will return but droop not, favoured youth, The apparition that before thee shone Obeyed a summons covetous of truth. From these wild rocks thy footsteps I will guide To bowers in which thy fortunes may be tried, And one of the bright three become thy happy bride.”
A fairer subject than this, for the imagination of the true painter, does scarcely exist in poetry. The gorgeous magnificence of Miss Southey—the wild, bird-like nature of Dora, the mystic, spiritual, meditative beauty of Miss Coleridge. Here is material enough for the highest effort of art.
A number of poems followed this exquisite “Triad”—viz., “The Wishing Gate,” in 1828—“The Lawn,” “Presentiments,” “The Primrose on the Rock,” “Devotional Incitements;” these last were written between 1828 and ’32. A number of gold and silver fishes presented to the poet by Miss H. J. Jewsbury, who subsequently died of the cholera in India,—and afterwards removed to the pond already alluded to, under the oak in “Dora’s field,” suggested the verses “Gold and Silver Fishes in a Vase,” and likewise “Liberty,” and “Humanity;” “The Poet and the caged Turtle Dove” was likewise suggested by real circumstances. Miss Jewsbury had given Dora a pair of these beautiful birds; one of them was killed by an un-necessary cat, and not a “harmless one;” the other survived many years, and had a habit of cooing the moment Wordsworth began “booing” his poems, as the country people called it.
Wordsworth gives an amusing account of a visit which he paid about this time to “Chatsworth.” He had undertaken to ride his daughter’s pony from Westmoreland to Cambridge, that she might have the use of it during a visit she was about to make to her uncle at Trinity; and on his way from Bakewell to Matlock, he turned off to see the splendid mansion of the great Duke of Devonshire. By-and-bye a tremendous storm came on, and the poet was drenched through to the very skin, whilst the pony, to make his rider’s seat the more easy, went “slantwise” all the way to Derby. Notwithstanding this, however, and the pelting of the pitiless storm, Wordsworth managed to hold sweet and sad converse with his muse, and composed his “Lines to the Memory of Sir George Beaumont,” who died 7th February, 1827. It is a picture which we cannot readily forget, and shows how completely the poet was master of himself. Sir George Beaumont and his lady were friends and benefactors of Wordsworth—he loved them both intensely. Walking through the grounds and gardens of Coleorton with Sir George—the successor in the Baronetcy to his friend—and after the death of Lady Beaumont, which took place in 1822, he comes suddenly to her ladyship’s grotto, near the fountain, and is overwhelmed with his feelings, and the recollection of the dead, and the happy memories which rush over his mind in connection with this place, so that he cannot speak for tears. On his return home he wrote the elegiac musings, already mentioned in these memoirs, which are full of love, and the sanctity of a sweet sorrow. In the same year (1831) were composed “The Armenian Lady’s Love,” “The Egyptian Maid,” and “The Russian Fugitive,” poems in which all the
beauties of language are pressed, along with the simplicity which marks the old English ballads. Lines on his portrait, painted by Pickersgill, and preserved with sacred veneration in St. John’s College, Cambridge, were likewise written in this year, as well as the inscription already quoted, for the stone at Rydal.
Besides these poetical compositions, however, Wordsworth interested himself in public affairs; and having fixed principles of political and social economy in his own mind, regarded all public measures at variance with them, as fatal errors, and subversive in their consequences of the highest human concerns. In 1806, he wrote a letter to a friend, who had consulted him respecting the education of his daughter—in which he gives some sound and excellent advice respecting the training and development of youthful minds. For Wordsworth had at an early period devoted his attention to the subject of education, and had his own views respecting it— views which were marked by the spiritual peculiarity of his mind. When he wrote “The Excursion,” he seems to have had the highest hopes for man, when education should become universal; and insisted that the State should teach those to obey, from whom she exacted allegiance:—
“O for the coming of that glorious time, When, prizing knowledge, as her noblest work And best protection, this imperial realm While she exacts allegiance, shall admit An obligation on her part to teach Them who are born to serve her and obey; Binding herself, by statute, to secure For all the children whom her soil maintains The rudiments of letters, and inform The mind with moral and religious truth, Both understood, and practised.”
Excursion, Book ix.
He was an avowed enemy, however, at a later period—for his views respecting the modus operandi of teaching, had undergone some change since “The Excursion” was written—to all Infant Schools, Madras Systems, and Bell Systems. The former he regarded as usurping the functions of motherly duty; the latter, as dead mechanism. Speaking of the education of girls, he says:—“I will back Shenstone’s ‘School Mistress,’ by her winter fire, and in her summer garden seat, against all Dr. Bell’s sour-looking
teachers in petticoats. What is the use of pushing on the education of girls so fast, and moving by the stimulus of Emulation, who, to say nothing worse of her, is cousin-german to Envy? What are you to do with these girls? What demand is there for the ability that they may have prematurely acquired? Will they not be indisposed to bend to any kind of hard labour or drudgery? And yet many of them must submit to it, or go wrong. The mechanism of the Bell System is not required in small places; praying after the fugleman, is not like praying at a mother’s knee. The Bellites overlook the difference: they talk about moral discipline; but wherein does it encourage the imaginative feelings? in short, what she practically understands is of little amount, and too apt to become the slave of the bad passions. I dislike display in everything; above all, in education.... The old dame (Shenstone’s) did not affect to make theologians and logicians; but she taught to read; and she practised the memory, often no doubt by rote, but still the faculty was improved; something, perhaps, she explained, but trusted the rest to parents and masters, and to the pastor of the parish. I am sure as good daughters, as good servants, as good mothers and wives, were brought up at that time as now, when the world is so much less humbleminded. A hand full of employment, and a head not above it, with such principles and habits as may be acquired without the Madras machine, are the best security for the chastity of wives of the lower rank.”
The above extract is from a letter dated 1828, and addressed to the Rev. Hugh Jones Rose, formerly principal of King’s College, London. It exemplifies, in a very striking manner, the change which had come over Wordsworth’s mind upon the subject of education, and does not strike me as being particularly creditable to him.
On the 13th of April, 1836, Wordsworth took part in the ceremony of laying the foundation-stone of certain new schools, about to be erected at Bowness, Windermere, and made a speech upon the occasion; in which he advocates a very humble kind of instruction for the working classes; forgetting that man is to be educated because he is a man, and not neglected because he happens to be one of the “lower orders.” I have no sympathy with this foolish cant about educating people according to their station, and am sorry that Wordsworth’s sanction can be quoted in its favour. I must reserve what I have to say upon this subject, however, for my analysis of the mind and writings of the poet.
In 1835, Wordsworth published his “Yarrow Revisited, and other Poems.” Speaking of “Yarrow Re-visited,” he says: “In the autumn of 1831, my daughter and I set off from Rydal, to visit Sir Walter Scott, before his departure for Italy. This journey had been delayed by an inflammation in my eyes, till we found that the time appointed for his leaving home would be too near for him to receive us without considerable inconvenience. Nevertheless we proceeded, and reached Abbotsford on Monday. I was then scarcely able to lift up my eyes to the light. How sadly changed did I find him from the man I had seen so healthy, gay, and hopeful, a few years before, when he said, at the inn at Patterdale, in my presence, his daughter, Ann, also being there, with Mr. Lockhart, my own wife and daughter, and Mr. Quillinan: ‘I mean to live till I am eighty, and shall write as long as I live.’ Though we had none of us the least thought of the cloud of misfortune which was then going to break upon his head, I was startled, and almost shocked, at that bold saying, which could scarcely be uttered by such a man, without a momentary forgetfulness of the instability of human life. But to return to Abbotsford. The inmates and guests we found there, were Sir Walter, Major Scott, Anne Scott, and Mr. and Mrs. Lockhart; Mr. Laidlaw, a very old friend of Sir Walter’s; one of Burns’s sons, an officer of the Indian service, had left the house the day before, and had kindly expressed his regret that he could not wait my arrival, a regret that I may truly say was mutual. In the evening, Mr. and Mrs. Liddell sang, and Mrs. Lockhart chaunted old ballads to her harp; and Mr. Allan, hanging over the back of a chair, told, and acted, odd stories in a humourous way. With this exhibition, and his daughters’ singing, Sir Walter was much amused, and, indeed, so were we all, as far as circumstances would allow.”
On the following morning (Tuesday) Sir Walter accompanied Wordsworth, and most of his friends, to Newark Castle, on the Yarrow, and it was upon this occasion that the lines, “Yarrow Revisited,” were written. On the morning of Thursday following, when the poet left Abbotsford, he had a serious conversation with Sir Walter, who spoke with gratitude of the happy life he had led. Sir Walter wrote also a few lines in Dora’s album, addressed to her; and when he presented her with the book, in his study, he said: “I should not have done a thing of this kind, but for your father’s sake; they are probably the last verses I shall ever write.” “They shew,” says, Wordsworth, “how much his mind was impaired; not by the strain of thought, but by the execution—some of the lines being imperfect, and one
stanza wanting corresponding rhymes.” Poor Sir Walter!—what a spectacle it was to see that colossal intellect tumbling into ruins.
Several poems were the result of this short tour, beside the “Yarrow Revisited,”—such as “The Place of Burial,” “On the Sight of a Manse in the South of Scotland,” &c., &c.—Wordsworth’s health, too, was much improved by this tour, and a violent inflammation of the eyes—a complaint to which he was much subject,—left him whilst walking through the Highlands, by the side of his “open carriage,” driven by Dora!
Amongst the poems contained in the volume entitled, “Yarrow Revisited,” were many of a political character, for they were written between the years 1830 and 1834, when the Revolution of France, and the Reform party in England, were agitating society to its centre. Wordsworth now hated revolution, and reform also; was opposed to a large and enlightened system of education; and to the admission of Dissenters to the Universities. His plea was the old constitution of things, which could not, he thought, be mended without being broken up and destroyed. “Since the introduction of the Reform Bill, I have been persuaded,” he says, “that the Constitution of England cannot be preserved. It is a question, however, of time.” The poem entitled, “The Warning,” will give the best idea of Wordsworth’s strong political opinions and feelings at this time. As a contrast, however, to these narrow yet patriotic views, we turn to the “Evening Voluntaries,” a collection of sweet poems, which were published in the same volume as the “Yarrow.” They were written on a high part of the coast of Cumberland, on April 7th (Easter Sunday), the author’s 63rd birth-day, between Moresby and Whitehaven, whilst he was on a visit to his son, who was then rector of Moresby.—Very beautiful, indeed, are these poems, which read like twilight vespers in some old abbey’s chancel. Wordsworth says of them—“With the exception of the eighth and ninth, this succession of voluntaries originated in the concluding lines of the last paragraph of this poem, [i.e. of the poem, written on the author’s birth-day, and marked No. 2, in the “Voluntaries,” commencing, “The sun that seemed so mildly to retire.”] With this coast I have been familiar from my earliest childhood, and remember being struck, for the first time, by the town and port of Whitehaven, and the white waves breaking against its quays and piers, as the whole came into my view from the top of the high ground, down which the road, that has since been altered, descended abruptly. My sister, when she first heard the voice of the sea from this point, and beheld
the scene spread before her, burst into tears. Our family then lived at Cockermouth, and this fact was often mentioned amongst us, indicating the sensibility for which she was remarkable.”
As a specimen of the “Evening Voluntaries,” take the following:—
“Calm is the air, and loth to lose Day’s grateful warmth, tho’ moist with falling dews. Look for the stars, you’ll say that there are none; Look up a second time, and one by one, You mark them twinkling out with silvery light, And wonder how they could elude the sight!
The birds, of late so noisy in their bowers, Warbled awhile with faint and fainter powers,
But now are silent as the dim-seen flowers. Nor does the village church clock’s iron tone
The time’s and season’s influence disown; Nine beats distinctly to each other bound In drowsy sequence how unlike the sound That in rough winter, oft inflicts a fear On fireside listeners, doubting what they hear!
The shepherd, bent on rising with the sun, Had closed his door before the day was done, And now with thankful heart to bed doth creep, And joins the little children in their sleep.
The bat, lured forth where trees the lane o’ershade, Flits and reflits along the dark arcade; The busy dor-hawk chases the white moth
With burring note, which industry and sloth Might both be pleased with, for it suits them both
A stream is heard I see it not but know By its soft music where the waters flow: Wheels and the tread of hoofs are heard no more; One boat there was, but it will touch the shore
With the next dipping of its slackened oar; Faint sound that for the gayest of the gay, Might give to serious thought a moment’s sway, As a last token of man’s toilsome day.”
Wordsworth does not seem, during any period of his life, to have been on intimate terms with any of his contemporaries. He preferred the flower of the literateurs, Coleridge, Scott, Southey; and these, with the exception
perhaps of Rogers, were his chief friends. We have letters of his, however, to much smaller fry; to Mrs. Hemans, and Miss Jewsbury, for example— and to sundry editors of other men’s wares; but there is little or no recognition of Byron, Shelly, Keats, Tennyson, Baily, Campbell, Moore, nor yet of Dickens or Bulwer. His letters represent his character even better than his poetry; they are Wordsworth in undress, without the “garland and singing robe,” and are worthy to be studied. I like much what he says to the Rev. Robert Montgomery, author of “The Devil and Father Luther,” and pious Robert would do well even at this late day to think on it. Montgomery had sent Wordsworth a copy of his poems, and in reply, the poet answers: “I cannot conclude without one word of literary advice which I hope you will deem my advanced age entitles me to give. Do not, my dear sir, be anxious about any individual’s opinion concerning your writings, however highly you may think of his genius, or rate his judgment. Be a severe critic to yourself; and depend upon it no person’s decision upon the merit of your works will bear comparison in point of value with your own. You must be conscious from what feeling they have flowed, and how far they may or may not be allowed to claim on that account, permanent respect; and above all I would remind you, with a view to tranquillise and steady your mind, that no man takes the trouble of surveying and pondering another’s writings with a hundredth part of the care which an author of sense and genius will have bestowed upon his own. Add to this reflection another, which I press upon you, as it has supported me through life—viz.: That posterity will settle all accounts justly, and that works which deserve to last will last; and if undeserving this fate, the sooner they perish the better.”
In the year 1836 the sister of the poet’s wife—Miss Sarah Hutchinson, who had resided with the family at Rydal, died, and was buried in Grasmere church, “near the graves of two young children removed from a family to which through life she was devoted.”
In the following year, 1837, Wordsworth, accompanied by his friend H. C. Robinson, Esq., set off from London for Rome, returning in August. The “Itinerary” of the travellers is contained in the “Memoirs,” along with some memoranda by the poet; but they are not of much interest. Many fine pieces, however, sprung as usual from the journey, as well as a goodly number of sonnets. They originally appeared in a volume entitled “Poems, chiefly of Early and Late Years,” in 1842. In 1839, Wordsworth received the degree of D.C.L., from the University of Oxford, which was conferred
on him in the Sheldonian Theatre, amidst shouts of rejoicing such as had never before been heard in that city, except upon the occasion of an unexpected visit of the Duke of Wellington. In 1838, Wordsworth prepared a new edition of his poems, to be published by Moxon, and continued to live at Rydal, in his quiet and musical manner, writing poems, taking rambles, and conducting his correspondence until 1843, when he was appointed Poet Laureate of England, Southey having died on the 21st of March of that year, and the appointment having been offered to Wordsworth on the 31st of the same month. One occurrence only broke the even tenor of the poet’s life in the interim alluded to, and this was an accident by which he was upset from his gig, and thrown violently into a plantation. The accident was owing to the carelessness and want of skill in the driver of a coach, which they met on the road. No serious consequences followed, however, and inquiries and congratulations flowed in on all sides, from the peasant up to Queen Adelaide.
From the time of Wordsworth’s appointment as Laureate,—which it ought to be said he at first refused, and only accepted with the understanding that it should be an honorary office,—he wrote very little poetry. His work, indeed, was done, his mission accomplished; and his old days were spent in rambling over the hills, and in the quiet enjoyment of his family, friends, fame, and fortune. Honours of a high order were subsequently heaped upon him. In the year 1838, the University of Durham took the initiative in conferring an academic degree on the poet; then the grand old Mother, Oxford, followed,—and in 1846 he was put in nomination, without his knowledge, for the office of Lord Rector of the University of Oxford, and gained a majority of twenty-one votes, in opposition to the premier, Lord John Russell. “The forms of election, however,” says Wordsworth, in a letter to Sir W. Gomm, of Port Louis, Mauritius, dated November 23, 1846, “allowed Lord John Russell to be returned through the single vote of the sub-rector voting for his superior. To say the truth, I am glad of this result, being too advanced in life to undertake with comfort any considerable public duty, and it might have seemed ungracious to have declined the office.”
On the 20th of January, 1847, Mr. William Wordsworth, the younger son of the poet, was married at Brighton, to Fanny Eliza Graham, youngest daughter of Reginald Graham, Esq., of Brighton, who was a native of Cumberland; and whilst the joy of this event was still fresh in the hearts of
the Rydal household, a dread calamity awaited them in the death of Mrs. Quillinan—the sweet Dora so often spoken of in these pages, the beloved daughter of the poet. As previously stated, she had accompanied her husband to Portugal for the benefit of her health,—and although the change seemed at first to have operated favourably upon her, it was soon evident, on her return home, that she was doomed for the silent bourne of all travellers in this world. She died on the 9th day of July, 1847, and was buried in Grasmere church-yard. Her death was a terrible blow to the venerable poet, now in his eightieth year,—but he bore up patiently, with the heart and hope of a Christian.
Three years after this sad loss, Wordsworth himself was summoned away. On Sunday, the 10th of March, 1850, he attended at Rydal chapel for the last time, visiting, during the day, a poor old woman, who had once been his servant, and another person who was sick, and as the poet said, “never complained.”
“On the afternoon of the following day, he went towards Grasmere, to meet his two nieces, who were coming from Town End. He called at the cottage near the White Moss Quarry, and the occupant being within, he sat down on the stone seat of the porch, to watch the setting sun. It was a cold, bright day. His friend and neighbour, Mr. Roughsedge, came to drink tea at Rydal, but Mr. Wordsworth not being well, went early to bed.”
From this time he gradually grew worse; and in order to convey to him the impressions of his physicians, Mrs. Wordsworth whispered in a soft voice, full of deep devotion, “Dear William, you are going to Dora.” How delicate, how affectionate, how poetical! But the poet did not hear, or did not seem to hear; and yet, twenty-four hours after, when one of his nieces came into the room, and gently drew aside the curtains of his bed, he caught a glimpse of her figure, and asked, “Is that Dora?”
On the 23rd of April—the birth-day, and death-day of Shakspeare, the great-hearted Wordsworth went back again to God.
He was buried on the 27th, in Grasmere church-yard.
Those who would know more of the poet must go to his writings; and, I may add, that the “Memoirs” of Dr. Wordsworth are indispensable to a full understanding both of the Poet and the Man. His letters, containing his most private thoughts, are printed there with plentiful profuseness; and the “Memoranda” respecting the origin of his poems are intensely interesting
and important to all students of Wordsworth. The reminiscences of various persons who knew him, set the character of the poet before us in strong relief. All agree in speaking of him as a most kindly, affectionate, and hospitable man, living with the simple tastes and manners of a patriarch, in his beautiful home. My limits prevent me from entering into an analysis of his mind and character, as I had intended to do; I must reserve this work, therefore, for another occasion, and will conclude with a few quotations from the poet’s “Table-Talk,” respecting his cotemporaries.—Speaking of Goethe, he says:—
“He does not seem to me to be a great poet in either of the classes of poets. At the head of the first I would place Homer and Shakspeare, whose universal minds are able to reach every variety of thought and feeling, without bringing his own individuality before the reader. They infuse, they breathe life into every object they approach, but you cannot find themselves. At the head of the second class, those whom you can trace individually in all they write, I would place Spenser and Milton. In all that Spenser writes, you can trace the gentle, affectionate spirit of the man; in all that Milton writes, you find the exalted, sustained being that he was. Now, in what Goethe writes, who aims to be of the first class, the universal, you find the man himself, the artificial man, where he should not be found; so that I consider him a very artificial writer, aiming to be universal, and yet constantly exposing his individuality, which his character was not of a kind to dignify. He had not sufficiently clear moral perceptions to make him anything but an artificial writer.
And again:—
“I have tried to read Goethe. I never could succeed. Mr.—— refers me to his ‘Iphigenia,’ but I there recognise none of the dignified simplicity, none of the health and vigour which the heroes and heroines of antiquity possess in the writings of Homer. The lines of Lucretius describing the immolation of Iphigenia are worth the whole of Goethe’s long poem. Again there is a profligacy, an inhuman sensuality, in his works, which is utterly revolting. I am not intimately acquainted with them generally. But I take up my ground on the first canto of ‘Wilhelm Meister;’ and as the attorney-general of human nature, I there indict him for wantonly outraging the sympathies of humanity. Theologians tell us of the degraded nature of man; and they tell us what is true. Yet man is essentially a moral agent, and there is that immortal and unextinguishable yearning for something pure and spiritual
which will plead against these poetical sensualists as long as man remains what he is.”
Of Scott he says:—
“As a poet, Scott cannot live, for he has never in verse written anything addressed to the immortal part of man. In making amusing stories in verse, he will be superseded by some newer versifier; what he writes in the way of natural description is merely rhyming nonsense. As a prose writer, Mr. Wordsworth admitted that Scott had touched a higher vein, because there he had really dealt with feeling and passion. As historical novels, professing to give the manners of a past time, he did not attach much value to those works of Scott’s, so called, because that he held to be an attempt in which success was impossibility. This led to some remarks on historical writing, from which it appeared that Mr. Wordsworth has small value for anything but contemporary history. He laments that Dr. Arnold should have spent so much of his time and powers in gathering up, and putting into imaginary shape, the scattered fragments of the history of Rome.”
And again:—
“He discoursed at great length on Scott’s works. His poetry he considered of that kind which will always be in demand, and that the supply will always meet it, suited to the age. He does not consider that it in any way goes below the surface of things; it does not reach to any intellectual or spiritual emotion; it is altogether superficial, and he felt it himself to be so. His descriptions are not true to nature; they are addressed to the ear, not to the mind. He was a master of bodily movements in his battle-scenes; but very little productive power was exerted in popular creations.”
Moore:—
“T. Moore has great natural genius; but he is too lavish of brilliant ornament. His poems smell of the perfumer’s and milliner’s shops. He is not content with a ring and a bracelet, but he must have rings in the ear, rings on the nose—rings everywhere.”
Shelley:—
“Shelley is one of the best artists of us all: I mean in workmanship of style.”
Tennyson:—
“I saw Tennyson, when I was in London, several times. He is decidedly the first of our living poets, and I hope will live to give the world still better things. You will be pleased to hear that he expressed in the strongest terms his gratitude to my writings. To this I was far from indifferent, though persuaded that he is not much in sympathy with what I should myself most value in my attempts—viz., the spirituality with which I have endeavoured to invest the material universe, and the moral relations under which I have wished to exhibit its most ordinary appearances.”
Hartley Coleridge—
He spoke of with affection. “There is a single line,” he added, “in one of his father’s poems, which I consider explains the after life of the son. He is speaking of his own confinement in London, and then says,—
‘But thou, my child, shalt wander like a breeze.’
“He thought highly also of some of Hartley’s sonnets. Southey—
He said had outlived his faculties. His mind he thought had been wrecked by long watching by the sick bed of his wife, who had lingered for years in a very distressing state.
Coleridge—
He said the liveliest and truest image he could give of Coleridge’s talk was that of “a mystic river, the sound or sight of whose course you caught at intervals, which was sometimes concealed by forests, sometimes lost in sand, and then came flashing out broad and distinct; then again took a turn which your eye could not follow, yet you knew and felt that it was the same river....[M] Coleridge had been spoilt as a poet by going to Germany. The bent of his mind, at all times very much inclined to metaphysical theology, had there been fixed in that direction.”
Lord Byron—
“Has spoken severely of my compositions. However faulty they may be, I do not think I ever could have prevailed with myself to print such lines as he has done, for instance—
‘I stood at Venice on the Bridge of Sighs, A palace and a prison on each hand.’
“Some person ought to write a critical review analising Lord Byron’s language, in order to guard others against imitating him in these respects.”
Emerson and Carlyle—
“Do you know Miss Peabody of Boston? She has just sent me, with the highest eulogy, certain essays of Mr. Emerson. Our—— and he appear to be what the French called esprits forts, though the French idols showed their spirit after a somewhat different fashion. Our two present Philosophes, who have taken a language which they suppose to be English, for their vehicle, are, verily, par nobile fratrum, and it is a pity that the weakness of our age has not left them exclusively to this appropriate reward—mutual admiration. Where is the thing which now passes for philosophy at Boston to stop?”
Such are a few random selections from the spoken opinions of the poet. He hated innovation, hence his attack upon the two last named authors, not made, I think, in the very best spirit. I must here leave him, however. He will stand well upon his honours in all future generations, and must certainly be ranked as a poet in the same category with Milton.
FINIS.
J. S. Pratt, Stokesley, Yorkshire.
FOOTNOTES:
[A] These remarks do not of course apply to Cowper and Burns, to whom our modern literature is so deeply indebted, but to their predecessors, from Pope downwards.
[B] Memoirs of William Wordsworth, by Dr. Wordsworth, vol. 1, page 7.
[C] De Quincy, Tait’s Magazine, for 1839.
[D] It is related by De Quincy, that during Wordsworth’s early residence in the lake country after his return from Cambridge his mind was so oppressed by the gloomy aspect of his fortunes, that evening card-playing was resorted to, to divert him from actual despondency.
[E] Dr. Wordsworth’s Memoir, page 53.
[F] Memoir, page 71-2.
[G] Chambers’ Papers for the People, article Wordsworth.
[H] Vol 1, page 149 to 154
[I] Memoirs, Vol. 1., page 156
[J] Dr. Wordsworth’s “Memoirs,” vol. 2, p. 94.
[K] “Memoirs,” vol 2, p 102-105
[L] Memoirs, vol. ii., p. 121.
[M] This view of Coleridge is confirmed by Carlyle, in his “Life of John Sterling,” just published
“Coleridge sat on the brow of Highgate-hill, in those years, looking down on London and its smoke tumult, like a sage escaped from the inanity of life’s battle; attracting towards him the thoughts of innumerable brave souls still engaged there. His express contributions to poetry, philosophy, or any specific province of human literature or enlightenment, had been small and sadly intermittent; but he had, especially among young inquiring men, a higher than literary, a kind of prophetic, or magician character. He was thought to hold, he alone in England, the key of German and other transcendentalisms; knew the sublime secret of believing by ‘the reason’ what ‘the understanding’ had been obliged to fling out as incredible; and could still, after Hume and Voltaire had done their best and worst with him, profess himself an orthodox Christian, and say and point to the Church of England, with its singular old rubrics and surplices at Allhallowtide, Esto perpetua. * * * * He distinguished himself to all that ever heard him as at least the most surprising talker extant in this world, and to some small minority, (by no means to all,) the most excellent The good man, he was now getting old, towards sixty perhaps, and gave you the idea of a life that had been full of sufferings; a life heavy-laden, halfvanquished, still swimming painfully in seas of manifold physical and other bewilderment. * * * * * I still recollect his ‘object’ and ‘subject,’ terms of continual recurrence in the Kantean province; and how he sung and snuffled them into ‘om-mmject’ ‘sum-m-mject,’ with a kind of solemn shake or quaver, as he rolled along. No talk, in his century or in any other, could be more surprising. * * * * *
“He had knowledge about many things and topics, much curious reading; but generally all topics led him, after a pass or two, into the high seas of theosophic philosophy, the hazy infinitude of Kantean transcendentalism, with its ‘sum-mmjects’ and ‘om m-mjects ’ Sad enough, for with such indolent impatience of the claims and ignorances of others, he had not the least talent for explaining this or anything unknown to them; and you swam and fluttered in the mistiest, wide, unintelligible deluge of things, for most part in a rather profitless, uncomfortable manner. Glorious islets, too, I have seen rise out of the haze; but they were few, and soon swallowed in the general element again. * * * * * * One right peal of concrete laughter at some convicted flesh-and-blood absurdity, one burst of noble indignation
at some injustice or depravity rubbing elbows with us on this solid earth, how strange would it have been in that Kantean haze-world, and how infinitely cheering amid its vacant air-castles, and dim-melting ghosts and shadows! None such ever came. His life had been an abstract thinking and dreaming, idealistic one, passed amid the ghosts of defunct bodies and of unborn ones. The mourning sing-song of that theosophico-metaphysical monotony left on you, at last, a very dreary feeling.”
