Polymers for Micropollutants Removal from Wastewater

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(1)Pol ymer sf orMi cr opol l ut ant sRemovalf r om Wast ewat er MohamadFai zbi nMohdAmi n. I SBN/ EAN 9789461089601. Pol ymer sf orMi cr opol l ut ant s Removalf r om Wast ewat er MohamadFai zbi nMohdAmi n.

(2) Polymers for Micropollutants Removal from Wastewater. Mohamad Faiz bin Mohd Amin.

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(4) Polymers for Micropollutants Removal from Wastewater. Proefschrift. ter verkrijging van de graad van doctor aan de Technische Universiteit Delft, op gezag van de Rector Magnificus prof. ir. K.C.A.M. Luyben, voorzitter van het College voor Promoties, in het openbaar te verdedigen op 07, April, 2015 om 10:00 Door Mohamad Faiz Bin MOHD AMIN Master of Science in Bioscience, Universiti Teknologi Malaysia, Malaysia geboren te Perak, Malaysia.

(5) Dit proefschrift is goedgekeurd door de promotor: Prof. dr. ir. L.C. Rietveld Samenstelling promotiecommissie: Rector Magnificus Prof. dr. ir. L.C. Rietveld Dr.ir. S.G.J Heijmann Prof.dr. M.R. Salim Dr. R. Steen Ir. P. Versteeg Prof.dr.ir. A. Verliefde Prof.dr.ir. J.B. van Lier Prof. dr. ir. J.P. van der Hoek. voorzitter Technische Universiteit Delft, promotor Technische Universiteit Delft, co-promotor Universiti Teknologi Malaysia, Malaysia Het Waterlaboratorium Hoogheemraadschap van Rijnland Ghent University, Belgium Technische Universiteit Delft Technische Universiteit Delft, reservelid. The research reported in this thesis is supported by the collaborative OPTIMIX research project (Waterboard Rijnland (the Netherlands), Agentschap (the Netherlands), Nalco Netherlands B.V and Delft University of Technology). The candidate supported by the scholarship from the Ministry of Education Malaysia and Universiti Malaysia Kelantan.. © 2015 by Mohamad Faiz bin Mohd Amin Email: mfaizamin@gmail.com mohamadfaiz@umk.edu.my ISBN/EAN: 9789461089601 Printed by : Gildeprint Cover design by: Azrol Kassim An electronic version of this dissertation is available at http://repository.tudelft.nl/ All rights reserved. No part of the material protected by this copyright notice may be reproduced or utilised in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without the prior permission of the author..

(6) For the trusts given to me….

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(8) Table of Contents CHAPTER 1. 1. INTRODUCTION 1.1.1 MICROPOLLUTANTS IN WATER 1.1.2 MICROPOLLUTANTS IN WASTEWATER TREATMENT 1.2 OBJECTIVE OF THE RESEARCH 1.3 THESIS OUTLINE REFERENCE. 1 1 2 3 4 4. CHAPTER 2. 7. 2.1 INTRODUCTION 2.2 INTERACTIONS OF PHARMACEUTICALS IN THE WATER MATRIX 2.2.1 SORPTION OF PHARMACEUTICALS ONTO PARTICLES 2.2.2 HUMIC ACIDS COMPLEXES WITH PHARMACEUTICALS 2.2.3 ADSORPTION OF PHARMACEUTICALS ONTO ADSORBENTS 2.2.4 PHARMACEUTICALS REMOVAL FROM WASTEWATER BY COAGULATION AND. 8 9 10 11 12. FLOCCULATION 2.3 POLYMER MECHANISMS OF ACTIONS 2.3.1 DIRECT ADSORPTION OF PHARMACEUTICALS ONTO POLYMERS 2.3.2 POLYMER INTERACTION WITH PARTICLES 2.3.3 POLYMER INTERACTION WITH HUMIC ACIDS 2.4 HYBRID PHARMACEUTICALS REMOVAL 2.4.1 COMBINATION OF POLYMERS WITH ACTIVATED CARBON 2.4.2 COMBINATION WITH CLAY 2.5 CONCLUSIONS REFERENCES. 13 15 15 15 16 18 18 18 19 21. CHAPTER 3. 27. 3.1 INTRODUCTION 3.2 MATERIALS AND METHODS 3.2.1 POLYMER SCREENING AND SELECTION 3.2.2 THE TESTED WASTEWATER 3.2.3 JAR TEST EXPERIMENTS 3.2.4 UV254 AND TURBIDITY REMOVAL 3.2.5 REMOVAL OF OTHER PARAMETERS 3.3 RESULTS AND DISCUSSION 3.3.1 TURBIDITY REMOVAL 3.3.2 UV254 REMOVAL 3.3.4 REMOVAL OF OTHER PARAMETERS 3.4 CONCLUSIONS REFERENCES. 28 29 29 30 31 32 32 32 32 33 34 35 35. CHAPTER 4. 37. 4.1 INTRODUCTION 4.2 MATERIALS AND METHODS 4.2.1 MATERIALS 4.2.2 ADSORPTION STUDIES 4.2.3 SURFACE TO VOLUME RATIO EFFECT (SVR) 4.2.4 POLYMER ADSORPTION 4.2.5 ANALYTICAL METHOD 4.3 RESULTS AND DISCUSSION 4.3.1 ADSORPTION STUDIES. 38 39 39 39 39 40 40 41 41. i.

(9) 4.3.2 SURFACE TO VOLUME RATIO EFFECT (SVR) 4.3.3 POLYMER ADSORPTION 4.4 CONCLUSIONS REFERENCES. 42 44 46 46. CHAPTER 5. 51. 5.1 INTRODUCTION 5.2 MATERIALS AND METHODS 5.2.1 CLAY SELECTION AND OPTIMISATION 5.2.2 CLAY FLOCCULATION WITH CATIONIC STARCH 5.2.3 SME-CS: ATRAZINE REMOVAL, FLOCCULANT DOSAGE AND TURBIDITY RELATION 5.2.4 ANALYTICAL METHODS 5.3 RESULTS AND DISCUSSION 5.3.1 CLAY SELECTION AND MAXIMISING THE ADSORPTION OF ATRAZINE ON CLAY 5.3.2 CLAY FLOCCULATION WITH CATIONIC STARCH 5.3.3 SME-CS: ATRAZINE REDUCTION, FLOCCULATION AND TURBIDITY RELATION 5.4 CONCLUSIONS REFERENCES. 52 53 54 54 54 56 56 56 57 59 60 61. CHAPTER 6. 63. 6.1 INTRODUCTION 6.2 MATERIALS AND METHODS 6.2.1 WASTEWATER 6.2.2 COMPOUNDS 6.2.3 ATRAZINE AND PHARMACEUTICAL REMOVAL BY CLAY FLOCCULATION WITH. 64 66 66 67. CATIONIC STARCH 6.2.4 ANALYTICAL METHODS 6.3 RESULTS AND DISCUSSION 6.3.1 CONCENTRATIONS OF PHARMACEUTICALS IN THE SECONDARY CLARIFIER 6.3.2 ATRAZINE REMOVAL 6.3.3 EFFECT OF SME WITH AND WITHOUT CS DOSAGE ON PHARMACEUTICAL REMOVAL 6.3.4 WASTEWATER PHARMACEUTICAL REMOVAL 6.4 CONCLUSION REFERENCES. 68 68 69 69 70 71 71 73 74. CHAPTER 7. 79. 7.1 GENERAL CONCLUSIONS POLYMERS FOR PHARMACEUTICAL REMOVAL ENHANCING SURFACE AVAILABILITY FOR POLYMER ATTACHMENT AIMED AT. 79 79. PHARMACEUTICAL REMOVAL 7.2 OVERALL CONCLUSIONS 7.3 RECOMMENDATIONS. 80 81 81. LIST OF ABBREVIATIONS. 83. SUMMARY. 84. SAMENVATTTING. 86. LIST OF PUBLICATIONS. 88. ACKNOWLEDGEMENT. 90. ABOUT THE AUTHOR. 91. ii.

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(12) Chapter 1 Introduction 1.1.1. Micropollutants in water. Recent studies have indicated that micropollutants are frequently present in the water environment at concentrations in the µg/L to ng/L range. Micropollutants especially the pharmaceuticals are considered to be a potential threat to environmental ecosystems (Loos et al., 2009; Virkutyte et al., 2010). The way that these compounds enter the environment depends on their use and the mode of application (Figure 1.1). The major routes for entry appear to be the discharges from municipal and industrial wastewater plants, sludge disposal and accidental spills (Mompelat et al., 2009). The wastewater treatment plant (WTTP) is viewed as the most important first line micropollutant removal step in the water cycle to limit the concentrations in the environment.. Figure 1.1 Micropollutants in the urban water cycle Once released into the environment, micropollutants are subjected to different processes, such as the distribution between different phases (solid, liquid, gas) and biological and abiotic degradation (Heberer, 2002). These processes contribute to their removal from the environment and hence affect their bioavailability. The role of the above-mentioned processes on the fate of micropollutants depends on the 1.

(13) physical-chemical properties of these compounds and the environment where the compounds are present (Virkutyte et al., 2010). Current information on the occurrence of micropollutants in the environment is usually limited to the original compound. Nevertheless, the discharge of the metabolites or by-products of some micropollutants might also occur, and these by–products may even be present in higher concentrations than the original compound (Miao and Metcalfe, 2003). Despite the release of micropollutants especially the pharmaceuticals into the environment, there are not many regulations for the ecological risk assessment regarding such releases (Virkutyte et al., 2010). For example, in the USA, environmental assessment of veterinary pharmaceuticals is required by the U.S. Food and Drug Administration (FDA) since 1980 (Boxall, 2003). With respect to human pharmaceuticals, environmental assessment reports should be provided in the cases where the expected concentration of the active ingredient of the pharmaceuticals in the aquatic environment is expected to be equal to or greater than 1 µg/L (FDACDER-CBER, 1998). In the Netherlands, several reports regarding the presence of pharmaceuticals in water bodies have been produced since the year 2000, primarily with a focus on drinking water (Van der Aa et al., 2008) and less on wastewater. The occurrence of pharmaceuticals in surface water and wastewater across the Netherlands are reported by the Institute for Inland Water Management and Wastewater (Schrap et al., 2003). All European countries are still subject to the, by the European Commission published, Directive 2001/83/EC, amended by Directive 2004/27/EC (for human pharmaceuticals), and Directive 2001/82/EC, amended by 2004/28/EC (for veterinary pharmaceuticals), with respect to regulating the presence of pharmaceuticals in water bodies. There are rare cases where there have been limiting values set for the presence of certain pharmaceuticals in the aquatic environment. 1.1.2. Micropollutants in wastewater treatment. There are several study available reporting on micropollutants especially pharmaceuticals treatments, measurements and monitoring in WWTP’s (Carballa et al., 2008; Heberer, 2002; Stumpf et al., 1999; Ternes, 1998). However, it can be suggested that current conventional wastewater treatments can be upgraded to improve the removal of micropollutants (Carballa et al., 2008; Heberer, 2002; Stumpf et al., 1999; Ternes, 1998). A possible solution can be the introduction of advanced flocculation or “hybrid-flocculation” processes in the treatment plant. The use of polymers in treating wastewater may have advantages over the use of metal coagulants, such as low dosage requirement and a denser sludge production, leading towards a more cost-effective treatment (Bolto and Gregory, 2007; Van Nieuwenhuijzen, 2002). The use of polymeric flocculants during treatment can thus be a two-pronged approach; upgrading the micropollutants removal while enhancing. 2.

(14) the effluent quality and reducing the costs by 25-30% compared to dosing of metal coagulants (Nozaic et al., 2001; Rout et al., 1999). Combination of polymer with conventional adsorbents could be potentially beneficial in micropollutants removal. Although some combinations have been implemented, few reports are available on their effectiveness in micropollutants’ removal from wastewater (Loureiro and Kartel, 2006). The use of natural and/or biodegradable components such as clays and polysaccharide-based polymers could further improve sustainability.. 1.2. Objective of the research. The main objective of the research is to optimise the removal of the micropollutants from wastewater using polymers in combination with clay as adsorbent. The clay is naturally abundant and relatively inexpensive, compared to currently used conventional adsorbents, like activated carbon. The usage of clay is hypothesised to provide a sufficiently large surface area for micropollutants adsorption, and polymer attachment enhancing this adsorption. The objectives of the research can be summarised as follows: i. ii. iii. iv.. Selection of a suitable polymer for the purpose. Investigating the ability and the mechanisms involved in the micropollutants removal by polymers, clay and clay-polymer combination. Development of a multi-purpose method that is suitable for both suspended solids and micropollutants removal from wastewater. Application of the developed method for micropollutants removal in wastewater.. In order to achieve the aforementioned objectives, the research is divided into four stages as shown in Figure 1.2:.

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(39) 1.3. Thesis outline. Chapter 2 starts with a review on the potential use of polymers in the removal of pharmaceuticals from wastewater. The review focuses on pharmaceuticals interaction with the water matrix; interaction with polymers and interaction with hybrid polymeradsorbent material. Current conventional treatment performance has also been reviewed. Chapter 3 describes the characterisation of two polymers: a synthetic and a biodegradable. Both polymers have been selected from a list of 21 different polymers for the purpose of micropollutants specifically pharmaceuticals removal. In this chapter both polymers are tested for its ability in wastewater on turbidity, UV254, phosphate and COD removal. Chapter 4 is a continuation of previous chapter that focuses on the ability of polymers in pharmaceuticals removal. In this chapter, atrazine is used as a model compound for removal from demineralised water. Chapter 5 discusses the combination of clays and polymers for atrazine removal. The chapter starts with clays selection and optimisation of the best-performing clays in atrazine removal. The best-performing clays are then combined with polymers in the flocculation process. The optimised dosage of clay and polymer has also been discussed. Chapter 6 used the developed clay-polymer method in chapter 5 for the removal of pharmaceuticals that are present in the actual wastewater. Atrazine has also been spiked to act as a reference compound for performance comparison between difference water matrices. Chapter 7 contains the general conclusions and recommendations of this research.. Reference Bolto, B., Gregory, J., 2007. Organic polyelectrolytes in water treatment. Water Res. 41, 2301–2324. Boxall, A., 2003. Peer Reviewed: Are Veterinary Medicines Causing Environmental Risks? Environ. Sci. Technol. 37, 286–294. Carballa, M., Fink, G., Omil, F., Lema, J.M., Ternes, T., 2008. Determination of the solid-water distribution coefficient (Kd) for pharmaceuticals, estrogens and musk fragrances in digested sludge. Water Res. 42, 287–295.. 4.

(40) FDA-CDER-CBER, 1998. Guidance for Industry Guidance for Industry Environmental Assessment of Human. Rockville. Heberer, T., 2002. Occurrence, fate, and removal of pharmaceutical residues in the aquatic environment: a review of recent research data. Toxicol. Lett. 131, 5–17. Loos, R., Gawlik, B.M., Locoro, G., Rimaviciute, E., Contini, S., Bidoglio, G., 2009. EU-wide survey of polar organic persistent pollutants in European river waters. Environ. Pollut. 157, 561–568. Loureiro, J., Kartel, M., 2006. Combined and hybrid adsorbents: fundamentals and applications, Vasa. Springer Netherlands, Dordrecht. Miao, X.-S., Metcalfe, C.D., 2003. Determination of carbamazepine and its metabolites in aqueous samples using liquid chromatography-electrospray tandem mass spectrometry. Anal. Chem. 75, 3731–3738. Mompelat, S., Le Bot, B., Thomas, O., 2009. Occurrence and fate of pharmaceutical products and by-products, from resource to drinking water. Environ. Int. 35, 803–814. Nieuwenhuijzen, A.F. Van, 2002. Scenario Studies into Advanced Particle Removal in the Physical-Chemical Pre-treatment of Wastewater. Delft University of Technology, Netherlands. Nozaic, D.J., Freese, S.D., Thompson, P., 2001. Longterm experience in the use of polymeric coagulants at Umgeni Water. Water Sci. Technol. Water Supply 1, 43–50. Rout, D., Verma, R., Agarwal, S., 1999. Polyelectrolyte treatment ? An approach for water quality improvement. Water Sci. Technol. 40, 137–141. Schrap, S.M., Rijs, G.B.J., Beek, M.A., Maaskant, J.F.N., Staeb, J., Stroomberg, G., Tiesnitsch, J., 2003. Humane en veterinaire geneesmiddelen in Nederlands oppervlaktewater en afvalwater. Lelystad. Stumpf, M., Ternes, T. a, Wilken, R.D., Rodrigues, S. V, Baumann, W., 1999. Polar drug residues in sewage and natural waters in the state of Rio de Janeiro, Brazil. Sci. Total Environ. 225, 135–141. Ternes, T. a, 1998. Occurrence of drugs in German sewage treatment plants and rivers. Water Res. 32, 3245–3260. Van der Aa, N.G.F.M., Kommer, G.J., Groot, G.M. de, Versteegh, J.F.M., 2008. Geneesmiddelen in bronnen voor drinkwater, Monitoring, …. Bilthoven. Virkutyte, J., Varma, R.S., Jegatheesan, V., 2010. Treatment of Micropollutants in Water and Wastewater Treatment of Micropollutants in Water and Wastewater, Current. IWA Publishing, London, UK.. 5.

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(42) Chapter 2. The potential use of polymer flocculants for pharmaceuticals removal in wastewater treatment. The appearance of pharmaceuticals in wastewater has become a significant concern to both the water treatment industry as well as consumers. The availability of advanced treatment methods has optimised the removal of these compounds present in wastewater sources. The latest development in polymers as flocculants and combining it with other treatment helps to reduce the quantities of these pharmaceuticals in the final wastewater effluent. This paper gives an insight on the potential usage of polymer flocculants and its combination with particles, organic substances and conventional adsorbents towards removing pharmaceutical compounds from wastewater. Polymer flocculants alone will have a limited ability in pharmaceuticals removal. The flocculation process combination with adsorption on natural components and particles is always necessary. Interaction of polymers with adsorbents in the wastewater could also play an important role in their removal by polymer flocculants due to its proven implementation. An understanding of the changes in processes and mechanisms involving the polymers is essential for achieving effective removal. Combination of polymer flocculants with conventional adsorbents such as carbon and clays during the treatment process could lead to a new effective and economic approach in removal of the pharmaceutical compound.. This chapter is based on: Mohd Amin, M.F., Heijman, S.G.J., Rietveld, L.C., 2014. The potential use of polymer flocculants for pharmaceuticals removal in wastewater treatment. Environ. Technol. Rev. 1–10.. 7.

(43) 2.1. Introduction. The appearance of pharmaceuticals in wastewater has become a significant concern to both the water treatment industry as well as consumers. The availability of advanced treatment methods has optimised the removal of these compounds present in wastewater sources. The latest development in polymers as flocculants and combining it with other treatments helps to reduce the quantities of these pharmaceuticals in the final wastewater effluent. This chapter gives an insight on potential usage of polymers and its combination with particles, organic substances and conventional adsorbents towards removing pharmaceutical compounds from wastewater. Pharmaceuticals interaction with adsorbents in the wastewater plays an important role in its removal by polymers due to its proven implementation. An understanding of the changes in processes and mechanisms involving the polymers is essential for achieving effective removal. Combination of polymers with conventional adsorbents such as carbon and clays during the treatment process could lead towards new effective and economic approach in removal of the pharmaceutical compound. Pharmaceuticals are complex molecules with molecular weights (MW) ranging from 200 to 1000 Dalton. These compounds are developed and used for their specific biological activities (Kümmerer, 2009). Non-steroidal anti-inflammatory drugs, anticonvulsants, lipid regulators and antibiotics are groups of pharmaceuticals that are often detected in aquatic environments. Typical representatives of non-steroidal antiinflammatory drugs are ibuprofen and diclofenac. Anticonvulsants are used in the treatment of epileptic seizures, and carbamazepine is the compound that is most often reported. It is estimated that approximately 1000 tons per year of carbamazepine is consumed worldwide (Zhang et al., 2008). Lipid regulators such as gemfibrozil are used to lower lipid levels. Finally, antibiotics are characterised by a high variety of substances such as penicillin, tetracycline, sulphonamides and fluoroquinolones. The presence of pharmaceuticals in the sources of contamination, such as wastewater treatment plant effluent (WWTP-eff) (human drugs) and animal farming (veterinary substances), is reduced to trace levels (µg/L to ng/L) after mixing with surface waters (Osenbrück et al., 2007). Pharmaceuticals may also undergo biotic, chemical and physical-chemical transformations in the water, even though pharmaceuticals are designed to resist microbial degradations and are chemically stable (Mompelat et al., 2009). The current concern in detecting pharmaceuticals in receiving waters may call for new approaches in wastewater treatment. WWTP are designed to deal with bulk substances that arrive regularly and in large quantities, which primarily include organic substances, and the nutrients nitrogen and phosphorus. Pharmaceuticals are single compounds with a unique behaviour in the treatment plant, and they represent only a minor part of the organic load on the WWTP (Larsen et al., 2004).. 8.

(44) The structure of these pharmaceuticals can influence their fate in wastewater treatment. A compound with an uncomplicated chemical structure can be easily biodegraded during wastewater treatment while pharmaceuticals with complex structures are likely to persist as parent compounds or as partially degraded compounds. The molecular structure of most compounds often includes two aromatic rings, which increases the resistance of such compounds to degradation processes (Cirja et al., 2007). Compounds such as diclofenac and diazepam are examples of molecules containing chlorine groups and are not efficiently removed by conventional WWTP processes (Cirja et al., 2007). The recalcitrance of these pharmaceuticals was attributed to the presence of halogen groups in their structure (Cirja et al., 2007). Current conventional wastewater treatments can be upgraded to improve the removal of pharmaceuticals (Carballa et al., 2008; Heberer, 2002; Stumpf et al., 1999; Ternes, 1998). A possible solution can be the introduction of advanced flocculation processes in the WWTP. The use of polymers in treating wastewater may have advantages over the use of metal coagulants, such as low dosage requirement and a denser sludge production, leading towards a more cost-effective treatment (Bolto and Gregory, 2007; Van Nieuwenhuijzen, 2002). The use of polymeric flocculants during treatment can thus be a two-pronged approach; upgrading the pharmaceuticals’ removal while enhancing the effluent quality and reducing the costs by 25-30% compared to dosing of metal coagulants (Nozaic et al., 2001; Rout et al., 1999). This chapter aims at emphasising the potential use of polymers in optimising pharmaceuticals’ removal during wastewater treatment. This chapter also intent in evaluating the potential removal pathways and its limitations in order to achieve optimal pharmaceuticals’ removal. The understanding of pharmaceuticals’ behaviour in the water and the flocculation mechanisms are important in predicting the overall treatment performance. Focus is also given to the polymer’s abilities to remove pharmaceuticals adsorbing components such as particles, humic acids and conventional adsorbents. Finally, at the end of the paper, the different pathways of removal are discussed, indicating the potential for removal of pharmaceuticals from wastewater.. 2.2. Interactions of pharmaceuticals in the water matrix. The fate of the compounds and their reactions in the water matrix have to be first understood in order to determine the removal mechanisms of pharmaceuticals by polymers from wastewater. As reported by Carballa et al. (2005) and Ternes et al. (2004), various types of pharmaceuticals are expected to undergo sorption onto particles that are present in wastewater. Thus, a significant part of the contaminants in wastewater is associated with particles and, consequently, a significant contaminant reduction may be expected as a result of particle elimination (Carballa et al., 2004). Rebhun et al. (1998) reported that pharmaceuticals also interact with natural organic 9.

(45) substances in wastewater. However, the interaction is not much reported by other researchers. 2.2.1. Sorption of pharmaceuticals onto particles. The sorption of pharmaceuticals onto particulate matter can be an important removal mechanism in WWTP. Under equilibrium conditions, the concentration of the pharmaceuticals sorbed onto the sludge is assumed to be related to the concentration in solution (Ternes et al., 2004). Sorption equilibrium is reached when the rate of sorption onto the solid phase is equal to the rate of desorption into the liquid phase. In wastewater treatment, diffusion is fast in comparison to the hydraulic retention time, and hence, solid-liquid partitioning can be assumed to be at equilibrium (Wang and Jr, 1995). This is in good agreement with the sorption experiments described by Ternes et al. (2004). Generally, hydrophobicity is the main property of a pharmaceutical that determines its removal effectiveness in the aquatic environment (Yu and Huang, 2005). The octanolwater partitioning coefficient (Kow) and the distribution coefficient (Kd) influence the sorption of pharmaceuticals onto particulate matter. The Kow value of an organic substance corresponds to its partitioning equilibrium between the organic phase and the liquid phase. The Kd value is used to describe the solid-liquid partitioning characteristics of the pharmaceutical compound and is dependent on the pH of the matrix (de Ridder et al., 2010; Ternes et al., 2004). The sorption of a pharmaceutical onto sludge as given by its Kd value, as is shown in equation 1, has been found to be strongly related to the properties of the sludge and the compound under consideration (Warren et al., 2003). Kd (L/Kg)= Cs/Cw. eq. 1. where, Cs: concentration of pharmaceutical in the sediments or sludge [µg/Kg] Cw: concentration of pharmaceutical in dissolved phase [µg/L] Kd values can vary over orders of magnitude depending on the type of sludge. For instance, Ternes et al. (2004) reported that the Kd values range from 1-500 L/Kg. While in Carballa et al. (2008), observed values from 2-10500 L/Kg, depending on the pharmaceutical properties and the sludge type that they were in. This variation is found to be caused by differences in the organic carbon content of the different sediments. As long as the organic carbon content is above a certain threshold level (Schwarzenbach et al., 2006). Therefore, the extent of sorption is often described in. 10.

(46) terms of the normalised partition coefficient with respect to organic carbon, which is also known as the Koc value, shown in equation 2. Koc (mL/g)=Kd/foc. eq. 2. Where, foc: the organic carbon weight fraction in the sediments or sludge (total organic carbon(TOC)/ total suspended solids (TSS)) [g/g]. The sorption of hydrophobic compounds is analogous to the adsorption of hydrophobic compounds from an aqueous phase into an organic solvent phase (Warren et al., 2003). Hydrophobic compounds are characterised by high log Kow values, greater than 4.0, which indicate poor water solubility and a high tendency to sorb onto the organic material of the sludge matrix (Stangroom et al., 2000; Yoon and Westerhoff, 2004). Pharmaceuticals with low log Kow values are characterised by a low hydrophobicity, and their sorption to sludge is not expected to contribute significantly to their removal via excess sludge withdrawal. Moderate sorption is expected for pharmaceuticals with log Kow values between 2.5 and 4. De Ridder et al. (2009) reported the log Kow values of 23 pharmaceuticals ranging from 0.24-4.77; with the lowest value for atenolol (0.24) and the highest for gemfibrozil (4.77). There is a strong correlation observed between the Koc value and the octanol-water partition coefficient Kow, being of the form (Warren et al., 2003): Log (Koc) = a Log (Kow) – y. eq. 3. Thus, it should theoretically be possible to predict Kd values from the octanol-water partition coefficients and the fractional organic carbon content found in sediments. 2.2.2. Humic acids complexes with pharmaceuticals. Humic acids are dissolved organic substances that are abundant in aquatic systems. Humic acids have been reported to bind pharmaceuticals via hydrophobic interactions, forming humic-pharmaceutical complexes in the aqueous phase (Rebhun et al., 1998). Hydrophobic sites on both the aliphatic and aromatic side chains of the humic molecules, especially the sites on the aromatic side chains, are responsible for the association occurring between humic acids and pharmaceuticals. The complexation of hydrophobic organic compounds has been investigated and described in several papers (Chiou et al., 1986; Rav-Acha and Rebhun, 1992; Rebhun et al., 1998). Complexation is commonly considered to be a liquid-liquid partitioning process, as evidenced by the observed isotherm linearity, the absence of competition in multi-. 11.

(47) solute systems, and the good relationships between the binding coefficients (Kb(oc)) and octanol-water partition coefficients (Kow). Rebhun et al. (1998) recorded Kb(oc) values, as defined in equation 4, of 5.08 x10-3, 5.06 x10-3 and 4.74 x10-3 L/Kg for pyrene, fluoranthene and anthracene respectively. Kb(oc) = Cbound/ Cfree [OCDHS]. eq.4. where, Cbound : concentration of the bound pollutants [µg /mL] : concentration of the unbound pollutants [µg /mL] Cfree [OCDHS]: concentration of the humic substances in terms of organic carbon [g/mL] 2.2.3. Adsorption of pharmaceuticals onto adsorbents. Activated Carbon Activated carbon can remove a broad spectrum of pharmaceuticals via adsorption because of its high specific surface area and, therefore, it is widely used in water treatment (Margot et al., 2013; Matamoros et al., 2009; Rossner et al., 2009; Snyder et al., 2009, 2003). With a dosage of 10-20 mg/L, powdered activated carbon is viewed as a more efficient option than the usage of granular activated carbon (Margot et al., 2013; Snyder et al., 2009; Thuy et al., 2008). However, only a few large-scale studies, evaluating the efficiency of pharmaceuticals’ removal via powdered activated carbon treatment in municipal wastewater, have been reported (Joss et al., 2008; Margot et al., 2013; Matamoros et al., 2009; Yoon et al., 2010). Other organic substances, present in wastewater, can compete for adsorption sites, influencing its efficiency for pharmaceutical removal (Margot et al., 2013; Rossner et al., 2009). Clay Clay minerals are aluminosilicates and believed to play important roles in environmental processes, mainly transporting pollutants in the air, water, soil and/or sediments (Liu et al., 2011). These natural materials possess layered structures, large surface areas and a high cation exchange capacity (Liu et al., 2011). Clay minerals may provide promising and economical applications for adsorption systems (Churchman and Gates, 2006). The removal of organic pollutants, such as dyes (Zhao et al., 2013), phenolic pollutants (Radian and Mishael, 2012), pesticides (Churchman and Gates, 2006), and pharmaceuticals (Drillia et al., 2005; Xu et al., 2009) has been reported. Avisar et al. (Avisar et al., 2009) investigated the sorption of sulfadimethoxine, sulfamethoxazole, tetracyclines, and oxytetracycline to sodium rich montmorillonite clay in synthetic effluent and wastewater effluent. In the study, both sulfadimethoxine, sulfamethoxazole showed a low sorption capacity, around 10% to 1.8 g/L clay, while the sorption of tetracyclines to clay showed a high 12.

(48) adsorption capacity (90% to 1.8 g/L clay). The differences in sorption capacities of tetracyclines and oxytetracycline in synthetic effluent and wastewater effluent, respectively, were attributed to the various concentrations of divalent cations in the effluent and their different molecular structures (Avisar et al., 2009). 2.2.4 Pharmaceuticals removal from wastewater by coagulation and flocculation In WWTP, the removal of pharmaceuticals such as diazepam, diclofenac, ibuprofen, naproxen, and sulfamethoxazole was suggested to be mainly due to the sorption of those compounds to sludge (Carballa et al., 2004) as shown in Table 2.1. The sorption was even more evident during the primary treatment process, which targets fat separation, where the lipophilic properties of these organic pollutants led to removal percentages ranging from 20 to 50%. Carballa et al. ( 2005) studied the removal of pharmaceuticals using several types of coagulants. They reported no significant influence of the coagulant dosage effect on the removal of pharmaceuticals, even at dosages of 250–350 mg/L for ferric chloride (FeCl3), 250–350 mg/L for aluminium sulphate (Al2(SO4)3), and 700–950 mg/L polyaluminium chloride at temperatures of 12 and 25°C. However, the removal efficiencies of specific pharmaceuticals were influenced by the coagulant used and pharmaceutical Kd value. When using higher dosages of poly-aluminium chloride (850 mg/L at 25°C) 50-70% of diclofenac could be removed, while the removal of diazepam and naproxen removals was less than 10%, due to the low Kd values of these compounds. Suarez et al. (2009) concluded from the treatment of hospital wastewater that, using two types of coagulants (25 mg/L of FeCl3 and 25 mg/L Al2(SO4)3), the maximum removal for diclofenac, naproxen and ibuprofen were 46%, 42%, and 23%, respectively. These low removal efficiencies were explained in relation to the expected low sorption tendency of these compounds to primary sludge. Their Kd values were reported to be less than 44 L/Kg (Ternes et al., 2004).. 13.

(49) 1. 194.1. Others Caffeine. -0.63. -1.09 1.69 0.35. 10.85. 1.0 12.71 1.0. 255.8. -0.07. 4.25 4.77 4.51. 2.45. 0.38. 10.4. 3.44 4.45 3.0. n.a.. 1.4. n.a.. n.a. n.a. n.a.. n.a. 25 FeCl3. n.a. 250 FeCl3 ; 300 Al2(SO4)3 25 FeCl3 n.a. n.a. 250 FeCl3 25 FeCl3 n.a.. 5: Jar test of hospital wastewater, Spain. 361.8 250.3 318.7. Lipid regulator Bezafibrate Gemfibrozil Fenofibric acid. 1.9. 41.4. 4.29 4.15 n.a.. 4.47. 4: Jar test of STP wastewater, Spain. 236.3. Anti-epileptic Carbamazepine. 0.44. 2.58. 0.35. 3.12 3.9. 3.97. n.a. n.a. 250 FeCl3 25 FeCl3. Coagulant /Flocculant dosage (mg/L). n.a: not acquired. 188.2. Phenazone. 1.0. -0.16. 2.3. 3.6 4.15. pKa. *: ACD/Labs’ ACD/PhysChem Suite, www.chemspider.com. 254.3 242.2. Ketoprofen Naproxen. 0.58. 1.28 4.51. LogKow. 3: Conventional STP across Brazil. 206.3. Ibuprofen. 1.0 5.5. pH7.4. pH7.4. -1.68 1.44. Koc*. LogD*. 1 and 2: Conventional STP across Germany. 180.1 296.2. Analgesic Aspirin Diclofenac. MW. >99. 27–83 16–69 6–64. 7–8 <45. 48–69 15–66 3-20 9-42 33. >90 0 7-23. 81-88 69–98 50-70 <46. Removal (%). (Heberer, 2002)1 (Suarez et al., 2009)5. (Stumpf et al., 1999)3 (Ternes, 1998)2, (Carballa et al., 2005)4 (Suarez et al., 2009)5 (Ternes, 1998)2. (Heberer, 2002)1 (Heberer, 2002)1 (Ternes, 1998)2, (Carballa et al., 2005)4 (Suarez et al., 2009)5 (Ternes, 1998)2; (Stumpf et al., 1999)3, (Carballa et al., 2005)4 (Suarez et al., 2009)5. Reference. (Heberer, 2002)1. (Ternes, 1998)2 (Ternes, 1998)2; (Stumpf et al., 1999)3 (Stumpf et al., 1999)3. Table 2.1 MW, LogD, Koc, LogKow, pKa and removal efficiencies of pharmaceuticals in wastewater.

(50) 2.3. Polymer mechanisms of actions. 2.3.1. Direct adsorption of pharmaceuticals onto polymers. Polymeric flocculants interact with oppositely charged pollutants, as in the case of cationic polymers interacting with negatively charged pharmaceuticals. Sorption via charge neutralisation can occur for low MW compounds such as phenazone and aspirin. Hankins et al. (2006) reported that the acidity and alkalinity of an aqueous environment influences the removal of pharmaceuticals by influencing the reaction mechanisms, sorption capability and the solubility of both pharmaceuticals and flocculants present in the wastewater. Polymers with of a high charge density and a high MW can affect the removal of pharmaceuticals via charge neutralisation, polymer bridging or a combination of both mechanisms. Currently, limited information is available on direct adsorption of pharmaceuticals to polymers. 2.3.2. Polymer interaction with particles. As discussed previously, pharmaceutical interaction with particles in water is to be expected. The addition of polymers as a flocculants stimulates floc formation and increased sludge production is expected, also removing the attached pharmaceuticals. The interaction of polymers with particles occurs with different mechanisms depending on the environmental circumstances, polymer specification and the particle properties. Bratby (2006) described that the bridging mechanism is predominant in polymer interaction with particles and works as follows: • • • •. dispersion of the polymer in the suspension; adsorption at the solid–liquid interface; settling of the adsorbed polymer; collision between adjacent polymer-coated particles forming bridges and thereby increasingly floc sizes.. High MW polymers could exhibit high viscosities and low diffusion rates in solution (Bolto and Gregory, 2007), while it is important that all polymer molecules are dispersed evenly throughout the suspension. The diffusion of the polymer to the solidliquid interface will lead to the initial sorption of a pollutant, while the rest of the chain stays free and extended into the solution (Bremmell et al., 1998). In time, the chain becomes successively attached at more points along its length due to continuous Brownian movement, until, eventually, there are no more chain ends extending into the solution phase. After adsorption has taken place, the polymers loops that extend into the solution will further become adsorbed onto adjacent particles, thus forming a number of bridges (Lipatov et al., 2005). The strength of the formed flocs depends on the number of 15.

(51) bridges, which is dependent on the number of available loops (Bratby, 2006). The number of loops available for mutual adsorption between adjacent particles is dependent on a number of factors related to both the suspension and the added polymers (Lipatov et al., 2005). A factor of crucial importance for bridging to occur is the availability of adsorption sites on particles to accommodate polymers loops from neighbouring particles. This availability is dependent on the quantity of added polymers. If too much polymers is added, too many adsorption sites per polymers will become occupied and bridge formation is prevented because the particles are then effectively destabilised (Bratby, 2006). It is found that the most effective polymers that promote bridging are linear chains with a MW of up to several million Dalton. In the case of polyelectrolytes, the charge density can have a large influence on the bridging effectiveness. The adsorption of similarly charged particles can be difficult when the charge density is high, as in the case of adsorbing negatively charged particles with anionic polyacrylamide. However, some degree of charge is beneficial because the repulsion between charged segments allows for chain expansion, which should enhance the bridging effect (Muhle, 1985). High particle removal efficiencies (80-98%) achieved in some studies (Bolto and Gregory, 2007; Ebeling et al., 2005; Van Nieuwenhuijzen, 2002) can be used as benchmarks to study the effectiveness of polymers in attached pharmaceutical removal. Van Nieuwenhuijzen (2002) for examples studied the efficiency of two cationic polymer types: high MW polyacrylamides and low MW polyamine polymers. The polyacrylamides required a relatively low dosage (5-10 mg/L), while with the polyamines a high particle removal was only achieved at a higher dosage (20-30 mg/L). For both polymers, the achieved particle removals were greater than 90%. 2.3.3. Polymer interaction with humic acids. Wei et al. (2009) investigated the removal of humic acids by several flocculants, including Polydiallyldimethylammonium chloride (PDADMAC) in synthetic wastewater. The PDADMAC removed approximately 79% of the humic acids (measured as UVA) present in the water at a dosage of 3 mg/L, which increased to a maximum of 84% at a dosage of 9 mg/L. In their study, charge neutralisation was assumed to play an important role in the flocculation of humic acids by PDADMAC. They also concluded that their results were in agreement with Kam and Gregory (2001). They found that the removal of humic acids from water by PDADMAC was highly dependent on the neutralisation of negative charges, while the bridging mechanism was unlikely to play a significant part when cationic polymers were used as flocculants. PDADMAC could effectively neutralise the negative charge of the humic acid molecules even at high pH (Wei et al., 2009).. 16.

(52) The removal of humic acids by PDADMAC was also studied by Hankins et al. (2006). They focused on the removal efficiency of humic acids with flocculation at varying initial humic acids concentrations, while keeping the pH constant at 7. The highest removal efficiencies were greater than 80%. In solutions with higher initial concentrations of humic acids (greater than 20 mg/L), bridging flocculation was speculated to occur more easily in the presence of shear at the same dosage ratio of PDADMAC to humic acids. Amy and Chadik (1983) also tested the removal of dissolved organics, which they measured as the removal of trihalomethane formation potential (THMFP) through 0.45 μm filters, using four different cationic polymers on seven different natural waters. They achieved THMFP removal efficiencies ranging from 37 to 65%, depending on the water and the polymer used. The polymer dosage required for water containing fulvic acids was 50 mg/L, compared to 30 mg/L for water containing humic acids. They concluded that the higher removal efficiencies of humic acids in comparison to fulvic acids were due to the lower charge density of the humic acid molecules. A summary of polymers, dosages and removal potential is listed in Table 2.2. Table 2.2 summaries of polymer, dosage and removal potential Polymer. MW. Remarks. Reference. n.a.. Dosage (mg/L) 0.5-9. Poly-DADMAC. 79% HS removal. (Wei et al., 2009). Polyacrylamide Polyamine. High Low. 5-10 20-30. 90% particle removal. Polyacrylamide Polyamine. 15-20 15-20. >93% particle removal. Poly-DADMAC. Low-very High Low-very High Medium. (Van Nieuwenhuijzen, 2002) (Ebeling et al., 2005). 20. >80% HS removal at pH 7. Alkyl-polyamine. Low. 30. 79% THMFP removal with the addition of kaolin 61% THMFP removal without the addition of kaolin. n.a: not acquired. (Hankins et al., 2006) (Amy and Chadik, 1983). Interactions of polymers and pharmaceuticals occur on different sites of the humic acids, a competition between humic acids and pharmaceuticals for the same interaction sites are not expected (Rebhun et al., 1998). The bound compounds in the humic-pharmaceuticals’ complex can be flocculated, and entrapped in polymeric flocs (Rav-Acha and Rebhun, 1992). However, the properties of the humic acids such as concentration and elemental content will have influences on pharmaceuticals’ removal.. 17.

(53) 2.4. Hybrid pharmaceuticals removal. With the view of optimising the pharmaceuticals’ removal by polymers, combining polymers with conventional adsorbents can be considered and potentially beneficial. Although some combinations have been implemented, few reports are available on their effectiveness in pharmaceuticals’ removal from wastewater (Loureiro and Kartel, 2006). 2.4.1. Combination of polymers with activated carbon. Combination of polymers as flocculants with activated carbons for pharmaceutical removal has been applied in the developed system of Veolia Actiflo-Carb (Treguer and Royer, 2011). This system is an upgrade of the initial Actiflo system, which is specifically designed to treat pharmaceuticals in the water, and has been widely applied throughout the world. Treguer & Royer (2011) reported that, the addition of activated carbon to the Actiflo system was able to remove several pharmaceuticals up to 75% at a powdered activated carbon dosage of 10 mg/L, with a slightly better removal for most of the molecules at a 20 mg/L dosage. Overall, regarding average removal, the order of performance for the 10 monitored compounds was the following: diltiazem > trimethoprim > triclosan > diphenhydramine > carbamazepine > ofloxacin > sulfamethoxazole > fluoxetine > caffeine > naproxen. 2.4.2. Combination with clay. In the last two decades, interest in the adsorption of polymers, especially polyelectrolytes, on clay surfaces for enhanced removal of organic micropollutants has grown significantly. Churchman (2002) demonstrated the removal of toluene by polystyrene–montmorillonite composites. Radian and Mishael (2012) showed that, at high loadings with PDADMAC on montmorillonite, the composite is positively charged, promoting the binding of anionic herbicides. In a recent study, the advantages of composites of poly-4-vinylpyridine-co-styrene and montmorillonite over PDADMAC–montmorillonite composites and activated carbon in the removal of atrazine from water, even in the presence of humic acids, were reported by Zadaka et al. (2009). Amy and Chadik (1983) also tested THMFP removal in four types of synthetic water and achieved a reduction of greater than 90%, with or without the kaolin addition to the water containing humic acids. For the water containing fulvic acids, the achieved removal efficiencies were 79% with the addition of kaolin and 61% without the addition of kaolin. The higher removal efficiencies with the addition of kaolin were achieved because of the presence of nucleation sites for flocs' formation provided by the clay particles. Thus, clay such as smectite is suitable to be used as a coagulant aid in wastewater treatment for destabilisation of the particles in water before flocs formation with polymers occurs (Churchman and Gates, 2006). The natural ability of the clay as. 18.

(54) pharmaceuticals’ adsorbent is an added advantage in reducing the treatment costs. Overview of pharmaceutical removal by polymer is show in Figure 2.1.. 2.5. Conclusions. This chapter highlighted that the relatively few works have investigated the use of polymers in the removal of pharmaceuticals. The understanding of the partitioning (soluble fractions, particle-bound fractions) of pharmaceuticals in wastewater is important to enhance the removal process. Polymers have shown a proven ability in the flocculation of particles and humic acids with average removals > 80%. The use of polymers with a long tail chain and high MW would have an advantage in the flocculation process whereby adsorption and bridging are dominant. Theoretically, high sorption onto particles and humic acid is expected for pharmaceuticals with log Kow >4 and limited sorption with log Kow between 2 and 4. However, the types and concentrations of particles and humic, present in the wastewater, are expected to influence the degree of pharmaceuticals’ sorption and are fluctuating. Pharmaceuticals with a log Kow <2 will unlikely be sorbed to particles or humic in wastewater. Thus, for these, pharmaceuticals the removal via this pathway is viewed as limited in wastewater treatment. Combination of polymers with conventional adsorbents in the treatment process could lead towards new approaches in the removal of pharmaceutical compounds. Adsorbents such as activated carbon and clays have been proven to be effective in pharmaceuticals’ removal. Although limited reports are available on pharmaceuticals’ removal from wastewater by the combination of adsorbents and polymers, a rough estimation can still be made. The extent of the pharmaceuticals’ removal will depend on its effective interaction with the adsorbents. This interaction depends on the adsorbents used, particle size, competition with other organics such as humic and the pharmaceutical’s concentration. For instance, if the sorption of the pharmaceuticals to adsorbent is 90%, the addition of polymers is expected to enhance the removal of the adsorbents by more than 80%; which will results in 50-70% of pharmaceuticals’ removal from the wastewater, depending on the characteristics of the pharmaceutical. Further study should be conducted to optimise the polymers-adsorbent combination.. 19.

(55) Hybrid Adsorbents • Adsorption to carbon or clay before flocculated by polymer. • Highly potential and proven treatments. Interaction with particles • Adsorption onto particles (e.g. sludge), then flocculated by polymers • Dependent on particle availability and suitability. P. P. Carbon/Clay. Carbon/Clay ay P. P. P P. P. Potential path of pharmaceuticals (P) removal using polymer. P. P. P. Particles. P. Carbon/Clay P. P P. Interaction with dissolved organic matter • Not as effective compared to adsorbents and particle • Highly dependent on dissolved organic concentration and type in water matrixes • Unproven for treatment in wastewater. P. P DoM P. DoM P. P. P. Figure 2.1 Model of the possible pathways of pharmaceutical removal by polymer. 20. P. P.

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(62) Chapter 3. Polymer selection for particle and humic acid removal from wastewater. In this chapter, two cationic polymers (Nalco 71305 and Nalco starch) were selected from a list of 21 different polymers. Both polymers were further tested for their ability in particle removal, humic acid removal and the decrease of other wastewater parameters. Jar test studies were used for experiments with polymer dosage in the range of 1-20 mg/L. Both Nalco 71305 and Nalco starch had almost similar performances in turbidity removal. A maximum of around 90% removal at 20 mg/L dosage was obtained. A comparison of humic acid removal in demineralised water and wastewater was made to study the wastewater matrix effect. High humic acid removal of around 70% was achieved in demineralised water compared to 30% in wastewater. Phosphate and COD removal were also reported.. 27.

(63) 3.1. Introduction. Wastewater contains, apart from dissolved fractions, a large amount of particles in suspended form. These particles are normally negatively charged (Van Nieuwenhuijzen, 2002). It is reported that a substantial percentage of the organic matter in wastewater is associated with particles, which can be fractionated into settleable and colloidal solids (Van Nieuwenhuijzen, 2002). In addition, particles can also be related with micropollutants removal from the wastewater as previously describe in chapter 2 (Carballa et al., 2004). In order to remove these particle-bound micropollutants, the application of physical and physical-chemical treatment unit processes is important, and the use of polymers improves particle removal (Bolto and Gregory, 2007). Large particles can be efficiently removed by the application of polymers, while the dissolved components of wastewater are more challenging and are expected to require combinations of techniques (Bolto and Gregory, 2007; Mohd Amin et al., 2014). The particle removal process is measured and optimised primarily with the removal of turbidity (Chang et al., 2005). Preliminary turbidity removal is normally studied with the use of jar test equipment (Aragonés-Beltrán et al., 2009). This equipment can also be used to determine the optimum operating conditions based on water matrix. Naturally occurring dissolved organic matter in wastewater mainly comprises around 40–60% of humic acids (El-Kalliny, 2013). Dissolved natural organic matter, such as humic acids, in wastewater is also expected to have an interaction with micropollutants. The concentration of natural organic matter that exists in wastewater is commonly represented by UV254 (m-1) absorbance (Grefte, 2013). Several researchers have reported a formation of humic–micropollutants complexes through this interaction in the water (Chiou et al., 1986; Rav-Acha and Rebhun, 1992; Rebhun et al., 1998). This formed complex can be removed from the water matrix by the application of charged polymers (Mohd Amin et al., 2014; Zahrim et al., 2010). The polymer ability in removing humic acids has also been reported by others (Hankins et al., 2006; Kam and Gregory, 2001; Wei et al., 2009). The use of a suitable polymer in terms of molecular weight and charges is important in achieving high humic acid removability (Kam and Gregory, 2001; Wei et al., 2009). In this chapter, a comparison of two selected polymers (Nalco 71305 and Nalco starch) from a list of 21 different polymers is made. Focus is given to the turbidity and UV254 removal that represent the humic acids in wastewater since it is hypothesised that both parameters have an influence on the reduction of micropollutants as discussed in Chapter 2 (Mohd Amin et al., 2014). Other parameters such as phosphate and COD reduction by both polymers were also studied for their added advantage for wastewater treatment.. 28.

(64) 3.2. Materials and Methods. 3.2.1. Polymer screening and selection. Suitable polymers for micropollutant removal were screened and selected from a list of 21 different polymers (Table 3.1) supplied by Nalco Netherlands B.V. With the main objective of the application in wastewater, two criteria were considered to be important in the selection process: having the ability to remove particles and the ability to remove dissolved organic matter from the water. Table 3.1 Properties of polymers used in the screening and selection process Type. Cationic flocculant. Anionic flocculant. Non-ionic flocculant. Coagulant. NALCO 71403 NALCO 71406 NALCO 71413. Active constituents Acrylamide-based co-polymer Acrylamide-based co-polymer Acrylamide-based co-polymer. NALCO 71305. Acrylamide-based co-polymer. CORE SHELL 71303 ULTIMER 7752 ULTIMER 1460 ULTIMER 1454 ULTIMER 71456 ULTIMER 71458 Nalco Starch EX10704 NALCO 71601 NALCO 71603 NALCO 71605 ULTIMER 7757 NALCO 71760 NALCO LYTE 7135 NALCO 8105 PLUS. Acrylamide-based co-polymer Acrylamide-based co-polymer Acrylamide-based co-polymer Acrylamide-based co-polymer Acrylamide-based co-polymer Acrylamide-based co-polymer Modified-potato starch Acrylamide-based co-polymer Acrylamide-based co-polymer Acrylamide-based co-polymer Acrylamide-based co-polymer Acrylamide-based homo-polymer. Code. n.a n.a. Solubility. Charge. MW. Optimal dosage. Emulsifiable. Medium. HMW. N.a. Emulsifiable. Medium. HMW. 0.01~0.05%. Emulsifiable. Medium ~high. HMW. 0.01~0.05%. Soluble. Low. n.a. 0.2~0.5%. n.a. Medium. n.a. 0.2~0.5%. White liquid. Dispersible. n.a. MMW. 0.5~2%. Appearance Off-white liquid Off-white liquid Off-white liquid Opaque offwhite emulsion Off-white emulsion. Milky white. Completely. n.a. MMW. 0.5~2%. White/opaque liquid. Completely. Low. HMW. 0.01~0.1%. White liquid. Completely. Medium. HMW. 0.01~0.1%. White liquid. Completely. Medium. HMW. 0.01~0.1%. Soluble. Medium. MMW. 0.01~0.05%. Emulsifiable. Low. HMW. 0.01~0.05%. Emulsifiable. Low. HMW. 0.01~0.05%. Emulsifiable. Medium. HMW. 0.01~0.05%. Milky white. Completely. Medium. MMW. 0.5~2%. Off-white liquid. Insoluble. n.a. HMW. n.a. Amber liquid. Completely. n.a. n.a. 1~100 mg/L. Completely. n.a. n.a. n.a. n.a. High. M~H MW. 1%. Flaked solid Off-white liquid Off-white liquid Off-white liquid. Light yellow liquid Pale yellow~amber liquid. CAT-FLOC 8103 PLUS. Polyelectrolyte. NALCO 77135. Aromatic heterocyclic compound, vegetable originated. Dark brown clear liquid. Completely. Medium. MMW. n.a. NALCO 8190. Polyampholytic. Clear liquid. Completely. n.a. HMW. 1~10mg/L. 29.

(65) The polymers were selected based on the ability to remove turbidity and dissolved organic matter in term of UV254 removal with a variation of screening dosage from 0 to 500 mg/L. From the selection process, the cationic organic polymers performed better than anionic polymers for turbidity removal of raw wastewater. All the cationic type polymers including Nalco 71305 and Nalco starch achieved a higher than 50% turbidity removal percentage while with the anionic and non-ionic based polymers the turbidity removals were lower than 50%. It was also concluded that most of the cationic flocculants had an optimal turbidity removal at a dosage in the range of 5 mg/L to 50 mg/L. Overdosing of the polymer resulted in restabilisation of the particles and decreased the turbidity removal. The polymers performance stability and reproducibility were also considered during the selection process. The coagulant type polymer in this selection process was only able to destabilise the particle in the wastewater and required additional dosing of flocculants to remove the particles. For the UV254 removal, all cationic type polymers achieved less than 35% removal percentage in wastewater. While, for the coagulant, anionic and non-ionic based polymers, the UV254 removals in wastewater were less than 5% or not removable. In the end, two cationic polymers, Nalco 71305 (synthetic) and Nalco starch (natural) were viewed as suitable and were selected to be used further in this study. Although both had almost similar performances, Nalco starch was selected because of its biodegradable properties and lower cost. The polymers were prepared based on standard preparation procedures given by the manufacturer.. 3.2.2. The tested wastewater. The experiment was performed using influent wastewater from a WTTP located in Leiden Noord (Zuid Holland, the Netherlands). The WTTP treats the water from the equivalent of approximately 136000 inhabitants from the centre of Leiden. The average daily flow is around 23000 m3. At the WTTP, the removal of coarse solids takes place, followed by nitrification and denitrification combined with chemical and biological phosphorous removal and finally sedimentation. The sampling was done after the grid filtration before any chemical coagulant or flocculants were added. The quality of the influent and effluent of Leiden Noord for the parameters total nitrogen (N-total), total phosphorus (P-total), COD and biochemical oxygen demand (BOD), in the period from January 2014 to July 2014, is shown in Table 3.2.. 30.

(66) Table 3.2 Average water quality parameters for Leiden Noord. 3.2.3. Parameter. Unit. Turbidity BOD COD N-total P-total. NTU mg/L mg/L mg/L mg/L. Influent Average 150 192.4 550 55.6 9.0. Effluent Average 20 2.3 30.3 3.22 0.18. Jar test experiments. Jar test equipment was used to evaluate the performance of both selected polymers in reducing turbidity and UV254 absorbance. The jar test experiments were carried out based on the manufacturer’s suggested procedures. For both Nalco 71035 and Nalco starch, the applied polymer dosages in a range of 0-20 mg/L were viewed as sufficient to achieve good results for the selected polymers. To simulate the coagulation, flocculation and sedimentation steps, standard jar test apparatus (Figure 3.1) was used according to STOWA(2001) (foundation for applied water research). It consists of six beakers with a volume of 2 L and stirrers, which can be adjusted to the same stirring conditions for all the beakers. The beakers were filled with 1.8 L of the sample, and the flocculant was added simultaneously to all the beakers. In order to achieve the best outcome from the polymers, which allowed maximum contact between particles and polymers, the optimal mixing conditions from the previous polymer screening process, were applied. After the polymer dosing, vigorous mixing at a G-value of around 350 s-1 was applied for 30 s. Then slow mixing was applied at a G-value of around 10 s-1 for 10 min before settling for 20 min. After settling, 100 ml of the sample was taken and prepared for analysis.. Figure 3.1 Standard jar test equipment. 31.

(67) 3.2.4. UV254 and turbidity removal. For the purposes of the experiment, humic acid was used as a representative of other natural organic matter due to its highly reported constituencies in the wastewater (ElKalliny, 2013). The experiment is setup in two matrixes; demineralised water and raw wastewater. The initial concentration of the humic acids used in the demineralised experiments was based on the initial measurement of UV254 absorbance value (25.5 m-1) in wastewater. The measured UV254 values were later used to determine the humic acid concentration (10 mg/L ± 0.5 mg/L) needed to spike the experiment in demineralised water. The concentration is based on the calibration curve of humic acid sodium salt (Sigma Aldrich) UV absorbance at 254 nm wavelength, based on the method used by El-Kalliny et al. (2013). Demineralised water was spiked with 10 mg/L ± 0.5 mg/L humic acids while, for the wastewater, no humic acids were dosed. The experiment was carried out with dosing of polymers solutions in the range of 0-20 mg/L. Approximately 20 mL of the supernatant was taken and filtered over a Whatman Spartan 30/0.45 RC 0.45 μm syringe filter before measurement using a Hach Lange DR 5000 spectrophotometer. Jar test experiment was use to study the turbidity removal by Nalco 71035 and Nalco starch, at dosages of 0-20 mg/L. 10 mL of the sample was taken for measurement after each test. The turbidity was measured using a Hach Lange DR 5000 spectrophotometer with pre-programed (test no. 747) measurements. Turbidity is expressed as formazin attenuation units (FAU), which is equivalent to a nephelometric turbidity unit (NTU). The wavelength (λ) of the measurement is 860 nm. 3.2.5. Removal of other parameters. The total phosphate and orthophosphate concentrations (0.05 - 5.0 mg/L PO43- / 0.5 25.0 mg/L PO43), and the chemical oxygen demand (COD test set: 10-150, 50 - 500 mg/l) were analysed using a Merck Reflectoquant® plus analysis kit according to the manufacture’s procedures. The test kits were then measured using a Merck Spectroquant NOVA 60.. 3.3. Results and discussion. 3.3.1. Turbidity removal. The turbidity levels, with an initial value of 80 ± 0.5 NTU, and with polymer dosages from 0-20 mg/L, are shown in Figure 3.2. Both Nalco 71305 and Nalco starch had similar performances in turbidity removal. Around 20% of the particles settled without any polymer added. The turbidity decreased to around 5 NTU, which translates to a maximum of around 90% removal. The results achieved were. 32.

(68) comparable to the study by Van Nieuwenhuijzen (2002) who reported turbidity removals by low molecular weight polymers of around 65-90% in wastewater with an approximate dosage of 20-30 mg/L. 5,. ! #' (. 4, 3, 2, 1, 0, /, ., -, , . . #'&(. ". 3-/,1. . . " . Figure 3.2: Turbidity removal by Nalco 71305 and Nalco starch from raw wastewater from WWTP Leiden Noord 3.3.2. UV254 removal. Figure 3.3 shows the removal percentages of UV254 from wastewater with an initial concentration of 25.5 m-1 and at different dosages of polymer (0-20mg/L). The removal of UV254 by Nalco 71305 and Nalco starch from wastewater was in the range of around 2 to 30%. The UV254 removal from wastewater by both Nalco starch and Nalco 71305 was quite low compared to the UV254 removal of spiked humic acids in demineralised water (18-70% removal), which is expected to be due to interference by other substances and compounds in the wastewater. Wei et al. (2009) reported that the UV254 removal in synthetic test water by poly-DADMAC was about 79% at a dosage of 3 mg/L and this increased to a maximum of 84% at a dosage of 9 mg/L. In their study, charge neutralisation was assumed to play an important role in the flocculation of humic substances by poly-DADMAC, while bridging was unlikely to play a major role when cationic polymers were used as flocculants. The UV254 removal by cationic polymers (poly-DADMAC) was also studied by Hankins et al. (2006). The highest UV254 removal efficiencies, with varying initial concentrations of humic acids, were all above 80%.. 33.

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