Tone-Lise Rustøen. Ås, - PDF

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Preface This master thesis is written as a part of the Nordic Road Water (NORWAT) research and development program directed by the Norwegian Public Roads Administration (NPRA). The purpose is for the NPRA

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Preface This master thesis is written as a part of the Nordic Road Water (NORWAT) research and development program directed by the Norwegian Public Roads Administration (NPRA). The purpose is for the NPRA to gather knowledge, in order to plan, build and operate the road network without doing unacceptable harm to the aquatic environment. NORWAT is not only of national interest, but the program also contributes to an exchange of knowledge across borders. The NORWAT project started in January First and foremost I would like to thank the NPRA, and the administrators of the NORWAT research program, for the initiative and funding of this thesis. Furthermore, I would like to thank my supervisor Elin Lovise Folven Gjengedal (NMBU) for always being available to discuss and tackle issues related to the thesis. Her willingness to put students first is greatly appreciated, and she can always be counted on when in desperate need of moral support. I would also like to thank my co-supervisors Sondre Meland (NPRA and NMBU) and Lene Sørlie Heier (NPRA), both of whom have been very patient and supportive throughout this process. I would also like to thank Solfrid Lohne, Johnny Kristiansen, Magdalena Rygalska, Irene Dahl and Oddny Gimmingsrud (NMBU) for laboratory assistance, motivational speeches and for always being available for questions regarding the laboratory facilities. I also owe Anne-Grethe Kolnes a special thanks for her help with the statistical analysis. Due to the lack of cars available to students at the university, I would like to thank my employer over the past five years, Jan Ole Damsgaard at Peppes Pizza Ski, for lending me one of the pizza delivery vans so that I could get back and forth to the construction site with the drilling fluid used in the experimental work. I would also like to aknowledge Primex (by Sigríður Vigfúsdóttir) for providing their product ChitoClear Chitosan, and FMC Biopolymer (by Sheena Loy) for providing their product Manugel sodium alginate for investigation in this thesis. They have both been very helpful through correspondence. Kemira Chemicals (by Emma Johansson) provided PIX-318, and lent me jar-test equipment free of charge. A great thank you to my fellow students at the department of Environmental Sciences for sharing stories during lunch and mutual encouragement. A special thank you to Bente Kristin Kjøllesdal for proofreading, moral support, and also for just being her delightful self. Tone-Lise Rustøen Ås, Summary Water used by different machines in the road construction phase, has to be purified in accordance with limitations in the discharge permit, set by the county governor. One of the main parameters set in this permit is suspended solids. Fluctuations in particle load, and also shifts in ph, can vary from day to day during the construction process. Overdosing of inorganic precipitating agents is therefore a common problem, as small variations in inlet water can change the required dose. This can result in an excess of coagulants in outlet water, and in the case of inorganic precipitating agents, this can be harmful for the aquatic environment. Naturally occurring organic polymers may be a better alternative to inorganic coagulants in treating water used in construction processes. Thus, the cationic polymer chitosan extracted from crustaceans, and the anionic polymer alginate extracted from brown seaweed, could replace the inorganic precipitating agents currently used in water treatment. This thesis researches the effectiveness of two types of both chitosan and alginate, compared to ferric chloride sulfate (PIX-318), tested on drilling fluid produced from bridge construction conducted at Knappstad, Norway. The discharge permit with regards to suspended solids at this project is a weekly average of 500 mg/l. The performance of precipitating agents was researched in both undiluted ( 6000 NTU) and diluted (4000, 3000, 2000, 1000 NTU) drilling fluid that held 21 ± 1 C. Experiments were conducted with the use of standardized jar- test equipment (Kemira AB Flocculator 2000), and turbidity measurements with the use of a laboratory turbidity meter (Model 2100AN IS, Hath Company). Residual turbidity 500 NTU was successfully obtained using both chitosan types in undiluted and diluted drilling fluid, whereas the same residual turbidity was not obtained using either types of alginate. The dose of PIX-318 required to achieve the same turbidity removal efficiency as chitosan, was almost 20 times lower in undiluted drilling fluid. Chitosan would be effective as a primary precipitating agent in treating water from piling under the conditions presented in this thesis. However, further research and investigation with regards to large scale use as well as the economic and environmental aspects has to be conducted before it can be recommended. Sammendrag Vann som brukes av ulikt maskineri i forbindelse med veibygging, må renses i henhold til begrensninger i utslippstillatelsen, gitt av fylkesmannen eller lokale myndigheter. En av de viktigste parametrene i denne tillatelsen er suspendert stoff, ofte målt ved turbiditet. Svingninger i partikkelbelastning og ph, kan variere fra dag til dag i en byggeprosess. Overdosering av uorganiske koagulanter er derfor et vanlig problem, ettersom små variasjoner i inntaksvannet kan endre den nødvendige dosen. Dette kan resultere i et overskudd av koagulant i utløpsvannet, og ved bruk av metal baserte fellingkjemikalier, kan dette være skadelig for vannmiljøet. Naturlig forekommende organiske polymerer kan være et bedre alternativ til uorganiske fellingkjemikalier i behandling av vann som brukes i byggeprosesser. Således, kan den kationiske polymeren chitosan - ekstrahert fra skalldyr, og den anioniske polymeren alginat ekstrahert fra brun tang, potensielt erstatte de uorganiske kjemikaliene som nå brukes i vannbehandling. Denne oppgaven undersøker renseeffekten av to typer kitosan og alginat, sammenlignet med jernklorid sulfat (PIX-318), testet på borevann produsert i forbindelse med brobygging utført i Knappstad, Norge. Utslippstillatelsen med hensyn til suspendert stoff for dette prosjektet er et ukentlig gjennomsnitt på 500 mg / L, noe som er tilnærmet lik 500 NTU. Effekten av de ulike koagulantene ble undersøkt i både ufortynnet ( 6000NTU) og fortynnet (4000, 3000, 2000, 1000 NTU) borevann, som holdt 21 ± 1 C. Eksperimentene ble utført ved bruk av standardisert jar-test utstyr (Kemira AB Flocculator 2000), og turbiditetsmålinger ved bruk av en laboratorieturbiditetsmåler (modell 2100AN IS, Hach Company). Slutt turbiditet 500 NTU ble oppnådd ved anvendelse av begge typer kitosan i ufortynnet og fortynnet borevann, dette var ikke tilfelle ved bruk av begge typer alginat. Det trengs 20 ganger lavere dose av PIX-318, sammenlignet med kitosan, i ufortynnet borevann for å oppnå lik renseeffekt. Kitosan vil være effektiv som primær koagulant i behandling av vann fra brobygging under de forutsetningene som presenteres i denne avhandlingen. Ytterligere forskning med hensyn til bruk i stor skala, sammt en grundig vurdering av både det økonomiske og miljørelaterte aspektet, må gjennomføres før en anbefaling kan foreligge. List of abbreviations CE DA DD DW EU HQGC MW NMBU NPRA PAC PIX TGC TR TW Coagulation Efficiency Degree of acetylation Degree of deacetylation Demineralized water European Union High Quality Grade Chitosan Molecular weight Norwegian University of Life Sciences (Norges miljø- og biovitenskapelige universitet) Norwegian Public Roads Administration Poly-aluminum chloride Ferric chloride sulfate Technical Grade Chitosan Turbidity removal efficiency Tap water Glossary Clay Coagulation Inorganic particle. Size 2 µm (0.002 mm) With respect to water treatment, the process of transforming a system from a stable to an unstable state Colloid Particle, whose size ranges from 10 nm ( mm) to 10 µm (0.01 mm) Destabilization Dispergation Flocculation Precipitating agent Sand The actual occurrence of a system from stable to unstable state Separation of a substance from a singular particle surface Formation of lager flocs in an unstable system, the direct consequence of destabilization A causative substance that effect the formation of suspension in solution Inorganic particle. Size 63 µm 2 mm Silt Inorganic particle. Size 2 63 µm Contents 1 Introduction Water from construction processes Background Study goals Theory Water treatment System stability Destabilization Turbidity removal efficiency Chitosan General introduction Chitin and chitosan chemistry Chitin and chitosan production processes Solubility of chitosans Chitosan characteristics and its significance for particle aggregation Chitosan in water treatment processes Alginate Alginate production process Structure and physical properties Alginate in water treatment processes Chitosan and alginate combined in water treatment Metal coagulants Experimental work Drilling fluid Precipitating agents Chitosans Alginates Ferric chloride sulfate (PIX-318) Jar-test experiment Investigated variables Residual turbidity as a function of dose Effect of settling time... 38 3.4.3 System ph Change in ionic conductivity Analytical techniques Turbidity ph Conductivity Suspended solids Particle size Cation exchange capacity (CEC) Determination of trace elements and anions (ICP-MS and IC) Statistical analysis Cleaning of glassware and jar-test equipment Flowchart for the experimental work Results Drilling fluid characteristics Preliminary experiments Chitosans Relationship between initial turbidity and polymer dose Calculation of turbidity removal efficiency Effect of settling time Change in conductivity System ph Alginate PIX Discussion Chitosan Comparison between technical grade- and high quality grade chitosan Influence of change in initial ph Choice of acid for protonation Efficiency of chitosan compared to other studies Evaluation of turbidity removal efficiency Alginate... 69 5.4 Evaluation of practical use and economical aspects Sources of error Further work Conclusion References Appendix A... I Appendix B... II Appendix C... III Appendix D... IV Appendix E... V Appendix F... VI Appendix G... XI Introduction 1 Introduction 1.1 Water from construction processes Good infrastructure is essential in modern society. Expansion of existing road networks, maintenance, and construction of new roads are important in order to obtain a functioning and operative system that has the capacity to handle increased traffic load. The Norwegian Public Roads Administration (NPRA) has more than 500 road projects with a total value of approximately 12 billion NOK running at all times (NPRA 2012). However, road construction and subsequent use can adversely affect both the terrestrial and aquatic environment (Angermeier et al. 2004; Wheeler et al. 2005). In 2007, the EU s Water Framework Directive was implemented in Norway. The main goal of the directive is to achieve good ecological and chemical status for all of Europe s surface waters and groundwater by 2027 (Fjellvær 2014). Hence, there has been an increased focus on water quality for the past decade. Particle erosion from road construction can cause siltation of water bodies which in turn might have direct and indirect negative effects on organisms (Trombulak & Frissell 2000). In order to avoid this, it is common to implement erosion control early in the construction process. The building of temporary or permanent sedimentation basins, extensive use of silt curtains, application of flocculants and ph adjustment are some measures that are adopted to avoid risk of causing unintended harm to the aquatic environment (Vikan & Meland 2012). The quality and chemical composition of water from different construction processes vary a great deal. It is well known that water from tunnel construction can have ph values 9, due to the use of cement based grout. Whereas water from drilling processes can be around ph 7. Thus, each case has to be considered separately in order to find the optimal treatment for each construction site. Before water from construction sites is discharged to a recipient, iron and alum based chemicals are often used in a purification process. Metal-based chemicals can accumulate in nature. There are however naturally occurring organic alternatives possible to use instead of chemicals. One is a positively charged (cationic) material, which is retrieved from the skeleton of different crustaceans, and is called chitosan. Another is a negatively charged (anionic) material, which is produced from brown seaweed, called alginate. This thesis will evaluate these organic 1 Introduction alternatives, with regards to turbidity removal efficiency when added to drilling fluid produced from bridge construction. 1.2 Background The Norwegian Public Roads Administration (NPRA) is building a new stretch of road (E18) between Ørje at the Swedish border in Østfold county and Vinterbro in Akershus county, Norway (figure 1). The road will be a 70 km 4-lane motorway, to be opened in The building project is divided into nine different parts, where smaller stretches of road or allotments, are continuously completed as individual sub-projects (figure 2). Allotment number seven, Figure 1: Geographical location of the construction site. Close-up in right corner. Modified after Google (2015) Knappstad- Retvet, crosses Hobøl River in Hobøl municipality, thus a bridge is a necessary part of the road construction. Figure 2: The E18 project. Allotments are numbered according to construction sequence. Modified after NPRA (2015) Due to unstable ground conditions, the bridge needs to be piled to rock. When drilling for the installation of piles, high turbidity drilling fluids (water + clay, sand and silt) is produced. The bridge is to be founded on 90 piles. With mountain depths ranging up to 60 meters, an excessive amount of drilling fluid is produced from this project (Eriksen 2015). The Hobøl River, which is part of Glomma river basin district (sub unit Morsa), is protected due to the habitation of river mussels and other animals found on the Norwegian red list of threatened 2 Introduction species. The river is characterized as having moderate ecological status, hence measures have been implemented in order to improve the water quality. To avoid pollution from the E18 project, the county authority demanded that the drilling fluid had to be treated on the construction site before being discharged into the Hobøl River. Discharge limits with regards to suspended solids (SS), was a weekly average of 500 mg/l. Thus, the drilling fluid was collected in ditches and pumped into a temporary water treatment facility established on the construction site. Ferric chloride sulfate was a coagulant used at the facility, to precipitate solids out of suspension. 1.3 Study goals This thesis will evaluate the organic alternatives chitosan and alginate, with regards to turbidity removal efficiency and applicability as primary coagulants in water treatment, compared to ferric chloride sulfate when added to high turbidity ( 6000 NTU) drilling fluid. The properties of two types of both chitosan and alginate with different characteristics will be evaluated. First, a theoretical study will be conducted in order to try to understand which properties are of importance in a coagulation process. Second, jar-test experiments will be conducted to investigate the dose of precipitating agent required to obtain residual turbidity below 500 NTU. Both the theory and jar-test experiments will form the basis for discussing the following aspects of organic polymers, compared to chemical agents; Turbidity removal efficiency Environmental impact Health and safety Economy 3 Theory 2 Theory 2.1 Water treatment There are many processes involved in water treatment, with regards to removing suspended solids. The most cost saving, but also often the most time consuming, is sedimentation (Håkonsen 2005). Because of the need for long retention time through a system, the mode of sedimentation is often combined with other processes where the aim is to speed up the sedimentation rate and reduce retention time. Slow sedimentation rate is due to the fact that the system in question has reached a form of stable state. In order to speed up the sedimentation process, one has to reduce some of the factors involved with keeping the system stable. Hence, forcing the system into an unstable state will increase sedimentation rate (Bratby 1980). The following subchapters will first present some of the basic concepts regarding factors causing slow sedimentation, followed by the different mechanisms involved in destabilization System stability Most impurities suspended in water can be removed successfully by sedimentation. The challenge arises when dealing with slow settling particles and non-settable colloids. In general, the stability of a suspension depends on the number, size, density and surface properties of solid particles in suspension and the density of the medium in which the particles are suspended (Bratby 1980). One of the fundamental properties of colloidal particles is that they have a very large specific surface area. Their capability to adsorb molecules, or ions, from the surrounding solution is an environmentally important feature, as pollutants often stick to their surface (vanloon & Duffy 2011). The adsorption properties allow pollutants to be temporarily or permanently removed from solution. Adsorption can occur in several ways. One is due to electrostatic attraction to a charged surface. 4 Theory Surface charge In an aqueous suspension, many common environmental colloids have a negative surface charge that is relatively constant in magnitude. An example is mineral clays (i.e. SiO2). They usually have negative electrical charges when ph is above 2, as this is their point of zero charge (pzc) or ph0 (vanloon & Duffy 2011). However, there are more variables associated with the colloid charge. Surface species, such as protonated or deprotonated functional groups, and other charged atoms in contact with the solution are affecting the charge properties of a colloid surface. These properties are often described in the terms of an electrical double layer. The colloid charge serves to attract oppositely charged counter ions from the surrounding solution, and these form a diffuse layer around the particle in question. This means that there is a larger abundance of oppositely charged counter ions near the colloid surface than that in the bulk solution; where positive and negative species are balanced (normal state). Moving further away from the colloid surface - where the charge potential is at its maximum - it gradually decreases to zero, until a normal state is reached. The thickness of the counterion layer is defined as the distance at which the potential has decreased to 1/e (0.37) of its value at the surface (vanloon & Duffy 2011). Under stable conditions the repelling forces of the electrical charge are greater than the attraction forces between particles, hence aggregation does not occur (vanloon & Duffy 2011). Furthermore the colloids are kept in suspension by Brownian motion - the constant thermal bombardment of the colloidal particles by the relatively small molecules around them (Çoruh 2005) Destabilization In order to sediment impurities such as non-settable colloidal solids and slow- settling suspended solids, a precipitating agent is usually added to water to produce rapid-settling flocs by coagulation and/or flocculation. Hence, one manipulates the system stability. This can be done in several ways. However, it is important to keep in mind that destabilization reactions of colloids in water are quite complex, and are affected by several mechanisms and factors. Colloid properties (such as surface charge, functional groups, hydrophilic/hydrophobic etc.) as well as 5 Theory factors affecting the prec
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