Loddby sulfitmassabruk var under sin verksamhetstid beläget vid Loddbyviken, cirka fem kilometer norr om Norrköping. På bruket bedrevs tillverkning av sulfitmassa mellan år 1899 och 1977 inom ett område som omfattar 18,6 hektar. Det före detta sulfitmassabruket anses idag vara förorenat till den grad att det medför en mycket stor risk för människors hälsa och miljön, men för att kunna besluta om åtgärder gällande den förorenade marken vid Loddby f.d. sulfitmassabruk behöver bland annat de hydrogeologiska förhållandena inom området klargöras. Detta examensarbete syftade till att kartlägga grundvattenströmningen vid Loddby f.d. sulfitmassabruk genom att utveckla en platsspecifik grundvattenmodell med modellkoden MODFLOW i programvaran Groundwater Modeling System (GMS). Dessutom avsåg examensarbetet att undersöka hur grundvattenströmningen i området påverkas av fluktuationer i den intilliggande Loddbyvikens vattennivå. Initialt utvecklades en konceptuell modell för området, där det hydrologiska systemet förenklat beskrevs med avseende på områdets geologi, hydrologi och klimat. Modellområdet avgränsades utefter topografiska vattendelare samt hydrologiska gränser och delades sedan vertikalt in i tre lager utefter de huvudsakliga jordmaterial som hade identifierats vid undersökningar i området: fyllnadsmaterial, lera och morän. I GMS delades modellområdet sedan in i ett rutnät med storleken 5x5 meter och dess ränder tilldelades lämpliga randvillkor. Genom att interpolera utsträckningen av modellens tre lager från sonderingspunkter med känd geologi kunde den konceptuella modellen beskrivas matematiskt i programvaran. För att öka modellens tillförlitlighet kalibrerades jordmaterialens hydrauliska konduktiviteter mot observerade grundvattennivåer i flertalet grundvattenrör inom Loddby f.d. sulfitmassabruk. Efter kalibrering var fyllnadsmaterialets, lerans samt moränens hydrauliska konduktivitet 2,1ˑ10-4 m/s, 5,7ˑ10-7 m/s respektive 3,9ˑ10-5 m/s. En känslighetsanalys utfördes slutligen för att undersöka hur valet av värden på jordmaterialens hydrauliska konduktiviteter samt grundvattenbildningen påverkar modellresultaten. Simuleringarna med den kalibrerade modellen visade bland annat att grundvattnet generellt rör sig från områdets västra delar mot Pjältån och Loddbyviken i norr och öster, dock runt de områden där bergytan når höga nivåer. Förändringar i Loddbyvikens vattennivå visade sig ha en viss påverkan på mängden vatten i systemet, men bedömdes inte medföra en större effekt på strömningsmönstret i området. Känslighetsanalysen visade att modellen var mycket känslig för värdet på grundvattenbildningen, samt att även den hydrauliska konduktiviteten för moränen hade en stor effekt på resultatet. Ett lågt värde på lerans genomsläpplighet visade sig kunna leda till modelleringssvårigheter och fyllnadsmaterialets konduktivitet hade generellt en liten påverkan på resultatet. / Loddby sulphite pulp factory was during its active days located next to Loddbyviken, approximately five kilometers north of Norrköping. Production of sulphite paper pulp was conducted between the years 1899 and 1977 within an area of 18,6 hectares. The former sulphite pulp factory is today considered polluted to the extent that it is entailing a great risk for human health and the environment, but to be able to decide what measures to take, the hydrogeological conditions in the area need to be clarified. The objective of this master’s thesis was to map the groundwater flow pattern within Loddby former sulphite pulp factory by developing a site-specific groundwater model with the groundwater flow model MODFLOW in the software Groundwater Modeling System (GMS). The master’s thesis also aimed at examining how the groundwater movement in the area is affected by fluctuations in the water level of Loddbyviken. A conceptual model was initially created to describe the hydrological system in a simplified way with regards to the geology, hydrology and climate within the area. The model domain was delimited by topographical water divides and hydrological boundaries, and was thereafter divided into three horizontal layers based on the main materials that have been identified during investigations within the area: filling material, clay and till. In GMS, the model domain was divided into a 5x5 meter grid and its borders were assigned appropriate boundary conditions. By interpolating the three model layers from scatter point data of known geology, the conceptual model could be described mathematically within the software. To increase the reliability of the model, the hydraulic conductivities of the materials were then calibrated against observed hydraulic head in several groundwater monitoring wells in the area. After the calibration, the hydraulic conductivities of the filling material, clay and till were 2,1ˑ10-4 m/s, 5,7ˑ10-7 m/s and 3,9ˑ10-5 m/s respectively. A sensitivity analysis was then performed in order to examine how the values of hydraulic conductivity and groundwater recharge would affect the model results. Simulations with the calibrated model showed that the groundwater generally moves from the western parts of the area towards Pjältån and Loddbyviken in the north and east. However, it moves around the areas where the impermeable bedrock is close to the ground surface. Changes in the water level of Loddbyviken proved to have some effect on the amount of water in the system, but they did not entail a greater influence on the groundwater movement pathways in the area. The sensitivity analysis showed that the model was very sensitive regarding the groundwater recharge and the hydraulic conductivity for the till. A very low conductivity of clay turned out to lead to some modeling difficulties and the conductivity of the filling material showed to only have a small effect on the result.

Constructed wetlands (CWs) are artificial systems used for wastewater treatment, whose objective is to reproduce, under controlled conditions, the treatment mechanisms that occur in natural environments, through the exploration and improve the processes that involve the vegetation, porous media and microbial assemblages. Horizontal subsurface flow constructed wetlands (HSSF-CWs) is characterized by flow in a horizontal direction, in a gravel or sand beds planted or unplanted with emergent macrophytes whose the inlet and outlet are horizontally opposed, which allows the wastewater flow through the rhizosphere and have contact with the biofilm formed in subsurface. Traditional studies about CWs focuses on the efficiency of contaminants removal look at systems as a "black-boxes" from empirical approaches and do not distinguish between the different active removals processes. The development of numerical models, in order to helping to identify and improve the role of each element acting in the treatment, whether the properties of the porous media, constructive geometry, flow characteristics, among others, appears as an alternative to reach a more detailed understanding of the internal processes involved in CWs. In general, numerical models consist of governing equations (derived from the mathematical combination of the water balance and Darcy's law), initial conditions (they refer to the distribution of the hydraulic head in the model domain) and boundaries conditions (define the hydraulic or physical boundaries that delimit the model domain). In the last decade, different 1D and 2D numerical models have been developed and applied for the simulation of subsurface flow CWs under conditions of saturated horizontal flow (CWM1-RETRASO and PHWAT), variably saturated vertical flow (FITOVERT and HYDRUS-CW2D) and vertical or horizontally saturated flow (HYDRUS-CWM1). However, few studies regarding the application of 3D numerical models for CWs simulation are reported in the scientific literature. In this study, the hydrodynamic simulation of the porous media in a horizontal subsurface flow constructed wetland was run through the application of a 3D numerical model. The flow patterns were simulated according to the project design and scenarios with changes in the porous media hydrodynamic (hydraulic conductivity) and in the positioning of the wastewater distribution mechanisms (distribution along the cross section with two pipes) in order to verify the influence of these factors in the flow pattern and also to indicate advantages and disadvantages that contribute to the design. The softwares MODFLOW and MODPATH, in the GMS family code, were used for to simulate the direction and flow velocity, hydraulic head and pathlines. The model proved to be a powerful tool to simulation, allowing observing the interdependence between the hydrodynamic parameters and the hydraulic characteristics in the porous media. The simulated scenarios showed the possibility of improving the flow patterns, mainly using two pipes to distribute the wastewater in a more homogeneous way along the cross section of the bed. The use of a porous media with lower hydraulic conductivity also showed improvement in flow characteristics evaluated. However, the general context of wastewater treatment facilities (pretreatment units and tributary loads) should be considered, since materials with low hydraulic conductivity are more susceptible to clogging. Proper design is crucial to improving the treatment conditions in the HSSF-CWs and also to avoid the occurrence of hydraulic problems and damage to the treatment, such as the clogging. / Wetlands construídos (WCs) são tecnologias empregadas para o tratamento de águas residuárias, cujo objetivo é reproduzir, sob condições controladas, os mecanismos de depuração que ocorrem em meios naturais, através da exploração e aperfeiçoamento dos processos que envolvem a vegetação, o substrato e os microrganismos. Wetlands construídos de escoamento subsuperficial de fluxo horizontal (WCFH) são caracterizados pelo fluxo em direção horizontal através de um leito de cascalho ou areia, vegetado ou não com macrófitas emergentes, cujas entrada e saída dos efluentes são horizontalmente opostas, o que permite que as águas residuárias fluam através da rizosfera e tenham contato com o biofilme formado em subsuperfície. Tradicionalmente, os estudos sobre WCs incidem apenas sobre a remoção das concentrações de contaminantes, considerando esses sistemas como “black-boxes” a partir de abordagens empíricas, sem fazer distinção entre os diferentes processos atuantes. O desenvolvimento de modelos numéricos, como forma de auxiliar a identificar e aperfeiçoar o papel de cada elemento atuante no tratamento, quer sejam as propriedades do meio poroso, a geometria construtiva, as características de fluxo, entre outros, surge como alternativa para o alcance de uma compreensão mais detalhada dos processos internos intervenientes nos WCs. De uma forma geral, os modelos numéricos são constituídos por equações governantes (derivada da combinação matemática da equação de balanço de água e da lei de Darcy), por condições iniciais (dizem respeito à distribuição da carga hidráulica no domínio do modelo) e por condições de contorno (definem as fronteiras hidráulicas ou físicas que delimitam o domínio do modelo). Na última década, diferentes modelos 1D e 2D foram desenvolvidos e aplicados para a simulação de WCs de escoamento subsuperficial em condições de fluxo horizontal saturado (CWM1-RETRASO e PHWAT), vertical variavelmente saturado (FITOVERT e HYDRUS-CW2D) e vertical ou horizontal variavelmente saturado (HYDRUS-CWM1). Porém, poucas experiências relativas à aplicação de modelos 3D para simulação de WCs são relatadas pela literatura científica. Neste trabalho, a simulação da hidrodinâmica do meio poroso de um sistema de tratamento de efluentes do tipo wetlands construídos de escoamento subsuperficial de fluxo horizontal foi realizada por meio da aplicação de um modelo numérico 3D. Foram simuladas as condições de fluxo conforme as especificações de um projeto de engenheria, e também cenários com mudanças nas características hidrodinâmicas do meio poroso (condutividade hidráulica) e no posicionamento dos mecanismos de distribuição das águas residuárias (distribuição ao longo da seção transversal por meio de duas tubulações) visando verificar a influência desses fatores no sistema de fluxo e também indicar vantagens e desvantagens que contribuam para a elaboração de projetos. Os softwares MODFLOW e MODPATH, executados por meio da interface GMS, foram utilizados para a simulação da direção e velocidade de fluxo, nível hidráulico e linhas de trajetória das partículas transportadas por advecção. O modelo provou ser uma ferramenta poderosa para a simulação, permitindo visualizar a interdependência entre os parâmetros hidrodinâmicos e as características hidráulicas do meio poroso. Os cenários simulados mostraram a possibilidade de melhoria dos padrões de fluxo, principalmente por meio do uso de duas tubulações para distribuição dos efluentes de forma mais homogênea ao longo da seção transversal do leito. O uso de materiais com menor condutividade hidráulica também apresentou melhoria nas características de fluxo avaliadas. Porém, deve-se considerar o contexto geral das instalações de tratamento das águas residuárias (unidades de tratamento preliminar e cargas afluentes), visto que materiais com baixa condutividade hidráulica são mais susceptíveis ao entupimento. A concepção adequada é crucial para melhorar as condições de tratamento verificadas nos WCFH e também para evitar a ocorrência de danos e problemas hidráulicos, como a estagnação de fluxo em zonas de baixa velocidade de escoamento.