Enhancing Engineering Education in Transport Phenomena Through Project-Based Learning with a Nature-Based Solution Approach

Abstract

This study investigates Project-Based Learning (PBL) to boost student engagement in a Transport Phenomena course at the Federal University of Mato Grosso do Sul (UFMS). Through a hands-on project involving Floating Treatment Islands (FTIs) for water quality improvement, PBL was hypothesized to enhance student involvement and analytical skills. Students designed and optimized FTIs, experimenting with configurations like root length and plant type. Quantitative outcomes reveal a standard deviation of 1.5 in project scores among top performers (course average > 6), reflecting diverse problem-solving strategies, while a standard deviation of 0.8 near the passing threshold (course average ≈ 6) indicates consistent efforts to improve grades. Additionally, 80% of students rated their experience ≥ 4 on a 5-point scale, signaling high satisfaction, although 40% identified data interpretation as a challenge requiring targeted support. Outcomes were assessed by analyzing score variability, revealing higher standard deviations among top performers, indicating diverse problem-solving approaches, while lower deviations near the passing threshold suggested uniform efforts to improve grades. Despite general satisfaction, some students faced data interpretation challenges, highlighting areas for instructional refinement. The results affirm PBL’s effectiveness in fostering engagement and practical skills but suggest that adaptive teaching methods are essential to support comprehension and maintain engagement across different performance levels.

1. Introduction

Engineering is the practical application of scientific principles to real-world challenges, playing a crucial role in addressing professional problems and developing solutions that benefit society (Baldock & Chanson, 2006). Engineering education programs are designed to equip graduates with a strong foundation in engineering, science, and mathematics while emphasizing adaptable communication and ethical awareness within global, economic, environmental, and societal contexts (ABET, 2022). However, many programs struggle to fully meet these standards, contributing to declining interest in engineering careers—particularly in fields like the built environment, where interdisciplinary and project-based learning experiences are increasingly valued (McKenna et al., 2018).

PBL is a dynamic, student-centered pedagogical approach that structures learning around complex, real-world projects, fostering a stronger connection between academic knowledge and practical application (Blumenfeld et al., 1991). This method immerses students in collaborative problem-solving activities that address meaningful questions or challenges within their field, promoting active participation and critical thinking (Thomas, 2000). By adopting a “learning-by-doing” approach, PBL not only enhances technical expertise but also develops essential soft skills, such as teamwork, communication, and problem-solving (Saad & Zainudin, 2022). As students take ownership of their projects, they apply theoretical concepts in practical contexts, deepening their understanding and preparing them to navigate real-world engineering challenges (Blumenfeld et al., 1991).

PBL projects are typically centered on guiding questions that tackle real-world problems, such as “How can we reduce pollution in urban waterways?” or “What strategies can we implement for sustainable urban development?” (Loyens et al., 2023). These questions serve as a foundation for investigative processes where students collaborate with peers and experts to produce tangible outcomes, such as reports, prototypes, or presentations. The iterative nature of PBL encourages reflection and refinement, fostering continuous learning and improvement (Grant & Branch, 2005). By granting students significant autonomy, this approach nurtures responsibility and active engagement in their educational journey (Helle et al., 2006).

A defining feature of PBL is its authenticity—students engage with challenges reflective of real-world professional problems. Instructors serve as facilitators, framing the project, guiding the investigation, and assessing both the outcomes and the learning process (Chiu, 2020). This approach bridges the gap between theoretical knowledge and practical application, equipping students with the problem-solving skills necessary for professional success and lifelong learning.

Given its extensive benefits, PBL stands as a powerful strategy for preparing future engineers by equipping them with the technical expertise and adaptability required in the professional world. Despite its advantages, the application of PBL in specific domains, such as Transport Phenomena, remains underexplored (McKenna et al., 2018). Several studies have demonstrated the effectiveness of PBL in fluid mechanics and water resources education, highlighting its impact on student engagement and learning outcomes. For example, projects integrating real-world experimental tasks, such as those in advanced fluid mechanics (Baldock & Chanson, 2006) and Computational Fluid Dynamics (Mokhtar, 2011), have fostered a deeper understanding of complex concepts. Similarly, the continuous application of PBL across different academic levels has shown improvements in hydraulic engineering learning (Pérez-Sánchez & López-Jiménez, 2020). Recent research also emphasizes the importance of real-world problem scenarios, such as designing water distribution systems and optimizing mechanical systems (Vanoye-Garcia & Menchaca-Torre, 2024), which develop both technical and soft skills. These findings underscore the versatility of PBL in fostering critical thinking, collaboration, and practical application of theoretical knowledge in the context of fluid mechanics and water resources education.

In particular, projects integrating nature-based solutions within this field are scarce. Incorporating such projects into engineering curricula is crucial for promoting sustainable solutions and preparing future engineers to develop innovative, resilient infrastructure. Emerging trends in engineering education highlight the need to embed sustainability within project contexts, foster multidisciplinary collaboration, and transform traditional laboratory experiments into open-ended PBL experiences (Fini et al., 2018).

Sustainability-focused PBL offers a dual advantage: students not only develop technical and soft skills but also engage with pressing environmental challenges, driving their solutions toward sustainable outcomes (Lavado-Anguera et al., 2024). A review of sustainability-oriented PBL initiatives found that many projects have led to tangible implementations, reinforcing students’ motivation and commitment to their work (Graham, 2010). Additionally, the ethical dimension inherent in these projects enhances the learning experience, as students recognize the broader societal impact of their engineering decisions. Expanding PBL in Transport Phenomena and related fields through sustainability-driven projects represents a crucial step toward equipping future engineers with the skills and ethical awareness necessary to address global challenges. This study evaluates the effectiveness of a PBL approach focused on nature-based solutions within a civil engineering course at the Federal University of Mato Grosso do Sul (UFMS).

The incorporation of Floating Treatment Islands (FTIs) within PBL offers a unique opportunity to connect theoretical learning with practical applications in civil and environmental engineering. FTIs serve as an excellent platform for understanding various Transport Phenomena. These systems allow students to explore fundamental principles such as dimensional analysis, the flow past immersed bodies, and the conservation of mass and energy (e.g., Bernoulli’s equation). FTIs provide practical examples of flow-analysis techniques, enabling students to observe and analyze real-world flow patterns and classifications of fluid flow (laminar, turbulent, etc.). By studying how water moves through and around the plants and structures of the FTIs, students can better grasp the kinematics of fluids and their role in environmental processes. Additionally, FTIs serve as a valuable educational tool for linking theoretical fluid dynamics with practical applications in ecological engineering, helping students understand the complexities of water treatment and the movement of contaminants in natural systems. This hands-on approach strengthens their comprehension of how Transport Phenomena manifest in both natural and engineered environments.

Creative thinking, integral to PBL, includes competencies essential for the 21st century, such as divergent thinking—the ability to generate multiple solutions to a problem. However, engineering education has traditionally emphasized convergent thinking, highlighting the need for curricular enhancements to better foster divergent thinking skills (Akcali et al., 2020). This study specifically assesses students’ divergent thinking abilities within the PBL framework.

Previous research indicates that student engagement tends to decline after completing a course (Cole & Spence, 2012; Lang et al., 2017). Conversely, studies have shown that PBL techniques enhance engagement, leading to a higher percentage of students meeting learning objectives and achieving better academic performance (Almulla, 2020; Jones, 2022). This study seeks to determine whether student grades influence engagement within a PBL framework—an aspect not extensively explored in prior research. Understanding how students interact with a course after earning a passing grade could provide valuable insights for course design. If students disengage post-assessment, even with PBL—a typically engaging approach—then course structures must be designed to maintain continuous involvement throughout the academic term (Lang et al., 2017).

In summary, this study aims to provide insights into the implementation and outcomes of a PBL approach in the Transport Phenomena course at UFMS, with a focus on nature-based solutions. Specifically, it examines the impact of this approach on student divergent thinking and engagement, contributing to the broader discussion on enhancing engineering education through sustainability-driven, PBL experiences.

2. Literature Review

In engineering education, Project-Based Learning (PBL) has been widely adopted since the mid-20th century due to its ability to enhance academic performance, motivation, and the development of critical professional competencies (Edström & Kolmos, 2014). By applying theoretical concepts to real-world scenarios, PBL fosters collaboration, problem-solving, and higher-order thinking, all of which are essential for engineering professionals (Brundiers & Wiek, 2013). PBL’s adaptability allows for implementation across different levels and settings, whether in single-subject courses or multidisciplinary environments, offering both problem-oriented and project-oriented approaches (Lehmann et al., 2008). Research indicates that PBL improves students’ grasp of engineering principles while also strengthening teamwork, confidence, and employability (Fini et al., 2018). Furthermore, integrating Bloom’s taxonomy into PBL curricula fosters cognitive development, encouraging students to analyze, evaluate, and create innovative solutions to engineering challenges (Loyens et al., 2023).

Despite its established benefits, the application of PBL in specific engineering domains remains unevenly explored. While studies have demonstrated its effectiveness in fluid mechanics and water resources education (Baldock & Chanson, 2006; Mokhtar, 2011; Pérez-Sánchez & López-Jiménez, 2020), its integration into Transport Phenomena courses, particularly with nature-based solutions, is limited. Recent studies from 2021 to 2025 further highlight this gap. Lavado-Anguera et al. (2024) reviewed PBL’s role in engineering education, noting deficiencies in addressing student challenges and integrating sustainability. Vanoye-Garcia and Menchaca-Torre (2024) demonstrated PBL’s success in enhancing sustainability competencies in fluid mechanics, while Jones and Ehlers (2021) emphasized hands-on experiments for deeper learning. These findings reveal a lack of research on PBL’s difficulty level and its specific application in Transport Phenomena using nature-based solutions like Floating Treatment Islands (FTIs).

This study addresses these gaps by implementing PBL with FTIs in the Transport Phenomena course at UFMS. Students engaged in hands-on experiments to design and optimize FTIs, focusing on parameters such as root length and plant type, to explore flow dynamics and pollutant removal. Data were collected through project scores, questionnaires, and velocity measurements using a SonTek Acoustic Doppler Velocimeter (ADV), analyzed to assess engagement, divergent thinking, and performance variability across academic standings. The findings, including a standard deviation of 1.5 among top performers and 80% student satisfaction, confirm PBL’s effectiveness while identifying data interpretation challenges, contributing new insights into its application in this context.

3. Methodology

3.1. Implementation of PBL in the Transport Phenomena Course

This study implemented PBL at the conclusion of the Transport Phenomena course to assess its impact on student engagement, comprehension, and overall performance. The project focused on FTIs as a solution for water quality improvement in canals, integrating theoretical knowledge with practical application. The methodology involved the following steps:

Project Introduction and Structure: Students were introduced to the concept of floating islands, their environmental significance, and the engineering principles involved in their design and implementation.

Group Formation and Collaborative Work: Students worked in interdisciplinary teams, fostering collaboration between Environmental and Civil Engineering students.

Experimental Setup and Data Collection: Students engaged in hands-on experiments involving plant quantity selection, system layout design, laboratory equipment operation, and data processing using specialized software.

Evaluation Criteria: Student performance was assessed based on the quality of reports, accuracy in data analysis, teamwork, and project execution. Project scores were collected via a 10-point rubric, validated by peer review, assessing criteria such as report length (2500–5000 words), topic structure, measured velocity graphs, mass removal calculations, all measurements presented, experimental uncertainty propagation, 1 photo of the island, no plagiarism, and ABNT-compliant references. ABNT (Associação Brasileira de Normas Técnicas) specifies citation style (e.g., NBR 6023:2018) for Brazilian academic work. Each of the nine criteria was evaluated on a scale of 0 to 10, and the final project score was calculated as the average of these individual scores, validating results through consistent application across all 34 submissions (Table 1). The evaluation was conducted over two weeks with no penalties for delays but extensions with justification. Feedback was gathered from both instructors and students to evaluate the efficacy of PBL in enhancing learning outcomes.

3.2. Academic Standing and PBL Performance Analysis

To explore the relationship between student performance on the project and their prior academic standing, data on course averages and project scores were analyzed. This study aimed to examine the variability in project score distributions among students with different course averages, identifying patterns related to engagement and effort levels. The population consisted of all 34 students enrolled in the Transport Phenomena course at UFMS, with all participating in the PBL project as a mandatory component. The sample size for performance analysis was thus 34 students. To categorize student performance, participants were grouped based on their course averages—those with scores above the passing threshold (greater than 6 on a scale of 0 to 10), those near the passing threshold (approximately 6), and those below the passing threshold (less than 6). Statistical analysis was conducted to calculate the standard deviation and dispersion of project scores within each group, providing insights into variability and trends in student engagement. The results were then compared with existing research on student engagement in project-based and online learning environments to contextualize the findings and draw comparisons with similar studies. Project scores were collected via a 10-point rubric, validated by peer review, assessing criteria such as report length (2500–5000 words), topic structure, measured velocity graphs, mass removal calculations, all measurements presented, experimental uncertainty propagation, 1 photo of the island, no plagiarism, and ABNT-compliant references.

3.3. Course of Transport Phenomena

The Transport Phenomena course is centered around understanding the fundamental principles of mass, momentum, and heat transport. The subject is structured into three main components: integral, differential, and empirical approaches. The syllabus covers introductory concepts, pressure distribution in fluids, integral relations for a control volume, differential relations for fluid flow, and dimensional analysis and similarity. The curriculum is designed not only to ensure that students grasp the content but also to develop their conceptual understanding and proficiency in solving complex engineering problems through a systematic approach. This includes problem identification, hypothesis formulation, and testing, as well as the ability to design and conduct experiments, analyze data, and interpret results. To achieve these educational objectives, the course employs a variety of methodologies and evaluation techniques, such as Peer Instruction (PI), engineering problem-solving exercises (including multiple-choice Fundamentals of Engineering Problems, Comprehensive Problems, and Design Projects), and PBL. The course consists of 102 contact hours, distributed into 5 h per week of lectures and 1 h per week of experimental work. Evaluation is a blend of conceptual problems, engineering problems, and the project discussed here.

3.4. Our PBL: Flow Distribution in FTIs Spanning the Channel Width

Initially, students were informed that hydrodynamics play a crucial role in optimizing FTIs for pollutant removal (Xavier et al., 2018), influencing two key factors. First, prolonged pollutant retention within the FTI enhances removal efficiency (Liu et al., 2019). Second, the mass removal within the root zone depends on the inflow rate, which supplies pollutants to the root zone. As inflow rates approach zero, residence times may significantly increase, but pollutant removal by the root zone tends towards zero due to the reduced delivery of pollutants.

To promote efficient mass flow into the FTI and ensure adequate retention time of water within the root zone, students conducted experiments in a recirculating flume with a horizontal bed. The flume was 20.00 m long, 0.40 m width, and 0.36 m depth, with a flow depth (H) of 0.30 m, controlled by a tailgate at the end of the flume. The mean channel velocity (U₀) varied between 8.25 and 12.90 cm/s. The Froude numbers, Fr = U₀/(gH)^0.5 (where g is the acceleration due to gravity), in all cases ranged between 0.048 and 0.075, indicating that the flow was subcritical. The Reynolds numbers, Re = U₀R/ν (where the kinematic viscosity ν was equal to 0.000001 m²/s and R is the hydraulics radius), in the model ranged between 9900 and 15,480, indicating that the flow was turbulent.

Students were tasked with designing FTIs using expanded polystyrene (EPS) material. The FTIs were constructed with a depth of 1.0 cm, width of 40.0 cm, and length of 30.0 cm, spanning the full width of the flume (Figure 1). The design, extending across the entire channel width, was inspired by the work of De Stefani et al. (2011). Two FTIs were fabricated and sequentially positioned within the flume by the participating student groups. Each group selected plant species, determined their growth stages, and established the longitudinal distance between the two FTIs. Measurements were taken along a specific section of the channel, located between 4 and 14 m from the inlet, to represent a flow regime reflective of natural conditions.

To characterize the flow field, students used a SonTek Acoustic Doppler Velocimeter (ADV) to measure velocity. The streamwise coordinate was denoted as x, and the velocity component measured was u. The vertical coordinate was denoted as z, with z = 0 at the channel bed, and the velocity component measured was w. Velocity data were recorded continuously over a 3 min period at a frequency of 50 Hz. Raw data with a low signal-to-noise ratio (SNR < 12), correlation (corr < 70), or amplitude (amp < 90) were excluded from analysis (McLelland & Nicholas, 2000). Students were free to choose the longitudinal positioning along the centerline of the channel for the ADV, collecting data at two specific depths: approximately mid-depth of the root zone and mid-depth of the region below the root zone. Students used this data to estimate the residence time within the root zone and the inflow rate. All measurements were conducted under academic and technical supervision within a duration of two to three hours.

Prior to the experiments, students were briefed on the general flow behavior through and around FTIs, based on findings by Liu et al. (2019) and Yamasaki et al. (2022). Specifically, they were informed that at the root level, a noticeable decrease in velocity occurs within the wake, immediately downstream of the root structure. Subsequently, the flow in the wake merges with the flow in the open channel, leading to an increase in velocity. During this recovery distance, the velocity remains lower than the upstream value of the FTI, resulting in varied inflow conditions for an FTI placed at different distances downstream from the first FTI. In the region below the root zone, the opposite behavior is observed. Due to the obstruction of the root zone, the velocity increases beneath the FTI. After reaching a maximum value, the flow beneath the FTI merges with that in the wake, leading to a decrease in velocity. The presence of a second FTI downstream of the first results in a repetition of this general velocity behavior. This described behavior can be partially observed in Figure 2. These preparatory discussions ensured that students had a comprehensive understanding of the expected flow patterns, equipping them to conduct their experiments more effectively and interpret their data accurately.

The PBL component was introduced in the second half of the Transport Phenomena course, following an initial period where students familiarized themselves with the fundamental theory of the subject. By the final phase of the PBL, during which students conducted experiments, analyzed results, and prepared their reports, they were already aware of their academic standing. At this point, some students had already passed the course, others were on the borderline with grades near the average, some were uncertain about passing, and a few had no chance of success.

To evaluate the implementation of PBL, a structured feedback collection process was employed to gain insights into students’ perceptions, experiences, and challenges faced during the floating islands project. The assessment utilized a questionnaire that incorporated both quantitative and qualitative components, ensuring a comprehensive understanding of the students’ learning journey. The questionnaire included five key questions designed to capture students’ views on the importance of the project, the challenges encountered, and their overall experience with floating islands as an engineering subject:

How would you assess the importance of this project in relation to the subject studied?

What challenges did you encounter while developing the project?

What improvements can be made to enhance the understanding of the topic and the execution of the project?

After completing the study, how do you evaluate floating islands as an engineering object?

How would you rate your overall experience with the project (5 being excellent and 1 being a completely negative experience)?

This format facilitated a standardized approach to data analysis while capturing the variability in student responses. The method provided a reliable framework for assessing the impact of PBL on student learning and engagement within the course.

The questionnaire was administered through an online platform at the conclusion of the project to ensure anonymity and encourage honest responses. A total of five students voluntarily participated in the evaluation, with verbal informed consent obtained prior to data collection. As no personally identifiable information was collected, and given the voluntary nature of participation with minimal risk, ethical approval was not required.

This structured approach enabled a quantitative analysis of student responses, offering a comprehensive assessment of the effectiveness of PBL in enhancing both conceptual understanding and practical application within environmental engineering contexts.

4. Results and Discussion

4.1. Exploring Divergent Thinking in Enhancing FTIs for Pollutant Removal

In this study, students were tasked with optimizing the flow dynamics within FTIs by manipulating parameters such as plant numbers, species diversity, root length, and longitudinal spacing between FTIs. This hands-on approach allowed students to directly engage with theoretical concepts and provided them with an opportunity to develop critical problem-solving and creative thinking skills. As students made decisions regarding plant configurations, they were challenged to understand and apply fluid dynamics principles—such as drag, residence time, and inflow rates—in the context of real-world water treatment systems.

The results demonstrated that increasing root length and density led to greater drag, which reduced inflow rates and extended residence times within the root zone. This was evident in the data presented in Figure 2, where the relationship between residence time and inflow velocity varied significantly across student groups, highlighting the impact of different plant configurations. This hands-on application allowed students to see firsthand how adjustments to plant characteristics could influence the efficiency of water treatment processes.

For example, students selected both Eichhornia and Pistia plants for the FTIs (Figure 3a). The root lengths of Eichhornia, which were comparatively shorter and more variable than those of Pistia, provided students the opportunity to investigate how variations in root morphology influence water flow dynamics. The observed variability in root lengths, plant densities, and longitudinal spacing between FTIs (Figure 3b–d) highlighted the range of strategies implemented by different student groups. This diversity in design choices emphasized the significance of cultivating creative problem-solving and critical thinking, enabling students to engage with complex, sustainable engineering challenges.

Moreover, the data shown in Figure 4 highlights two distinct strategies used by different groups to optimize flow dynamics. One group created a downstream recirculation zone (Figure 4a) using a combination of Pistia and Eichhornia plants with varying root lengths. This setup resulted in negative velocities downstream, indicating significant resistance. In contrast, another group opted for a more porous design using Eichhornia plants (Figure 4b), leading to reduced drag and higher flow velocities. The contrasting outcomes from these configurations demonstrated how varying root lengths and plant configurations directly influenced flow dynamics, encouraging students to critically analyze their design decisions.

This diversity in approaches provided an excellent opportunity for students to engage with divergent thinking—exploring various strategies and recognizing the implications of their design choices. By analyzing figures such as Figure 4, which illustrates longitudinal velocity measurements, students could evaluate the effectiveness of their setups and better understand the flow dynamics in relation to plant configuration and root length.

The collaborative nature of the project also allowed students to engage in discussions, share insights, and refine their strategies, enhancing both their communication and teamwork skills. This cooperative learning process is essential for developing future engineers who will work together in multidisciplinary teams to tackle complex environmental challenges.

The practical nature of the PBL approach allowed students to directly observe the impacts of their design choices on fluid dynamics, providing them with a deeper understanding of theoretical principles. The connection between theoretical learning and practical application is clearly illustrated through the velocity profiles in Figure 4, where students were able to correlate their design decisions with real-time data, bridging the gap between concept and practice.

Overall, this study underscores the educational value of PBL in fostering critical thinking, problem-solving, and collaboration. Through the hands-on exploration of FTIs, students were able to apply fluid dynamics concepts in a real-world context, equipping them with essential skills for their future careers in engineering.

4.2. Impact of Academic Standing on PBL Outcomes

The application of PBL at the conclusion of the Transport Phenomena course presents an opportunity to explore the relationship between student performance on the project and their prior academic standing. This analysis is visually represented in Figure 5a, which plots final scores with PBL against final scores without PBL for all 34 students. A 45-degree reference line is included, representing the scenario where final scores with and without PBL are equal, a common benchmark in comparative performance studies to assess intervention effects. A notable trend emerges; for students with lower final scores without PBL, there is a significant upward deviation of points above the 45-degree line, indicating a substantial improvement in performance with PBL. This suggests that PBL particularly benefits underperforming students, potentially through scaffolded learning that provides structured support and practical application to enhance comprehension. As final scores without PBL increase, the deviation above the line diminishes, with some high-performing students’ scores aligning with or falling below the line, reflecting a possible ceiling effect where pre-existing proficiency limits additional gains. This non-linear pattern highlights the context-dependent impact of PBL, varying by baseline performance, and is supported by educational theory, including scaffolded learning for low performers and ceiling effects for high performers, to provide a detailed qualitative description of these trends.

Further insights into performance variability are provided by analyzing the standard deviation of project scores across different course average groups, as illustrated in Figure 5b. For students with course averages above the passing threshold (greater than 6 on a scale of 0 to 10), a higher standard deviation in PBL scores is observed, suggesting a diverse range of approaches and outcomes. This may reflect varying levels of effort, with some students excelling through significant investment while others engage less vigorously. Conversely, students with course averages near the passing threshold (approximately 6) exhibit a lower standard deviation, indicating a more uniform effort to secure a passing grade, likely viewing PBL as a critical opportunity to improve their standing. For students with low course averages (below 6), a notable increase in standard deviation is evident, pointing to a wide dispersion in outcomes. This could stem from differing degrees of engagement, understanding, or resource allocation among those facing academic challenges.

Our findings align with broader research on grading and student engagement. Lang et al. (2017) observed in Massive Open Online Courses (MOOCs) that students passing courses often accelerate through materials, reduce engagement, and avoid challenging tasks, a trend mirrored in our high-performing group’s potential ceiling effect. Similarly, Cole and Spence (2012) noted a decline in engagement post-passing in a first-year fluids course with 230 engineering students, despite continuous assessment. These studies suggest that motivation shifts after academic milestones, supporting our observation of varied PBL impact. To sustain engagement, Lang et al. (2017) proposed delaying grade notifications until course end, while Cole and Spence (2012) advocated for structured assessments throughout. In our context, implementing PBL prior to final grade disclosure may enhance its effectiveness, a strategy we recommend for future iterations.

These insights underscore the dynamic nature of student motivation and engagement following academic milestones such as passing thresholds. They emphasize the imperative for educators to adapt their teaching methodologies accordingly. For instance, Lang et al. (2017) suggested reconsidering the timing of informing learners about their final course grades, proposing delayed notification until after the course concludes to potentially sustain learner engagement. Furthermore, there is a question regarding the course structure: if students exert less effort after passing a course, traditional instructional models with periodic assignments and a final project or exam may foster deeper learning outcomes (Cole & Spence, 2012; Lang et al., 2017). In our specific context, implementing PBL before students receive final grades may be more beneficial.

4.3. Feedback from Instructors on Implementing PBL in the Transport Phenomena Course

The incorporation of PBL into the Transport Phenomena course was a deliberate strategy aimed at enhancing students’ understanding of complex theoretical concepts through hands-on engagement. This pedagogical approach effectively bridged the gap between abstract knowledge and practical applications, addressing the common challenges students face with theoretical concepts and the demanding mathematical computations inherent to the course.

During the course, students not only improved their academic performance but also gained a deeper understanding of key principles in Transport Phenomena. For instance, by working with FTIs, students were able to observe the concept of mass conservation in action. In fluid dynamics, mass conservation refers to the principle that mass cannot be created or destroyed in a fluid flow, but rather is conserved. This means that the mass entering a system must equal the mass exiting the system, assuming the system is closed and there are no additional sources or sinks of mass within it.

Additionally, students were able to observe the wake behind the FTI, where the velocity of the fluid recovered and returned to values similar to those observed upstream of the FTI. This demonstrated how the flow reestablished its velocity after interacting with the FTI, with the total mass flow rate remaining constant. The formation of this wake further validated their understanding of how disturbances in flow (due to obstacles like FTIs) can lead to changes in velocity but still respect the fundamental principle of mass conservation.

Furthermore, some students observed the difference between more porous and less porous root zones, which influenced the flow patterns. In more porous areas, water could move more easily through the root zone, resulting in less drag and a less noticeable velocity drop. On the other hand, in less porous areas, the velocity dropped more significantly due to higher resistance. Students also observed how in certain cases, a recirculation zone formed behind the FTI, where the fluid flowed in a circular motion, creating turbulent eddies. In other cases, no recirculation zone formed, and the flow returned to a more uniform pattern. These differences illustrated how variations in material properties (like porosity) could influence flow dynamics, reinforcing students’ understanding of fluid behavior and how mass conservation operates even in complex systems.

Additionally, students explored the variation in velocity across the canal, which allowed them to classify the flow as non-uniform. Non-uniform flow occurs when the velocity at different points in the flow varies, which is a common feature in natural systems. By observing how the water flowed at different speeds across the channel, students could classify the flow as either laminar (smooth and ordered) or turbulent (chaotic and mixed), helping them understand how the Reynolds number—a dimensionless quantity used to predict flow patterns—affects flow behavior. This classification helped students grasp the significance of velocity distributions and how they affect Transport Phenomena in real-world applications.

Through these hands-on experiences, students were able to directly connect theoretical principles such as mass conservation, flow dynamics, and velocity distributions with practical phenomena. The experiments with FTIs allowed them to visualize abstract concepts like drag, wake formation, and recirculation, strengthening their comprehension of how Transport Phenomena manifest in both natural and engineered environments. This hands-on approach enriched their understanding of how fluids behave in both theoretical and practical contexts, providing them with a deeper appreciation for the complexities of Transport Phenomena in environmental engineering.

Furthermore, the collaborative nature of the experiments allowed students from various engineering disciplines to improve their decision-making skills and teamwork, preparing them for real-world challenges in the field. The inclusion of interdisciplinary knowledge helped students apply theoretical knowledge in ways that could solve practical problems, reinforcing the course’s educational goals.

In conclusion, the integration of PBL into the Transport Phenomena curriculum not only increased student engagement but also facilitated a much stronger understanding of Transport Phenomena, bridging theory with practice. The continued investment in such initiatives is essential for developing future engineers who are well-prepared to address the complex challenges in their professional careers.

4.4. Feedback from Students on Implementing PBL in the Transport Phenomena Course

The feedback obtained from five participant evaluations provides valuable insights into perceptions, experiences, and challenges encountered during the implementation of the PBL project focused on floating islands for water quality improvement in canals.

A significant majority (80%) of engineering students recognized floating islands as a viable solution for enhancing water quality in canals, highlighting the potential of PBL in cultivating positive attitudes towards innovative environmental technologies (Figure 6a). This consensus underscores the practical effectiveness of floating islands in real-world scenarios, contrasting with the 20% of respondents who expressed reservations, primarily due to perceived gaps in evidential support for broader conclusions. Importantly, none of the participants viewed floating islands solely as aesthetically pleasing features, emphasizing their practical utility.

Student feedback regarding their project experience was overwhelmingly positive, with 60% rating it as excellent (5 on a scale of 1 to 5) and the remaining 40% rating it very positively (4) (Figure 6b). This distribution reflects high levels of satisfaction and engagement with the PBL approach employed in studying FTIs, demonstrating its efficacy in promoting profound learning and application of engineering principles in environmental contexts.

Moreover, participants overwhelmingly endorsed the pedagogical value of the project, with 80% perceiving it as more engaging and effective than traditional classroom instruction (Figure 6c). This finding underscores the educational impact of experiential learning approaches like PBL in enhancing understanding and application of complex engineering topics related to environmental management.

From a practical standpoint, 20% of respondents acknowledged using the project to meet academic requirements, highlighting its dual role in academic assessment and educational enrichment (Figure 6d). This perspective aligns with observations from the Transport Phenomena course, indicating that PBL initiatives such as the floating islands project not only enhance conceptual understanding but also fulfill academic assessment needs through alternative methodologies. The variability in project scores among students with different academic standings further illustrates the project’s strategic value in improving academic performance and ensuring success.

However, challenges encountered during project implementation underscore areas for improvement. Forty percent of participants faced difficulties in developing reports and interpreting data, signaling a need for enhanced guidance in data analysis and academic reporting within PBL frameworks (Figure 6e). Similarly, 40% encountered execution challenges that were resolved with instructor support, emphasizing the crucial role of mentorship and support structures in navigating complex, hands-on projects like studying floating islands.

To enhance understanding and execution of future projects, several strategies can be considered based on participant feedback:

Ensure Comprehensive Information Transmission: Addressing concerns from 40% of respondents, it is crucial to effectively communicate all project-related information throughout the course. This may involve reviewing and restructuring content delivery to ensure clarity and relevance to project objectives, as highlighted by the majority (80%) valuing clear project communication.

Incorporate Floating Islands Concept Throughout the Course: Another 40% of participants recommended integrating floating islands consistently across various course modules. This continuous exposure can establish a strong theoretical foundation early on, enabling students to connect classroom learning with practical applications later in the project. Consistent reinforcement of these concepts is essential for enhancing retention and application of knowledge, as affirmed by the 60% who found the project’s educational value exemplary.

Integrate Relevant Questions into Exercise Lists: Although not specifically mentioned, incorporating exercises linking theoretical concepts to practical applications of floating islands could solidify understanding. Designing exercises requiring application of learned concepts to scenarios involving floating island technologies can deepen comprehension and engagement.

Provide Practical Demonstrations: Approximately 20% of respondents expressed interest in practical demonstrations of floating island applications in a laboratory canal setting. Integrating such demonstrations can provide valuable hands-on experience, allowing students to observe firsthand the principles discussed in class and reinforcing theoretical knowledge with practical application. This approach aligns with recommendations for more interactive learning opportunities.

5. Conclusions

This study on PBL in the Transport Phenomena course at the Federal University of Mato Grosso do Sul (UFMS) focused on nature-based solutions for improving water quality in urban canals has provided valuable insights into engineering education and practice. Through hands-on experiments with Floating Treatment Islands (FTIs), students not only explored complex flow dynamics but also demonstrated innovative thinking in optimizing FTIs for pollutant removal based on varying parameters such as root length and plant density. The results underscored the significant impact of student engagement and prior academic standing on project outcomes within the PBL framework, with a standard deviation of 1.5 among top performers (course average > 6) and 80% rating their experience ≥ 4 on a 5-point scale, confirming enhanced engagement and diverse approaches, though 40% reported data interpretation challenges necessitating instructional support. Students with diverse academic performances approached the project with varying levels of rigor and innovation, highlighting the need for tailored educational strategies to maintain high levels of student involvement throughout the course. Moreover, this study reinforced the efficacy of experiential learning in bridging theoretical knowledge with practical applications in engineering education. The observed 80% satisfaction rate and qualitative feedback on engagement suggest a positive impact, though specific quantitative improvements in engagement or problem-solving skills require further investigation to align fully with the study’s objective to enhance learning outcomes. Integrating PBL early in the curriculum can enhance problem-solving skills and creativity, essential for addressing contemporary engineering challenges effectively.

Author Contributions

Conceptualization, R.B.P., F.R.d.C., and J.G.J.; methodology, R.B.P., F.R.d.C., and J.G.J.; formal analysis, R.B.P., L.E.F.M., and J.G.J.; investigation, R.B.P., F.R.d.C., L.R.d.C., L.E.F.M., B.J., V.M.F., and J.G.J.; resources, J.G.J.; data curation, R.B.P., and J.G.J.; writing—original draft preparation, R.B.P., L.R.d.C., B.J., J.G.J.; writing—review and editing, J.G.J.; visualization, R.B.P., F.R.d.C., L.E.F.M., and J.G.J.; supervision, R.B.P., and J.G.J.; project administration, R.B.P., and J.G.J.; funding acquisition, J.G.J. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Ethical review and approval were waived for this study due to the voluntary nature of participation, the absence of personally identifiable information, and the minimal risk involved. Verbal informed consent was obtained from all participants prior to data collection.

Informed Consent Statement

Verbal informed consent was obtained from all subjects involved in the study. No personally identifiable information was collected.

Data Availability Statement

The data presented in this study are not publicly available due to privacy and ethical restrictions, as the dataset contains anonymized but sensitive educational responses from a small group of participants. Data may be made available from the corresponding author upon reasonable request.

Conflicts of Interest

None of the authors have a conflict of interest to disclose.

Footnotes

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Figures and Table

Figure 1 The FTI prepared by a group of students in the laboratory, using two different plant species.

Figure 2 Relationship between non-dimensional residence time in the root zone and inflow velocity in FTIs across all groups.

Figure 3 Box-and-whisker plot of (a) root lengths employed by the students in both FTIs for Pistia and Eichornia plants, (b) Pistia root lengths employed by each group of students in the upstream FTI (group 5 did not employ Pistia root, and groups 8 and 9 did not present their results), (c) number of plants per FTI (upstream FTI), and (d) distance between velocity measurement sections employed by each group of students.

Figure 4 Longitudinal profile of the time-averaged streamwise velocity u, normalized by the channel-average velocity U₀. The root zone, denoted by the two vertical gray lines, has a length of 0.30 m. (a) Group 4; (b) Group 5.

Figure 5 (a) Comparison of final scores with PBL versus final scores without PBL for 34 students. The 45-degree line indicates equal performance (final score with PBL = final score without PBL). Points above the line signify PBL improvement, with a pronounced upward shift for lower initial scores, diminishing as scores increase, and some high performers aligning with or falling below the line, suggesting a non-linear, context-dependent effect. No regression line or correlation coefficient is included, as the trend’s complexity (e.g., ceiling effect) is better conveyed through this descriptive analysis. (b) Distribution of standard deviation in PBL scores across course average groups (passing >6, near 6, <6) for 34 students, highlighting variability in performance outcomes. A higher deviation above 6 suggests diverse efforts, lower near 6 indicates uniform improvement focus, and increased deviation below 6 reflects dispersed outcomes among challenged students.

Figure 6 Pie chart illustrating responses to the following questions: (a) “After completing the study, how do you evaluate FTIs as an engineering object?”. (b) “How would you rate your overall experience with the project? (5 being excellent and 1 being a completely negative experience).” (c) “How would you assess the importance of this project in relation to the subject studied?” (d) “What challenges did you encounter while developing the project?” (e) “What improvements can be made to enhance the understanding of the topic and the execution of the project?”

Table 1

Provisional grading matrix.

Criterion	Excellent (9–10)	Good (7–8.9)	Satisfactory (5–6.9)	Needs Improvement (<5)
Report Length (2500–5000 words)	Fully meets word count	Slightly below/above	Significantly off target	Incomplete
Topic Structure	Clear, logical flow	Minor organizational issues	Disorganized structure	Unclear or missing
Measured Velocity Graphs	Accurate, well-labeled	Minor errors or labels	Incomplete or unclear	Absent or incorrect
Mass Removal Calculations	Precise, correct	Minor errors	Significant errors	Absent or incorrect
All Measurements Presented	All included, detailed	Most included	Some missing	Few or none presented
Experimental Uncertainty	Thoroughly propagated	Partially propagated	Minimal propagation	Not addressed
1 Photo of the Island	High-quality, relevant	Acceptable quality	Poor quality	Missing
No Plagiarism	Fully original	Minor citation issues	Notable plagiarism	Significant plagiarism
ABNT-Compliant References	Fully compliant	Minor formatting errors	Major errors	Absent or incorrect

Note: This provisional matrix is based on the 0–10 scale per criterion, with the final score as the average. Performance thresholds will be refined with raw data analysis in the next revision.

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