Sanitary Sewerage Master Plan for the Sustainable Use of Wastewater on a University Campus

: Wastewater collection, transport, and treatment systems are essential to ensure human and environmental well-being. The Escuela Superior Polit é cnica del Litoral (ESPOL), has been implementing various sanitary sewerage systems; however, population growth has given rise to discussion on the installed capacity versus the necessary capacity for the future population in the sustainable management of water resources. Therefore, this study aimed to develop a sanitary sewerage master plan by analysing the existing situation and applying technical criteria for the sustainable use of wastewater on a university campus. The methodology consisted of (i) evaluation and diagnosis of the area studied through data collection and processing, (ii) design of the sanitary sewerage system considering area-expansion zones, and (iii) SWOT analysis of a proposal to enhance wastewater transport and treatment systems. The proposal contemplates designing a sanitary sewer system that will manage the collection, transport, and treatment of wastewater over 15 years for 5667 inhabitants located in three expansion zones with occupation periods of 5, 10, and 15 years. The sewerage system comprises a pipe network 1.19 km long and 200 mm in diameter, transporting 12.37 L/s of wastewater generated to two treatment systems that guarantee efﬁcient depuration and subsequent reuse. This design was complemented by a SWOT analysis of the existing sanitation system developed by experts in the area, which included optimising existing treatment systems and reusing wastewater for irrigation of green areas as tertiary treatment within the circular economy. The methodology used in the study allows us to offer a tool for efﬁciently managing wastewater on a university campus, guaranteeing human well-being, and promoting the circular economy of water.


Introduction
Approximately 70% of the Earth's surface is covered by water. However, less than 3% is freshwater [1]. As a result, domestic, industrial, and agricultural use of freshwater generates significant amounts of liquid waste, also called residual water, black water, or sewage [2], of which more than 80% is discharged into rivers or the sea without having been purified [3].
Raw wastewater comprises organic and inorganic matter: the remains of vegetables, animals, fats, oils, and small or large solids, such as fabrics, plastics, chemicals, and sand [4], which can be categorised as physical, chemical, and biological. To characterise these, some parameters have been defined, such as suspended and dissolved solids, biochemical oxygen demand (BOD 5 ), chemical oxygen demand (COD), and coliforms, among others, which represent worrying contamination agents [5]. The discharge of these contaminants into

Study Area
The study area is located Guayaquil, Guayas al Oeste, Ecuador ( Figure 2), with elevations from 25-380 m above sea level (m.a.s.l.). The lithology of the area corresponds to agglomerates, shale, and sandstone belonging to the Cayo Formation. The existing soils correspond to clayey sand and silty clay. The university campus has a primary and secondary forest called La Prosperina, which includes a diversity of flora (ceibo, carob, pechiches, among others) and fauna (birds, iguanas, squirrels, sloths, among others) [44]. The area has an average temperature of 26 °C, with two seasons: summer (June to December) and winter (January to May), with less than 2000 mm annual rainfall [45].

Study Area
The study area is located Guayaquil, Guayas al Oeste, Ecuador ( Figure 2), with elevations from 25-380 m above sea level (m.a.s.l.). The lithology of the area corresponds to agglomerates, shale, and sandstone belonging to the Cayo Formation. The existing soils correspond to clayey sand and silty clay. The university campus has a primary and secondary forest called La Prosperina, which includes a diversity of flora (ceibo, carob, pechiches, among others) and fauna (birds, iguanas, squirrels, sloths, among others) [44]. The area has an average temperature of 26 • C, with two seasons: summer (June to December) and winter (January to May), with less than 2000 mm annual rainfall [45].

Stage I: Data Collection and Processing
The work began with the topographical analysis of the study area. In this case programs as Google Earth (7.3.4.8642 version), ArcGIS (10.5 version), and Global Ma (23 version) were used to obtain contour lines every 5 m and generate a topographic Subsequently, the historical population of the university was reviewed from 2002 to to analyse the population's behaviour from 2021 for 15 years. According to INEN

Stage I: Data Collection and Processing
The work began with the topographical analysis of the study area. In this case, such programs as Google Earth (7.3.4.8642 version), ArcGIS (10.5 version), and Global Mapper (23 version) were used to obtain contour lines every 5 m and generate a topographic map. Subsequently, the historical population of the university was reviewed from 2002 to 2020 to analyse the population's behaviour from 2021 for 15 years. According to INEN 5:9:1 regulations [46], at least three population-projection methods must be used. This study used four: arithmetic, simple interest, geometric, and exponential. The objective of the analysis was to determine the population behaviour of the university campus to define the potential location of expansion zones that supply the population for the analysed design period. For the site of these areas, it was necessary to review the plans, record the characteristics of the existing sewerage system, project restrictions due to its location within a protected area, and combine it with the population analysis.
Finally, through limited field trips, given the health situation due to COVID-19, the current state of the sanitary sewer system was inspected. Likewise, the existing treatment systems were reviewed according to the type of treatment they carry out, the contribution areas they satisfy, and the flow they receive. The objective of this evaluation was to determine if the existing system can purify the additional flow that future expansion zones will generate in accordance with the regulations of book six of the Unified Text of the Secondary Legislation of the Ministry of Environment (TULSMA) [47].

Stage II: Technical Proposal Design
The results of Phase I formed the basis for designing the new sewerage network in the proposed expansion areas. From the projected population to 2035, the number of inhabitants occupying the expansion zones in the next 15 years was selected. For calculating the volume of wastewater collected by the sewerage network and due to the nature of the project (a set of buildings for educational purposes), the study considered the endowment values proposed by chapter 16 of the Norma Hidrosanitaria NHE-AGUA [48]. Through hydraulic relations, the system was designed to meet the minimum requirements of slopes, diameters, and speeds. Furthermore, the network design that supplies the expansion zones verified that the existing sewerage network that continues after the wells where one system will be connected to another could satisfy current and future demand. For this, the flow generated by the expansion zones was added to the flow proposed by studies [49,50], and similarly the minimum requirements were verified. These minimum considerations follow the recommendations of the INEN 5:9:1 standard INEN 5:9:1 [46] and the Manual de Diseño de Redes de Alcantarillado of the drinking water and sewerage concession company of Guayaquil Interagua [51] ( Figure 3).

Stage III: SWOT Analysis
The study ended with a strength, weakness, opportunity, and threat (SWOT) analysis [52] of the existing sewer system and proposed system for expansion zones. This analysis

Stage III: SWOT Analysis
The study ended with a strength, weakness, opportunity, and threat (SWOT) analysis [52] of the existing sewer system and proposed system for expansion zones. This analysis will make it possible to define strategies to guarantee the proper functioning of wastewater transport and treatment systems in present and future scenarios, considering the social, environmental, and economic axis. Three focus groups carried out the analysis: (i) experts in wastewater management (civil and chemical engineers), (ii) authorities of the institution, and (iii) the study authors.

Results
The results of this study are shown through maps, figures, and tables detailing the topography, protection zones, existing and projected sewerage network for the expansion areas, historical and future population, and current status of sewage treatment systems, among others.

Existing Information
The campus is in an area with an irregular morphology that includes elevations between 25 and 450 m above sea level ( Figure 4) and maximum slopes of 45 • . This allows the formation of a series of natural drainage systems that preserve the protected forest and flow through a storm drainage system that avoids flooding problems on campus. The main buildings, where most of the university's activities occur, are mainly in the light-green zone.  For management and planning purposes, the ESPOL property is divided into 14 zones, excluding the low reserve property of 17.36 ha on the other side of Perimeter Road. Zones Z1 and Z8, with an area of 200 and 186.39 ha, respectively, occupy the most space. Most of the Z4, Z8, and Z10 zones belong to the Prosperina protected forest ( Figure 5).   For management and planning purposes, the ESPOL property is divided into 14 zones, excluding the low reserve property of 17.36 ha on the other side of Perimeter Road. Zones Z1 and Z8, with an area of 200 and 186.39 ha, respectively, occupy the most space. Most of the Z4, Z8, and Z10 zones belong to the Prosperina protected forest ( Figure 5). Zone 1 has the smallest population, despite having the most significant area. According to the data analysed, zones 2, 3, 8, 9, 11, and 12 contain most of the population (Table  1).  Zone 1 has the smallest population, despite having the most significant area. According to the data analysed, zones 2, 3, 8, 9, 11, and 12 contain most of the population (Table 1). From the map of protection zones, we can distinguish between the intervention zone map, with an area of 325.69 ha (existence of infrastructure), and the zones where intervention is not allowed for forest-preservation purposes. These zones include core zone 1, core zone 2, the permanent protection zone and the buffer zone, which cover an area of 332.30 ha, not including the area generated by the right of way of the polyduct (17.76 ha) that crosses the property ( Figure 6).
Water 2022, 14, x FOR PEER REVIEW 7 From the map of protection zones, we can distinguish between the intervention map, with an area of 325.69 ha (existence of infrastructure), and the zones where inter tion is not allowed for forest-preservation purposes. These zones include core zone 1, zone 2, the permanent protection zone and the buffer zone, which cover an area of 3 ha, not including the area generated by the right of way of the polyduct (17.76 ha) crosses the property ( Figure 6).

Sewerage and Treatment System
The campus has a sewer system that conveys the wastewater discharge of the current population. The system is connected to infrastructure that performs storage and treatment functions, comprising a WWTP-MBR, a WWTP-DAF, an activated sludge plant, two stabilisation ponds, and 16 septic tanks (Figures 8 and 9).

Sewerage and Treatment System
The campus has a sewer system that conveys the wastewater discharge of the current population. The system is connected to infrastructure that performs storage and treatment functions, comprising a WWTP-MBR, a WWTP-DAF, an activated sludge plant, two stabilisation ponds, and 16 septic tanks (Figures 8 and 9).
According to the layout of the networks, there are four contributing areas. In contribution area one (CA1), most of the population is concentrated and includes the engineering faculties, administrative buildings, and sports and green areas. In contrast, contribution area two (CA2) is the second-most populated area because it contains the university's research centres, sports areas, public companies, and an educational institution belonging to ESPOL. On the outskirts of the campus is contribution area three (CA3), where the admissions building is located, with a considerable population because it receives those students who are taking a levelling period for access to the university. Finally, the fourth contribution area (CA4) corresponds to the Information Technology Centre-ITC, with a smaller population ( Figure 8).  According to the layout of the networks, there are four contributing areas. In contribution area one (CA1), most of the population is concentrated and includes the engineering faculties, administrative buildings, and sports and green areas. In contrast, contribution area two (CA2) is the second-most populated area because it contains the university's research centres, sports areas, public companies, and an educational institution belonging to ESPOL. On the outskirts of the campus is contribution area three (CA3), where the admissions building is located, with a considerable population because it receives those students who are taking a levelling period for access to the university. Finally, the fourth contribution area (CA4) corresponds to the Information Technology Centre-ITC, with a smaller population ( Figure 8). Based on the fieldwork and the information available on the operation of the wastewater treatment systems, it was determined that the MBR plant corresponded to the system with the largest capacity on campus, while the septic tanks represented the systems with the smallest treatment capacity based on their size (Table 2). In general, all systems require maintenance, improvements, and upgrades.  Based on the fieldwork and the information available on the operation of the wastewater treatment systems, it was determined that the MBR plant corresponded to the system with the largest capacity on campus, while the septic tanks represented the systems with the smallest treatment capacity based on their size (Table 2). In general, all systems require maintenance, improvements, and upgrades. Pond systems (a) It consists of a maturation lagoon and a facultative lagoon that operate as a series system. The estimated volume of the facultative lagoon is 637.10 m 3 , and of the maturation, the lagoon is 812.90 m 3 . It is in a condition to continue operating with the appropriate improvements. (b) The lagoons' volume is generally insufficient to ensure hydraulic retention times for pollutant load removal. (c) During the rainy season, treated water from the MBR plant is discharged into the lagoon system, which decreases the retention time of the system and slows down its treatment process. (d) The system has specific overflow areas that do not comply with the maximum BOD 5 limit for discharge to freshwater bodies. (e) A lack of preliminary treatment to remove coarse solids hinders the treatment process. The entire campus Septic tank They require cleaning and maintenance.
According to the analysis performed in the Avalos and Guerrero study [49], the concentration of TSS, COD, and BOD 5 of wastewater samples from CA1 was able to be estimated (Table 3). Based on previous studies, a set of technical proposals for improving and optimising treatment systems has been proposed (Table 4). Table 4. Proposals for improvement of existing treatment systems.

Area
Type of Treatment System Description Pond systems (a) Survey the dimensions of the stabilisation ponds to know the real volume of sewage that can be stored to determine the maximum influent that must be received to achieve sufficient retention times and acceptable pollutant load removal percentages. (b) Design of desander to protect the performance of the pumps and the treatment system. (c) Diversion of the MBR plant is treated water discharge, currently discharged into the lagoon system to a natural drainage point [49].

CA2
Stabilisation ponds (a) Optimising the existing system, transforming it into a horizontal sub-surface flow wetland with the exact dimensions to comply with secondary treatment processes, where it was estimated that 80% of TSS and 31% of BOD 5 would be removed, complying with the parameters established in the standard. (b) Design a desander 4.40 m long, 1 m wide, and 2 m deep as a preliminary treatment so that 25% of TSS and 20% of BOD 5 will be removed, complying with the parameters established in the standard [54].
The entire campus Septic tank (a) Design a wastewater collection system to carry the water stored in the wells to the stabilisation pond located in CA2 ( Figure 8).

Population Projection
Due to the population decrease as of 2015, the trend of the projection methods used was compared with the population growth from 2002 to 2014. Based on the results obtained, the arithmetic and simple interest methods were the ones that best matched the historical growth. Through these methods, the average of both methods was equal to 24,698 inhabitants for 2035 (Figure 10), which corresponds to the design population.

Definition of Expansion Areas
Not including the ZEDE zone, in 2019 the populated area was 14.80 ha, with a dens of 28.92 person/ha, while for 2035 it was estimated to be 25.36 ha, with a density of 39 person/ha. Therefore, the required expansion area, obtained from the difference betwe the populated area of both years, was equal to 10.56 ha (Table 5). Considering the limitations of the protected areas, topography, proximity to acc roads, and the availability of essential services, three expansion zones of 7.04, 2.56, a 1.07 ha were located, corresponding to expansion zones 1, 2, and 3 (EA1, EA2, EA3), spectively ( Figure 11). The three zones total 10.61 ha, and their occupation is proposed 5, 10, and 15 years.

Definition of Expansion Areas
Not including the ZEDE zone, in 2019 the populated area was 14.80 ha, with a density of 28.92 person/ha, while for 2035 it was estimated to be 25.36 ha, with a density of 39.84 person/ha. Therefore, the required expansion area, obtained from the difference between the populated area of both years, was equal to 10.56 ha (Table 5). Considering the limitations of the protected areas, topography, proximity to access roads, and the availability of essential services, three expansion zones of 7.04, 2.56, and 1.07 ha were located, corresponding to expansion zones 1, 2, and 3 (EA1, EA2, EA3), respectively ( Figure 11). The three zones total 10.61 ha, and their occupation is proposed in 5, 10, and 15 years.

Sewerage Design in Expansion Areas
With an initial endowment of 50 L/inhab•day, it was considered that for each year of the design period (15 years), the endowment increases at a rate of 1.5%. Finally, the projected endowment resulted in 62.5 L/inhab•day for 2035 (Table 6). The design flow rates for EA1 were calculated based on the endowment values in Table 6, obtaining a maximum flow rate equal to 0.0124 m 3 /s ( Table 7). The hydraulic design of the network was checked through the parameters of minimum slope (S), which fluctuates between 0.015 and 0.030 m/m, flow velocity (v), with a range between 0.72 and 0.94 m/s, and the tractive force (τ) between 5.44 and 6.67 N/m 2 . Diameters of Ø200 mm were obtained for both systems (Table 8).

Sewerage Design in Expansion Areas
With an initial endowment of 50 L/inhab·day, it was considered that for each year of the design period (15 years), the endowment increases at a rate of 1.5%. Finally, the projected endowment resulted in 62.5 L/inhab·day for 2035 (Table 6). The design flow rates for EA1 were calculated based on the endowment values in Table 6, obtaining a maximum flow rate equal to 0.0124 m 3 /s ( Table 7). The hydraulic design of the network was checked through the parameters of minimum slope (S), which fluctuates between 0.015 and 0.030 m/m, flow velocity (v), with a range between 0.72 and 0.94 m/s, and the tractive force (τ) between 5.44 and 6.67 N/m 2 . Diameters of Ø200 mm were obtained for both systems (Table 8). Table 7. Design flow rates for expansion zone 1.  The capacity of the existing sewer network that continues from manhole MN-8 (the existing connection well that receives the discharge from EA1) to WWTP-MBR was verified. As a result, the diameter required to supply the current and future demand fluctuates between 130 to 147.4 mm ( Table 9). On the other hand, the diameter of the pipes downstream of MN-8 is Ø200 mm and was verified by fieldwork. Additionally, the hydraulic design of the system was reviewed according to the values of slope, velocity, and tractive force (Table 10).  The same procedure was followed for designing the sewerage network in EA2-3. First, based on Table 6, the design flow rates were calculated, obtaining a maximum flow rate of 0.0067 m 3 /s (Table 11). Then, with the parameters of the slope, velocity, and tractive force, whose values fluctuate between 0.009 to 0.001 m/m, 0.63 to 0.69 m/s, and 3.36 to 3.77 N/m 2 , the hydraulic design of the system was carried out (Table 12). Table 11. Design flow rates for expansion zones 2 and 3. Likewise, the capacity of the existing sewerage network from manhole MN-18 (the existing connection well that receives the discharge from EA2-3) to the CA2 stabilisation pond was reviewed. The diameter required to supply the current and future demand ranges from 153.9 to 200 mm (Table 13). Finally, the hydraulic design was reviewed through slope, velocity, and tractive force (Table 14).  Table 14. Hydraulic parameters of the pipeline connecting to the sewerage system of EA2-3.  The capacity of the WWTP-MBR to meet the additional demand generated by the sewerage network proposed for EA1 was also analysed. For this purpose, two scenarios were considered: Considering the endowment and return coefficient values in Table 6 and the fact that the campus maintains 16 h of activity, the values of average flow (from CA1) and design flow (from EA1) were calculated to analyse the proposed scenarios (Tables 15 and 16). However, for capacity analysis during the day, the WWTP-MBR, due to each pump's startup and shutdown processes, has a total operating time of 6 hours per day; therefore, this net operating period was taken. Based on the future flow, the capacity at which the plant would be operating for both scenarios during its net operation period was determined, obtaining the highest capacity for scenario two (91.90%) (Table 17). The capacity of the WWTP-MBR to meet the additional demand generated by the sewerage network proposed for EA1 was also analysed. For this purpose, two scenarios were considered: Considering the endowment and return coefficient values in Table 6 and the fact that the campus maintains 16 h of activity, the values of average flow (from CA1) and design flow (from EA1) were calculated to analyse the proposed scenarios (Tables 15 and 16). However, for capacity analysis during the day, the WWTP-MBR, due to each pump's startup and shutdown processes, has a total operating time of 6 h per day; therefore, this net operating period was taken. Based on the future flow, the capacity at which the plant would be operating for both scenarios during its net operation period was determined, obtaining the highest capacity for scenario two (91.90%) (Table 17). In the case of the sewerage network for EA2-3, which connects to the CA2 lagoon, based on the estimates made by the studies of Arias Vivanco and Fernández Cuesta [50] and Quiñonez Zambrano and Vintimilla Peña [54] on the lagoon located in CA2, based on the hydraulic retention time, it was determined that it did not have sufficient capacity to meet current and future demand (Table 18).

SWOT Analysis
The SWOT analysis used in this study made it possible to establish specific strategies for the existing sanitation system (Table 19) through the combination of internal and external characteristics that include management, design, environmental, financial, academic, and social aspects. As a result, the proposed strategies will make it possible to manage wastewater, minimising the environmental impact sustainably. Specifically, the analysis provided by the three focus groups establishes as the primary strategy the contribution of academia in projects to optimise the existing sanitation system, guaranteeing water reuse for irrigation. Table 19. Strengths, weaknesses, opportunities, and threats (SWOT) matrix analysis of current and proposed sewer system. The SWOT combines the internal environment (strengths and weaknesses) identified by numbers 1 to 4 and the external environment (opportunities and threats) identified by letters (a) to (d).

External Environment
Strengths Weaknesses  3.c. Implement tertiary treatment to limit the discharge of nutrients to water bodies, e.g., the use of green filters.

Discussion
This study raises the possibility of achieving sustainable development by starting with the elaboration of a master plan that-based on an evaluation and diagnosis of the existing situation-foresees whether or not the current infrastructure will be able to meet the future demands of wastewater production and its treatment before being discharged into the environment. Better yet, it proposes that these effluents be used sustainably in the irrigation of gardens, for example, in the extensive green areas that the ESPOL campus has, promoting the circular economy of water.
According to the population projection, ESPOL will increase to 24,698 inhabitants in 2035. Therefore, the plan includes three expansion areas (EA1, EA2 and EA3), totalling 10.61 ha, corresponding to three development phases of 5, 10, and 15 years. For this, the design of the sewer network complies with the technical and regulatory criteria in terms of speed, slope, and tractive force to avoid sedimentation and erosion problems as stipulated in this design [55]. Likewise, these zones were in the sites with the most negligible impact on the protective forest environment, delimited by the buffer zones defined by the physical infrastructure management (GIF).
The MBR plant supplies the current and future capacity fully; however, it requires maintenance and equipment replacement to improve pollutant removal efficiency. In addition, the anaerobic lagoon (in design, but not in implementation) located in CA2, due to the low level of the water mirror, should be wholly redesigned as proposed by some initiatives that did not include the contribution of the EA3 [50,54]. Currently, these anaerobic systems are usually avoided for domestic wastewater because they do not have high levels of pollutant load [56][57][58]. On the other hand, these systems are very effective in industrial processes [59,60]. However, considering that the pollutant load of CA2 is very low, a viable alternative could include the implementation of a subsurface horizontal flow lagoon as proposed by [54]. Population projections in land design and planning studies do not always reflect the actual behaviour of urban development, resulting in inefficient designs with excess capacity and high operating costs [61][62][63]. Therefore, the construction of new treatment systems or the adaptation of existing systems, when developed in stages, would reduce operation and maintenance costs, in addition to guaranteeing operation in future scenarios [64][65][66].
The master plan of this study is reinforced by the SWOT analysis, which contemplated the proposal of corrective, preventive, and predictive strategies for the existing sanitation system's short, medium, and long term. Specifically, the analysis conducted by the three focus groups determined that the existing sanitation system requires optimisation activities for future scenarios and preventive maintenance of infrastructure. Of the proposals put forward, the following stand out: • Conduct evaluation studies of the sewerage system and treatment systems for the establishment of sustainable techniques in the management of wastewater, which supply the current and future demand, promoting the sustainable development of the campus. • Promote effective water reuse through tertiary treatment systems, which contemplate the installation of green filters for future irrigation plans and agricultural experimentation. Unconventional treatments, such as nature-based treatment systems, represent efficient tools in wastewater purification with low implementation, operation and maintenance costs, as well as limited energy use [67][68][69]. Within these systems, the vegetation filters and soil application system or commonly called green filters, allow reaching levels of purification suitable for the reuse of water [70,71], through mechanisms of absorption in the soil, biodegradation and absorption by plants, processes responsible for eliminating contaminants in the water [72,73].

•
Develop educational workshops on sustainable water management at the institutional and inter-institutional levels.

•
Establish academic-business cooperation alliances to promote research and financing for projects that seek to implement the circular water economy. • It is proposed that treated wastewater be used for irrigation of green areas and for studying crops in the area of the university's Agricultural Experimental Farm due to its nutrients [74]. • Provide the opportunity for students and other professionals to research the consumption of products produced from treated wastewater [37,[75][76][77].
This methodology can be replicated in other universities and at the urban level because it promotes wastewater management and seeks the alternative of more environmentally friendly treatment systems [78,79]. In addition, this is aesthetically appealing as it can boost recreational and academic activities [80,81]. This type of study is widely employed in such countries as Bali [82], Indonesia [83], the USA [84], Tanzania [85], China [86], Vietnam [87], and Ecuador [88].
The rural areas of Ecuador are characterised by the absence of sanitary systems that guarantee the transportation and purification of wastewater (e.g., [89][90][91][92][93][94]). In many cases, it is discharged directly into bodies of water, polluting the environment and compromising the health of the inhabitants and ecosystems. Few studies have focused on improving the country's sanitary system at the rural level (e.g., [55,[95][96][97]). However, they serve as management models that can be executed at the municipal level with individual plans for prevention, mitigation, and correction of environmental impact. Considering that one of the productive axes of Ecuador is agriculture, future studies could include the implementation and optimization of purification systems that guarantee their use in irrigation systems for the productive sector, promoting the sustainability of water resources.
According to UI Green metric World University Ranking, ESPOL is among the green universities in the world, being the first at the national level [98], so the contribution of this research provides a management tool that promotes the sustainable use of water, opening the possibility of obtaining a higher ranking. On the other hand, considering that the university campus has sites of relevant geological interest that can be used in geo-education strategies [99], sustainable wastewater management will serve as a geoconservation strategy. Therefore, implementing the proposed design will minimise environmental contamination, avoid the degradation of geosites and sites of natural interest [100,101], and guarantee good conditions for geo-tourism and geo-educational activities.
Furthermore, this contributes to training young professionals who are more aware of sustainability [98,102]. Young people are the real drivers and architects of the change of paradigms on this planet and can effectively manage to protect a valuable and irreplaceable resource, such as water on Earth.

Conclusions
ESPOL, located in southwest Ecuador, is an example of a university campus that must strengthen its health system to supply future scenarios. This study developed a master plan that defines the location of future expansion zones complemented by the existing wastewater transportation system, as well as medium-and long-term improvement strategies that ensure the hydraulic performance of the sewer network and effective treatment processes.
As a result, the design and proposals established in this study highlight three main aspects: (i) The sewerage system for the proposed EAs will be made up of 200 mm diameter pipes that will supply a maximum flow of 12.37 L/s for a design period of 15 years. The new discharge generated will be connected to two existing inspection wells, connected by pipes with adequate dimensions, guaranteeing the transport of residual water to the treatment systems. (ii) From the existing treatment systems, the WWTP-MBR and the adjoining pond system in CA1, together with the stabilisation pond located in CA2, will receive the new discharge from the proposed systems. Therefore, the evaluation of these systems, together with the SWOT analysis, included preventive, corrective, and predictive strategies: (i) evaluation of the capacity of the treatment systems, (ii) permanent analysis of water quality that guarantees the required removal percentages, and (iii) implementation of tertiary treatment systems that contemplate the effective reuse of water. (iii) The importance of the master plan is that it allows the identification of problems associated with poor management and improves it through a comprehensive management model that provides solutions based on technical and sustainable criteria, being the innovative part that opens the opportunity for studies carried out by the same students under the supervision of professionals; allowing to strengthen learning.
Finally, this study demonstrates that joint participation among academia, research, and authorities allows the efficient management of wastewater, promoting the circular economy in a context of sustainability.