FILTER GARDENS A NATURE-BASED SOLUTION FOR GRAY WATER TREATMENT

Purpose: Analyze the feasibility of implementing a filtering garden, as an alternative technology for gray water treatment. Theoretical framework: The lack of adequate sanitation can lead to the improper discharge of sewage into bodies of water, thus deteriorating the quality of the water available for supply. Built wetlands appear as a social technology, providing a possibility for advancement and universalization of basic sanitation, also in line with the Sustainable Development Goals of the UN 2030 Agenda. Method: Hypothetical-deductive approach and study of the potential and difficulties encountered in implementing a filter garden with subsurface drainage and horizontal flow, using unusual plants. The volume of water that entered the garden daily was observed and also the efficiency between the input and output of the COD, BOD, DO and dissolved solids parameters. Results and discussion: Based on the volume of water observed, it was not possible to establish a consumption pattern in this building. For the variables analyzed, a removal of approximately 85% of COD, 97% of BOD and 68% of TDS and an increase of 49% of DO was obtained. Implications of the research: The garden installed was efficient and could be replicated in other areas of the University. However, more research and ongoing monitoring are needed to ensure its successful implementation and operation on a large scale. Originality/value: The results obtained suggest that the filter garden is a promising technology, even using plants that are not usual for this purpose, for the treatment of lavatory effluents, offering an effective, sustainable and economical solution for water purification and being aligned with the objectives of sustainable development.


INTRODUCTION
Water is a natural, renewable and vital resource for all living beings, for the economic development of any region and for social well-being.And over time, it is gradually becoming a good with a great threat of scarcity, whether due to high demand or increasing pollution of sources.
The availability of water resources places Brazil in a privileged position, as the country concentrates around 12% of the world's fresh water, however, its distribution does not occur uniformly across the national territory, so that the North region is the less populated and holds most of the national water ( Marengo ;Tomasella ;Nobre, 2017).Pollution occurs when water quality is compromised in some way, harming the safety and wellbeing of living beings.It is generally caused by sewage and garbage improperly dumped into the water.This improper discharge of sewage into water bodies can lead to the incidence of waterborne diseases, whether due to natural or synthetic contaminants ( Bekkari ;Amiri ;Hadjoudj , 2022;Rezende et al., 2021).
There are many countries where available freshwater resources are already compromised and, to prevent a water crisis, they must use water more efficiently.Optimally manage supply and demand, pollute less and reduce the environmental impacts of the growing population, preserving water resources ( Angelakis , 2018).It is essential that greater efficiency policies are established, thus making sanitation an important strategy in mitigating or reversing the impacts caused, controlling factors in the physical environment.
The issue of water and sanitation is transversal, that is, it cuts across and has an impact on different sectors of life, such as health, environmental quality and the economy.In the current water situation, it is essential to adopt simple treatment alternatives that enable water reuse .These reuses positively imply social, economic and environmental benefits.
The technology used in water and sewage treatment is highly advanced, however, it still faces significant challenges, especially in terms of costs, which vary according to the concentration of pollutants.The quality of water resources in springs has been decreasing, being impacted by irregular land occupation and the direct release of effluents without adequate treatment ( Iaqueli , 2016).wetlands ( WCs ) stand out as a highly efficient and accessible ecotechnology , providing water reuse and promoting the creation of biodiverse ecosystems .These toilets represent an environmentally friendly solution for wastewater treatment, being widely used in the purification of various types of effluents, including domestic sewage, industrial effluents, rainwater and urban runoff.
The filtering garden, a type of wetland , is an example of an alternative system for treating effluents, whose objective is to provide an appropriate destination for the water used.
The water goes to a waterproof reservoir with a layer of gravel and another of sand, where above are plants that act as absorbers of nutrients and contaminants.Thus, the operation consists of filtering water through the roots of macrophyte plants, the filtered water can be reused or simply returned to the environment correctly (Silva;Ramos, 2018).

4
The importance of plants for the system is mainly due to the root zone, which concentrates bacteria that consume organic matter and carry out biochemical processes to remove nutrients.
In order to seek simplified, sustainable and low-cost solutions to the problems mentioned above, countries around the world have studied feasible ways of treating effluents ( Albalawneh et al., 2016).The possibilities and potential forms of reuse depend on local characteristics, conditions and factors, such as political decision, technical availability and economic, social and cultural factors.Therefore, it is essential to seek alternative sources of water supply, such as reuse for non-potable purposes, such as irrigation, ornaments, washing floors, patios and use in toilets ( Collivignarelli et al., 2020).
The objective of wastewater treatment is to eliminate elements that are toxic to humans and ecosystems, fulfilling hygiene and environmental functions.Treating this wastewater through unconventional systems such as constructed wetlands is a widely used approach with reliable and efficient results ( Gorgoglione ;Torretta , 2018).These ecological engineering systems are effective in removing many pollutants, such as organic compounds, pathogens, and also emerging pollutants ( Kujala et al., 2019).
The United Nations (UN), in its Sustainable Development Goals (SDGs), lists several goals to be achieved, with the purpose of providing water in quality and quantity that provides the well-being of the population, due to the connection with health (UNDP, 2019).Furthermore, World Water Development Report (WWDR) or World Water Development Report 2021, made public quantitative data on the increase in freshwater consumption, mainly driven by population growth, economic development and consumption patterns, in addition to qualitative data, which indicate a decrease of the quality of the resource (UN, 2021).
The contemporary search for clean, sustainable and economical technologies brings relevance and emphasis to this study, which seeks results on the efficiency of this type of treatment, as well as benefits to the environment through the replication of a natural ecosystem, with low implementation and maintenance costs.Reaffirming its magnitude, the research speaks to the SDGs of the 2030 Agenda, directly with goals 3 -health and well-being, which has as one of its focuses combating waterborne diseases, and 6 -drinking water and sanitation, which has the central concern with the existence of safe, drinking water for everyone.
Therefore, the study aims to analyze the feasibility of implementing a filtering garden, as an alternative technology in the treatment of gray water.To achieve this general objective, the following specific objectives were introduced: Check the daily volume of gray water that reached the garden; Identify the potentialities and weaknesses in the filtering garden system implementation processes; Check the efficiency of the treatment in terms of reducing physicalchemical parameters.
This work takes into account the problem of lack of access to basic sanitation in many locations, this impossibility causes a reduction in the quality of life and well-being of the population, preventing them from developing in a sustainable manner.A viable solution is then sought using filter gardens, which have great utility, not only being useful for water treatment, but can also be used for decorative purposes, in order to contribute to reducing demand in the public water system.sanitation.

THEORETICAL FRAMEWORK
Brazil is privileged in terms of water availability since it holds around 12% of the world's fresh water, in addition to having equatorial and tropical climates that provide high rainfall, but the distribution of water is not uniform within the territory.Lakes and rivers are the most relevant source of drinking water, however, they represent less than 0.01% of the global amount of water (Tucci;Hespanhol ;Netto, 2000;Marengo , 2014).

WATER AND SANITATION
Increased water consumption and pollution of water sources are rapidly reducing the availability of fresh water in the world.This is worrying, as water is essential for agricultural, urban and industrial development.Water pollution, caused by inappropriate discharges of industrial and agricultural waste and domestic sewage, affects human, animal and plant health.( Hespanhol , 2002;Matos, 2020).
According to data attributed by the National Sanitation Information System (SNIS) (2015), Sergipe was the state that had the greatest water waste in the Northeast, and causes such as leaks in pipelines, networks, branches, connections and reservoirs of water providers services responsible for supply caused a loss of 59.3% between treatment and distribution.In 2021, the State's rate was 48.4% (SNIS, 2022), which represents a waste of almost half of all treated water that was distributed to the population.In the Northeast, Sergipe was only behind Maranhão, Rio Grande do Norte and Alagoas.
For Gadelha et al. (2021), a serious problem in Brazil is pollution from domestic effluents, causing constant concerns about water safety, which includes the potential presence Currently, there are rare exceptions in which available water sources are not subject to critical pollution conditions, with both traditional and emerging pollutants.( Hespanhol , 2015).
Emerging pollutants are compounds that encompass various residues that should not be found in the environment, among which we can highlight pharmaceutical products, contraceptives, fragrances, sunscreen, medicines, pesticides and illicit drugs, whose presence in this ecosystem can cause damage to health.human.( Maximino , 2018).
With this, Gadelha et al. (2021) indicate some obstacles encountered when talking about basic sanitation.Highlights include the lack of commitment from authorities responsible for managing public health problems and the lack of knowledge on the part of a significant proportion of people regarding basic hygiene principles.Such factors effectively contribute to diseases such as cholera, yellow fever, leptospirosis, schistosomiasis, etc. , already extinct in the past, returning to infect Brazilian populations, especially the most vulnerable.
In 2021, according to data from the SNIS, the total water supply service index showed relatively high values, with a national index of 84.2%.However, in terms of sanitation, treatment assistance was much lower, with a national rate of 51.2%.It was observed that 35.7% of Brazilians use alternative measures to deal with waste, whether through septic tanks, rudimentary septic tanks or dumping sewage directly into rivers.Furthermore, in Sergipe only 38.3% of the population has a sewage network, these numbers show the current situation of basic sanitation in Brazil.
To deal with these challenges, the Brazilian government instituted Law No. 14,026/2020, which deals with the new regulatory framework for basic sanitation, hoping to resolve the problems of water supply and sewage collection.(Gadelha et al., 2021).The new milestone is inserted in the context of the UN Agenda 2030 SDGs, being closely linked to Goal 06, which talks about drinking water and sanitation for all.
In this sense, non-centralized and sustainable social technologies for sewage treatment may be a possibility for implementation in distant or rural locations, with low population density.Among these forms of treatment are Filter Gardens, which are based on purifying sewage through physical, chemical and biological processes from flooded regions and plants.

WATER REUSE
Reuse is defined as the direct or indirect use of water that has already been used to meet other needs.Reuse water is determined by the reuse of water, which comes from treated effluents.Reuse can be classified as an instrument for reducing water consumption and a complementary water resource (Morais et al., 2015) .
Through reuse , drinking water can be used for essential purposes, allowing reused water to be used for agricultural activities, for example.The use of reused water in agricultural irrigation is justified, as irrigation is one of the factors that contribute to a scenario of increasing scarcity ( Schaer -Barbosa;Santos;Medeiros, 2014;Rebouças, 2003).
The filtering garden is an alternative for the proper disposal of sewage from sinks, tanks and showers, called gray water.Gray water is any wastewater resulting from domestic actions, such as washing dishes, clothes and taking a shower, and corresponds to 50% to 80% of all sewage produced in homes.Gray water is different from black water (toilet sewage) due to the quantity and composition of chemical products and biological contaminants, receiving its name from its cloudy appearance.If there is no interest in reusing gray water after passing through the filter garden, it will be free of contaminants and can be discarded into the environment (Silva, 2016).
The practice of reusing effluents is increasingly becoming an essential part of water management, promoting the conservation of high-quality water and reducing both environmental pollution and the high costs associated with supply.It is an effective local solution to the problem of water scarcity, helping to avoid pollution ( Al-Hamaiedeh , 2010).
The water reuse activity appears as an alternative that has several applicability, depending on the final quality of the effluents.According to ABNT NBR 13969/97, parameters such as turbidity, pH, thermotolerant coliforms, dissolved solids, residual chlorine and dissolved oxygen are decisive for inclusion in one of the non-potable reuse classes.
Resolution No. 542005 of the National Water Resources Council ( CNRH) ( BRAZIL, 2005) considers following the guideline adopted by the Economic and Social Council of the United Nations -UN.According to this guideline, unless there is great availability, no good quality water should be used in activities that tolerate lower quality water.
In 2023, the Senate approved Bill 175/2020, which obliges the Union to adopt measures aimed at reducing water waste and encouraging reuse in new constructions, as well as in landscaping, agricultural, forestry and industrial activities.For non-potable purposes, the reuse of rainwater and gray water should be prioritized.
In this sense, the reuse technique meets the principles of environmental sustainability.
The reuse of water makes it possible to rationalize this resource for future generations.
Therefore, sustainable practices must align human needs with the potential of available resources (Boff, 2012;Hespanhol , 2002).

SOCIAL TECHNOLOGY
Social Technology (TS) is a term that comprises a product, technique and/or methodology that can be replicated and developed together with the community to effectively solve socio-environmental problems, presenting itself as an innovative development proposal.9 effective and reapplicable, providing social development on a large scale (Archanjo Junior;Gehlen , 2020;Fundação Banco do Brasil, 2017).Social Technologies emerge in the opposite direction to conventional technology, seeing science as an obvious path to building possibilities that can overcome social inequalities, especially in countries considered to be developing (Girão et al ., 2019).Baumgarten (2008, p.104), says about the topic:

ST combines popular knowledge, social organization and technical-scientific knowledge, being
The debate on sustainability and its relations with the production of knowledge has become central in global society, notably in countries on the global semi-periphery such as Brazil, which are characterized by high levels of economic and social exclusion.This debate refers to the relationship between the production of science, technology, innovation and social needs and the growing importance of the appropriation, by different social actors, of scientific knowledge that can be socially incorporated to solve problems, generating social innovation.These questions bring to the fore the concepts of conventional technology and social technology and their relationships with development and social inclusion.
This concept therefore symbolizes a different way of reflecting technological development, divergent from conventional scientific thinking, as it proposes the development of sustainable, participatory technologies managed by the communities themselves.TS develop an ability to confront social problems by seeking to associate different actors around the design of solutions that promote social inclusion and environmental conservation.To guarantee the realization of this potential, it is essential that there is a combination of knowledge, bringing together scientific knowledge with traditional knowledge ( Dagnino , 2014).
According to Dagnino (2014), one reason that underlies the relevance of ST today is the still initial competence of public organizations responsible for scientific and technological production to ensure the development of applicable and qualified ST to cause positive impacts on social inclusion.Baumgarten (2008) corroborates that the debate refers to the relationship between doing science, technology, innovation and social demands and the progressive relevance of appropriation, by different social actors, of scientific knowledge that can be added socially to solve problems, generating social innovation .In this way, social technology becomes a basis for articulating a network of social actors and also as a tool for social emancipation.
To reduce the damage caused by the lack of basic sanitation in isolated locations, the implementation and effectiveness of a social technology will only be favorable if associated 10 with continuous education processes, through constancy and information (Marques et al ., 2012).TS, in the rural sanitation scenario, intends to include the population and provide access to sanitation services, especially for family farming, which is not adequately served by conventional technologies.Some social technology options for sewage treatment have been successfully implemented in rural areas.Among them, we can highlight the biodigester septic tanks , developed by the Brazilian Agricultural Research Corporation -EMBRAPA (Ramos, 2017).
Another social technology alternative, in the ecological sanitation environment, are Filter Gardens, which can be classified as a Social Technology because of their purpose of conserving renewable natural resources, the plurality of plants used and enabling inclusion and benefits for all communities (PINOTTI, 2022).

FILTER GARDENS
The filter garden is an artificial wetland used to clean gray water (Figure 1).Constructed wetlands, also known as constructed wetlands , are effluent treatment systems based on the principles of water quality modification that occur in natural wetlands.In wetlands , effluents are treated through a combination of biological, chemical and physical mechanisms (Von Sperling , 2005).

Figure 01
Filter garden scheme.this problem would be alleviated, as this sewage would have a suitable destination through the garden.And second, there is the possibility of reusing water for non-potable purposes, as problems such as worsening water scarcity are faced (Silva;Ramos, 2018).
The garden is a small lake with stones, sand and aquatic plants, where sewage treatment is carried out through the action of plants and microorganisms in this ecosystem.In Brazil, it was adapted by Embrapa, and is a technology that complements the use of septic tanks in the treatment of rural domestic effluents (Silva;Marmo;Leonel, 2017).
Natural processes play a fundamental role in autonomously purifying water, directly contributing to maintaining its quality.The technique known as phytoremediation takes advantage of the ability of bacteria present in plant rhizomes to interact with different types of contaminants.This interaction triggers chemical reactions that result in the formation of compounds that are not harmful to the ecosystem.The use of aquatic macrophyte plants for water treatment is justified by their remarkable ability to absorb nutrients and their rapid growth (Magalhães Filho;De Souza Filho;Paulo, 2021;Mendes, 2018).According to Nilava et al.
(2019) the presence of plants has a greater influence in horizontal flow wetlands.
The system is inspired by ecosystems in which partial or total flooding occurs during certain periods of the year, as in the case of swamps or the Brazilian Pantanal, where the ability to modify water quality is verified through natural processes in which macrophytes and the microbial population present in the root region degrades and sequesters contaminants ( Salati , 2003).
According to Salati (2003), there are three types of filtering gardens (Figure 02), with regard to the way water passes: a) Surface flow system, the most similar to natural ecosystems in flooded areas (marshes and marshes ), whose water surface is easily visible, more similar to a lake; b) vertical flow, in which the effluent runs vertically through the sand and gravel structure, passing through the macrophyte plants that treat the water through their roots; c) horizontal subsurface flow, in which water is distributed horizontally through the structure similar to the vertical flow system.
In the wetland constructed of subsurface horizontal flow, the liquid is introduced into the entrance zone, where it passes through an initial layer of gravel.It then slowly travels through the main area of the bed, made up of filtering material, until it reaches the exit area at the opposite end.The main flow occurs horizontally along the bed, with the liquid level below the surface of the filter material.This flow takes place in a hydraulically saturated medium, where the spaces between the grains of the filtering material are filled with the liquid being treated (Von Sperling ;Sezerino , 2018).In this anoxic environment , significant chemical processes such as denitrification and phosphate solubilization occur due to the low oxygen transfer capacity.Therefore, the horizontal filter is highly effective in reducing the parameters of Total Nitrogen, Total Phosphorus, BOD and COD (Mendes;Pina, 2023).
Aquatic plants have an intense nutrient absorption capacity, in addition to accelerated growth, having high efficiency in improving effluent quality parameters.The low implementation cost and high production of widely used biomass are positive attributes that justify the use of plants (Rodrigues;Brandão, 2017).
The garden consists of a trench in the ground approximately 50 cm deep and with a surface area of 2.0 m²/resident.The bottom is waterproofed with an EPDM (Ethylene Propylene Terpolymer Rubber ) geomembrane and the inlet and outlet pipes are connected at opposite points of the box.The effluent, before reaching the garden, passes through a solids retention box and, subsequently, through a grease trap, to avoid clogging of the pores.After waterproofing, the box is filled with a layer of gravel and a layer of coarse sand, which act as physical filters for particulate matter, support for plants and in the formation of biofilm (a set of bacteria that grow and form a type of capsule of protection).It is then saturated with water.13 After the support medium has been placed, the species are planted to create a pleasant environment.(Leonel;Martelli ;Silva, 2013;Da Silva et al., 2017).

METHODOLOGY
The work adopted the hypothetical-deductive method, starting from an initial observation about the low rate of sewage collection and treatment in Brazil, especially in Sergipe.A conjecture was proposed, involving the implementation of filter gardens, followed by the falsification stage, in which the propositions were refuted by comparing the results with other research on the topic.The research was of an applied nature, focused on solving a practical problem, with an objective nature and a quantitative-qualitative approach to analyzing the parameters.The objectives were descriptive and explanatory, describing the functioning of the filter gardens and establishing relationships between the parameters.The work was developed based on bibliographic references, documents and an experimental phase.

CHARACTERIZATION OF THE STUDY AREA
The State of Sergipe, located in northeastern Brazil, has a population of 2,210,004 people, according to the last census of 2022.It has an area of 21,938.188km², a demographic density of 100.74 inhabitants /km² and is divided into 75 municipalities (IBGE, 2022).The experiment was carried out at the São Cristóvão Campus of the Federal University of Sergipe, with the prototype mounted at the back of the agricultural engineering laboratory building, chosen for its ease of access and proximity to the bathrooms.

EXPERIMENT SETUP
The type of garden filter chosen was subsurface drainage with horizontal flow, as it is the most suitable for gray water and prevents the proliferation of insects.For assembly, a 1,000L water tank was used, which was buried in the ground (Figure 03).A layer of crushed stone nº 1 and another of sand were used as support and filtering media , with a screen between the layer of crushed stone and sand in order to avoid mixing between them and reducing the volume of the garden (Figure 04).To take water from the washbasins to the experiment, a connecting pipe was made between the siphon and the garden entrance and a water meter was installed to check the daily volume of water (Figure 05).And in the lower part opposite the water inlet, a pipe was installed to serve as a drain and enable the collection of garden effluent for later analysis.

Figure 05
Pipe to take effluent to the garden Source: Author (2023).
In the first attempt, the peace lily plant ( spathiphyllum wallisii ) (Figure 06), the choice was made because it is an easily found macrophyte and has great visual attractiveness.However, it did not adapt to the location where the garden was located, as it is a plant that likes shade and there is a lot of exposure to the sun (Figure 07).The plants had to be replaced.When the peace lily was removed it was noticed that the soil was waterlogged and it would not be viable to plant any new plants.Therefore, we waited 24 hours for the water present in the area to drain, the next day another layer of soil was added and then the new plants were placed in place.
The desert rose ( Adenium) was chosen for the new phase obesum ), the icsory ( Ixora coccinea L.) and Croton ( Codiaeum variegatum ) because they adapt well in environments with sun exposure and because of their pleasant aesthetics (Figure 08).

PARAMETER ANALYSIS
The study evaluated the effectiveness of a filter garden in removing contaminants present in bathroom sink effluents.Analyzes of physicochemical parameters were carried out before and after treatment in the filter garden, comparing the results with the quality standards established by CONAMA 357/05 and 430/11.The effluent was collected at the entrance and exit of the filter garden for analysis at the Technological and Research Institute of the State of Sergipe.The analyzes followed the standardized SMEWW methods, including COD, BOD, DO, TDS, Ammonia Nitrogen and Soluble Reactive Phosphate.The analyzed parameters were defined based on NBR 13,969/1997, which regulates technical procedures for the treatment of liquid effluents from septic tanks.

RESULTS AND DISCUSSION
During the period from 10/16/2023 to 12/08/2023, totaling 54 days, the volume of water that passed through the hydrometer was monitored.The objective was to identify consumption patterns and determine the days of the week with the highest and lowest water use.However, throughout the experiment, it was not possible to establish a consistent profile due to the irregular variation in the daily volume of water.This fluctuation can be influenced by seasonal and climatic factors, events in the building, among others.To better understand this distribution, the mean and standard deviation of the water volume were calculated, grouped weekly into 6 weeks, since the final data was reset.This was done to evaluate the efficiency of the filter garden in handling different volumes of water over time and its treatment capacity.A large variability is observed during Week 4, with a high standard deviation, indicating an unusual water input on some days.This anomaly in volume can be attributed to the start of the 2023/02 academic term, which began on November 13, 2023.
The high dispersion in the volume of water that enters the filter garden can negatively impact plant development.Abrupt variation in water supply can create unfavorable conditions for healthy plant growth.This inconsistency in the water regime can affect the plants' ability to absorb nutrients and carry out essential metabolic processes, compromising their health and, consequently, the efficiency of the greywater treatment system.This instability in the growing environment can represent a significant challenge for maintaining the quality and effectiveness of the filter garden in the long term (Silva;Domingues, 2023).
When considering the implementation of a filter garden, it is essential to evaluate its strengths and weaknesses.These systems, also known as constructed wetlands , offer significant environmental, economic and social benefits.Its application goes beyond wastewater treatment, contributing to the restoration of aquatic ecosystems and providing local economic opportunities.An important advantage is their operational and maintenance simplicity, depending mainly on natural biological processes, which reduces the need for energy and chemical products, making them especially suitable for tropical regions.
The absence of sludge generated, common in conventional treatment plants, is another strong point of wetlands .Da Silva et al. (2017) found in their study that during 3 years of operation, it was not necessary to remove sludge or maintain the pipes.Furthermore, the plants used in the process can be reused as fertilizer, closing the nutrient cycle and promoting sustainability.When properly maintained, these areas meet environmental requirements such as those of Conama ( Iaqueli , 2016).
According to Magalhães Filho, De Souza Filho and Paulo (2021), measurements or records of the amount of water must be obtained, the water in the filter must be distributed evenly and invasive plant species and weeds must be removed.At a domestic level, it is beneficial to separate the kitchen sink section so that less maintenance is required.
However, some obstacles may arise during the implementation and operation of filter gardens.Among them, the need for adequate space for its installation stands out, especially in urban areas.Furthermore, regular maintenance is essential to ensure system efficiency (Ribas; Oliszeski ; Abdala, 2020).
Regulatory restrictions and issues related to public awareness can also pose significant challenges.It is essential to obtain the necessary authorizations and educate the community about the benefits of filter gardens, addressing concerns and resistance that may arise.
When analyzing water quality parameters, a significant reduction in the concentration of various contaminants was observed after treatment in the filter garden.For example, the chemical oxygen demand (COD) was reduced from 83 mg/L to 12 mg/L, indicating efficient removal of organic matter.Similar results were observed for biochemical oxygen demand (BOD), which decreased from 15.3 mg/L to 0.45 mg/L, demonstrating a removal of more than 60%, as established by Conama 430/2011 for this parameter.These results corroborate previous studies that highlight the ability of filter gardens to promote the decomposition of organic matter through microbial action and natural filtration provided by soil and plants.
According to Magalhães Filho, De Souza Filho and Paulo (2021), their wetland proved to be effective in treating greywater without the presence of effluent from the kitchen sink.The authors found in their research a BOD removal close to 95%, while Mendes and Pina (2023) obtained a reduction of 96%, results that are in line with the findings of the present study, which achieved a BOD removal of around 97%.It is important to highlight that, without the kitchen sink component, the BOD must remain below 110 mg/L, values recommended to avoid clogging in wetlands (Von Sperling ; Sezerino , 2018).
In the second phase of their experiment, the authors 20 Furthermore, analysis of total dissolved solids (TDS) revealed a reduction in concentration after treatment in the filter garden, indicating partial removal of dissolved salts.
However, the values remained within the acceptable limits established by quality standards, reflecting the effectiveness of the system in retaining suspended solids and sediments.
According to Conama 357/05, TDS values must be below 500 mg/L.Mendes and Pina (2023) obtained a removal of 97.6% for this parameter, this result may have been achieved because the authors' study was carried out with a combination of horizontal and vertical flow filters and a planted pond.
As discussed by Nivala et al. (2019), the concentration of dissolved oxygen in water is an important indicator of its quality.According to the standards established by Conama 357/05, DO levels must be greater than 4 mg/L.In this context, the results of this study are in accordance with the resolution, since the average output effluent was 6.42 mg/L.As for nutrients, ammonia nitrogen and soluble reactive phosphate were tested, but the results obtained were not significant, with concentrations below the method's quantification limit even in the input analysis.

CONCLUSION
It is important to highlight that the results presented here are promising, however, they may vary according to the specific conditions of each filter garden, such as the type of soil, vegetation, water flow rate and adequate maintenance of the system.Continued studies are needed to investigate the influence of these factors on treatment efficiency and to optimize the performance of filter gardens in different environmental and operational contexts.21 Due to its organic nature, it is possible to identify certain adversities associated with the vulnerability of plants to climate variations, for example.In summary, the results obtained suggest that the filter garden is a promising technology, even using plants that are not usual for this purpose, for the treatment of lavatory effluents, offering an effective, sustainable and economical solution for water purification.
Individual habits and practices directly affect the quality of gray water.Finally, it is worth highlighting that the main disadvantage of nature-based solutions is the lack of standards in Brazil, which prevents the definition of project guidelines for their execution and implementation.Suggestions for future research include conducting studies on the plants used in the garden, implementing a combination of horizontal and vertical flow filter gardens to increase efficiency, and conducting long-term studies to evaluate garden variations over time.
different seasons of the year.

Filter
Gardens A Nature-Based Solution for Gray Water Treatment ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.4 | p.1-25 | e05358 | 2024.6 of chemical contaminants, including organic and inorganic compounds and metals from industrial, urban and agricultural sewage.

Filter
Gardens A Nature-Based Solution for Gray Water Treatment ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.4 | p.1-25 | e05358 | 2024.7 2.2 WATER QUALITY PARAMETERS Untreated sewage is one of the main sources of pollution of water bodies in Brazil.In addition to water quality, it also compromises the environmental balance and represents a threat to aquatic living beings.This occurs because the bacteria that decompose the organic matter of effluents in natural environments demand large amounts of Dissolved Oxygen (DO) in the water.Reduced oxygen causes fish deaths and algal blooms due to increased nutrients.The processes used in Sewage Treatment Stations ( STPs ) reduce the Biochemical Oxygen Demand (BOD) for the degradation of organic matter in aquatic environments.The National Environmental Council (Conama/MMA), through Conama Resolution nº 430/2011, establishes the conditions and standards for the discharge of treated effluents into water receiving bodies.Conama Resolution No. 430/2011 determines that the treatment of domestic sewage reduces, at least, 60.0% of the Biochemical Oxygen Demand (BOD) in the decomposition of organic matter.The lower the BOD, the better the water condition.The conditions are directly associated with the quality classes of water bodies in Conama Resolution No. 357/2005, which includes the guarantee of multiple uses, including public supply.The Resolution establishes the quality class as a set of criteria that define the necessary quality of water to meet its predominant uses, both current and future.According to article 3 of the Resolution, waters are categorized into thirteen quality classes, based on the quality requirements required for their predominant uses.
Source: Embrapa Instrumentação (2015).Filter Gardens A Nature-Based Solution for Gray Water Treatment ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.4 | p.1-25 | e05358 | 2024.11 Two problems are solved with the implementation of filter gardens.Firstly, regarding the various locations which do not have sewage collection, where it is disposed of in the open,

Figure 03
Figure 03Excavation of the installation site

Filter
Figure 06Garden with peace lilies

Figure 07
Figure 07Details of sunburnt leaves

Table 1
Average (m³) and standard deviation of weekly water volume

Table 2
Filter garden input and output parameters