investigating the potential of floating plant raft using peace lily spathiphyllum in surface water treatment of artificial pond

The number of plants is divided by 5 stems and 3 stems in each media planted which remarks as Investigating the Potential of Floating Plant Raft Using Peace Lily Spathiphyllum in Surface

INTRODUCTION

Research rationale

The water ecosystems have been under pressure due to the global climate change and anthropogenic activities (deforestation, land use change, expansion of agriculture and development of industry, urbanization, and wastewater production) (Paerl et al., 2014) The urban population relates to water resource utilization and lead to increase in wastewater discharge, for example, 1% increase in the urban population leads to 0.925% increase in total water resource utilization (Wang, 2020; Wen et al.,

2017).Besides the total of water utilization, the quality of water also depends on both natural and human influences The natural factors influence water quality in the way of evapotranspiration, deposition of dust and salt by wind, natural leaking of organic matter and nutrients from soil, and biological processes in the aquatic environment On the other side, human activities from rural and urban areas play role in water quality in the form of sewage discharge, industrial discharge, and agricultural run-off The lack of awareness among the users, quality of sanitation, and disposal need to be considered as the aspect of water resource management The human activities or known as anthropogenic factors affect the water quality in order to fulfil the needs for human’s daily life Animal husbandry as the branch of agriculture produces the waste from animal raising activities in the form of food waste and manure which may contain pathogens such as E Coli, hormones, antibiotics, nutrients (nitrates, phosphorus, and ammonium), and heavy metals The contaminants from this activity can pollute the surface water through run-off and affect the drinking water wells and water systems though groundwater (CDC, 2022) However, the environmental impact of aquaculture

2 also depends on the species, the process of production, and the location of farm The initial intention of fish farming is to increase the food system However, the environmental problems are following behind The problems are linked to the nutrient, effluents, and environmental degradation due to the location of ponds The waste from fish has potential to pollute the surrounding area and tends to deplete the oxygen in water, create algal blooms, and dead zones (GSA, 2019) Hence, the water management practices (mainly to remove chemical oxygen demand (COD), biochemical oxygen demand (BOD), total phosphorus (TP), heavy metals, and other contaminants/pollutants must be conducted to improve the water quality and to sustain the water utility (Bao & Chen, 2015; Bao & Zou, 2017; Ma et al., 2016; Zhao et al.,

2015) The water management practices include the water usage reduction and wastewater recycling for several purposes (Adams, 2021) The practice of wastewater recycling includes the wastewater treatment approaches, the wastewater can be recycled to reuse or discharged to environment without harming the surrounding area One of the solutions to recycle wastewater is constructed wetlands Constructed wetlands are the organic wastewater treatment systems that effectively purify the wastewater The concept of constructed wetlands relies on the aquatic plants, natural microorganisms, and a substrate (sand, soil, or gravel) Constructed wetlands are normally used for secondary or tertiary phase of wastewater treatment The natural components and affordable costs make this practice seems comfortable to use The collaboration of water plants, microorganisms and substrate to filter the contaminants in wastewater will advance the possibility to remove the contaminants (CSE, 2022) Several designs exist in constructed wetlands system, for example, floating wetlands

(floating plant raft) that use floating mats and plants that can be planted in a pilot scale system to treat multiple kinds of wastewater The components in constructing the floating treatment wetlands play important role in the remediation process, one of the most important factors is the selection of plant used, the speed in remediation process and the support from the appearance of the plant itself can promote the goal of floating treatment wetlands in public spaces In order to achieve successful treatment of floating treatment wetlands, the use of ornamental plants can be considered As mentioned by Zanin et al., (2018), FTWs have multi purposes of improving the quality of treated water and the potency to adorn the appearance of the water bodies through the aesthetic-ornamental values within the plants According to Barco and Borin (2020a), there are four criteria of constructing appealing floating wetlands, such as: 1) the selection of plants with colourful flowers, 2) the mixture of different plant species with colored flowers, different blooming time is preferable, 3) the use of species with broad aesthetic characteristics (the color of leaves, shape, the motif, etc), or 4) the use of plants which can maintain the green coverage of floating mats Thus, the purpose of plant species to enhance the water purification and ornamental look has been acknowledged in floating treatment wetlands In this study, the efficiency of peace lily (Spathiphyllum) which is an ornamental plant in surface water treatment of artificial pond using floating plant raft is tested

Peace lily is well-know is beautiful hybrid plant with white flower that people commonly put inside the house of Vietnamese, planted with soil, whereas, this plant is also applicable to put on the water According to Swiderski (2017), in the report on global volunteers page stated that peace lilies are commonly found around Hoan Kiem

4 lake Hanoi and in any cities in Vietnam Peace lily from genus Spathiphyillum and species Spathiphyllum wallisii had several tests in its ability for air purification, the study by Morgan et al., (2022), proved that this species was applicable in remediating the air pollutant from environmental tobacco smoke (ETS) or cigarette smoke This species successfully acted as botanical biofilter to remove volatile organic compounds with total efficiency of 43.26% Regarding the fact above, no studies have reported the use of peace lily for water remediation, especially in floating treatment wetlands For this reason, this thesis aimed to assess the ability of peace lily in surface water remediation in a pilot scale of FTWs in Vietnam.

Research’s objectives

The aim of this thesis is to investigate the efficiency of peace lily/Spathiphyllum in surface water treatment of artificial pond using floating plant raft media In order to achieve this aim, there are several specific objectives pursued:

1 To compare the efficiency of two different plant raft media based on the water analysis categories

2 To assess the effect of some factors including, the media for constructed wetlands; plant densities on the water treatment efficiency

Research questions and hypothesis

1 How does plant raft system reduce the contaminants in polluted natural surface water?

2 How impactful is the peace lily in reducing the contaminants in artificial pond surface water?

3 What are the differences of the media (five-planted peace lily, three-planted peace lily, and control) with the response to artificial pond surface water?

4 How much are the differences in the efficiency between the treated pond wastewater in this research and Vietnamese standard for surface water effluent?

5 The null hypothesis is that “There is no significant difference between media with five-planted boxes and three-planted boxes in this water remediation”

Limitations

There were two limitations of this research, covering the period of research time and lack number of prior research studies on the topic, type of plants, and conditions to scale up the experiments Research time period really affect the whole result since floating treatment wetlands need some times to show the full efficiency of the treatment Lack number of prior research affects the sources which could support the result of this study However, the advantage of lack prior research add the novelty of this research

ENPV economic net present value

LITERATURE REVIEW

The use of floating plant raft system in surface water treatment and natural water

Floating plant raft system is also well-known as constructed floating wetland designs A study by Bi et al., (2019) which did a study in in-situ condition, found that the well-designed constructed wetlands will decrease the pollutants and heal the ecosystem which is proven by the lower algae, more fish, and more diverse aquatic communities This study also mentioned about some scenarios that affect succeed of constructed wetlands due to the accelerated growth of the plants and pollutant uptake rates by higher temperature However, the rainfall intensity could lower the efficiency of constructed wetlands because of the shorter hydraulic retention times and more existence of pollutants in solid form The subdivision of Ohio state which works of soil and water conservation mentions that floating treatment wetlands (FTWs) are useful media to increase the water quality, especially for ponds and lakes Since the aim of FTWs is to uptake the excessive nutrients in the water which is the main contributor to aquatic weed growth in ponds The nutrients that enter the ponds through runoff from fertilizers and animal waste enhance the growth of aquatic weed and algae and decrease the pond biodiversity The aquatic plants attached to FTWs will uptake the excessive amount of nutrients Although aquatic plants can grow naturally on the ponds, but the plants are not always optimal in the nutrients uptake due to the location and fluctuating water levels (Butlerswcd, 2018) The statement that FTWs are useful to apply in ponds, river, and lakes is also supported by the study from

Gaballah et al., (2021) which proves that floating treatment wetlands have successfully applied for pollution control in rivers, lakes, and ponds with fluctuating water levels and FTWs are also compatible solution to promote green solution for urban water management The use of FTWs in controlling the water pollution in water bodies is also proven by Takavakoglou et al., (2021) in the side of socioeconomic impact on the area This study mentioned that there is a positive result in economic analysis of FTWs after the economic net present value (ENPV) of this study showed positive results that indicate that FTWs may increase the social welfare Thus, this system is desirable from socioeconomic perspective In terms of economic perspective, Bi et al., (2019) also expressed in the study that constructed wetlands obtain the spot as the natural- based solution for pollution control Floating wetlands are an eco-engineering tool that supports water body restoration with effective cost, environmental, social, and economical friendly.The consideration of effective cost of natural floating wetlands comes from the construction materials that combine large quantities of floating mats, sediment, and wetland plants (Nichols et al., 2016) According to Wang et al., (2020), most of the floating designs use polyethylene, polypropylene, polyurethane or polyvinyl alcohol foam to ensure the buoyancy In the study of Wang et al., (2020), the author reviewed that the floating beds of FTWs are not able to develop without artificial polymers Aside of the economic side, the potential of floating treatment wetlands in purifying wastewater is also confirmed by Karsten et al., (2021) through the research of floating treatment wetlands in treating urban stormwater Due to the setting of floating treatment wetlands that place the plants to grow on a floating mat instead of on the sediments, thus, the plants can tolerate the fluctuation of water,

9 especially in stormwater system, without worrying about the plants to get stressed Thus, Headley and Tanner (2008) mentioned that the design of floating treatment wetlands is to tolerate the contact between the root of plants and the pollutant water passing by the system Since the plants float on the water surface, the plants will not be affected by the water levels that may soak the plants Floating treatment wetlands are also designed to operate in the detention basin to treat the runoff then to be released after several days The advantage of floating treatment wetlands designs is not only derived from the ability to secure the plants position However, floating treatment wetlands planted with variety of macrophytes (water plants) also offer the habitats for wildlife Based on the research of Karstens et al., (2021), the percentage of birds visited the monitored floating wetlands was 48%, the most seen species was grey heron (Ardea Cinerea) Followed by gulls (Chroicocephalus Ridibundus), blackbird (Turdus Merula), mallard (Anas Platyrhynchos), and sparrow (Passer Indet) Besides birds, water frog (Rana Esculenta), grass snake (Natrix Natrix), fish, crustacean, molluscs, insects, and juvenile eels (Anguilla Anguilla) were also detected coming to the wetlands Regarding this, floating treatment wetlands offer other advantages within the main function to treat the wastewater Since the floating media have specific objectives to secure the position of macrophytes on the water surface, the construction materials should be considered in terms of cost, durability, and the effectiveness (Dotro et al., 2017).In order to support the wastewater treatment, floating treatment wetlands should be supported by other factors that may complete the design

Figure 1 Floating mat in laboratory scale (Source: Shahid et al., 2019) The figure above comes from the research by Shahid et al., (2019) that shows floating mat which is used to secure the position of plants that are floating on the wastewater The material used for the floating mat is polyethylene foam

Figure 2 Batch experiment for floating wetlands

(Source: Shahid et al., 2019) The figure above describes the media performed in the research of Shahid et al.,

(2019) using polyethylene boxes for treating wastewater from river withTypha domingensis and Leptochloa fusca

In order to improve the natural quality of water, floating treatment wetlands are considered as the eco-friendly technology as this technology has long life span and minimal environmental intervention (Ijaz et al., 2015) Garcia Chance et al., (2018)

11 also mentioned that floating treatment wetlands are mainly used for treating effluents containing excessive nutrients and degraded wastewater compounds Abbasi et al.,

(2019) investigated the application of hybrid method of combining floating treatment wetlands and horizontal flow constructed wetlands (HFCW) as primary treatment in order to increase the removal efficiency Floating treatment wetlands are not only useful for water quality improvement, but also for habitat enhancement, and ornamental addition for ponds and lakes as well as to prevent the algae growth in ponds and lakes (Headley and Tanner, 2012; West et al., 2017) Colares et al., (2020) also studied about the advantages of floating treatment wetlands compared to subsurface constructed wetlands, the study stated that floating wetlands are applicable in the absence of substrate (such as sand, clay, or gravel), which leads to lower cost of construction and enhances the contact of water and the roots Floating treatment wetlands also have capability to treat several kinds of wastewater, such as urban, storm, domestic, and industrial wastewater (Tara et al., 2019) Benrahmane et al.,

Macrophytes, especially in small communities and rural areas, provide an effective and affordable solution for treating domestic wastewater (2022) Floating treatment wetlands enhance the treatment process by facilitating closer interactions among plant roots, biofilm, and water nutrients, resulting in increased removal of phosphorus and nitrogen (Finnemore et al., 2019) A New Zealand study employing floating treatment wetlands for landfill leachate treatment demonstrated exceptional removal rates for total suspended solids (Finnemore et al., 2019).

Jones et al., (2017), found that floating treatment wetlands can support the natural aquatic habitat through 10-20 cm thick buoyant mats which is combined with inorganic substrate (sand, silt, and clay) and organic materials that led the plants to consistently grow The design on floating treatment wetlands is always adapted to facilitate the plant growth Pavlineri et al., (2017) found that the combination of floating treatment wetlands design is made of inorganic (PVC pipes, plactic, polyethylene foam, and ceramic pellet) and organic (bamboo, furnace slag, lake sludge) materials According to research by Barco and Borin (2020b), floating treatment wetlands provide treatment for many types of wastewater, such as stormwater runoff, eutrophicated river water, and animal slurries According to the finding by Pappalardo et al., (2017), floating treatment wetlands also contribute to reduce water turbidity The collaboration between roots and rhizomes acts as a physical filter for suspended solids, especially when natural events happen and affect the suspended particles in river wastewater According to James et al., (2004) and Xu et al., (2013), the management of urban lakes is important to reduce the risk of eutrophication to improve the biodiversity in the lake Natural macrophytes have been known to retain the resuspension of sediments to fix the water quality of the lake.

According to Henny et al., (2019), the practice of floating treatment wetlands is not commonly found in Indonesia However, Henny et al., (2019) did a study to explore the efficiency of floating treatment wetlands that was planted with different type of plants in decreasing the excessive nutrient and suspended solid concentration in urban lake in Megacity, Jakarta This study used vetiveria zizanioides and heliconia

13 densiflora The researchers also found that this lake was home to myriophyllum verticillatum, which led the researchers to also evaluate the effectiveness of this species in nutrient and suspended solids reduction

According to Henny et al., (2014a) and Henny et al., (2014b), urban lakes in

Jakarta are facing serious problems as other water bodies in being the disposal site and receiving water runoff from other areas Eutrophication and water pollution are the serious problems as the consequences from unmanaged urban development and sanitation services Contaminated lake ecosystem has been a major concern since most lakes are also used as source of water supply for drinking water, irrigation, and fishery

Floating wetlands have demonstrated their effectiveness in improving water quality Studies have shown that the floating wetland species M Verticillatum can remove nutrients and total suspended solids by over 60% Additionally, other floating wetland species have been found to remove total nitrogen, total phosphorus, and total suspended solids by up to 60% and 40%, respectively These findings highlight the potential of floating wetlands as a cost-effective and eco-friendly approach to improve water quality in urban environments, effectively removing excess nutrients and suspended solids from water bodies.

M Verticillatumthan two other species in floating treatment wetlands This should be noted that the plant harvesting is important to avoid the overgrown macrophytes which can lead to problem in the lake ecosystem and the activities around the lake For example, Cibuntu and some other lakes in Jakarta are the habitat for M Verticillatum

However, the abundant situation of this species causes lake siltation (Henny et al.,

2014c) Henny et al., (2019) also suggested that floating wetlands system should be accompanied with routine harvesting to promote the long-term stability for the lake

14 quality Floating treatment wetlands are beneficial for removing nutrients and solids in water bodies through the presence of the water plants However, the concern in the application of floating treatment wetlands is in the presence of over abundance water vegetation, which needs to be controlled and also add management cost

In Vietnam, urban wastewater is facing problem for human health and environmental protection In Ho Chi Minh city, there are only 10% of sewage areas treated due to lacking of treatment systems According to Jegatheesan et al., (2023), floating treatment wetlands and waste stabilization ponds are recognized as suitable strategies for wastewater treatment to support sustainable urban planning to improve the quality of urban environment According to World Bank, (2013), Vietnam is concerning on adjusting environmental management with urbanization The effectiveness of water treatment in Vietnam has not been applied well The researchers still find a research gap in treatment of domestic wastewater by floating treatment wetlands in Vietnam, regarding the design, efficiency, and social aspects In the study by Jegatheesan et al., (2023), five experimental floating wetlands in Vietnam were reviewed by the researchers These experimental floating wetlands were implemented in Bung Xanal in Can Tho city in Vietnam and were observed from March to May

Factors affect floating treatment wetlands (FTWs) performance

Besides the components to construct the design of floating treatment wetlands, there are several factors should be considered to successfully remove the pollutants from wastewater using floating treatment wetlands

Aside from biomass harvesting, the selection of plants also affects the removal rate of nutrients and contaminants in wastewater According to Ijaz et al., (2015), plant selection is one of the most important steps in the planning of floating treatment wetlands system The water plants (macrophytes) are in charge in nutrients uptake, sedimentation and trapping, organic matter degradation, and a shelter for natural wildlife The statement above is also supported by the research by Dotro et al., (2017), which stated that the roots of plants are permanently in contact with the water during the treatment process because the roots absorb the contaminants and nutrients from the water The relation of roots, rhizomes, and biofilm supports the biochemical and physical processes, such as filtering and trapping the particles Root development in floating wetlands system also provides larger area for biofilm development (Walker et al., 2017) As observed by Lucke et al., (2019), biofilm in wetlands play role as a niche for some bacteria communities and the core of the sequestration process of nutrients uptake from water, through nitrification, denitrification, and phosphorus adsorption (Lucke et al., 2019) The importance of plant selections in designing

16 floating treatment wetlands is confirmed by many studies that test different number of plants in removing any types of contaminants One of the studies by Ladislas et al.,

(2013), used floating treatment wetlands (FTWs) to improve the quality of urban storm-water The analysis was to evaluate the potential of two macrophytes species,

Juncus effuses and Carex riparia to remove heavy metals (cadmium, nickel, and zinc)

Both plant species exhibited high efficiency in removing heavy metals from water sources Analysis revealed that the roots accumulated significantly higher concentrations of cadmium and nickel compared to the shoots of both species This indicates the plants' ability to sequester and store these metals within their root systems.

The technique of using plants or organic materials in wastewater treatment is called phytoremediation According to Eksperusi et al., (2019) and USDA (2019), there were several water plants species used in wastewater treatment, such as Pistia stratiotes, Salvinia molesta, Lemna spp., Azolla pinnata, Landoltia punctata, Spirodela polyrhiza, Marsilea mutica, Eichhornia crassipes , and Riccia fluitans, submerged plants, such as Hygrophilla corymbosa, Najas marina, Ruppia maritime, Hydrilla verticillata, Egeria densa, Vallisneria Americana, and Myriophyllum aquaticum, and emergent plants, such as Distichlis spicata, Cyperus spp , Imperata cylindrical, Iris virginica, Nuphar lutea, Justicia americana, Diodia virginiana, Nymphaea spp , Typha spp , Phragmites autralis and Hydrochloa caroliniensis Due to the high capacity of absorption, those plants are capable to treat heavy metals and other organic pollutants from wastewater, especially produced by agricultural, industrial, and domestic sectors (Mustafa and Hayder, 2021) Research by Goala et al., (2021), also found that Azolla pinnata successfully captured the contaminants in the dairy wastewater with the efficiency result at 75%

Another research by Rezania et al., (2015), also supported that the use of water hyacinth is usable to treat contaminated water because of the rapid growth, easy

17 availability, high yields, easy harvesting, and high absorption capability Chandanshive et al., (2017) in their research successfully remediated heavy metals, such as As, Cd, Cr, and Pb from textile wastewater by Typha angustifolia and Paspalum scrobiculatum Guittonny-Philippe et al., (2015) also proved that remediation of heavy metals can be achieved by several plants, such as Alisma lanceolatum, Carex cuprina, Epilobium hirsutum, and Juncus inflexus in remediating

Cd, Cu, Cr, Fe, Mn, Ni, Pb, Zn, and other organic pollutants from industrial wastewater Plants have ability to remove organic and inorganic contaminants depending upon the species and environmental conditions (Antoniadis et al., 2017)

According to research by Kafle et al., (2022), the research stated that several mechanisms can be applied using plants in remediation process One of mechanisms is called phytodegradation, which can decompose the contaminants in the plant tissue Parts in plants also have the ability to remediate the organic pollutants, for example organic pollutants in pesticides In phytodegradation, plants absorb the pollutants, decompose them into smaller less harmful compounds, then transfers them within plant tissues The rates in remediating the pollutants depend on the types of plants and mechanisms Phytodegradation is one of the methods included in phytoremediation, which is a promising technology because of the effective cost and environmental- friendly solution The use of plants is applicable to remediate pollutants, such as heavy metals, organic pollutants, radionuclides, pesticides, petroleum wastes, and antibiotics The effectiveness of plants in remediating the soil is different depending on the targeted contaminants Therefore, the plants selection is crucial Higher accumulation of toxics absorbed is in the plant roots and shoot tissues (Asgari Lajayer et al., 2019)

Based on the research by Bian et al., (2020), macrophytes must have fast-growing phase with high biomass production while provides economic benefits.

Seasons and temperature are also known as the factors that influence the efficiency of floating treatment wetlands performance as stated by Shahid et al.,

Temperature significantly influences nitrogen removal efficiency in wastewater treatment wetlands Studies have shown that the optimal temperature range for nitrogen removal is between 5 and 15°C, as bacteria involved in nitrification and denitrification are highly temperature-sensitive Optimal temperatures for nitrification specifically have been found to range between 32.8 and 34.1°C, with increasing temperatures up to 35°C enhancing nitrification rates However, further temperature increases beyond 35°C hinder nitrification Temperature not only affects microbial activity but also impacts dissolved oxygen concentrations, emphasizing the importance of maintaining suitable temperatures to achieve optimal nitrogen removal.

According to Li et al., (2014) and Wang et al., (2013), the surroundings around the treatment plants are important and can bring impact to the adaptability of the plants According to Olguín, E J., & Sánchez-Galván, G et al., (2017), floating treatment wetlands have several advantages, the major advantage is the operational area of this system which does not need a lot of supporting requirements in the design

This system can easily place in situ without any land However, there are several conditions that affect the efficiency of floating treatment wetlands, such as season, initial concentration of nutrients, the type of plants According to the case found by Olguín et al., (2017), in Mexican urban lakes, the most effective time in running floating treatment wetlands is in the hottest season (summer) The case found in Mexico is also in line with the finding by Alisawi (2020), which stated that temperature affects the efficiency of wastewater treatment plants, the research emphasized that normal temperature enhances the conversion process and increases the removal rate The supporting statement issued by Abdulla et al., (2020) and

Alisawi (2020) was about the temperature as the crucial parameter in the removal efficiency of BOD, COD and TSS from wastewater treatment plant The study also observed that the best time to remove BOD is in the summer season because the rate of removal efficiency is only around 73.68% in winter season Other than that, COD removal was also found to be more effective in summer with 47% of maximum rate in winter Meanwhile, the research did not find the significant impact of temperature to TSS Research by Hughes et al., (2021) concluded that biological treatment in wastewater is significantly affected by the change in wastewater temperature Alisawi (2020) also proved that wastewater temperature also plays role in nitrification rate, which leads the improvement of the nitrification rate The increase in temperature decreases the effluent of ammonium concentration, which accelerates the ammonium removal from the system The increase in temperature also influences the increase in TSS effluent due to the increase in microbial community growth However, the efficiency of phosphorus removal is lower due to the increase in temperature

According to the research by Zhou et al., (2017), macrophytes or water plants in floating treatment wetlands are in charge of absorbing the excessive nutrients in the wastewater as they will use the nutrients for their growth, the harvesting of biomass is functioned to increase the N and P removal According to the journal review and bibliometric analysis by Colares et al., (2020), they found that older plants release back the nutrients into the water/environment through decomposition In other words, when the plants decay, they will return the removed nutrients uptake Colares et al.,

(2020) confirmed through the review analysis linked the “pruning” to Nitrogen removal, such as, total nitrogen, ammonium ion, ammonium, nutrient removal and nutrient uptake Thus, the plant harvesting had more effect on N process, instead of P process

Colares et al., (2020) also implicated that the process of pruning will lead to more biomass uptake because the macrophytes will undergo the growth that needs more biomass and nutrients in that process, which make the relationship between plant harvesting, biomass uptake, and growth is obvious The old leaves and stems harvested are potentially to turn into sediments in the floating wetlands system, which can also reduce the biomass However, Shahid et al., (2018), mentioned in the research that biomass harvesting depends on the species used and the climate conditions The same species of plants can have different growth and biomass containment, for example, local climate conditions The fact is that plant tissues present lower concentration of Nitrogen and Phosphorus in their tissues as they become more mature A research done by Colares et al., (2019) was about to test the efficiency of hymenachne grumosa

21 in treating secondary effluent from University of Santa Cruz do Sul (UNISC), in southern Brazil They observed the removal efficiency of TN, NH 3 -N, and total organic carbon (TOC) increased after pruning or harvesting The increase of total removal was probably due to the accelerated plant growth and season (spring) after pruning However, Sun et al., (2019) did not find any significant distinction in the removal rate of NH 4 + -N after pruning in FTW system They also mentioned that there are two effective ways of vegetation pruning, such as above-ground tissue harvesting and whole plant harvesting The differences are that whole plant harvesting is only suitable for vegetative that is difficult to harvest because removing the whole plant will trigger the reproductive problems and nutrient allocation In above-ground harvesting or half plant harvesting, the season in harvesting is necessary, for example, summer provides descent solar radiation which will support the growth for plants, while winter provides higher water temperature

Shahid et al., (2018) also pointed that external condition of the plants should be considered, such as the temperature change which can influence the transfer of nutrients from the soil to plant tissues This is because biomass harvesting is a crucial step to do in FTW system and the prediction of nutrients accumulation in the plant should be precise, in other words, when the accumulation of nutrients in the plant tissues achieves the highest peak.Borne et al., (2015) also suggested in the research that biomass harvesting in FTW structure should be done only once a year, in early summer Afzal et al., (2019) also added that FTW system store more metals in the plant tissues at each harvest time, the translocation of metals from roots to leaves are presented by bacteria in the rhizoplane The importance of biomass harvesting is also

Advantages and disadvantages of using floating plant raft system

According to Jegatheesan et al., (2023), floating wetlands system is beneficial for water purification and beautiful landscape for public Floating wetlands that are applied in public space also provide the jobs for the maintenance staffs and strengthen the relationship among the stakeholders Based on the research by Colares et al.,

(2020), floating treatment wetlands are the inventions to support lots of services, such as wastewater treatment, bioremediation, and stromwater treatment Due to the simple design and operation, floating treatment wetlands are considered effective, especially to be combined with hybrid constructed wetlands This article also found that there is relation between the number of plants and the treatment efficiencies due to higher number of microorganisms attached in the roots However, there is a gap between the

26 use of plants and waste of decay plants since there are still lacking of research in utilizing the harvested parts of floating wetlands plants On the other hand, the harvested biomass from plants can be transformed into animal feeds to generate more income According to Sharma et al., (2021), floating treatment wetlands are sustainable and suitable for treating any water bodies without causing structural changes in the pond The advantages in floating treatment wetlands are also in the ability of these systems in handling the challenges due to toxic heavy metals, nutrients, suspended solids, and other pollutants from wastewater The removal efficiency of floating treatment wetlands are supported by buoyant materials that are placed with floating plants, which will support the biofilms attached to the floating wetlands systems, and periodic aeration The application of FTWs in public water stream is already common as demonstrated by Shahid et al., (2019) in the research of remediating polluted river by floating treatment wetlands The development of industrialization, agriculture, and urbanization also triggers the increase of water pollution in rivers (Pan et al., 2016) According to Winston et al., (2013), floating treatment wetlands are possible to place in pond or river without damaging the soil since the application of FTWs does not need surface soil and does not degrade the water volume as well In addition, the installation of FTWs also becomes the habitat for wildlife, both underwater species and insects (Mietto et al.,2013; White &

Cousins,2013; Keizer-Vlek et al.,2014) The excessive nutrients from water will be absorbed directly by the roots and the roots also provide the habitat for microbes to help transforming the nutrients (Zhang et al., 2016; Ashraf et al., 2018)

Despite the advantages of floating plant raft systems for phytoremediation, limitations exist Research highlights the need for longer-term studies as short-term experiments may not accurately represent real-world conditions over an extended period Additionally, the efficacy of phytoremediation is influenced by the growth rate of the plant species employed Climate variability and the presence of other organisms at the site can also impact the effectiveness of phytoremediation, necessitating site-specific optimization of techniques.

In the remediation process, plants can only tolerate certain amount of contaminants, especially heavy metals, radionuclides, or antibiotics However, the mixed and local species of plants can lower the problems Long and deep roots will enhance the efficiency of remediation process because the contaminants must be within the reach of plant roots In addition, phytoremediation process is slower than other conventional methods and this process might require three to five years of operation to show the full results Furthermore, the handling of proper disposal of decay plants should put forward.Based on the research by Oliveira et al., (2021), floating treatment wetlands as the alternative solution for in situ wastewater treatment has advantage and limitations, especially in the maintenance of the system, which is also related to the effluent and condition of the installation site Moreover, the type of plants used should also be taken care from the presence of invasive species that can

28 bother the planted macrophytes in the site Moreover, the foreign objects which enter the system can also be the source of pollution (Yeh et al., 2015) In addition, Chang et al., (2017), found out that the floating treatment wetlands need additional systems in designing and in operating to support the efficiency of treating wastewater Therefore, more research is required to match the combination of other treatment plants to increase the efficiency and to observe the parameters that affect the removal rate On the other hand, the type of plants used is also an important factor in order to turn the plant biomass to valuable products

According to Pavlineri et al., (2017), the removal rate of phytoremediation process depends on a few factors based on the findings by some researchers Through the meta-analysis procedure, Pavlineri et al., (2017) concluded that the removal rate of phytoremediation process depends on the experiment duration and root harvesting Root harvesting is essential practice for preventing the plants to release back the uptake nutrients Thus, plant harvesting should be included in the management tool of the floating treatment wetlands

According to some researches, there are several important things should be considered in floating construction wetlands system to suppress the damage to plants and biofilm which leads to lower removal efficiency of floating treatment wetlands The design of floating treatment wetlands is important to follow the targeted pollutants, the management of the wetlands should follow the rate of pollutant removal and the site environment, and budget of the construction Several studies used aeration to upscale the performance of floating treatment wetlands (Chance and White 2018; Verdejo et al., 2015) and hybrid floating treatment wetlands (Chen et al 2013; Saeed

29 et al 2019; Song et al 2019) According to Ting et al., (2018), hybrid floating treatment wetlands, which mean the combination of FTWs with other water treatment technologies or multistage FTWs Hybrid FTWs systems are attracting the attention due to more efficiency gained than single FTWs system Based on the research by Rozema et al., (2016), the efficiency of single FTWs design is not much effective for agricultural wastewater There are several points that should be considered in applying FTWs systems, such as temperature since the growth of plants, removal efficiency of nutrient, and microbial activities are influenced by temperature (Liu et al., 2016)

According to Ting et al., (2018), the limitation of FTWs is also found in the position of the plants and the floating beds The position of plants and floating beds potentially blocks the penetration of sunlight through water surface which can hinder the photosynthesis of underwater aquatic life

PART III MATERIALS AND METHODS

The water sample for the experiment was collected from the artificial ponds around Advanced Education Program office at Thai Nguyen University of Agriculture and Forestry The area was chosen since that pond area becomes the place to hold the rainwater Since the artificial pond in this area becomes one of the main attractive ponds for people passing by and people are likely to do activities, for example fishing and taking photos Those reasons above encouraged this research to be conducted

Figure 6 The artificial pond for water sampling This artificial pond is located inside the area of Thai Nguyen University of Agriculture and Forestry The function of this pond is as the recreational area and is also to store water runoff from rain The depth of this pond is 3.5 m, with length and width is around 15 and 20 m The water quality of this pond is described below on Table 1:

Table 1 The input water based on Vietnamese regulation standard

A1= number of pollutants allowed for domestic water supply (after treatment), commonly for aquatic flora and fauna conservation

A2= number of pollutants allowed for domestic water supply (after appropriate treatment), but the grade is under A1

B1= number of pollutants allowed for irrigation or other external use purposes, the water quality is similar to B2

B2= number of pollutants allowed for purposes with low amount of water quality

Table 1 presents the allowable pollutant concentrations for day 0 in surface water, as defined by QCVN 08-MT:2015/BTNMT Analysis of the results reveals that nutrient levels (ammonium, nitrite, and phosphorus) are below A1 standards, indicating a safe environment for aquatic life However, elevated levels of total suspended solids (TSS) and chemical oxygen demand (COD) suggest the presence of contamination.

32 demand (COD), where TSS level is lower than A2 but higher than A1 standards, which means that this pond water is still safe to fulfill the domestic supply, although the level can still be lower than A1 standard COD value based on the table is higher than B1, yet is lower than B2, which defines that COD level is quite high and potentially damaging the aquatic life

RESEARCH OBJECTS AND METHODS

Research methods

The following figure represents the experimental set up procedure

Figure 9 Diagram of experimental set up procedure

According to USDA (n.d.), peace lily has biological nomenclature as mentioned below:

Table 2 Biological nomenclature of peace lily

Family Araceae Juss – arum family

Species Spathiphyllum wallisii Regel – peace lily

Figure 10 The roots of peace lily

In the construction of floating treatment media, several materials needed as listed below:

1 9 Styrofoam boxes with length× width × height, 35× 30 × 40 cm

2 9 Polyethylene foams (floating mats) with length× width × thickness, 30.2× 28.5×

The experimental setup for this study is referred to the study from Shahid et al., (2019) in remediating polluted river water using Phragmites australis

Floating media construction was started by placing 32 stems of peace lily (Spathyphyllum) in the tap water for 30 days before plantation to see the growth of plants and to make adaptable situation for plants After that, the polyethylene foam as the plant holder was trimmed into the size that could fit the Styrofoam boxes and was placed on the top of the styrofoam boxes as the floating treatment wetlands At the same time, 20 liters of water sample was inputted into the boxes The stem of plants was put into the styrofoam boxes as Figure 7 and 8 and labelled as T1 and T2, which indicated as T1 was styrofoam boxes with 5 holes/stems, styrofoam boxes with 3 holes/stems, and one was labelled as control After 30 days, each plant stem was placed in each hole and was observed for 5 days/120 hours

The collection phase of sample was started by preparing 9 styrofoam boxes (4 boxes were for 5 stems of plants in holes, 4 boxes were for 3 stem of plants in holes, and 1 box was for control (sample surface water without plants) The samples were

37 collected from the artificial pond around Advanced Education Program, Thai Nguyen University of Agriculture and Forestry with plastic can

The sample from the floating treatment media was placed in the plastic tube and was stored in the chiller at 4ºC if the sample was not analyzed on the same day as collection day The sample was tested using LAMBDA 365+ UV/Vis Spectrophotometer, model N4100022 The sample was observed for 5 days straight to see the difference between the floating treatment wetlands The water sample was taken every morning from the box

Plant density is calculated as formula below:

The test of COD follows the regulation of SMEWW 5200D-2017 The analysis of COD refers to Standard Methods Committee of the American Public Health Association, American Water Works Association, and Water Environment Federation

5220 chemical oxygen demand (cod) In: Standard Methods for the Examination of Water and Wastewater Lipps WC, Baxter TE, Braun-Howland E, editors Washington DC: APHA Press DOI: 10.2105/SMWW.2882.103.

The test of total phosphorus follows the regulation of QCVN 08-

MT:2015/BTNMT is a regulation that aligns with Vietnam's National Technical Regulation on surface water quality It establishes maximum chemical limits in surface and wastewater based on intended use The regulation provides guidelines for assessing surface water quality, protecting and utilizing water resources, planning water usage, and monitoring and measuring water quality to optimize and restore water bodies.

The test of TSS follows the regulation of standard methods 2540 D which is regulated in National Environmental Methods Index which is referred to www.standardmethods.org This regulation leads to solids analysis in order to stabilize the biological and physical wastewater treatment process

The ammonium test complies with TCVN 6179-1:1996, aligning with ISO 7150-1;1984 (E) This standard guides the determination of ammonium in water quality through a manual spectrometric method Refer to https://qcvn.com.vn/phan-tich-amoni-trong-nuoc/ for the online source (accessed on 21/6/2023).

The test of nitrite follows the regulation of TCVN 6178:1996 This regulation is under the technical Committee for Standards TCVN/TC/F9 and proposed by the

General Department of Standards – Metrology – Quality and was issued by the Ministry of Science, Technology, and Environment of Vietnam.

Data processing

Data of T1, T2, and Control from each parameter for 5-day observation was gathered on Microsoft Excel, then the average of those data was measured to see the remediation capability from each media (T1, T2, and Control) The graph of media (T1, T2 and Control) was made per day from day 0 to day 5 for each parameter (COD, TSS, TP, Ammonium, Nitrite) to see the comparison The average number was also used for further statistic analysis using ANOVA one-way analysis of variance to statistically measure if there is any effect of the number of plants (T1 with 5 plants and T2 with 3 plants) to the remediation capability of each parameter

RESULTS

Efficiency of suspended solid removal

The figure 11 below describes the difference between the total of suspended solids in the water sample after the treatment

Figure 11 TSS removal efficiency of floating treatment wetlands

The amount of TSS in this research is quite high In T1 batch, the results are fluctuating day by day with the highest amount is on day 4 by 28.47 mg/l and the lowest amount is on day 5 by 22.93 mg/l In T2 batch, the peak point is on day 0 with the amount of 27.47 mg/l and the lowest amount in T2 is found on day 2 by 19.13 mg/l The results of the highest and lowest number are slightly different between T1 and T2 However, the number of result is not too distinct between T1 and T2 batches Table 3 ANOVA table for TSS in the water sample after 5 days of treatment

Variation SS Df MS F P-value F crit

ANOVA table above describes the relation of between and within group variation, between group variation about is much lower than within group variation in

SS, Df, and MS value This makes the value of F-statistic lower and p-value is higher than 0.05, which implies that there is no any significant effect between the number of plants to the removal efficiency At the same time, F value is lower than F criteria value, this also means that both criteria (T1 and T2 batches) does not have any significant difference at all Regarding the removal efficiency, the efficiency of T1 batch is higher than T2 batch with the results as 15.07 and 9 %, respectively

Figure 12 The example of filtered solids in TSS analysis

Figure 12 shows the example of the filter paper with more particles left on the paper

Efficiency of organic removal (COD)

Figure 13 bellow illustrates COD results in the water sample after the treatment

Figure 13 The removal efficiency of COD test in floating treatment wetlands

The concentration of chemical oxygen demand (COD) exhibits a distinct pattern over a 5-day period in both T1 and T2, although with varying magnitudes In T1, COD levels start high at 50 mg/l on day 0, drop to 34 mg/l on day 1, and rise again to 53 mg/l on day 2 This is followed by a steady decline until day 5, reaching a minimum of 24 mg/l T2 displays a similar pattern, but with lower overall COD values compared to T1 The difference between the COD levels at each time point is less pronounced in T2.

T2's water measurements exhibited a fluctuating pattern, starting at 32 mg/l on Day 1 and rising to 45 mg/l on Day 2 A subsequent decline occurred from Day 3 to Day 5, with measurements dropping to 36, 35, and 28 mg/l, respectively.

Table 4 ANOVA table for COD in the water sample after 5 days of treatment

Variation SS df MS F P-value F crit

The ANOVA table of COD proves that the null hypothesis (number of plants has no significant effect to the removal efficiency) cannot be rejected because the value of F is also lower than F criteria value This means that the number of plants do not have specific effect to the value of COD Based on the removal efficiency, T1 and T2 removal efficiency are 52 and 33.33 %, respectively.

Efficiency of nitrogen removal

Figure 14 bellow illustrates ammoniumresults in the water sample after the treatment

Figure 14 The removal efficiency of ammonium test in floating treatment wetlands The figure 13 above describes the average range of treatment to total ammonium in the treatment box In T1, the graph is fluctuate, from day 0, the amount of ammonium was 0.010 mg/l The concentration of ammonium increased in the first and second day with the equal number at 0.036 mg/l Yet, on the third day, ammonium value slightly decreased to 0.029 mg/l On the fourth and fifth day, the amount of

44 ammonium highly increased as shown on the graph, where the amount reached 0.394 mg/l for day 5

In T2, the pattern of graph is similar to T1, where day 0 has the lowest number at 0.010 mg/l The total of ammonium also increases on day 1 and 2 by 0.036 and 0.041 mg/l, respectively On day 3, the content of ammonium decreases to 0.029 mg/l Same as T1, T2 batch has the highest peak on day 5 by 0.192 mg/l

Table 5 ANOVA table for ammonium in the water sample after 5 days of treatment

Variation SS df MS F P-value F crit

Statistical analysis revealed that the null hypothesis, which stated no significant effect of plant number on removal efficiency, was accepted ANOVA demonstrated that media with 5 or 3 boxes exhibited no significant distinction However, removal rates differed, with -3840% and -1820% removal rates for ammonium in T1 and T2, respectively.

Figure 15 Ammonium analysis procedure Figure 15 illustrates the result of ammonium test, which all color is yellow in the day 2 for control, T1 and T2 Yellow color indicates that the sample was clean and the concentration of ammonium was very low

Figure 16 The visual of color exchange in ammonium experiment

Figure 16 also shows the ammonium reaction emerged by the samples The green color indicates high concentration of ammonium As the green color is thicker, this

46 means higher concentration of ammonium Otherwise, if the color remains yellow after the reaction process, this means that the concentration of ammonium is lower Yellow color also refers to the possibility that there is no any ammonium contamination in the water

Figure 17 The example of ammonium result of T1 and T2 Figure 17 above is the example of the difference between the water that contains higher and lower amount of ammonium The color changing is the result after reaction process

Nitrite removal efficiency was analyzed and the result shown below:

Figure 18 The removal efficiency of nitrite test in floating treatment wetlands

Nitrite also becomes the parameter in this research The result of nitrite is quite different compared to ammonium As shown in the graph, from day 1 to day 5, there is decline in the amount of nitrite in T1, the only value that goes up is on day 0 The amount on day 1 is 0.0295 mg/l, then the concentration gets lower until day 5 by 0.0096 mg/l This case is similar to T2, where the line is going lower each day, the difference is only at day 3 to day 4, where the concentration of nitrite for both days is same at 0.012 mg/l The highest amount in T2 is also found on day 1 by 0.0285 mg/l The fifth day is the lowest with concentration only at 0.0117 mg/l

Table 6 ANOVA table for nitrite in the water sample after 5 days of treatment

Variation SS df MS F P-value F crit

Same as previous parameters, ANOVA table of nitrite also does not reject the null hypothesis (the number of plants does not have significant effect to removal efficiency) because F value is lower than F criteria value, which means that the number of plants in the boxes does not have any specific effect to the removal efficiency In terms of removal rate percentage, T1 has bigger removal rate efficiency compared to T2 with the percentage of 61.29 and 51.25 %, respectively

Figure 19 The example of color changing in nitrite experiment

Figure 19 shows the example of how the color changes due to the reaction of nitrite test The left side means that the concentration of nitrite is high because the color shows thicker pink compared to the right side glass, where the color of reaction changes to pale pink The color will change to pink if the sample contains higher

49 amount of nitrite and the color remains white if the concentration of nitrite is lower or no concentration at all.

Efficiency of total phosphorus removal

Total Phosphorus has very different result compared to other parameters Total phosphorus result is minus, which is under the approved standard After the treatment, total phosphorus level is lower than A1 for whole batch In TSS level, both T1 and T2 level is lower than A2 standard

DISCUSSION AND CONCLUSION

Discussion

Conventional wastewater treatment has been used widely, yet, this method is expensive and is not environmental-friendly This method also takes professional expertise and the process takes long period of time and money (Carolin et al., 2017;

Rottle et al., 2023) According to some researchers, floating treatment wetlands can avoid the obstacles that conventional wastewater treatments have (Castellar et al.,

2022) The system in this floating treatment wetland fully relied on the roots as the center for absorbing the particles in the treated surface water without any additional substrate The role of roots in macrophytes is very important due to the direct contact of roots with the water In biological treatment, the roots, rhizomes, and attached biofilms have important functions to filtrate and capture the particles (Dotro et al.,

2017) Since the roots of plants in floating treatment wetlands are important , peace lily was chosen in this study, since the roots of peace lily is strong and long to support the contact of the plant roots and the surface water as seen in Figure 10 Roots in this study also holds the role as the area for biofilm to attach Biofilms also serve niche for microorganisms and essential for taking up nutrients through nitrification for nitrogen and adsorption for phosphorus (Lucke et al., 2019)

The absence of substrate is also as the goal to see if peace lily is competent enough for water treatment because this plant is compatible for air purification as shown by Morgan et al., (2022), where peace lily successfully removed 43.26% of volatile organic compounds from cigarette smoke However, the result from suspended

51 solids test is very fluctuating as seen in Figure 11, where the line neither seem going lower nor going higher, even the result for T1 and T2 in each observation day is always lower than A2 standard (see Table 1) Figure 12 shows how the small particles are left in the filter paper, which means that these particles floated in the water and were not fully absorbed by the roots Regarding total suspended solids, the pollutants are mostly filtered by the substrate, for instance, gravel, sand, etc According to this, plants in floating treatment wetlands have limited effect on absorbing the pollutants However, macrophytes support the pollutant uptake, especially when the root grows rapidly (Younas et al., 2022) In this study, the filtering process was fully supported by direct contact of plant roots and the surface water, as also mentioned by Hoeger (1988) that floating treatment wetlands physically filter suspended solids by direct contact of plant roots and water Based on the statement by (Borne et al., 2013), suspended particles in the influent are filtered by biofilm, which are attached in the roots of plants, then the particles will both stuck in the bed of the wetlands and adsorb by microorganism to break down The biofilm around the roots was very important in this study due to the absence of other filters

Figure 13 illustrates how the COD process works in each day of observation, the result shows that the removal of COD for T1 and T2 was better than control (without plants) and all the results for T1 and T2 significantly decreased, compared to control media (without plants), where the result is more fluctuating The result decreased in each day until both T1 and T2 reached below the standard of B1 (based on Table 1) Figure 14 in ammonium shows different result compared to COD, where the number of

52 ammonium increased each day and reached the highest peak on day 5, both for T1 and T2 Another nitrogen content, which is nitrite, has different result, compared to ammonium as shown in Figure 18, where the number of nitrite in the tested surface water decreased each day However, among all the parameters, phosphorus has the most distinguished result, where the result for this test is below 0, which means that the result is so much lower than the A1 standard for phosphorus as seen in Table 1 The root has important role in COD, ammonium, and nitrite removal as mentioned by Shah et al., (2015), the efficiency of COD removal depends on the phytoremediation process which includes the relationship among macrophytes, microorganisms, wastewater, and supported materials (bed media) In the remediation with natural organisms, the perks come from the natural process which indicates the process of pollutant uptake, metabolisms in the macrophytes, and root systems of the plants Shah et al., (2015) mentioned that the effectiveness of organic removal depends on the microbial activity of aerobic and anaerobic bacteria due to the pH, temperature, oxygen, and operating conditions of the water treatments Worku et al., (2018), emphasized that the use of macrophytes in wastewater treatment accelerates pollutant removal due to the biomass production and this biomass production takes place in the root system of the plants The combination of selected macrophytes, period of treatment, and water temperature will enhance the removal efficiency Root system absorbs the pollutants, where the process is called rhizofiltration Rhizofiltration is the way of plant roots absorbs the contaminants, especially to remove the toxic from groundwater (Abdullah, 2015) Rhizofiltration is commonly used for removing the toxic from surface water, sewage, and wastewater which is impacted by low amount of

Plants with extensive root structures are recommended for phytoremediation due to their ability to absorb heavy metals or radionuclides These pollutants can be converted into nutrients that support plant growth with the help of microorganisms (Rezania et al., 2016; Euis & Wahyu, 2010).

Plant roots also play important role in nutrient removal (Borne et al., 2013)

The possibilities of nutrient removal in floating treatment wetlands are the uptake nutrients by roots of plants, assembled in biomass, or be degraded by the bacteria (Shehzadi et al., 2016; Shahid et al., 2019) The finding is also in line with the research by Aerslan et al (2017), Shehzadi et al., (2014), and Winston et al., (2013), which stated that interaction of plants and bacteria boosts the removal of organic pollutants from wastewater Microorganisms degrade inorganic nitrogen by nitrification and denitrification process (Debusk, 1999) Nitrogen in wastewater, both in form of organic and inorganic, is able to be absorbed by plants, which will be finally removed through harvesting the plants in the wetlands system (Qin & Chen, 2016)

Thus can be seen that root system has important role in floating treatment itself because the removal of contaminants is also affected by the biofilm that grows around the roots Regarding the number of ammonium that goes higher, EPA (2007) reports that the ammonium will be higher than nitrite if the nitrifying bacteria just grows at the time, when ammonium volume is going lower, nitrite will rise since the nitrification process is undergoing, because in nitrification process, ammonium will be converted to nitrite and nitrite to nitrate by nitrifying bacteria Regarding this, in this study, the nitrifying bacteria was just about to grow and this can be seen that T1 has its number going higher each day, which marks that the growth of nitrifying bacteria is quite well

According to Borne et al., (2013), summer season is the right season for running floating treatment wetlands since high temperature can enhance the denitrifying and plant growth rate and more nitrogen uptake

However, phosphorus is also part of nutrients, same to ammonium and nitrite, but the low number of phosphorus is mostly caused by the location of the sampling area itself as seen in Figure 6, which is not around the farming area According to EPA (2022), nutrients which contain nitrogen and phosphorus are used by farmers in form of fertilizers, which are useful for the growth of the crops According to Rahman et al., (2022), phosphate also is contained by detergent waste that enters water bodies though the runoff, especially from domestic use

Apart from the summer season that also supports the run of this floating treatment wetlands, the observation day is also important According to Shahid et al.,

(2019b), 96 hours of observation day of floating treatment wetlands with Phragmites australis and Brachia mutica, shows good result, where the removal efficiency of COD reached 85.6% for Phragmites australis Shahid et al., (2019a) also made another research using different type of ornamental plants which were Typha domingensis and L fusca, which resulted that these two plants successfully removed

COD, BOD 5 , and TOC during 96 hours of observation using the pilot scale as shown in Figure 1 Author had made the experiments in winter version, started from January

2023 until Mei 2023, however, the result was very bad, and some of the parameters (COD, nitrite, and total phosphorus) were below the lowest minimum standard (see Table 1)

One way ANOVA table in each parameter also has important role to find if there is any statistically significant difference between T1 and T2 in handling the surface water in this context However, all the results for each parameter show that there is no any significant difference between the number of plants with the removal efficiency, which means that based on statistical approach, there is no any difference between T1 and T2 in removing the contaminants in the tested surface water, although the removal efficiency of T1 is still a bit higher than T2 in every parameter, but statistically this difference is not significant enough

This is essential to consider further research with peace lily in treating different type of water with additional supporting substrate and probably with more number of plants.

Conclusion

The conclusions of this study are as described below:

1 The whole process in this study was made by the roots and microorganisms grew in the roots due to the absence of supporting substrate

2 According to one way ANOVA result for each parameter, there is no any significant difference However, removal efficiency of T1 was still slightly higher than T2

3 According to the results, the use of peace lily is effective in the surface water treatment However, the absence of substrate affect the removal efficiency, especially for TSS

4 Some parameters, such as COD and TSS, are treated enough in this research as seen in Figure 11 and 13, compared to the standard in Table 1, especially COD number which the result decreases each day

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1 10 ml of phosphate solution to 100 ml of distilled water

2 1.5 ml of phosphate solution to 50 ml of distilled water

1 35 ml of sample is poured into the volumetric glass

2 5 ml of amstrong and 1 ml of ascorbic acid are added into the glass of sample

3 The sample is put in the oven at 121℃ for 40 minutes

4 Then, 1 mg of potassium peroxodisulfate is added

5 The sample is measured using UV-VIS at 880 nm

1 40.0 g ± 0.5 g 4 -aminobenzene sufonamide (NH2C6H4SO2NH2) in a mixture of

100 ml ± 1 ml of octophosphoric acid (4.1) with 500 ml ± 50 ml of water in a beaker glass is dissolved

2 2.00 g ± 0.02 g N (1 naphtyl) 1.2 diamonietane dihydrochloride (C10H7- NH-CH2- CH2-NH2- 2HCl) in the resulting solution is dissolved

3 The reagent is transferred to a 1000 ml volumetric flask and dilute to volume, shaking well

4 The reagent is stored in amber glass jar, solution is stable for 1 month if kept at 2- 5℃

1 ml of standard nitrite solution (p00mg/l) is transferred to a 1000 volume volumetric flask and dilute to volume with water

1 Standard solutions with nitrite concentrations is prepared evenly spaced over the entire working range from working solutions with nitrite concentrations between 0.1 mg/l and 0.5 mg/l

2.A series of 5 rinsed 100 ml volumetric flasks, rinse with distilled water, and then proceed in the following order Standard concentration is calculated per 40 ml of sample

1 NO2- standard solution concentration (mg/l) 0.1 0.2 0.3 0.4 0.5

2 standard solution suction volume (ml) 1 2 3 4 5

Measure the blank and standard samples after performing the coloration on the UV- VIS instrument at 540 nm with 10mm cuvettes

1 40 ml of the test portion is transferred into a 50 ml volumetric flask

2 1 ml of color reagent solution is added to 40 ml of sample and mix well

3 The samples are placed in room temperature for 20 minutes

4 The samples are put in UV-VIS Lambda 25 - cuvette photometer with optical path length of 40 mm at maximum wavelength of about λ = 540 nm

5 The blank is prepared as the test portion, but replaces the test portion with 40 ml of distilled water and proceeds parallel to the test portion

Data analysis and calculation results

The result of the measurement is expressed in terms of the units of mg/l for each sample, the nitrite index, in mg/l, is calculated by the formula:

C NO2 -  N is the concentration of nitrite in the sample in terms of nitrogen (mg/l)

C NO2 - is the concentration of ammonium measured in the spectrometer (mg/l)

14 is the atomic mass of nitrogen (g/mol)

46 is the atomic mass of nitrite (g/mol)

500 ml K 2 Cr 2 O 7 , 167 ml H 2 SO 4 , and 33.3 g HgSO 4 are dissolved into volumetric glass

1 2.5 ml of sample was poured into glass tube

2 1.5 ml of the reagent is mixed into the sample

3 3.5 ml of H 2 SO 4 is added into the sample

4 The tube lid is closed and mixed

5 The sample and blank is put in the spectroquant TR-200 at 148℃ for 2 hours

6 The samples are measured with UV-VIS at 420 nm

1 130g ± 1g sodium salicylate (C7H6O3Na) and 130g ± 1g trisodium cytrate (C6H5O7Na3.2H2O) is dissolved in water in a 1000 ml volumetric flask

2 Distilled water is distilled to give the total volume of the liquid about 950 ml and then add 0.970g ±0.005g Sodium nitrosopentacyano iron(III) dihydrate [sodium nitroprusiat,{Fe(CN)5NO}Na2.2H2O] to the solution

3 The solution is diluted with distilled water to the mark

4 The reagent is stored in an amber glass vial and is stable for at least 2 weeks

1 32.0g ±0.1g sodium hydroxide is dissolved in 500ml ±50ml water

2 The solution is cooled in room temperature and add 2.0 g ±0.02 g Sodium dichloroisocyanurate{C2N3O3Cl2Na.2H2O} to the solution

3 The solution is diluted and transfer to a 1000 ml volumetric flask and make up to the mark with water

4 The reagent is stored in an amber glass vial and is stable for at least 2 weeks

3.4.5.3.1 Ammonium stock solution 10mg/l (working solution 1)

1 1ml of 1000mg/L ammonium stock solution is dissolved into a 100 ml volumetric flask and make up to volume with distilled water

2 This solution is stable for one week

Ammonium stock solution 1mg/l (working solution 2)

1 10 ml of 10 mg/L ammonium stock solution is dissolved into a 100 ml volumetric flask and make up to volume with distilled water

CAUTION – Do not allow ammonium to enter or come into contact with skin

1 Standard solutions of evenly spaced ammonium concentrations over the entire working range from working solutions (1), (2) with ammonium concentrations of 1 mg/l and 10 mg/l (1.2.3) )

2 A series of 8 washed 50 ml volumetric flasks, rinse with distilled water, and then proceed in the following sequence The standard concentration was calculated per 40 ml of sample

1 Standard solution concentration NH4 + (mg/l) 1 1 1 1 10 10 10

2 standard solution suction volume (ml) 0 0,4 2 4 1,6 2,4 4

Blank and standard samples are measured after performing coloration on UV-VIS equipment at 655 nm with 10mm cuvettes

1 Water containing organic compounds containing alcohols and aldehydes must be distilled before determination

2 If the water contains too much or too much ammonium, the water should be diluted before performing the analysis

3 The test sample is stored in a glass or polyethylene vial

4 Samples should be analyzed as quickly as possible or should be efrigerated at between 20°C and 50°C or acidified with sulfuric acid to pH < 2 for storage to avoid ammonium contamination

A maximum test portion volume of 40 ml can be used for the determination of ammonium nitrogen concentration ρN = 1 mg/l

Note: For test pieces with a larger ammonium content, a smaller test sample may be used as appropriate Samples containing suspended particles must be settled or filtered through water-coated glass wool before sampling, or may be distilled

Pipette the test portion into a 50 ml volumetric flask and if necessary dilute with water to 40 ml ± 1 ml