WO2022103339A1

WO2022103339A1 - A soil-based media

Info

Publication number: WO2022103339A1
Application number: PCT/SG2021/050703
Authority: WO
Inventors: Jiangyong Hu; Say Leong ONG; Fang Yee LIM; Teck Heng NEO; Huiling GUO
Original assignee: National University Of Singapore; Ngee Ann Polytechnic
Priority date: 2020-11-16
Filing date: 2021-11-16
Publication date: 2022-05-19

Abstract

A soil-based media There is provided a soil-based media for a bioretention system comprising a soil mixture and a hydrogel, wherein the soil mixture comprises at least one carbon source. There is also provided a bioretention system comprising the soil-based media.

Description

A soil-based media

Technical Field

The present invention relates to an improved soil-based media for use in a bioretention system.

Background

Stormwater runoff carries numerous pollutants such as total suspended solids (TSS), nutrients such as nitrogen and phosphorus, heavy metals and debris. It is a primary contributor to downstream erosion and may cause water quality deterioration and flooding.

Accordingly, bioretention systems are used in controlling the quality of the water from stormwater runoff, as well as the quantity of water retained. Different media for the bioretention systems have been considered. Further, most existing bioretention systems require a submerged layer and/or an anoxic zone for effectively removing nutrients such as nitrogen. This in turn requires the bioretention system to accommodate extra piping such as elevated drainage outlet pipes, as well as construction of a deep filter media or incorporation of a submerged internal water storage (IWS) zone.

There is therefore a need for an improved bioretention system.

Summary of the invention

The present invention seeks to address these problems, and/or to provide an improved soil-based media, particularly for use in a bioretention system.

According to a first aspect, there is provided a soil-based media for a bioretention system comprising a soil mixture and a hydrogel, wherein the soil mixture comprises at least one carbon source.

The hydrogel may be any suitable hydrogel. For example, the hydrogel may be a polymeric hydrogel. In particular, the hydrogel may be a potassium-based cross-linking polymeric hydrogel.

The soil-based media may comprise a suitable amount of hydrogel. For example, the soil-based media may comprise 0.01-5 vol % hydrogel based on the total volume of the soil-based media. The soil mixture comprised in the soil-based media may comprise suitable components. According to a particular aspect, the soil mixture may comprise soil. The amount of soil comprised in the soil mixture may be any suitable amount. For example, the soil mixture may comprise 50-60 vol % soil based on the total volume of the soil-based media.

The soil mixture may further comprise sand. The soil mixture may comprise a suitable amount of sand. For example, the soil mixture may comprise 20-35 vol % sand based on the total volume of the soil-based media.

The sand may comprise sand particles of various sizes. According to a particular aspect, the sand may comprise sand particles having an average particle size of 0.06-1.5 mm.

The at least one carbon source comprised in the soil mixture may be any suitable carbon source. For example, the at least one carbon source may be an organic carbon source. According to a particular aspect, the organic carbon source may comprise plant-based compost. Examples of plant-based compost comprise, but is not limited to, coconut fibres, palm fibres, rice husk, jute fibres, wood chips, or mixtures thereof.

The soil mixture may comprise a suitable amount of organic carbon source. For example, the soil mixture may comprise 5-15 vol % organic carbon source based on the total volume of the soil-based media.

The soil mixture may further comprise a waste component capable of adsorbing dissolved phosphates. For example, the waste component may comprise water treatment residue. In particular, the waste component may be derived from a water treatment plant.

The soil mixture may comprise a suitable amount of waste component. For example, the soil mixture may comprise 8-20 vol % waste component based on the total volume of the soil-based media.

The soil-based media may be capable of removing a suitable amount of total nitrogen (TN), total phosphorus (TP) and/or total suspended solids (TSS) from water in contact with the soil-based mixture. According to a particular aspect, the soil-based media may remove > 30% of TN from water in contact with the soil-based media. According to a particular aspect, the soil-based media may remove > 80% of total phosphorus TP from water in contact with the soil-based media. According to a particular aspect, the soilbased media may remove > 80% of TSS from water in contact with the soil-based media.

According to a second aspect, the present invention provides a bioretention system comprising a soil-based media according to the first aspect for filtering and/or treating water. The bioretention system may be any suitable bioretention system.

Brief Description of the Drawings

In order that the invention may be fully understood and readily put into practical effect there shall now be described by way of non-limitative example only exemplary embodiments, the description being with reference to the accompanying illustrative drawings. In the drawings:

Figure 1 shows average removal efficiencies of total suspended solids (TSS), total phosphorous (TP), and total nitrogen (TN) by the soil-based media according to one embodiment during the first column test;

Figure 2 shows removal efficiencies of pollutants during the second column test;

Figure 3 shows removal efficiencies of pollutants during the third column test;

Figure 4 shows comparison of TN removal efficiencies for soil-based media according to one embodiment, media without hydrogel, and media with soil and sand only; and

Figure 5 shows comparison of nitrate removal efficiencies for soil-based media according to one embodiment, media without hydrogel, and media with soil and sand only.

Detailed Description

As explained above, there is a need for an improved soil media for use in a bioretention system.

In general terms, the invention relates to a soil-based media which does not need a special design for internal water storage (IWS) to remove pollutants, such as but not limited to TN, particularly from stormwater runoff, thereby reducing the filter depth required for the bioretention system in which the soil-based media is used. In this way, the amount of the soil-based media required may be reduced, thereby lowering cost of the bioretention system. Further, with a shallower filter depth, it is easier to connect the bioretention system with existing runoff drainage systems.

The hydrogel may be any suitable hydrogel. The hydrogel comprised in the soil-based media need not be pre-treated prior to its use. For example, the hydrogel may be a polymeric hydrogel. In particular, the hydrogel may be a cross-linking polymeric hydrogel. The cross-linking polymeric hydrogel may be an alkali metal-based cross-linking polymeric hydrogel. Even more in particular, the hydrogel may be a potassium-based cross-linking polymeric hydrogel. For example, the hydrogel may comprise cross-linked polymer of potassium acrylate and uncross-linked potassium acrylate homopolymer.

The hydrogel comprised in the soil-based mixture may be able to increase the water holding capacity of the soil and therefore reduce irrigation frequency. Further, the hydrogel may be able to hold nutrients in the soil and enable slow release of the nutrients, thereby enhancing microbial activity in the soil and enhancing plant growth.

The hydrogel comprised in the soil-based media enables the soil-based media to improve its water holding and retention capacity, which in turn is favourable for TN and NO removal from stormwater runoff in contact with the soil-based media.

The soil-based media may comprise a suitable amount of hydrogel. For example, the soil-based media may comprise 0.01-5 vol % hydrogel based on the total volume of the soil-based media. In particular, the soil-based media may comprise 0.05-5 vol %, 0.1-4.5 vol %, 0.5-4.0 vol %, 1.0-3.5 vol %, 1.5-3.0 vol %, 2.0-2.5 vol % hydrogel. Even more in particular, the soil-based media may comprise 0.05-0.1 vol % hydrogel based on the total volume of the soil-based media.

The soil mixture comprised in the soil-based media may comprise suitable components. For example, the soil mixture may comprise soil. The soil may be any suitable soil. For the purposes of the present invention, the term soil may refer to soil that is formed by cycles of nature. The soil may comprise naturally occurring soil components, inorganic and organic matter in random proportions. The amount of soil comprised in the soil mixture may be any suitable amount. According to a particular aspect, the amount of soil may be 50-60 vol % based on the total volume of the soil-based media. In particular, the amount of soil may be 40-60 vol %, 41-56 vol %, 42-55 vol %, 43-54 vol %, 45-50 vol %, 47-48 vol % based on the total volume of the soil-based media. For example, the amount of soil may be 40-60 vol %, 40-55 vol % based on the total volume of the soil-based media. Even more in particular, the amount of soil may be 54-56 vol % soil based on the total volume of the soil-based media.

The soil mixture may further comprise sand. The sand may be of any suitable type. The sand may be coarse or fine sand, and may comprise finely divided rock and mineral particles.

The sand may have a suitable average particle size. According to a particular aspect, the average particle size of the sand may be 0.06-1.5 mm. For the purposes of the present invention, the average particle size refers to the largest dimension of the particle of sand such as the height, length or width. In particular, the average particle size may be 0.07-1.0 mm, 0.08-0.75 mm, 0.09-0.5 mm, 0.1-0.45 mm, 0.15-0.40 mm, 0.2-0.35 mm, 0.25-0.3 mm. Even more in particular, the average particle size of the sand may be 0.06- 0.5 mm, particularly 0.25-0.5 mm.

Any suitable amount of sand may be comprised in the soil mixture. According to a particular aspect, the amount of sand may be 20-35 vol % based on the total volume of the soil-based media. In particular, the amount of sand may be 22-35 vol%, 24-35 vol %, 25-35 vol %, 26-34 vol %, 27-33 vol %, 28-32 vol %, 29-30 vol % based on the total volume of the soil-based media. Even more in particular, the amount of sand may be 24- 26 vol % soil based on the total volume of the soil-based media.

The at least one carbon source comprised in the soil mixture may be any suitable carbon source. For example, the carbon source may be, but not limited to, an organic carbon source. The organic carbon source may be any suitable source which comprises organic carbon such as, but not limited to, plant-based compost. Examples of plant-based compost may comprise, but is not limited to, coconut fibres, palm fibres, rice husk, jute fibres, wood chips, or mixtures thereof.

Any suitable amount of organic carbon source may be comprised in the soil mixture. According to a particular aspect, the amount of organic carbon source may be 5-20 vol %, particularly 5-15 vol % based on the total volume of the soil-based media. In particular, the amount of organic carbon source may be 7-20 vol %, 9-20 vol %, 10-20 vol %, 11- 19 vol %, 12-18 vol %, 13-17 vol %, 14-16 vol %, 15-15.5 vol % based on the total volume of the soil-based media. Even more in particular, the amount of organic carbon source may be 9-11 vol % soil based on the total volume of the soil-based media.

The soil mixture may further comprise a waste component capable of adsorbing dissolved phosphates. The waste component may be any suitable waste component and may be processed or unprocessed from any source such as, but not limited to, household, landfill, industrial, agricultural, marine, municipal, sewer, drain, or a combination thereof. For example, the waste component may comprise water treatment residue (WTR). According to a particular aspect, the waste component may be derived from a water treatment plant.

The waste component may comprise aluminium-based or ferric-based components. In particular, the waste component may comprise aluminium hydroxide, ferric hydroxide, or a mixture thereof, which may provide adsorption of dissolved phosphates.

The waste component may be of a suitable size. For example, the waste component may have an average particle size of 0.1-1.2 mm. In this way, the waste component may intrinsically have a high surface area-to-volume ratio and therefore improve the adsorption of phosphates. With improved removal of phosphates, the overall TP removal from polluted stormwater runoff may be improved resulting in cleaner filtered effluent entering the drains and waterways.

The amount of waste component comprised in the soil mixture may be any suitable amount. For example, the amount of waste component may be 8-20 vol % based on the total volume of the soil-based media. In particular, the amount of waste component may be 9-20 vol %, 10-20 vol %, 12-18 vol %, 13-17 vol %, 14-16 vol %, 15-15.5 vol % based on the total volume of the soil-based media. Even more in particular, the amount of waste component may be 9-12 vol % soil based on the total volume of the soil-based media.

The soil-based media may remove a suitable amount of TN, TP and/or TSS from water in contact with the soil-based media. For the purposes of the present invention, TN, used with reference to a volume of water, refers to a sum of nitrate-nitrogen (NO3-N), nitritenitrogen (NO2-N), ammonia-nitrogen (NH₃-N) and organically bonded nitrogen in that volume of water. For the purposes of the present invention, TP, used with reference to a volume of water, refers to a sum of reactive, condensed and organic phosphorus, which may be in dissolved form (orthophosphate), inorganic form (reactive plus condensed or acid hydrolysable phosphate) and organically bound forms in that volume of water. For the purposes of the present invention, TSS refers to a parameter for quantifying total amount of suspended matter in a liquid, which may be retained on a filter paper and dried at about 103-105°C.

The water may be any suitable water such as, but not limited to, influent water stream, stormwater, rainwater runoff, or a mixture thereof. According to a particular aspect, the water may be running through the soil-based media.

According to a particular aspect, the soil-based media may remove > 30% of total nitrogen (TN) from water in contact with the soil-based media. In particular, the soilbased media may remove 30-45%, 32-44%, 35-40% of TN from water in contact with the soil-based media.

According to a particular aspect, the soil-based media may remove > 80% of total phosphorus (TP) from water in contact with the soil-based media. In particular, the soilbased media may remove 80-95%, 82-92%, 85-90%, 86-88% of TP from water in contact with the soil-based media.

According to a particular aspect, the soil-based media may remove > 80% of total suspended solids (TSS) from water in contact with the soil-based media. In particular, the soil-based media may remove 80-98%, 82-97%, 85-95%, 86-92%, 88-90% of TSS from water in contact with the soil-based media.

It can be seen that the soil-based media of the present invention is suitable for effectively removing TN from polluted water in contact with the soil-based media. In particular, the presence of organic matter in the soil-based media may enable denitrification to convert NO₃- in the polluted water in contact with the soil-based media to N2 gas. The soil-based media may also be effective in TSS and TP removal from polluted water in contact with the soil-based media. Accordingly, the soil-based media may be applied in bioretention system and rooftop gardens for stormwater runoff quality improvement or reuse. It has also great potential to treat wastes from industrial and agricultural activities. The soil-based media of the present invention, without providing a reservoir of water, is still able to effectively remove pollutants such as TN, TP and/or TSS from polluted water in contact with the soil-based media. This may be achieved in view of the hydrogel comprised in the soil-based media. The hydrogel may increase the water retention capacity of the soil-based media since the hydrogel is able to absorb water very effectively, up to 100 times its volume, thereby stopping soil denudation and water loss and thus increase microbial activity. The increase in microbial activity enables effective denitrification. The hydrogel enables water it has absorbed to be released slowly, and hence creating an anoxic zone within the soil-based media.

The soil-based medial of the present invention, not only enables effective removal of pollutants, but also supports plant growth. The plants may provide additional benefits of maintaining the porosity and moisture of the soil-based media, thereby enhancing the microbial activity for pollutant removal. For example, the pH of the soil-based media may be 5.5-8.5. In particular, the pH of the soil-based media may be 6-8, 6.5-7.5, 7-7.2.

Having now generally described the invention, the same will be more readily understood through reference to the following example which is provided by way of illustration, and is not intended to be limiting.

Example

Materials and methods

Preparation of water treatment residue (WTR)

WTR were obtained from a local water treatment plant. The collected WTR were dried under sun for 1 day. The dried WTR were then crushed or blended into smaller sizes of 0.15-1.18 mm.

Preparation of organic materials Rice husk or coconut fibre were supplied by local landscaping and nursery supplies. The moisture content of the rice husk or coconut fibre was determined using oven-drying method in accordance to British Standard (BS) 1377-2:1990. The organic content of the rice husk or coconut fibre was determined using Method C as stated in ASTM D 2974 - 97, which involved igniting an oven-dried sample from the moisture content test in a muffle furnace at 440°C.

Preparation of soil

Top soil was obtained from local landscaping and nursery supplies. The moisture content of the top soil was determined using oven-drying method in accordance to BS 1377- 2:1990. The organic content of the top soil was determined using Method C as stated in ASTM D 2974 - 97, which involved igniting an oven-dried sample from the moisture content test in a muffle furnace at 440°C. The particle size distribution of the soil was determined using dry sieving method in accordance to BS 1377-2:1990.

Preparation of sand

Medium size sand (0.06-0.5 mm) was used. The sand was washed before mixing. The moisture content of the sand was determined using oven-drying method in accordance with BS 1377-2:1990.

Preparation of hydrogel

Hydrogel was supplied by Chemtex Speciality Limited Company.

As one of the key compositions for the soil-based media, the hydrogel used was a potassium-based cross-linking hydrogel polymer that may influence the soil permeability, density, structure, texture, evaporation, and infiltration rate of water through the soil. It was used without any pre-treatment.

Mixing

The properties of each component of the soil-based media were determined prior to mixing. Mixing (based on volume percentage) was performed by adding soil and sand first, followed by adding in the WTR. The fine WTR had a high surface area-to-volume ratio, providing excellent adsorption capabilities for the soil-based media. Rice husk/coconut fibre and hydrogel were added in smaller batches into the mixture while performing the mixing. It was ensured that the soil-based media was not compacted during mixing and pouring processes. After mixing, the soil-based media was ready to be utilized as the filter media layer for a bioretention system.

The soil-based media was tested for its pH, saturated hydraulic content, nutrients, organic and heavy metal content. The values were compared against the requirements of the ABC Waters Guideline from the Public Utilities Board (PUB) of Singapore, as shown in Table 1.

Table 1 : Comparison against ABC Waters Guideline

Example 1 - First Column Study

The soil-based media having the composition as shown in Table 2 was used for laboratory tests.

Table 2: Composition of soil-based media for laboratory tests

Each column was prepared with four layers to simulate a typical bioretention system. Glass wool layer was placed at the bottom of column to retard the outflow of soil mix. About 2 cm height of gravel (particle size range 3-6 mm) layer was placed between glass wool and soil mix layer to support the upper layer. Soil mix layer, the most important part to remove pollutants and filtrate stormwater, was set as the third layer. The topmost layer was made of coarse gravel to distribute the stormwater runoff evenly and to avoid stormwater bypass. After all columns were set up, they were flushed with deionised water daily. This operation was performed for one week. Water was pumped in the column and flowed from top layer to bottom layer. The bottom valves were turned on to allow effluent flow water out of column. The washing of column was to avoid the influence of nutrients background of filter media. Washing of column allowed the nutrients in engineered soil to leach out as much as possible and help to reduce the leaching problem in the subsequent processes. This process also helped to reduce the time needed for columns to stabilize.

The experiment procedures were separated into two sections, namely synthetic stormwater dosing and sample testing. Synthetic stormwater was prepared for each rainfall cycle. The weighted chemicals used to simulate target pollutants were added into deionized water. Magnetic stirrer was used to ensure homogenous solution. The synthetic stormwater with different concentrations of pollutants was then dosed into the columns. The concentrations of pollutants in synthetic stormwater were according to pollutants concentration in Singapore natural environment. All influent stormwater and treated run-off water quality analyses were conducted in accordance to the Standard Methods for Water and Wastewater Analysis.

The soil-based media achieved the following average water quality improvements: total suspended solids (TSS) removal of 97%, total phosphorous (TP) removal of 92% and total nitrogen (TN) removal of 29 %, as shown in Figure 1.

For TN, the highest removal efficiency was 44 % (data not shown). Components in the soil-based media such as hydrogel, soil and coconut fibre helped in water quality improvement by taking up some nutrients, holding them tightly, and delaying their dissolution.

Biological processes also played a very important role in controlling the nitrogen transformation and fate. Rice husk and coconut fibre provided carbon source for the microbiological activities. The water holding capacity of the soil-based media, in view of the media comprising hydrogel, was favourable for NOs' removal. These biological processes involved in TN removal were slow such that significant change was only observed after stabilization period. This was because nitrogen has a complex biogeochemical cycle and the removal of nitrogen is microbially facilitated. The above TN data was based on 11 cycles of stormwater runoff dosing. Better performance may be expected after several subsequent stormwater runoff dosing.

Example 2 - Second Column Study

A second column study was conducted for about 2 months. The soil-based media reduced pollutants with average removal efficiency of 96.47%, 91.45%, 43.49% and 34.53% for TSS, TP, TN and NOs', respectively. The performance of the developed soil media for individual runs are shown in Figure 2.

Example 3 - Third Column Study

A third column study was conducted a few months later. The columns were dosed daily with synthetic stormwater runoff. The soil-based media reduced pollutants with average removal efficiencies of 95%, 92%, 60% and 55% for TSS, TP, TN and NOs', respectively. The performance of the developed soil media for individual runs are shown in Figure 3.

Good removal of TSS (95%) was due to effective mechanical filtration by the developed soil media. Good removal of TP (92%) indicated that adsorption and chemical precipitation processes occurred. This was attributed to the addition of water treatment residue in the soil media. In addition, the results also showed good TN and NO removal. Hydrogel in the soil-based media could retain water, thereby creating anoxic zones in the soil which was suitable for denitrification. These anoxic zones may existed between small micropores of the soil aggregate structure or individual soil particles in the soilbased media. Therefore, nitrate that had been trapped in the anoxic zones could undergo denitrification to convert to N2 gas. The developed soil media demonstrated good removals of TN from stormwater runoff. It provided an ecological and effective way to remove contaminants especially TN (which is the most problematic contaminant) in full- scale system.

Example 4 - First Pot Study

The soil-based media was set up in 2 separate pots. A plant (Ipomoea aquatica) was planted in one of the pots, the other was a control pot. The pots were dosed daily with synthetic stormwater runoff to evaluate their removal efficiencies of TSS, TP and TN. The results are shown in Table 3.

Table 3: Results of first pot study using the soil-based media (EP - Pot with plants; EN - Pot without plants) Good TSS and nutrient removal efficiency were noted, even for the pot without plants. The pot study also displayed the feasibility of the soil-based media in supporting plant growth.

Example 5 - Second Pot Study

A second pot study was conducted. The results are shown in Table 4.

Table 4: Results of second pot study using the soil-based media (EP - Pot with plants; EN - Pot without plants)

Both pots removed TSS and TP effectively. The removal efficiencies of TSS and TP were about 97% and 94%, respectively. Pot with plant (EP) enhanced TN removal from 60.81% to 67.06%. The soil-based media may therefore serve as growing medium for plants, including Ipomoea Aquatic. Ipomoea Aquatic planted in the soil-based media was found to offer additional benefits of enhancing TN removal. Example 6 - Comparison Study

Comparison of the performance of the soil-based media with controls were done using (1) media without hydrogel; and (2) sand and soil (50 % each). The same setup as per previous pot studies was used. The composition (by volume %) of the media are shown in Table 5.

The pots were dosed daily with synthetic stormwater runoff. The study was conducted for 2 types of media, developed media and media without hydrogel (as control). The experiments were also designed to observe the impact of plant (Ipomoea Aquatica) for TN removal. The results showed that pot with developed media outperformed the pot without hydrogel in terms of TN removal. Pots with plant showed better TN performance compared to pots without plants, e.g. 67% vs 61 % (soil-based media of the present invention) and 56% vs 43% (media without hydrogel). Plant could enhance denitrification due to readily available organic carbon in the rhizosphere from root exudates. Plant could also increase nitrate removal through the growth of diverse soil microbial communities.

Table 6 shows the total nitrogen (TN) removal efficiencies.

and media without hydrogel

Figures 4 and 5 show the TN and nitrate removal efficiencies for developed media vs controls, e.g. media without hydrogel and 50% of soil + 50 % of sand only. TN removal rate of the soil-based media was increased by 16.82% compared to soil media without hydrogel and by 46.68% compared to soil and sand (Figure 4).

Column with soil-based media (with hydrogel) had the highest nitrate removal efficiency, with an average removal efficiency of 55.49%. It can be seen from Figure 5 that the nitrate removal was poorer without hydrogel (average removal efficiency of 37.92%). Bioretention media with 50% of sand and 50% of soil showed little effect on nitrate removal (7.92%). Nitrate is a monovalent anion and a weak ligand. Hence, the removal of nitrate relies primarily on denitrification.

Based on the results above, it can be seen that hydrogel plays a crucial role in affecting TN and nitrate removal in the soil-based media. The presence of hydrogel could increase the water retention capacity of the soil-based media, stop soil denudation and water loss and increase microbial activity. Furthermore, it acts as “mini-water reservoirs” in the soil column and pot. It can slowly release water which was absorbed during irrigation to soil. Hydrogel also played a role of taking up some nutrients (TN and nitrate), holding them tightly, and promoting denitrification for the removal of nitrate. Whilst the foregoing description has described exemplary embodiments, it will be understood by those skilled in the technology concerned that many variations may be made without departing from the present invention.

Claims

1. A soil-based media for a bioretention system comprising a soil mixture and a hydrogel, wherein the soil mixture comprises at least one carbon source.

2. The soil-based media according to claim 1, wherein the hydrogel is a polymeric hydrogel.

3. The soil-based media according to claim 1 or 2, wherein the hydrogel is a potassium-based cross-linking polymeric hydrogel.

4. The soil-based media according to any preceding claim, wherein the soil-based media comprises 0.01-5 vol % hydrogel.

5. The soil-based media according to any preceding claim, wherein the soil mixture comprises 50-60 vol % soil based on the total volume of the soil-based media.

6. The soil-based media according to claim 5, wherein the soil mixture further comprises sand.

7. The soil-based media according to claim 6, wherein the sand has an average particle size of 0.06-1.5 mm.

8. The soil-based media according to claim 6 or 7, wherein the soil mixture comprises 20-35 vol % sand based on the total volume of the soil-based media.

9. The soil-based media according to any preceding claim, wherein the at least one carbon source is organic carbon source.

10. The soil-based media according to claim 9, wherein the organic carbon source comprises plant-based compost.

11. The soil-based media according to claim 10, wherein the plant-based compost comprises: coconut fibres, palm fibres, rice husk, jute fibres, wood chips, or mixtures thereof.

12. The soil-based media according to any of claims 9 to 11 , wherein the soil mixture comprises 5-15 vol % organic carbon source based on the total volume of the soil-based media.

13. The soil-based media according to any of claims 5 to 12, wherein the soil mixture further comprises a waste component capable of adsorbing dissolved phosphates.

14. The soil-based media according to claim 13, wherein the waste component comprises water treatment residue.

15. The soil-based media according to claim 13 or 14, wherein the waste component is derived from a water treatment plant.

16. The soil-based media according to any of claims 13 to 15, wherein the soil mixture comprises 8-20 vol % waste component based on the total volume of the soil-based media.

17. The soil-based media according to any preceding claim, wherein the soil-based media removes > 30% of total nitrogen (TN) from water in contact with the soil-based media.

18. The soil-based media according to any preceding claim, wherein the soil-based media removes > 80% of total phosphorus (TP) from water in contact with the soil-based media.

19. The soil-based media according to any preceding claim, wherein the soil-based media removes > 80% of total suspended solids (TSS) from water in contact with the soil-based media.

20. A bioretention system comprising a soil-based media according to any preceding claim for filtering and/or treating water.