
==== Front
Sci Rep
Sci Rep
Scientific Reports
2045-2322
Nature Publishing Group UK London

72777
10.1038/s41598-024-72777-2
Article
Examining the efficacy of biological filters in the removal of agricultural pesticides and nutrient elements from agricultural drainage water
Kianpour Ali 1
Yargholi Bahman yar_bahman@yahoo.com

2
Shrafati Ahmad 1
Akhavan Karamat 3
1 grid.411463.5 0000 0001 0706 2472 Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
2 grid.473705.2 0000 0001 0681 7351 Agricultural Research, Education and Extension Organization, Agricultural Engineering Research Institute, 31585-845, Karaj, 3135913533 Alborz Iran
3 Agricultural Engineering Research Department, Ardabil Agricultural and Natural Resources Research and Education Center, AREEO, Ardabil, Iran
14 9 2024
14 9 2024
2024
14 2150714 6 2024
10 9 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
The high water consumption in agriculture has led to an obvious water crisis in this sector, and the use of unconventional water sources, especially agricultural drains, is considered necessary. For this purpose, the present study was carried out to evaluate the efficiency of biological filters with different types of substrates for treating agricultural wastewater in Khuzestan province, located in the south of Iran, to use receptive resources and reuse them in agriculture. Next, the efficiency of four types of biological filters for treating agricultural drainage water with different retention times was evaluated. Sawdust, cotton stalks, wheat straw, stubble, and rice husk were used as filters. Qualitative factors included agricultural pesticides (Atrazine, Randup, Paraquat, and 2, 4-D) and nutrients (nitrate, nitrogen, phosphate, and phosphorus). By examining the trend of increasing the retention time and the corresponding removal percentage, it was observed that the retention time has a direct relationship with the amount of removal efficiency of nutrients and agricultural toxins. As the residence time increases, the average amount of nutrient compounds in different filters decreases, and their removal percentage increases. The highest removal percentage of nitrate, total nitrogen, phosphate, and total phosphorus was 74.03, 71.66, 57.97, and 61.85% in the sawdust filter and was assigned to 10 days. The highest percentage of removal of Atrazine, Tofudi, Paraquat, and Roundup toxins with a removal efficiency of 91.73, 84.27, 89.81, and 88.46% was also observed in the treatment of sawdust for 10 days. The sawdust filter showed a good performance in removing the parameters of agricultural toxins and nutrient compounds in a retention time of 10 days compared to other filters and retention times. As a general result, the sawdust filter can be cited as a reliable substrate with acceptable efficiency compared to other filters.

Keywords

Nutrient compounds
Removal efficiency
Agricultural drainage
Agricultural pesticides
Biological filter
Subject terms

Environmental social sciences
Sustainability
issue-copyright-statement© Springer Nature Limited 2024
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pmcIntroduction

Agriculture drainage plays an important role due to its large volume and decentralized nature. Agricultural drains are one of the most significant sources of return water because of their large volume. Drains will have different characteristics depending on the location and the activity. The quality of water is a relative term that represents its physical, chemical, and biological characteristics and affects its use for a specific purpose1. Accordingly, the important qualitative parameters of agricultural drains include electrical conductivity, special ions (sodium, chlorine, and boron), nutrients (phosphorus and nitrogen), as well as toxins and pesticides. Various physical and chemical processes exist to remove these metals, including sedimentation, filtration, evaporation, ion exchange, membrane separation, solvent extraction, etc. However, these methods are not entirely effective for low metal concentrations are expensive, and cannot completely separate metals. In addition, some of these methods require expensive equipment. Recently, bio sorption has been promoted as an efficient and cheap process. Heavy metals can be removed from wastewater with inexpensive materials such as algae, wheat straw, and crab skin2,3. Inexpensive materials, especially agricultural waste, can create favorable environmental conditions during the treatment process. However, plants that are compatible with drainage water quality are more suitable.

Considering the presence of nutrients in agricultural drainage water for irrigation of crops, one of the factors that reduce their quality is the presence of various ions, which, if they accumulate in the soil, make it difficult for the roots to absorb nutrients. In recent years, a lot of research has been done in the field of using natural materials with the ability to absorb pollutants. Robertson and Merkel4 treated drainage effluent in a pond containing sawdust to the dimensions of 1*2.5*20 meters and found after analyzing the water that the concentration of nitrates increased from 4.8 to 1.04 mg. The use of wood sawdust bioreactors is recommended for reducing nitrate levels in drainage systems5. The research conducted at the University of Waterloo was conducted on the efficiency of the sawdust filter in removing suspended phosphorus (insoluble) in agricultural runoff derived from surface drainage systems; As a result of its high porosity, permeability, surface roughness and plate-like particle structure, sawdust is observed to be very efficient in physical filtration of phosphorus particles6. In a study, treated wastewater using a three-layer combined biological filter (charcoal, ion exchange, coarse sand mixture) for agriculture in Baghdad was investigated. The results showed that BOD and COD decreased by more than 60%7.

Using a multilayer filter with artificial straws for gray water treatment, research was conducted to evaluate the performance of the combined system. It was found that artificial reeds account for more than 60% of the efficiency of the system8. In a study, the effectiveness of the combination of microfiltration and ion exchange was investigated in the treatment of wastewater from dairy factories that contained high amounts of organic matter and salinity, and it was concluded that organic matter and salinity were reduced by 95% and 83%, respectively9.

A study conducted on a wetland with a subsurface flow filled with a bed of sawdust to treat agricultural runoff has found that the efficiency of this system in removing total nitrogen is approximately 53%10.

In a study, the drainage channel of agricultural irrigation water was treated by absorption methods using sawdust. The results showed that the use of sawdust-activated carbon led to the removal of unwanted odors from the KSD water channel and increased salt in the channel water, which was increased by EC, TDS, heavy metals (Na, Mg, Ca, Cl, So4), and SAR or pH decreased in irrigation standards11. The possibility of water purification for agricultural irrigation drainage channels including the main agricultural irrigation water channel and the main KSD agricultural irrigation water channel contaminated with sewage using multimedia filtration technology with (three layers) (commercial coal, coarse sand, and mixed ion exchange) in Three flow rates (0.24, 0.32, 0.48) m2/hr were investigated for contact time (two hours). A comparison of the results showed that the best removal for both channels was obtained after contact time 2 h12. A constructed wetland with a non-permeable surface flow (SFCW), which treats agricultural drainage water in northern Italy, was investigated to obtain information on the potential for effective pesticide reduction. A mixture of imidacloprid, fungicide dimethomorph, and herbicide glyphosate herbicide was used, simulating a rain event13. Studies show that the biological adsorption process can be used as an efficient filter along with other conventional purification processes to remove pesticides in urban water treatment plants14.

In the direction of sustainable development and preservation of the environment, especially in rivers, the control of runoff coming from agricultural lands into rivers is of particular importance. Runoff from irrigation and drainage networks should be efficiently managed so that it is disposed of or optimally removed from them. Considering the extensive extent of lands covered by drainage networks and the necessity for their development, as well as their growing trend, it is expected that the amount of drainage will grow, and planning for their utilization is necessary. Records and studies available indicate that comprehensive and documented research in the field of methods of purification and recycling of agricultural drains has not been conducted, and only a few studies have been conducted in the laboratory. The conduct of applied research in field pilot conditions to test the feasibility of treating and reusing drain water is an important research priority. Considering that the present study was conducted to evaluate the efficacy of biological filters with different substrate types in the treatment of agricultural wastewater in Khuzestan province, located in the south of Iran. Conducting practical research on the efficiency of biological filters in the purification of pollutants caused by agricultural drainage water, in particular residues of chemical fertilizers (nutrients) from drains, and engineering its design and operation can be a significant achievement in wastewater treatment.

The contributions of this article are as follows:

Investigating the effectiveness of biological filters with various substrates for treating agricultural wastewater and reusing them in agriculture.

Evaluating the efficiency of four types of biological filters for the treatment of agricultural drainage water with different retention times.

Investigating the relationship between retention time and removal efficiency of nutrients and agricultural toxins.

Introducing the best treatment to remove agricultural toxins.

Materials and methods

Experimental site

This study was carried out in Khuzestan province, located in the south of Iran using the drainage water from Amirkabir and Mirza Kochak Khan’s sugarcane agro-industries (March to September 2020) (Fig. 1). Amirkabir and Mirza Kochak Khan’s sugarcane agro-industries is one of seven companies to develop sugarcane agro-industries in the southern region of Khuzestan. Sugarcane farms discharge 25 m3/s of drainage water into Naseri Wetlands. It is located approximately 17 Km north of Khorramshahr city at latitude 303805.94′ N and longitude 480759.86′ E. The source of water used in the sugarcane fields is the Karun River. In terms of salinity, this drainage water is in the range of 6 dS/m, but it has limitations due to residues of toxins and chemical fertilizers as well as heavy metals15. Due to the limited quality of the effluent, it is currently discharged into surface water sources, causing pollution and nutrient contamination. In Khuzestan province, the climate is classified as semi-desert in low-latitude areas, with an average annual temperature exceeding 18 degrees Celsius, dry summers, and fog in winter. According to a statistical analysis of the existing meteorological stations, Khuzestan and its adjacent coasts are among the warmest regions in the world. Since the average annual temperature ranges between 24 and 30 °C, there is no equivalent in terms of heat in its latitudes. The average annual rainfall is 358 mm.

Fig. 1 Geographical location of Mirza Kochak Khan’s agriculture and industry [https://earth.gosur.com/?gad_source=1&gclid=Cj0KCQjwsaqzBhDdARIsAK2gqnd03_pn48acVn6ZbveuftHA7j1ZerZlUtps300416zbuK5zklZ3BQAaAthaEALw_wcB].

Construction of a drainage water treatment system (bio filters)

This project was implemented on a site measuring 60*12 square meters and included four pools (bed treatment) measuring 1*5*10 meters in parallel. The implementation map of the plan is shown in Fig. 2. Each pool was insulated using a geomembrane cover. Before building a field pilot, synthetic adsorbents were pre-tested according to the concentration of harmful substances in the used drain, and the amount and speed of absorption of the filters were determined in the laboratory. For this purpose, four parallel ponds were constructed near the drain. According to the research records and the abundance of materials in the area, substrate treatments included straw and wheat stubble, sawdust, rice husks, and cotton stalks (Fig. 3). Table 1 presents the physical characteristics of the investigated filters.

Fig. 2 The implementation map of the plan.

Fig. 3 The materials used as biological filters.

Table 1 A description of the filters used in the research.

Biological filter	Hydraulic conductivity (m/day)	Balk density (ρb) (gr/cm3)	particle density (ρs) (gr/cm3)	Volumetric mass (kg/m3)	Porosity (%)	Density inside the pool (%)	
Straw and wheat stubble	720	0.071	0.093	71.2	68	50	
Sawdust	550	0.11	0.17	109	78	50	
Rice husks	960	0.24	0.62	273	63	30	
Cotton stalks	610	0.053	0.12	55	69	30	

About 80% of the pool space is occupied by filters. Over the filters, a layer of permeable sand and gravel with an average diameter of one centimeter was placed to a depth of 20 cm. After determining the characteristics of the bio-filters, including the hydraulic conductivity coefficient and preliminary field testing, the inlet flow rate of the filters was determined. Bio-filters are a biological method for water and wastewater treatment with different types. The common feature of all of them is the presence of a substrate for the stabilization and growth of microorganisms, which adheres to the substrate in the form of a biological layer (biofilm) and plays the main role of biological purification. These filters are divided into different groups according to the type of material and the way they are placed. The types and materials of the substrates can be different (various materials such as plastic and PVC, wood, wheat straw, sand, etc.), and four different types of substrates were used in this study. The mechanism of pollutant purification in this system is as follows:

Physical processes, including sedimentation, and filtration.

Biological processes: including consumption of pollutants by microorganisms fixed on the substrate (biofilm).

Chemical processes, including absorption, oxidation, and reduction reactions that contaminated water or sewage, upon entering the system, passes through a substrate covered with microorganisms (biofilm), during which the pollutants in the water include physical, chemical, organic substances, nutrients, etc. They are refined through three types of processes.

Through a drainage pipe installed in the bottom of the pool, purified water was drained. A flexible pipe was connected to the drainage pipe at the outlet of the bio-filter. Due to the flexibility of the bio-filter output, it was possible to control the flow rate and change the load drop by changing the output height. It was tried to consider the design and construction of the investigated system as economical in terms of its potential for implementation by farmers in the future. From the beginning of spring 2020, after the completion of the executive operation of the pilot construction, drainage water entered the pilot construction and data was collected.

The selection of materials used as biological filters

A major factor in the selection of materials used as biological filters is the type of material, which has been investigated and found to be capable of absorbing materials. Next, the type of material was examined based on its abundance in the region so that it could be easily prepared and utilized. In choosing the type of material, the porosity of the material was also taken into consideration, and only materials with high porosity were used to create a larger surface area for water contact. The polluting material in the drainage water has also been considered in the selection of the type of material. The polluting material is selected based on its type. The majority of the research conducted in this field has been conducted in a laboratory where the incoming water for purification was artificially prepared and contained high levels of pollutants. However, the real conditions on the farm resulted in different results and the amount of substances in the incoming water was much lower, which made controlling the situation much easier. In this project, different types of purifying materials were selected and agricultural wastes such as rice paddy husk, straw, and wheat stubble, cotton stalks, and sawdust were used as filters. A major objective of this research was to assess the possibility of reusing purified drain water in agriculture according to its quantitative-qualitative condition and its qualitative fluctuations.

A description of the mechanism of action of the proposed bio-filters

In the beginning of the system, the sand and gravel layer acts as a filter, removing garbage and suspended substances from incoming drainage. It also prevents suspended particles from entering the bio-filter and disrupting the purification process (biological absorption and decomposition). In a biological filter system, physical, chemical, and biological processes are used to purify water. Sedimentation and filtration are physical processes. During a six-month period, weekly samples were collected from the inlet and outlet of the pilot (after the purification process) to evaluate the effectiveness of the research system. Qualitative factors under investigation include agricultural toxins (Atrazine, Roundup, Paraquat and 2, 4-D) and nutrient elements and compounds (nitrate, nitrogen, phosphate, and total phosphorus), which are provided in Table 2 for assessing the quality of the incoming effluent.

Table 2 The concentrations of qualitative factors in the incoming drainage water of the study area.

Seasons	NO3 (mg/lit)	TN (mg/lit)	PO4 (mg/lit)	TP
(mg/lit)	Atrazine (ppb)	Roundup (ppb)	Paraquat (ppb)	Tofordi (ppb)	
Spring	13.02	13.32	0.27	0.38	15.60	11.25	12.60	8.40	
Summer	15.38	15.74	0.32	0.45	16.67	10.98	10.90	7.58	
Autumn	15.17	15.52	0.32	0.44	11.27	10.17	7.93	5.60	
Winter	13.56	13.84	0.27	0.34	6.93	5.50	7.80	4.33	
Total average	14.28	14.61	0.29	0.39	13.32	15.74	15.53	13.85	

In general, the reasons for choosing the investigated factors were as follows:

The presence of the desired pollutants in the researched drainage: based on the investigations, the residues of agricultural toxins and nutrients are considered the most important pollutants of the researched drainage.

The extent of their negative effects on the quality of the receiving water resources of these drains: considering that the drains are discharged into surface water sources (rivers), agricultural toxins and nutrients have destructive effects on the quality of these receiving sources. In particular, agricultural pesticides cause the death of aquatic life and nutrient elements increase the growth of algae.

Agricultural poisons: selected poisons have been selected from among the most used poisons in the study area.

The cost of conducting experiments: due to the financial limitation of the research, an attempt has been made to select the most important factors and manage costs.

Initially, the system was launched with a delay of two days, and a month was spent testing its compatibility and stability. In biological purification systems, it takes some time for the system to reach a stable state. Essentially, the microorganisms responsible for wastewater treatment become accustomed to the quality conditions and hydraulic load (adapt) and the population of microorganisms, as well as the biological layer, are formed and reach a stable level of efficiency and performance in the treatment process. Upon reaching stability in the output results, the duration was gradually increased to 5 and then to 10 days. Weekly sampling and testing were performed on the input and output of the treatments. The input and output of treatments were sampled and tested at weekly intervals throughout any retention period, and the results of both sampling and testing were analysed. The present research was conducted in the form of a split plot in the form of a completely random design and with SPSS software, and the comparison of means was done by Duncan’s multi-range test, and the appropriate statistical combination was obtained by using tables and graphs. During this study, four different types of bio-filters, including sawdust, cotton stalks, wheat straw and stubble, and rice husks, were investigated as main factors and three retention times, 2, 5, and 10 days, as sub-main factors.

Results and discussion

Effects of biological filters and retention time on nutrient composition

The variance analysis of the obtained information indicated that the main factor of filter type and the sub factor of retention time had a significant effect at the probability level of 1% on the amount of nitrate, total nitrogen, phosphate, and total phosphorus. Furthermore, the interaction between filter type and retention time was significant for nitrate, total nitrogen, phosphate, and total phosphorus (Table 3). Examining the present results with similar study30 implemented with a similar system for the purification of Moghan agricultural sewage shows that the system used in Khuzestan is more effective in removing total nitrogen and total phosphorus, 5% and 8%, respectively. The reason can be the relatively warm temperature of the Khuzestan region compared to Moghan30. Yargholi and Kanani15 achieved an efficiency equal to 80% in removing nitrogen compounds, 83% in removing phosphorus compounds and an efficiency of more than 90% for removing phosphorus toxins, which is more satisfactory compared to the present results. But, considering that artificial reed requires a large area compared to bio-filter, the stated efficiency needs more investigation.

Table 3 Variance analysis of nutrient compounds under the influence of different treatments.

Sources of changes	df	Mean squared	
Nitrate	Total nitrogen	Phosphate	Total phosphorus	
retention time	2	8596.8**	8578.6**	4970.4**	4509.7**	
Filter type	3	260.4**	269.6**	158.0**	359.6**	
Filter type × retention time	6	13.7**	40.1**	9.9**	32.0**	
Error	36	1.9	1.5	1.1	1.2	
Note: **significant at 1% probability level and *significant at 5% probability level.

Examining the results shows that in the biological filter, which is a type of attached biological process (formation of biofilm on the substrate), the performance for removing agricultural toxins and nutrients (nitrogen and phosphorus compounds) is much higher than the biological processes of suspended growth (such as Activated sludge) in which, unlike the attached growth methods, the microorganisms responsible for the treatment are suspended in the liquid (sewage)31,32.

Microorganisms responsible for removing nitrogen and phosphorus compounds have a slow growth rate and it takes more time for their population to increase effectively33. In attached growth processes, because the microorganisms are connected to the surface of the substrate, they are not separated from the system along with the outflow, and this causes the gradual increase of bacteria responsible for removing nitrogen and phosphorus and their species dominate34. In suspended growth systems, these conditions are not provided, microorganisms leave the system along with the outflow, and there is not enough opportunity for nitrogen and phosphorus-purifying bacteria to multiply and dominate. The substrate used in biological filters, as an absorbent material, has a significant contribution to the removal of nitrogen compounds, phosphorus, and agricultural toxins. In addition, as a source of carbon, it is available to purify bacteria, and providing the required carbon causes the continuation of the purification process and increases the efficiency35,42.

Influence of biological filters on nutrient removal efficiency

Due to the use of chemical fertilizers upstream, the incoming water contains a high level of nitrates, thus making it necessary to treat all water drains. Based on the results of the study, it was found that nitrate levels were high in the incoming water, and that all biological filters were effective in reducing nitrate levels. According to the results, the treatment of the studied filters was relatively effective. In examining the effect of filter type on filtration efficiency for nitrate, total nitrogen, phosphate, and total phosphorus in incoming effluent, it was determined that the average quality improvement (for three periods of 2, 5 and 10 days) for rice husk, straw and stubble, cotton stems and sawdust for nitrate was 44.31, 42.69, 49.73 and 52.68%, respectively (Table 4).

Table 4 The independent effects of biological filters and retention times on nutrient compounds (%).

Parameter	Treatment	
Nitrate	Total nitrogen	Phosphate	Total phosphorus	
Retention time	10	69.37a	66.51a	54.64a	53.49a	
5	49.52b	44.19b	46.47b	43.89b	
2	23.17c	20.21c	20.86c	20.83c	
Filters	rice husks	44.31c	40.77c	39.16c	35.53c	
straw and wheat stubble	42.69d	39.02d	36.37d	34.68d	
cotton stalks	49.73b	45.16b	42.54b	40.90b	
sawdust	52.68a	49.60a	44.57a	46.50a	

Based on the results of the study, the straw and stubble treatment was slightly less effective for reducing nitrate than the other three treatments, and of the current treatments, sawdust was the most effective at reducing nitrate by 52.68%. In terms of total nitrogen, this performance equates to 40.77%, 39.02%, 45.16% and 49.60%, respectively, for rice husk, wheat straw and stubble, cotton stalk and sawdust. Similar to the nitrate factor, for the total nitrogen factor, straw and stubble have the lowest yield with the slightest difference, whereas sawdust has the best yield with a relatively significant difference and equals 49.60. According to the results for the phosphate factor, rice husk, wheat straw, cotton stalk, and sawdust achieved 39.16%, 36.37%, 42.54%, and 44.57% efficiency, respectively. The sawdust treatment with 44.57% has the highest efficiency as compared to straw and stubble with 36.37%. The performance pattern for total phosphorus is similar to that for total nitrogen, and straw and stubble have the lowest efficiency (34.68%) and sawdust has the highest efficiency (46.50%). This factor showed that rice husk and cotton stalk treatments had 35.53% and 40.90% efficiency removal, respectively. Based on the results of the filter material treatments, it can be concluded that sawdust is more efficient and performs better than the other three filters16–18. Bio sorbents are effective in absorbing nitrate from aqueous solutions in the laboratory environment19,20. The results of determining the appropriate amount of adsorbent to have maximum efficiency showed that the most appropriate amount of adsorbent is 1 gr/40 ml of solution. As the amount of adsorbent decreases, the efficiency of the adsorbent decreases. Nitrate uptake by sawdust decreased from 4.8 to 1.04 mg/L when sawdust was used as a medium for nitrate uptake21,22.

Effects of different retention times on nutrient removal efficiency

Results of the analysis of effluent from biological filters with a residence time of 2, 5 and 10 days are presented in Table 4. Nitrate, total nitrogen, phosphate, and total phosphorus levels decrease as residence time increases. Different retention times have different effects on the removal efficiency of nitrate, total nitrogen, phosphate, and total phosphorus. It was observed that the retention time has a direct relationship with the amount of nutrients by examining the increase in the retention time and the removal percentage that corresponds to it. In other words, in the retention time used in this research, with the increase in retention time, the average nitrate, total nitrogen, phosphate and total phosphorus in different filters decreases and the percentage of removal efficiency of nutrient compounds increases (Table 4). So that the highest removal percentages of nitrate, total nitrogen, phosphate and total phosphorus were 69.37, 66.51, 54.64 and 53.39%, respectively, for the 10-day period.

The difference in removal efficiency between the remaining times was significantly different from one another. There was an increase in removal efficiency of nitrate, total nitrogen, phosphate, and total phosphorus under the retention time of 10-days compared to the retention time of 2 days by 52.18, 69.61, 59.63 and 61.05, respectively. Overall, the results indicate an increase in removal efficiency compared to the retention time in the system. Results indicate that by doubling the retention time for each of the investigated factors, the removal efficiency did not double, but increased by 40, 50, 17.58 and 21.87% compared to a retention time of 5-days (Table 4). The results of this study indicate that removal efficiency and absorption capacity are directly related to retention time. The goal of this research and similar studies is to identify the optimal retention time, as a short retention time will not result in the appropriate performance, and a long retention time may result in ammonium accumulation23,24. Since increasing the retention time allows for better performance of the reactors, it is expected that increasing the retention time will improve the reactors’ performance in removing nitrate.

Rivas et al.25 showed that the efficiency of nitrate removal by biological reactors increases with increasing retention time. In addition, the rate of nitrate removal increases with increasing retention time. Because more time allows the bacteria to decompose the organic substrate, leading to higher nitrate removal efficiency, which is consistent with the results of the present study. Increasing the retention time provides a longer period of time for microbes to interact with each other26,27.

Interaction effects between biological filter type and retention time in nutrient removal efficiency

Table 5 illustrates the interaction effects of filter types (rice husk, straw and stubble, cotton stalk and sawdust) in removing nitrates, total nitrogen, phosphates, and total phosphorus pollutants over the retention time of 2, 5 and 10 days. In the evaluation of the filter’s ability to remove nitrate from the incoming wastewater, it has been found that the nitrate removal efficiency varied from a minimum of 17.94% during the retention time of 2 days with straw and stubble treatment to a maximum of 74.03% during the retention time of 10 days with sawdust treatment. After 10 days, straw and stubble filters were able to remove 74.03% of nitrate, while cotton stem filters lowered their performance to 71.23% and ranked second. The results indicate that the sawdust filter had a higher removal percentage compared to the other treatments at a retention time of ten days28,29,43, whereas the cotton stem treatment had a removal percentage of 68.31 after the sawdust treatment with a retention time of 10-days and was ranked highest in terms of nitrogen removal.

Table 5 The interaction effect of different filters at different retention times on nutrient compounds (%).

Parameter	Retention time	Filters	
Rice husks	Straw and wheat stubble	Cotton stalks	Sawdust	
Nitrate	10	64.69 d	67.56c	71.23b	74.03a	
5	47.32g	42.57h	52.07f	56.12e	
2	20.93k	17.94 l	25.91j	27.90 i	
Total nitrogen	10	61.68d	64.41c	68.31b	71.66a	
5	40.91g	35.58h	46.25f	54.01e	
2	19.74j	17.06k	20.93j	23.12 i	
Phosphate	10	52.27b	50.00g	58.31a	57.97a	
5	45.66e	76.40f	47.58d	51.90 b	
2	19.54i	18.34i	21.73h	23.82 g	
Total phosphorus	10	46.93d	48.27d	56.91b	61.85a	
5	38.95f	38.93f	44.46e	53.24c	
2	20.73h	16.84 i	21.32h	24.41g	

Based on the results, the phosphate removal efficiency ranged from 18.34% in the straw and stubble treatment for a retention time of 2 days to 58.31% in the cotton stem treatment for a retention time of 10 days. With a removal efficiency of 57.97% during retention time of 10 days, the cotton stalk filter ranked first in phosphate removal, and the sawdust filter ranked second after the cotton stalk filter. A removal efficiency of total phosphorus was observed from a minimum value of 16.84 in two days in the straw and stubble treatment to a maximum value of 61.85 in ten days in the sawdust filter. Based on the results of this study, the sawdust filter showed a higher removal rate than the other treatments over a period of retention time of 10 days. Cotton stem treatment ranked second in total phosphorus removal after sawdust treatment after 10 days’ retention period with 56.91% removal, which is consistent with similar research results36,37,44.

In similar studies, the effectiveness of the system in removing total nitrogen from agricultural runoff was investigated38–40,45. In the natural state, the efficiency with a retention time of 5 days is equivalent to 65%, and if organic materials are added and the retention time is increased to 15 days, the performance of the system can be increased to 100% (32, 46). The studies showed that according to the 75% efficiency of removing nitrogen compounds during the ten-day retention time and without adding organic substances, the researched system has an acceptable efficiency, which is in agreement with the results of the present study36.

The effects of biological filters and retention times on agricultural pesticides

The results indicate that the effects of retention time on the levels of Atrazine, Tofordi, Paraquat, and Rundap at the level of probability of 1% are significant. According to the results, the main factor of filter type had a significant effect on Atrazine poison at a 5% probability level, while their influence on Tofordi, Paraquat, and Roundup was significant at a 1% probability level. Based on the results of the statistical analysis, the interaction effect of filter type and retention time on the amount of Atrazine was significant at 5% probability, which is in agreement with similar studies40,41. Alternatively, the amount of Tofordi, Paraquat, and Roundup was significant at the 1% level (Table 6).

Table 6 Variance analysis of agricultural pesticides under the influence of different treatments.

Sources of changes	df	Mean squared	
Atrazine	Roundup	Paraquat	2, 4-D	
Retention time	2	20283.6**	19327.5**	20029.5**	15734.5**	
Filter type	3	5.9*	76.3**	39.5**	57.3**	
Filter type × retention time	6	5.2*	17.1**	9.5**	12.3**	
Error	36	2.0	1.6	1.3	1.3	
Note: **significant at 1% probability level and *significant at 5% probability level.

The effect of biological filters on the removal efficiency of agricultural runoff toxins

Each of the biological filters was effective in removing the agricultural toxins Atrazine, Tofordi, Paraquat, and Rundap from the agricultural drainage (Table 7). Based on the comparison of the averages, the results indicated that various types of biological filters reduce the levels of Artesine toxin. Rice paddy biological filters reduced Artesine poison in drain water by 61.76%, compared to other biological adsorbents, and were recognized as the most suitable biological adsorbent for Artesine poison. In comparison with straw and stubble, cotton stem sawdust biological filters, this biological filter reduced the amount of Artesine toxin in drainage water by 2.28, 2.62 and 1.74, respectively. Following rice paddy, sawdust filter with 60.70% reduction and straw with 60.38% reduction showed the highest reduction. Based on the positive effects of rice paddy biological filters in reducing Artesine toxins, especially in large quantities, it is feasible to use these biological filters to purify drain water of Artesine toxins (Table 7).

Table 7 The independent effects of biological filters and retention times on agricultural pesticides (%).

Parameter	Treatment	
Atrazine	Roundup	Paraquat	2, 4-D	
Retention time	10	90.60a	86.92a	88.37a	80.84a	
5	70.32b	53.87b	55.75b	63.11b	
2	21.34c	17.44c	17.67c	19.88c	
Filters	Rice husks	61.76a	51.69c	53.39b	53.46c	
Straw and wheat stubble	60.38b	49.76d	51.61c	52.27d	
Cotton stalks	60.18b	54.05b	55.56a	55.51b	
Sawdust	60.70ab	55.46a	55.16a	57.20a	

The results of the comparison of the average independent effects of biological filters on the removal efficiency of Tofordi indicated that the sawdust filter reduced Tofordi poison with the highest removal efficiency of 56.20% compared to other biological filters. The effectiveness of this biological filter was significantly greater than the performance of the cotton stem and rice paddy biological filters, respectively, in reducing the amount of Tofordi toxin in drain water by 3.04, 9.43, and 6.99%, respectively. Following sawdust, cotton stalk filter reduced by 55.51%, rice straw and paddy reduced by 53.46%. The sawdust filter has had the greatest effect on the reduction of the Tofordi poison parameter (Table 7). Compared with other biological adsorbents, cotton stem and sawdust biological filters both reduced Paraquat poison levels in drain water with target efficiencies of 55.56 and 55.16%, respectively. These biological adsorbents have been proven to be the most effective in purifying Paraquat poison from drain water. In comparison to cotton stems and sawdust, rice paddy, straw and stubble showed a reduction of 53.39%, followed by rice straw and paddy at 51.61%. With the acceptable efficiency of the cotton stem filter and sawdust in reducing Paraquat poison, especially in large amounts, it is possible to apply these biological filters to the treatment of Paraquat poison in drains. According to the study, sawdust biological filters reduced 55.46% of Roundup poison in effluents more than other biological filters, while cotton stalks, rice paddy, straw, and wheat stubble decreased 54.05, 51.69 and 49.76% of Roundup poison, respectively. In general, sawdust biological filters were effective in reducing Roundup poison, while straw and stubble biological filters were less effective in removing Roundup poison.

Effects of different retention times on the removal efficiency of agricultural pesticides

The retention time is an important parameter for the proper use of an adsorbent in practical applications and it represents the speed at which the adsorbent absorbs among the various parameters that should be considered. The trend of the changes in the removal efficiency of Atrazine, 2, 4-D, Paraquat, and Roundup for 2, 5 and 10 days is illustrated in Table 7. It is evident that different time delays had different effects on the removal efficiency of Atrazine, 2, 4-D, Paraquat and Roundup toxins. Therefore, since increasing the retention time creates enough opportunity for the reactor to perform better, it is expected that increasing the retention time will increase the efficiency of the reactors.

It was observed that the highest removal efficiency was obtained with each of 2, 5 and 10-day retention times. There was a significant difference between the removal efficiency for each of the remaining times. So that the highest removal efficiency of Atrazine, 2, 4-D, Paraquat and Roundup toxins was observed with the amount of 90.60, 80.84, 87.37 and 86.92% in the 10 days’ retention period and then in the 5 days’ retention with acceptable removal efficiency equal to 70/32, 63/11, 55/75 and 53/87 had a better performance in removing Atrazine, Topodi, Paraquat and Roundup toxins. The removal efficiency of Atrazine, 2, 4-D, Paraquat, and Randap toxins were 76.44, 75.4, 80, and 79.9%, respectively, under a 10-day retention time, compared to a 2-day retention time. A removal efficiency of 22.38, 21.9, 36.9 and 38% was observed after 10-day retention time compared to 5-day retention time. According to the results, the removal rate of Atrazine, 2, 4-D, Paraquat, and Randap toxins increased with an increase in retention time from 2 days to 10 days (Table 7).

Interaction effect of biological filter type and retention time on nutrient removal efficiency

The Table 8 presents the comparisons of the effectiveness of different filter types (rice husks, straw and stubble, cotton stalks and sawdust) in removing the agricultural toxins Atrazine, Tofordi, Paraquat, and Roundup from agricultural drains at retention times of 2, 5 and 10 days. Using the sawdust filter for purifying Atrazine from incoming wastewater shows that the amount of Atrazine decreases between the minimum value of 20.84% in the two-day period and the maximum value of 91.73% in the 10-day period. This filter removed the greatest amount of Atrazine in retention times of 10 days as compared to the other three filters. The removal rate of Tofordi ranged from 18.66% in the retention times of 2 days in rice paddy to 84.27% in sawdust after a retention times of 10 days. Based on the results, the sawdust filter had a higher removal percentage than the other treatments during the retention time of 10 days. Regarding the removal efficiency of Tofordi, the cotton stem treatment in the retention time of 10 days with an 81.14% removal rate ranked second after the rice paddy treatment.

Table 8 The interaction effect of different filters at different retention times on agricultural pesticides (%).

Parameter	Retention time	Filter	
Rice husks	Straw and wheat stubble	Cotton stalks	Sawdust	
Atrazine	10	90.22a	89.73a	90.71a	91.73a	
5	72.71b	70.71c	68.80c	69.52c	
2	22.34d	21.14d	21.04d	20.84d	
2, 4-D	10	80.04bc	78.93c	81.14g	84.27a	
5	61.68f	58.23g	65.14e	67.38d	
2	18.66j	19.65hi	20.25hi	20.95h	
Paraquat	10	87.89b	87.43b	88.34ab	89.81a	
5	55.27e	51.23f	59.31c	57.20d	
2	17.01hi	16.16i	19.06g	18.47gh	
Roundup	10	86.41b	85.84b	86.98ab	88.46a	
5	52.20e	47.88f	56.51d	58.87c	
2	16.48h	15.56h	18.65g	19.06g	

The trend of changes in the removal efficiency of Paraquat was similar to that of Atrazine and Tofordi. Thus, the highest removal efficiency of Paraquat (89.81%) was observed in the sawdust filter in the retention time of 10 days, whereas straw and stubble treatment with 2-days of retention time with 16.16% had the lowest removal efficiency of Paraquat from the incoming effluent. Roundup removal efficiency ranged from a minimum value of 15.56% in the retention time of 2-day and in the straw and stubble treatment to a maximum value of 88.46% in the retention time of10-day in the sawdust treatment. Rice paddy filter with a removal efficiency of 86.41% took second place following sawdust treatment for its effectiveness in removing Paraquat poison. The sawdust filter performed the best in removing Roundup from incoming drainage water in in the retention time of 10 days when compared to other filters and in different retention periods. According to the results of filter material treatments at different retention times, sawdust performed better and was more efficient than rice husk, straw, stubble, and cotton stalk for each of the retention times of 2, 5, and 10 days. It is important to consider this point when choosing and proposing a filter for each region. A suitable filter must be selected for each region in every respect.

Compared to other filters and retention times, the sawdust filter demonstrated a good ability to remove agricultural pesticides and nutrient compounds in a retention time of 10 days, and significantly reduced the amount of these parameters in the incoming drainage water. In comparison to other types of filters, this type proved to be much more effective in reducing the levels of agricultural pesticides and nutrient compounds. Due to the availability of sawdust throughout the country, the results of this research are important, and as a general result, this filter can be cited and used as a reliable substrate with satisfactory efficiency compared to other filters. In light of the type of filters used, it is important to note that despite sawdust’s relative superiority, the other filters also possess acceptable efficiency with some slight differences. According to the geographical location and availability of the desired materials, they can also be used as substrates in biological filters for drain purification.

Conclusion

The results of the present research demonstrated that the use of biological filters with different retention times may be a suitable solution for removing nutrients and agricultural toxins from agricultural drainage water. In accordance with the results, biological filters were capable of removing nutrient compounds and agricultural toxins at different retention times. By the retention time increases, the average of nitrate, total nitrogen, phosphate, and total phosphorus decreases. Different retention times result in different removal efficiency of nitrate, total nitrogen, phosphate, and total phosphorus. Based on an analysis of retention time and removed efficiency of nutrients, retention time is directly related to nutrient removal. In other words, in this research has been found to increase with increasing retention time, decreasing average nitrate levels, total nitrogen levels, phosphate levels, and total phosphorus levels, and resulting in increased removal efficiency of nutrient compounds. In comparison with other biological filters used to reduce nitrates in drain water, straw and wheat stubble had the highest removal efficiency. In comparison to the initial amount of nutrient compounds in the inlet drainage water, the removal efficiency for nutrient compounds in biological filters decreased dramatically after the filters were utilized, and this decrease increased with the increasing retention time. Therefore, compared to other biological filters and retention times, the sawdust biological filter showed the highest removal efficiency with a retention time of 10 days. The results indicated that the sawdust biological filter had a significant effect on reducing nutrients and agricultural toxins in comparison to other filters. According to the results of filter material treatments at different retention times, sawdust performed better at retention times of 2, 5, and 10 days than rice husk, straw, stubble, and cotton stalk. In selecting and proposing the type of effective filter for each region, this point should be noted. The filter selected must be suitable in all respects for implementation in each region. The present study demonstrated that the sawdust filter had a good performance in removing agricultural toxins and nutrient compounds in a retention time of 10 days as compared to other filters and retention times, and significantly reduced the amount of these parameters in the incoming drainage water and this type of filter was much more effective in reducing the parameters of agricultural toxins and nutrient compounds. For future directions, long-term retention periods, different seasons, and biological filters and their comparison in the form of biochar should be investigated to get a better view.

Author contributions

A.K., B.Y., and A.Sh. designed the study, analyzed and discussed the data and results. A.K. and B.Y. performed the experiments and simulations. A.Sh. and K.A. prepared the hybrid proposed model/ materials/equipment’s/irrigation system. All authors reviewed the manuscript.

Data availability

The datasets generated during and/or analyzing for the current study are available from the corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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References

1. Yargholi, B., Sepehri, S. & Kanani, E. Removal of heavy metals from agricultural runoff using constructed wetland; traces pollutants in reed bed sediments and plant biomass. Wetl Ecol. Manag. 2023, 1–20 (2023).
2. Gadd, G. M. Microbial control of heavy metal pollution. Microb. Control Pollut. 1992, 59–88 (1992).
3. Sangi M Shahmoradi A Zolgharnein J Azimi G Ghorbandoost M Rimoval and recovery of heavy metals from aqueous solution using Ulmas carpinifolia and Fraxinus excelsiortree leaves J. Hazard. Mater. 2008 155 513 522 10.1016/j.jhazmat.2007.11.110 18191021
Sangi, M., Shahmoradi, A., Zolgharnein, J., Azimi, G. & Ghorbandoost, M. Rimoval and recovery of heavy metals from aqueous solution using Ulmas carpinifolia and Fraxinus excelsiortree leaves. J. Hazard. Mater. 155, 513–522 (2008).18191021 10.1016/j.jhazmat.2007.11.110
4. Robertson WD Merkley LC In-stream bioreactor for agricultural nitrate treatment J. Environ. Qual. 2009 38 230 237 10.2134/jeq2008.0100 19141813
Robertson, W. D. & Merkley, L. C. In-stream bioreactor for agricultural nitrate treatment. J. Environ. Qual. 38, 230–237 (2009).19141813 10.2134/jeq2008.0100
5. Zoski ED Lapen DR Gottschall N Murrell RS Schuba B Nitrogen, phosphorus, and bacteria removal in laboratory-scale woodchip bioreactors amended with drinking water treatment residuals Trans. Am. Soc. Agr. Biol. Eng. 2013 56 1339 1347
Zoski, E. D., Lapen, D. R., Gottschall, N., Murrell, R. S. & Schuba, B. Nitrogen, phosphorus, and bacteria removal in laboratory-scale woodchip bioreactors amended with drinking water treatment residuals. Trans. Am. Soc. Agr. Biol. Eng. 56, 1339–1347 (2013).
6. Choudhury, T. Woodchip biofilters for treatment of particulate phosphorus in agricultural runoff (Master’s thesis, University of Waterloo) (2017).
7. Ali, S. A. K. & Lazim, S. M. Treatment of water from irrigation drainage by multimedia filtration. In JEASD, First Online Scientific Conference for Graduate Engineering Students 58–81 (2020).
8. Wulandari LK Bisri M Harisuseno D Yuliani E Reduction of BOD and COD of by using stratified filter and constructed wetland for blackwater treatment IOP Conf. Ser.: Mater. Sci. Eng. 2019 469 1 012024 10.1088/1757-899X/469/1/012024
Wulandari, L. K., Bisri, M., Harisuseno, D. & Yuliani, E. Reduction of BOD and COD of by using stratified filter and constructed wetland for blackwater treatment. IOP Conf. Ser.: Mater. Sci. Eng. 469(1), 012024 (2019).10.1088/1757-899X/469/1/012024
9. Woskowicz, E., Łożyńska, M., Życki, M. & Kowalik-Klimczak, A. Hybrid processes combining microfiltration and adsorption/ion exchange for dairy wastewater treatment. J. Mach. Constr. Mainten. -Problem. Eksploatacji (2019).
10. Hoffmann CC Larsen SE Kjaergaard C Nitrogen removal in woodchip-based biofilters of variable designs treating agricultural drainage discharges J. Environ. Qual. 2019 48 6 1881 1889 10.2134/jeq2018.12.0442
Hoffmann, C. C., Larsen, S. E. & Kjaergaard, C. Nitrogen removal in woodchip-based biofilters of variable designs treating agricultural drainage discharges. J. Environ. Qual. 48(6), 1881–1889 (2019).10.2134/jeq2018.12.0442
11. Ali, S. A. K., Lazim, S. M. & Nasret, H. H. Treatment of agricultural irrigation water drainage channel by adsorption methods using Sawdust. IOP Conf. Ser. Earth Environ. Sci. 779(1), 012107 (2021).
12. Ali, S. A. K. & Lazim, S. M. Treatment of Water from irrigation drainage by multimedia filtration. J. Eng. Sustain Dev. (JEASD), (Conf. Proceed.) (2020).
13. Braschi I Removal and fate of pesticides in a farm constructed wetland for agricultural drainage water treatment under Mediterranean conditions (Italy) Environ. Sci. Pollut. Res. 2022 29 5 7283 7299 10.1007/s11356-021-16033-4
Braschi, I. et al. Removal and fate of pesticides in a farm constructed wetland for agricultural drainage water treatment under Mediterranean conditions (Italy). Environ. Sci. Pollut. Res. 29(5), 7283–7299 (2022).10.1007/s11356-021-16033-4
14. -Tahmasebi AA Beni AS Azhdarpoor A Moeini Z The application of granular and biological activated carbon columns in removal of organochlorine and organophosphorus pesticides in a water treatment plant J. Water Process. Eng. 2023 56 104383 10.1016/j.jwpe.2023.104383
Tahmasebi, A. A., Beni, A. S., Azhdarpoor, A. & Moeini, Z. The application of granular and biological activated carbon columns in removal of organochlorine and organophosphorus pesticides in a water treatment plant. J. Water Process. Eng. 56, 104383 (2023).10.1016/j.jwpe.2023.104383
15. -Yargholi B Kanani E Performance evaluation of natural reed bed in removal of organic matter and phosphorus compounds from Khuzestan sugarcane fields drainage water Irrig. Drain. Struct. Eng. Res. 2022 23 86 1 18
Yargholi, B. & Kanani, E. Performance evaluation of natural reed bed in removal of organic matter and phosphorus compounds from Khuzestan sugarcane fields drainage water. Irrig. Drain. Struct. Eng. Res. 23(86), 1–18 (2022).
16. Nnaji CC Afangideh BC Ezeh C Performance evaluation of clay-sawdust composite filter for point of use water treatment Nigerian J. Technol. 2016 35 4 949 956 10.4314/njt.v35i4.33
Nnaji, C. C., Afangideh, B. C. & Ezeh, C. Performance evaluation of clay-sawdust composite filter for point of use water treatment. Niger. J. Technol. 35(4), 949–956 (2016).10.4314/njt.v35i4.33
17. -Chikri R Elhadiri N Benchanaa M El Maguana Y Efficiency of sawdust as low-cost adsorbent for dyes removal J. Chem. 2020 2020 1 8813420
Chikri, R., Elhadiri, N., Benchanaa, M. & El Maguana, Y. Efficiency of sawdust as low-cost adsorbent for dyes removal. J. Chem. 2020(1), 8813420 (2020).
18. -Eliche-Quesada D Corpas-Iglesias FA Pérez-Villarejo L Iglesias-Godino FJ Recycling of sawdust, spent earth from oil filtration, compost and marble residues for brick manufacturing Constr. Build. Mater. 2012 34 275 284 10.1016/j.conbuildmat.2012.02.079
Eliche-Quesada, D., Corpas-Iglesias, F. A., Pérez-Villarejo, L. & Iglesias-Godino, F. J. Recycling of sawdust, spent earth from oil filtration, compost and marble residues for brick manufacturing. Constr. Build. Mater. 34, 275–284 (2012).10.1016/j.conbuildmat.2012.02.079
19. Dey S Basha SR Babu GV Nagendra T Characteristic and biosorption capacities of orange peels biosorbents for removal of ammonia and nitrate from contaminated water Clean. Mater. 2021 1 100001 10.1016/j.clema.2021.100001
Dey, S., Basha, S. R., Babu, G. V. & Nagendra, T. Characteristic and biosorption capacities of orange peels biosorbents for removal of ammonia and nitrate from contaminated water. Clean. Mater. 1, 100001 (2021).10.1016/j.clema.2021.100001
20. Dey S Haripavan N Basha SR Babu GV Removal of ammonia and nitrates from contaminated water by using solid waste bio-adsorbents Curr. Res. Chem. Biology 2021 1 100005 10.1016/j.crchbi.2021.100005
Dey, S., Haripavan, N., Basha, S. R. & Babu, G. V. Removal of ammonia and nitrates from contaminated water by using solid waste bio-adsorbents. Curr. Res. Chem. Biol. 1, 100005 (2021).10.1016/j.crchbi.2021.100005
21. Keränen A Leiviskä T Gao BY Hormi O Tanskanen J Preparation of novel anion exchangers from pine sawdust and bark, spruce bark, birch bark and peat for the removal of nitrate Chem. Eng. Sci. 2013 98 59 68 10.1016/j.ces.2013.05.007
Keränen, A., Leiviskä, T., Gao, B. Y., Hormi, O. & Tanskanen, J. Preparation of novel anion exchangers from pine sawdust and bark, spruce bark, birch bark and peat for the removal of nitrate. Chem. Eng. Sci. 98, 59–68 (2013).10.1016/j.ces.2013.05.007
22. Fatima I Ahmad M Vithanage M Iqbal S Abstraction of nitrates and phosphates from water by sawdust-and rice husk-derived biochars: their potential as N-and P-loaded fertilizer for plant productivity in nutrient deficient soil J. Anal. Appl. Pyrol. 2021 155 105073 10.1016/j.jaap.2021.105073
Fatima, I., Ahmad, M., Vithanage, M. & Iqbal, S. Abstraction of nitrates and phosphates from water by sawdust-and rice husk-derived biochars: their potential as N-and P-loaded fertilizer for plant productivity in nutrient deficient soil. J. Anal. Appl. Pyrol. 155, 105073 (2021).10.1016/j.jaap.2021.105073
23. Baquerizo G Maestre JP Machado VC Gamisans X Gabriel D Long-term ammonia removal in a coconut fiber-packed biofilter: Analysis of N fractionation and reactor performance under steady-state and transient conditions Water Res. 2009 43 8 2293 2301 10.1016/j.watres.2009.02.031 19297002
Baquerizo, G., Maestre, J. P., Machado, V. C., Gamisans, X. & Gabriel, D. Long-term ammonia removal in a coconut fiber-packed biofilter: Analysis of N fractionation and reactor performance under steady-state and transient conditions. Water Res. 43(8), 2293–2301 (2009).19297002 10.1016/j.watres.2009.02.031
24. Aboukila AF Deng Z Two variable residence time-based models for removal of total phosphorus and ammonium in free-water surface wetlands Ecol. Eng. 2018 111 51 59 10.1016/j.ecoleng.2017.10.014
Aboukila, A. F. & Deng, Z. Two variable residence time-based models for removal of total phosphorus and ammonium in free-water surface wetlands. Ecol. Eng. 111, 51–59 (2018).10.1016/j.ecoleng.2017.10.014
25. Rivas A Improving accuracy of quantifying nitrate removal performance and enhancing understanding of processes in woodchip bioreactors using high-frequency data Sci. Total Environ. 2023 880 163289 10.1016/j.scitotenv.2023.163289 37023810
Rivas, A. et al. Improving accuracy of quantifying nitrate removal performance and enhancing understanding of processes in woodchip bioreactors using high-frequency data. Sci. Total Environ. 880, 163289 (2023).37023810 10.1016/j.scitotenv.2023.163289
26. Zhao J He Q Chen N Peng T Feng C Denitrification behavior in a woodchip-packed bioreactor with gradient filling for nitrate-contaminated water treatment Biochem. Eng. J. 2020 154 107454 10.1016/j.bej.2019.107454
Zhao, J., He, Q., Chen, N., Peng, T. & Feng, C. Denitrification behavior in a woodchip-packed bioreactor with gradient filling for nitrate-contaminated water treatment. Biochem. Eng. J. 154, 107454 (2020).10.1016/j.bej.2019.107454
27. Feyereisen GW Performance of agricultural residue media in laboratory denitrifying bioreactors at low temperatures J. Environ. Qual. 2016 45 3 779 787 10.2134/jeq2015.07.0407 27136142
Feyereisen, G. W. et al. Performance of agricultural residue media in laboratory denitrifying bioreactors at low temperatures. J. Environ. Qual. 45(3), 779–787 (2016).27136142 10.2134/jeq2015.07.0407
28. Jin S Effect of sawdust dosage and hydraulic retention time (HRT) on nitrate removal in sawdust/pyrite mixotrophic denitrification (SPMD) systems Environ. Science: Water Res. Technol. 2019 5 2 346 357
Jin, S. et al. Effect of sawdust dosage and hydraulic retention time (HRT) on nitrate removal in sawdust/pyrite mixotrophic denitrification (SPMD) systems. Environ. Science: Water Res. Technol. 5(2), 346–357 (2019).
29. Ekpunobi UE Agbo SU Ajiwe VIE Evaluation of the mixtures of clay, diatomite, and sawdust for production of ceramic pot filters for water treatment interventions using locally sourced materials J. Environ. Chem. Eng. 2019 7 1 102791 10.1016/j.jece.2018.11.036
Ekpunobi, U. E., Agbo, S. U. & Ajiwe, V. I. E. Evaluation of the mixtures of clay, diatomite, and sawdust for production of ceramic pot filters for water treatment interventions using locally sourced materials. J. Environ. Chem. Eng. 7(1), 102791 (2019).10.1016/j.jece.2018.11.036
30. Tewolde H Sistani KR Rowe DE Adeli A Phosphorus extraction by cotton fertilized with broiler litter Agron. J. 2007 99 4 999 1008 10.2134/agronj2006.0237
Tewolde, H., Sistani, K. R., Rowe, D. E. & Adeli, A. Phosphorus extraction by cotton fertilized with broiler litter. Agron. J. 99(4), 999–1008 (2007).10.2134/agronj2006.0237
31. Razdan S Adler J Barua D Barua S Multifunctional Biofilter to effectively remove toxins ACS Appl. Bio Mater. 2020 4 1 731 741 10.1021/acsabm.0c01282
Razdan, S., Adler, J., Barua, D. & Barua, S. Multifunctional Biofilter to effectively remove toxins. ACS Appl. Bio Mater. 4(1), 731–741 (2020).10.1021/acsabm.0c01282
32. Elbehiry, F., Alshaal, T., Elhawat, N. & Elbasiouny, H. Environmental-friendly and cost-effective agricultural wastes for heavy metals and toxicants removal from wastewater. In Cost-Efficient Wastewater Treatment Technologies 107–127 (Springer Int. Publishing, 2021).
33. Silva LID Phosphorus-solubilizing microorganisms: A key to sustainable agriculture Agriculture 2023 13 2 462 10.3390/agriculture13020462
Silva, L. I. D. et al. Phosphorus-solubilizing microorganisms: A key to sustainable agriculture. Agriculture 13(2), 462 (2023).10.3390/agriculture13020462
34. Saini S Tewari S Dwivedi J Sharma V Biofilm-mediated wastewater treatment: A comprehensive review Mater. Adv. 2023 4 6 1415 1443 10.1039/D2MA00945E
Saini, S., Tewari, S., Dwivedi, J. & Sharma, V. Biofilm-mediated wastewater treatment: A comprehensive review. Mater. Adv. 4(6), 1415–1443 (2023).10.1039/D2MA00945E
35. Wang Y Realization process of microalgal biorefinery: The optional approach toward carbon net-zero emission Sci. Total Environ. 2023 901 165546 10.1016/j.scitotenv.2023.165546 37454852
Wang, Y. et al. Realization process of microalgal biorefinery: The optional approach toward carbon net-zero emission. Sci. Total Environ. 901, 165546 (2023).37454852 10.1016/j.scitotenv.2023.165546
36. Yang S Kaggwa RJ Andrade-Sanchez P Zarnstorff M Wang G Lint yield compensatory response to main stem node removal in upland cotton (Gossypium hirsutum) J. Agron. Crop. Sci. 2016 202 3 243 253 10.1111/jac.12142
Yang, S., Kaggwa, R. J., Andrade-Sanchez, P., Zarnstorff, M. & Wang, G. Lint yield compensatory response to main stem node removal in upland cotton (Gossypium hirsutum). J. Agron. Crop. Sci. 202(3), 243–253 (2016).10.1111/jac.12142
37. Poletika NN Chlorpyrifos and atrazine removal from runoff by vegetated filter strips: Experiments and predictive modeling J. Environ. Qual. 2009 38 3 1042 1052 10.2134/jeq2008.0404 19329692
Poletika, N. N. et al. Chlorpyrifos and atrazine removal from runoff by vegetated filter strips: Experiments and predictive modeling. J. Environ. Qual. 38(3), 1042–1052 (2009).19329692 10.2134/jeq2008.0404
38. Chen H Grieneisen ML Zhang M Predicting pesticide removal efficacy of vegetated filter strips: A meta-regression analysis Sci. Total Environ. 2016 548 122 130 10.1016/j.scitotenv.2016.01.041 26802340
Chen, H., Grieneisen, M. L. & Zhang, M. Predicting pesticide removal efficacy of vegetated filter strips: A meta-regression analysis. Sci. Total Environ. 548, 122–130 (2016).26802340 10.1016/j.scitotenv.2016.01.041
39. Akhavan K Yargholi B Evaluation capability biological filters for treatment of agricultural drain water: Case study of moghan irrigation and drainage network Irrig. Drain. Struct. Eng. Res. 2017 18 69 135 144
Akhavan, K. & Yargholi, B. Evaluation capability biological filters for treatment of agricultural drain water: Case study of moghan irrigation and drainage network. Irrig. Drain. Struct. Eng. Res. 18(69), 135–144 (2017).
40. Rodríguez-Espinosa T Pérez Gimeno A Almendro Candel MB Gómez Lucas I Navarro-Pedreño J Low-quality irrigation water treated using waste bio-filters Water 2023 15 13 2464 10.3390/w15132464
Rodríguez-Espinosa, T., Pérez Gimeno, A., Almendro Candel, M. B., Gómez Lucas, I. & Navarro-Pedreño, J. Low-quality irrigation water treated using waste bio-filters. Water 15(13), 2464 (2023).10.3390/w15132464
41. Rahimi S Modin O Mijakovic I Technologies for biological removal and recovery of nitrogen from wastewater Biotechnol. Adv. 2020 43 107570 10.1016/j.biotechadv.2020.107570 32531318
Rahimi, S., Modin, O. & Mijakovic, I. Technologies for biological removal and recovery of nitrogen from wastewater. Biotechnol. Adv. 43, 107570 (2020).32531318 10.1016/j.biotechadv.2020.107570
42. Farasati M Haghighi S Boroun S Cd removal from aqueous solution using agricultural wastes Desalin. Water Treat. 2016 57 24 11162 11172 10.1080/19443994.2015.1043588
Farasati, M., Haghighi, S. & Boroun, S. Cd removal from aqueous solution using agricultural wastes. Desalin. Water Treat. 57(24), 11162–11172 (2016).10.1080/19443994.2015.1043588
43. Koohi Z Farasati M Seyedian M Gholizadeh A The effect of Brassica napus, wheat and their composition biochar on nitrate adsorption and leaching from soil J. Water Soil. Conserv. 2020 26 6 247 261
Koohi, Z., Farasati, M., Seyedian, M. & Gholizadeh, A. The effect of Brassica napus, wheat and their composition biochar on nitrate adsorption and leaching from soil. J. Water Soil. Conserv. 26(6), 247–261 (2020).
44. Farzi S Farasati M Bansouleh BF Pirsaheb M Evaluation of batch and continuous adsorption kinetic models of cadmium from aqueous solutions using sugarcane straw nano-structure absorbent Desalination Water Treat. 2018 115 135 144 10.5004/dwt.2018.22450
Farzi, S., Farasati, M., Bansouleh, B. F. & Pirsaheb, M. Evaluation of batch and continuous adsorption kinetic models of cadmium from aqueous solutions using sugarcane straw nano-structure absorbent. Desalin. Water Treat. 115, 135–144 (2018).10.5004/dwt.2018.22450
45. Nazarpoor R Farasati M Fathaabadi H Gholizadeh M Nitrate removal from water by using Cyperus alternifolius plants in surface flow constructed wetlands Desalin. Water Treat. 2021 224 197 205 10.5004/dwt.2021.27162
Nazarpoor, R., Farasati, M., Fathaabadi, H. & Gholizadeh, M. Nitrate removal from water by using Cyperus alternifolius plants in surface flow constructed wetlands. Desalin. Water Treat. 224, 197–205 (2021).10.5004/dwt.2021.27162
