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Article

Effectiveness of Biochar and Zeolite Soil Amendments in Reducing Pollution of Municipal Wastewater from Nitrogen and Coliforms

by
Hamid Reza Asghari
1,*,
Günther Bochmann
2 and
Zahra Taghizadeh Tabari
1
1
Department of Agronomy and Plant Breeding, Faculty of Agriculture, Shahrood University of Technology, Shahrood 3619995161, Iran
2
Institute for Environmental Biotechnology, University of Natural Resources and Life Sciences Vienna|Boku, 1180 Wien, Austria
*
Author to whom correspondence should be addressed.
Sustainability 2022, 14(14), 8880; https://doi.org/10.3390/su14148880
Submission received: 23 June 2022 / Revised: 12 July 2022 / Accepted: 16 July 2022 / Published: 20 July 2022
(This article belongs to the Special Issue Sustainable Management of Water Resource and Environmental Monitoring)
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Abstract

:
A greenhouse experiment with soil cores and wastewater application was carried out to investigate the effects of biochar and zeolite on the mobility of nitrogen and coliform bacteria during the leaching of columns repacked by a silty loam soil. Triticum aestivum plants were grown in cores with and without biochar and zeolite irrigated with municipal wastewater for 4 months in the greenhouse. Cores were then flushed with 800 mLof distillate water and, finally, the leachate was collected. Application of biochar or zeolite significantly (p ≤ 0.05) reduced nitrate and ammonium loss in soil after leaching process, compared to their non-treated counterparts. In addition, interactions of biochar and zeolite significantly decreased nitrate and ammonium content in leachate. Biochar had higher removal effects of coliform bacteria in leachate than zeolite. Lower nitrate and ammonium content in leachate was related to the increased retention of soil amendments. Application of 5% w/w of biochar also reduced the volume of leachate by 11% compare to control, but using 5% w/w and 10% w/w of zeolite increased the volume of leachate compared with non-treated columns by 21% and 48%, respectively. Taken together, these data highlight the need to consider the potential benefits of biochar and zeolite as soil amendment to reduce nitrogen mobility and remove coliform bacteria in the leaching process of municipal wastewater in agricultural systems.

1. Introduction

Water resources are of great importance due to the high volumes that are necessary. It is estimated that about 70% of fresh water is used for the irrigation of croplands in the world [1]. Irrigated agriculture will play a dominant role in the sustainability of crop production in years to come. On the other hand, the world water deficit is a recent phenomenon. In many arid and semi-arid regions of the world water has become a limiting factor, particularly for agricultural and industrial development. Besides water-saving methods, finding new water resources or renewable resources is ineluctable. Wastewater is a renewable resource within the hydrological cycle. On a world-wide basis, wastewater is the most widely used low-quality water, particularly for agriculture. Application of wastewater in agricultural fields may causes some environmental and health problems. Soil, water resources and plant contamination with heavy metals, chemicals and microorganisms substances are some side effects of wastewater application in croplands [2,3,4].
Municipal wastewater contains 99.9% water with relatively small concentrations of suspended and dissolved organic and inorganic solids. The actual proportion of each constituent within any given wastewater varies depending on the spatial and temporal differences, but it mainly contains carbohydrates, lignin, fats, soaps, synthetic detergents, proteins are some organic substances of municipal wastewater. In addition, it also contains a variety of inorganic substances from domestic and industrial sources, including a number of potentially toxic elements such as arsenic, cadmium, chromium, copper, lead, mercury, zinc, etc., which may affect human and plant health. Pathogenic micro- and macro-organisms are the most important contamination of wastewater in agricultural use. About 20 million hectares of arable land worldwide are irrigated with wastewater. This source of irrigation water may be a source of pollution, and can affect the health of users, consumers and the environment if safe practices are not applied [5,6].
The removal of heavy metals and organic pollutants in wastewater has been assisted by several technologies, including ion exchange, membrane separation, absorption, coagulation and flocculation, and photocatalytic degradation. Adsorption is unique among these approaches due to its ability to effectively remove pollutants via chemisorption and physisorption when using synthetic and natural materials. There is a significant difference between chemical and physical adsorption in that chemical bonds are formed through electron exchange in the former, whereas, in the latter, pollutants are adsorbed through van der Waals forces, hydrophobicity, hydrogen bonding, polarity, as well as static and electrostatic interactions. Current studies show that activated carbon, natural or modified biochar, and clay minerals are the main kinds of adsorbents for wastewater [7]. Recently, there has been increasing interest in the use of combined-modification clay–biochar composites for the simultaneous uptake of different wastewater. It represents promising candidates for the removal of heavy metals, antibiotics, phenolic compounds, and dyes from various types of wastewaters [8,9]. Sorption played an important role in pathogen removals in bioreactors with adsorbents [8]. Among adsorption systems, remediation of heavy metals by natural and modified zeolites and biochar has been developed [10].
Biochar has been used as a soil amendment for several centuries, but the scientific research and application of biochar goes back to the 19th century. During recent years, biochar has begun to interest researchers again, being used for soil improvement and the mitigation of environmental problems. Biochar is a carbon-enriched, fine-grained and porous material produced via the pyrolysis process. The materials for producing biochar may include wood, tree bark, animal manure, forestry and agricultural residues, and sewage sludge [11,12]. Due to its molecular structure, biochar is more stable than the original fresh form. Biochar remain stable for hundreds to thousands of year in soils, which is important in sustainable agriculture. The effect of biochar as a soil amendment has become an important topic in soil science in the past few years. It is generally acknowledged that biochar additions can increase soil’s sorption and retention capacity for nutrients and water [13]. Biochar possibly also has a high potential for use in water purification, replacing coal-based activated carbon as a sorbent for contaminants and pathogens [14].
De Rozari et al. (2016) have reported about 71–87%, 81–93% and 65–79% removal rates for TN, NO3-N and NH4-N loads from sewage water treated with a constructed wetland containing different amounts of biochar. Enhanced removal of nutrients and coliforms from domestic wastewater in cattle dung biochar packing has been reported [15]
Zeolites are, naturally, crystalline aluminosilicates that come from volcanic earth deposits with a porous structure. Pores and voids in zeolites structure are the key characteristics, which can be occupied with water and cations. These aluminosilicates are characterized by a high and selective cation-exchange capacity (CEC), reversible dehydration and molecular sieving that can strongly influence soil physico-chemical characteristics. Zeolites are a low-cost material with broad applications in agriculture and environmental engineering. Zeolite has been applied in agriculture for the controlled release of standard pesticides, herbicides, fungicides and fertilizers and as a trap for heavy metals in soils [10]. It may also function as a cation exchanger in soil, providing plants with nutrients such as calcium and potassium and increasing water-binding capacity. In addition, it has been shown that zeolite can flocculate, followed by the adsorption of organic pollutants in wastewater [14,16]. Zeolite was proven to be a good material for the efficient adsorption of ammonium [15].
Use of some soil amendments such as biochar and zeolite will decrease the unfavorable effects of wastewater in soil and crops on one hand, and, on the other hand, they could be used to improve plant-growth-promoting bacteria communities, and prevent fertilizer leaching as a “slow fertilizer releaser” [8].
Our main objective is to explore the potential of zeolite and biochar in the removal of pollutants. While there have been many studies on the performance and prospects of different biochar and zeolite adsorbents, there have been few studies about comparative assessments and their combination effects. Based on a literature review, adsorption is primarily determined by size, structural features, molecular mass, and solution concentration, so the combination of biochar and zeolite with different absorption properties may enhance the pollutant removal process. Therefore, this study investigated the potential of zeolite and biochar for the reclamation of municipal wastewater in a greenhouse column experiment. Specific objectives were to: Assess the potential of zeolite or biochar and their combination to reduce nitrate and ammonium mobilization in soil and leachate, and also evaluate their potential in reducing soil and leachate pollution from total and fecal coliforms after using municipal wastewater.

2. Materials and Methods

Biochar used in this study was obtained from slow pyrolysis process of sugarcane bagasse at 350 °C in laboratory furnace for 3 h [17]. The biochar produced was ground to a particle size of about 1–5 mm. Some physical and chemical properties of biochar used in this study were listed in Table 1.
Natural zeolite clinoptilolite, originated from west of Semnan (West of Semnan, Central Alborz Mountains, 200 km east of Tehran, Iran) was obtained from Afrazand Company. The particle size of zeolite was between 1 and 2 mm. Some physical and chemical properties of zeolite were listed in Table 2.

2.1. Experimental Design

A glasshouse experiment was conducted to investigate the effects of zeolite and biochar on reclamation of municipal wastewater for agriculture uses. The experiment was conducted as a factorial experiment based on a completely randomized block design. The treatments consisted of zeolite in three levels (0, 5% and 10% w/w) and biochar in two levels (0 and 5% w/w). Each treatment was replicated four times, giving a total of 24 experimental columns.

2.2. Soil Collection and Preparation

The soil used was collected from Shahrood University of Technology Research Farm (north-eastern Iran). The soil was a silty loam with a bulk density of 1.3 g cm3, pH of 8.36, EC of 0.71 dS m−1, plant available (Olsen) P of 5.54 mg kg−1, total C of 0.45% and total N of 0.066% (H.R. Asghari, unpublished data). The soil was air dried and passed through a 5 mm sieve, then mixed with 5% (w/w) cow manure and 10% (w/w) sand; this mixture is referred to as soil hereafter. The soil was added to the columns alone (control), mixed with zeolite, mixed with biochar, or both. Then, plants were grown in PVC columns (110 mm diameter and 350 mm deep) with a PVC cap (with a central, 16 mm diameter hole) fitted to the base. A sterile cotton mesh layer was placed at the base of each column. To each column, 2.7 kg of treated or untreated soil was added. Once all soil had been added to the columns, there was enough space between the soil surface and the top of the column, allowing room for irrigation and for nutrients addition to the treatments.
Four seeds of Triticum aestivum L. (Sirvan variety) were planted in each column and were covered with a 10 mm layer of sand to minimize surface evaporation. Columns were kept moist with distilled water, and, after 4 weeks, seedlings were thinned to two per column. Columns were then irrigated after their treatments (to weight) with municipal wastewater every two days, for 4 months, to 80% of water-holding capacity, to ensure that no water leached out of the columns during the plant growth [18]. Municipal wastewater was collected from Shahrood wastewater before treated plants. A sample of municipal wastewater was collected and the chemical and biological properties were analyzed (Table 3).
Wheat plants were grown in a glasshouse on the Shahrood University of Technology research farm from November 2018 to March 2019. Mean day and nighttime temperatures were about 20 °C and 15 °C, respectively. Ten weeks after planting, nutrients were added to the columns. These nutrient additions are similar to fertilizer application in wheat cropping systems in the region (Shahrood Agriculture Organization, unpublished data). The nitrogen addition was established by adding 20 mL of ammonium nitrate solution (containing 0.154 g NH4NO3) to each column, which was equivalent to 200 kg/ha [19]. Phosphorus and potassium were added as soluble potassium phosphate (KH2PO4) fertilizer equal to 100 kg/ha.

2.3. Harvesting and Leachate Collection

All test columns were destructively harvested four months after planting. The shoots of plants were removed (to eliminate water loss via transpiration), and the columns immediately flushed with 800 mL of distilled water to leach soil nutrients and coliform bacteria from the columns. The leachate was collected from the columns after 4 h, then a subsample of the leachates (100 mL) of each treatment was collected in a sterile glass bottle and immediately analyzed for total and fecal coliforms bacteria density. According to the standard methods [20], each tube containing 10 mL of double-strength lactose broth was inoculated with 10 mL of leachate sample and incubated at 35 °C for 24–48 h. The tubes that were positive for total coliforms, as indicated by the production of acid or gas, were then confirmed in brilliant green lactose bile (BGLB) broth and EC broth for the presence of total and fecal coliforms, respectively. The same method was used to determine number of total and fecal coliform bacteria in 10–15 cm soil depth.
The concentrations of NH4-N and NO3-N were determined in the leachate colorimetrically, as for soil extracts (see below). Soil samples were collected from 10–20 cm layer for analysis of soil NH4-N and NO3-N concentrations. The soils were extracted using a 2 M KCl solution and inorganic nitrogen content determined colorimetrically using a method modified by Miranda et al. [21]. After plant harvesting, plant material was dried at 60 °C, and dry weight of stem, head and grain were determined. Data were analyzed using statistical analysis variance with MSTATC program and treatments means were compared by using the least significant difference (LSD) test (p < 0.05).

3. Results

3.1. Plant Growth

There were no significant differences (p ≤ 0.05) in shoot dry weight, stem dry weight, head and grain weight among any of the experimental treatments (Appendix A, Table A1).

3.2. Leachate Volume

The results of the ANOVA table revealed that application of biochar and zeolite had significant effects on the volume of leachate. Biochar and zeolite had different results in terms of the amount of water leachate from the cores. The average of the volume of leachate collected from 0 and 5% biochar treatments was 425.9 ± 17 and 376 ± 23 mL, respectively, whereas the average for 0, 5 and 10% of zeolite was 325 ± 12, 394 ± 33 and 483 ± 23 mL, respectively (Table 4). Application of biochar reduced the volume of leachate, but application of zeolite increased the volume of leachate compared with non-treated columns. The highest level of leachate volume was harvested when 10% w/w of zeolite were used with or without biochar (Figure 1).

3.3. Leachate and Soil NO3 and NH4

The concentration and content of NO3-N in the leachate reduced significantly following biochar and zeolite application (Table. 4). The results showed that application of 5% (w/w) biochar and 5% (w/w) zeolite reduced NO3–N concentration in leachate by 23% and 55%, respectively. A nitrate-content reduction trend via biochar or zeolite application was also found in leachate. The concentration of NH4-N in the leachate collected from biochar- or zeolite-treated columns was significantly lower than non-treated columns, where application of 5% (w/w) biochar reduced NH4-N concentration in leachate by 32% and application of 5% and 10% zeolite reduced NH4-N leachate concentration by 47% and 72%, respectively. The same trend was found in NH4-N content in leachate. Interactions of biochar and zeolite decreased nitrogen content in leachate (Figure 2 and Figure 3). Although use of 5% zeolite decreased NH4-N content in leachate, the reduction was more effective when 5% of zeolite was used with 5% of biochar (Figure 2). There were no significant differences between the use of 10% zeolite alone and the mixture of 10% zeolite with 5% biochar on NH4-N content in the leachate (Figure 2). Combined use of biochar and zeolite (5 or 10%) significantly decreased NO3–N content in leachate compared to non-treated columns, and a greater reduction was found in the combination of 5% biochar and 5% zeolite (Figure 3).
Results of the ANOVA table showed that application of biochar and its interaction with zeolite had significant effects on NO3-N concentration of soil (data not shown). A significant effect of both soil amendments and their interactions was found for NH4-N concentration in soil. At the end of the experiment, the amount of NO3-N remaining in the 10–20 cm soil layer of cores with 5% biochar was significantly higher than non-biochar-treated cores (Figure 4). Although there were no differences between biochar-treated and non-biochar-treated samples in terms of soil NO3 concentrations at 0 level of zeolite, the differences were significant at 5 or 10% of zeolite. Biochar-treated soil with 5 or 10% zeolite had higher NO3-N concentrations compared with non-biochar treated soils (Figure 4).

3.4. Total and Fecal Coliforms in Leachate and Soil

The concentrations of total and fecal coliforms in leachate collected from cores after 4 months’ growth of Triticum aestivum with different treatments are shown in Table 5. Biochar had significant effects on total and fecal coliforms concentration in collected leachate, but no any effects were found for zeolite with or without biochar. Biochar decreased the number of total coliforms colonies in leachate by 7.6 fold. However, most importantly, there was no fecal bacteria colony forming in the collected leachate treated with biochar. The concentrations of total and fecal coliforms in the soil of columns in 10–15 cm depth under biochar and zeolite treatments were determined. The soil concentration of total and fecal coliforms in the control treatment was higher than the biochar and zeolite treatment (Table 5).

4. Discussion

It is well-documented that biochar can change soil physical and hydraulic properties [22,23,24]. Besides the effects of biochar on soil bulk density, biochar has a special structure that can increase water-holding capacity [25]. It has an extremely complex structure that contains networks of pores and channels, within which most of the pores are capable of holding water available to plants. The pyrolysis conditions used can affect the surface morphology and the physical properties of biochar, and the majority of pores ranging from 0.5 to 50 μm can be classified as storage pores [26]. Sugarcane bagasse biochar has been used in this study, which has a small pore size, and high specific surface area and total pore volume. Results of a study indicated that sugarcane bagasse biochar had high porosity and zeta potential, which create a high water-holding capacity [26]. By contrast, the application of zeolite decreased soil volume (by about 20%), which may lead to an increase in leachate volume.
It is clear that the impact of zeolite application varies in soils with different textures. Clay soils have high water- and nutrient-retention capacity but have less water aeration and permeability than sandy soils [27,28]. Zeolites have the ability to change the amount of soil water by changing the soil bulk density and water infiltration rate. In other words, adding zeolite to heavy textured soils may reduce water-holding capacity and, thus, increase leachate [29]. In addition, increased soil bulk density in light texture soils treated with zeolite has been documented [30,31]. The increase in leachate in zeolite treated columns can be caused by a reduction in the effective porosity due to soil compaction and pore clogging. Zeolite has been recognized as a soil amendment for developing water-holding capacity and soil water retention, but this study showed different results.
The results showed that columns treated with biochar and zeolite had a lower leachate nitrogen concentration and content relative to non-treated columns. On the other hand, the soil of columns containing biochar had higher NO3-N concentrations in the 10–20 cm layer. The potential of biochar to retain nitrogen in soil and decrease nitrogen leaching depends on some biochar production conditions such as pyrolysis temperatures, pH and origin of feedstock [32,33]. The biochar used in this study was produced at a low pyrolysis temperature (350 °C) and had a high specific surface area, large CEC and alkaline pH (Table 1). These properties, together, increased nitrogen retention in cores. Increase in water-holding capacity and nutrient retention in soil by wood biochar, meanwhile, lead to decreased nutrient leaching, as reported previously [34]. In another column experiment, a reduction in nitrogen leaching by corn-straw biochar was reported to contribute to increased water-holding capacity, enhanced microbial biomass and changed the bacterial community structure of the soil [35].
Natural zeolites, mainly consisting of Si, Al and O, have a microporous crystalline structure which adsorbs weakly cations such as Na+, K+, NH4+ and so on [36]. Many researchers have used zeolites in soils or wastes to absorb NH4+ and eventually inhibit the transformation of NH4+ to nitrate in the biological process of nitrification. In this process, ammonium is firstly converted to nitrite and then to nitrate by some specific aerobic bacteria. The ability of zeolite to absorb ammonium and prevent the nitrification process has been confirmed by some researchers [37]. This natural mineral also has the ability to reduce nitrate leaching in the soil. For instance, Malekian et al. [38] found that the nitrate concentration in the lysimeter leachates ranged 13–42 mg L−1 during the growth season of maize and reduced to 7–25 mg L−1 when they used 60 g natural zeolite kg-1 soil. Soudejani et al. [39] concluded that the reduced leaching of nitrate by the application of natural zeolite and/or zeolite combined with compost was because of improved soil properties, thereby enhancing the growth and development of plant roots. Gamze and Nuri [40] showed that nitrate and ammonium leaching reduced in proportion to the addition of zeolite to municipal compost. It is generally expected that zeolite, due to negative charges on its surface, causes the repulsion of nitrate and, thus, increases its leaching from the soil. However, some studies have shown that, due to the presence of micro-pores and channels in the zeolite structure, the nitrate leaching from the soil reduced unexpectedly.
The effects of biochar or zeolite on nitrogen retention in soil are well-documented, but there is a little information about the combination effects of these amendments for nitrogen leaching. The results of this study showed that the potential of biochar or zeolite for reducing nitrogen leaching will increase when these two amendments are used together. Results confirmed our hypotheses that biochar and zeolite had impacts on nitrate sorption in soil and reducing nitrogen leaching. Increased retention of nitrogen in soil via the interactions of biochar and zeolite may relate to increased ion-exchange capacity, specific surface area or inducing nitrifying bacteria. Although the inhibition effect of biochar on soil ammonia-oxidizing bacteria was reported by some researchers [41,42], increased soil nitrification via the increased activity of soil ammonia microorganisms has been reported by others [43,44]. Awasthi et al. [45] also found that the combined applications of biochar and zeolite improved environmental conditions for the activity of nitrifiers. On the other hand, biochar’s specific structure and surface area may help to retain nitrate in soil. For instance, Wu et al. [46] introduced biochar (5%) and zeolite (5%) into a soil mixed with some agricultural wastes (i.e., rice straw and vegetable leaf) for composting purposes. They found that the combined use of these two amendments increased the activity of ammonium-oxidizing bacteria and nitrogen retention during composting when compared to biochar or zeolite alone. However, it should be pointed out that, at a high rate of zeolite (10%), the application of biochar did not significantly reduce leachate volume nor the concentrations of nitrate and ammonium in the leachate. It seems that the result of nitrogen leaching by zeolite application depends on the amount of zeolite used.
In soil treated with biochar, concentrations of total and fecal coliforms were lower than soil treated with zeolite. The results of this study are in agreement with previous studies, in which biochar-treated columns as a biofilter reduced Escherichia coli concentrations in storm water under a wide range of field conditions [47,48]. Different mechanisms of bacterial-removal control by biochar have been reported previously. Coliform bacterial removal in soil and leachate may relate to biochar’s highly porous structure and the specific surface area in soil, which increase attachment sites in the biochar-treated columns. Other reasons for bacterial attachment by biochar are Derjaguin–Landau–Verwey–Overbeek (DLVO), hydrophobic, or Lewis acid–base interactions [49,50]. In addition, physical straining is a possible mechanism for the retention of coliform bacteria, which are governed by the particle size (particularly micro-size biochar) and physical and chemical surface properties of biochar as well as the geometry of microbial cells or colloids [51,52].

5. Conclusions

The use of wastewater in agriculture fields of arid regions is unavoidable, but nutrient content and biological contamination of this resources is a big challenge when they contaminate croplands and fresh water resources. This study showed that the application of biochar and/or zeolite allows nitrogen retention in soil and decreased nitrogen leaching, where combination effects were more effective to retain nitrate in soil and reduce nitrate loss via leaching. It also provides important results in removing of coliform bacteria by biochar application in leachate and decreasing the pollution risk of soil and groundwater sources nearby. Moreover, in soil treated with biochar, concentrations of total and fecal coliforms were lower than soil treated with zeolite. The potential of soil amendments to remove chemical (via biochar and zeolite) and biological (via biochar) pollutants of wastewater may be important to amend wastewater for agricultural use in arid region.

Author Contributions

H.R.A. conceived and designed the analysis and performed writing—original draft preparation and supervision; Z.T.T. contributed to data collection and review and editing. G.B. carried out funding acquisition. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported financially by cofounding of Kharazmi University and Ministry of Science, Research, and Technology (MSRT) of Islamic Republic of Iran under IMPULS projects. Grant number: 4-11769.

Institutional Review Board Statement

The study did not require ethical approval.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Acknowledgments

The author would like to acknowledge the financial sponsorship provided by cofounding of Kharazmi University and Ministry of Science, Research, and Technology (MSRT) of Islamic Republic of Iran under IMPULS projects. In addition, the author would like to thank Austria (OeAD) for supporting the research facilities. Lastly, the author thanks AfsanehYahyaei for her excellent technical assistance.

Conflicts of Interest

The authors declare no conflict of interest.

Appendix A

Table
Table A1. Analysis of variance (mean of squares). The effects of biochar and zeolite on growth of Triticum aestivum. Values are means ± s.e. (n = 4). Significance levels are shown: not significant at p < 0.05.
Table A1. Analysis of variance (mean of squares). The effects of biochar and zeolite on growth of Triticum aestivum. Values are means ± s.e. (n = 4). Significance levels are shown: not significant at p < 0.05.
S.O.VdfTotalStemHeadGrain
Replication31.35 ns0.067 ns2.245 ns0.453 ns
Biochar15.54 ns0.390 ns2.40 ns0.540 ns
Zeolite21.33 ns0.440 ns0.226 ns0.053 ns
Biochar × Zeolite21.02 ns0.063 ns0.762 ns0.608 ns
error151.790.2480.9730.243
Total231.44
CV (%)-13.9116.7417.5817.32
Sustainability 14 08880 g0a1 550
Figure A1. The experimental setup.
Figure A1. The experimental setup.
Sustainability 14 08880 g0a1

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Sustainability 14 08880 g001 550
Figure 1. Volume of leachate collected from cores after 4 months’ growth of Triticum aestivum with different treatments; zeolite (0, 5 and 10% (w/w) and biochar (0 and 5%, open and solid bars, respectively). Cores were irrigated with 800 mL distillated water (values followed by the same letter (s) are not significantly different at p ≤ 0.05 according to the LSD test).
Figure 1. Volume of leachate collected from cores after 4 months’ growth of Triticum aestivum with different treatments; zeolite (0, 5 and 10% (w/w) and biochar (0 and 5%, open and solid bars, respectively). Cores were irrigated with 800 mL distillated water (values followed by the same letter (s) are not significantly different at p ≤ 0.05 according to the LSD test).
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Figure 2. NH4 content of leachate collected from cores after 4 months’ growth of Triticum aestivum with different treatments; zeolite (0, 5 and 10% w/w) and biochar (0 and 5%, open and solid bars, respectively). Cores were irrigated with 800 mL distilled water (values followed by the same letter(s) are not significantly different at p ≤ 0.05 according to the LSD test).
Figure 2. NH4 content of leachate collected from cores after 4 months’ growth of Triticum aestivum with different treatments; zeolite (0, 5 and 10% w/w) and biochar (0 and 5%, open and solid bars, respectively). Cores were irrigated with 800 mL distilled water (values followed by the same letter(s) are not significantly different at p ≤ 0.05 according to the LSD test).
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Figure 3. NO3 content of leachate collected from cores after 4 months’ growth of Triticum aestivum with different treatments; zeolite (0, 5 and 10% w/w) and biochar (0 and 5%, open and solid bars, respectively). Cores were irrigated with 800 mL distillated water (values followed by the same letter(s) are not significantly different at p ≤ 0.05 according to the LSD test).
Figure 3. NO3 content of leachate collected from cores after 4 months’ growth of Triticum aestivum with different treatments; zeolite (0, 5 and 10% w/w) and biochar (0 and 5%, open and solid bars, respectively). Cores were irrigated with 800 mL distillated water (values followed by the same letter(s) are not significantly different at p ≤ 0.05 according to the LSD test).
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Figure 4. The effects of biochar and zeolite on NO3-N soil concentration from cores (10–20 cm depth) after 4 months’ growth of Triticum aestivum. Open and solid bars received 0 and 5% biochar (w/w), respectively (values followed by the same letter(s) are not significantly different at p ≤ 0.05 according to the LSD test).
Figure 4. The effects of biochar and zeolite on NO3-N soil concentration from cores (10–20 cm depth) after 4 months’ growth of Triticum aestivum. Open and solid bars received 0 and 5% biochar (w/w), respectively (values followed by the same letter(s) are not significantly different at p ≤ 0.05 according to the LSD test).
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Table
Table 1. Some physical and chemical properties of biochar.
Table 1. Some physical and chemical properties of biochar.
ParameterUnitValue
pH-7.5
ECdS/m
SiO2%67.83
Al2O3%11.64
Fe2O3%0.54
CaO%0.84
SO3%0.20
Na2O%4.5
K2O%4.32
CECCmol/kg2.64
Specific surface aream2/g47.2
Table
Table 2. Some physical and chemical properties of zeolite.
Table 2. Some physical and chemical properties of zeolite.
ParameterUnitValue
pH-7.55
ECdS/m0.84
Carbon%69.63
Nitrogen%0.28
Hydrogen%3.3
Oxygen%19.51
Ash%5.5
Bulk densityg/cm30.13
Cation exchange capacityCmol(+)/kg36.3
Specific surface aream2/g160
Table
Table 3. Some chemical and biological properties of urban wastewater.
Table 3. Some chemical and biological properties of urban wastewater.
ParameterUnitValue
pH-8.51
ECdS/m1.5
BODmg/L O260
CODmg/L O2174
Ammoniummg/L6.1
Nitratemg/L42
Total Dissolved Solidmg/L1000
Total Phosphorousmg/L2
Chloridemg/L262
Thermotolerant Coliform-MPNcfu/mL1200
Table
Table 4. The effects of biochar and zeolite on leachate nitrogen content from cores after 4 months’ growth of Triticum aestivum. Values are means ± s.e. (n = 4). Significance levels are shown: *, p < 0.05; **, p < 0.01; ***, p < 0.001; ns, not significant at p < 0.05.
Table 4. The effects of biochar and zeolite on leachate nitrogen content from cores after 4 months’ growth of Triticum aestivum. Values are means ± s.e. (n = 4). Significance levels are shown: *, p < 0.05; **, p < 0.01; ***, p < 0.001; ns, not significant at p < 0.05.
TreatmentLeachate Volume
mL		NO3 Concentration
mg/L		NO3 Content
mg		NH4 Concentration
mg/L		NH4 Content
mg
Biochar0%425.9 ± 1720.4 ± 1.58688 ± 1574.7 ± 0.82002 ± 67
5%376.3 ± 2315.9 ± 1.15983 ± 2523.3 ± 0.51242 ± 55
Zeolite0%325.6 ± 1228.5 ± 1.29335 ± 986.7 ± 1.22243 ± 124
5%394.3 ± 3313.1 ± 0.85350 ± 1113.6 ± 0.91404 ± 98
10%483.5 ± 2313.0 ± 1.56268 ± 3221.9 ± 0.5894 ± 304
Biochar ***********
Zeolite **************
Biochar × Zeolite ********
Table
Table 5. The effects of biochar and zeolite on leachate total and fecal coliforms concentration collected from cores after 4 months’ growth of Triticum aestivum. Values are means ± s.e. (n = 4). Significance levels are shown: ***, p < 0.001; ns, not significant at p < 0.05.
Table 5. The effects of biochar and zeolite on leachate total and fecal coliforms concentration collected from cores after 4 months’ growth of Triticum aestivum. Values are means ± s.e. (n = 4). Significance levels are shown: ***, p < 0.001; ns, not significant at p < 0.05.
TreatmentTotal Coliforms Concentration
cfu/mL		Fecal Coliforms Concentration
cfu/mL
Biochar0%230 ± 1027 ± 7
5%30 ± 40 ± 0
Zeolite0%230 ± 2223 ± 6
5%230 ± 1519 ± 4
10%230 ± 2519 ± 6
Biochar ******
Zeolite nsns
Biochar × Zeolite nsns
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Asghari, H.R.; Bochmann, G.; Tabari, Z.T. Effectiveness of Biochar and Zeolite Soil Amendments in Reducing Pollution of Municipal Wastewater from Nitrogen and Coliforms. Sustainability 2022, 14, 8880. https://doi.org/10.3390/su14148880

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Asghari HR, Bochmann G, Tabari ZT. Effectiveness of Biochar and Zeolite Soil Amendments in Reducing Pollution of Municipal Wastewater from Nitrogen and Coliforms. Sustainability. 2022; 14(14):8880. https://doi.org/10.3390/su14148880

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Asghari, Hamid Reza, Günther Bochmann, and Zahra Taghizadeh Tabari. 2022. "Effectiveness of Biochar and Zeolite Soil Amendments in Reducing Pollution of Municipal Wastewater from Nitrogen and Coliforms" Sustainability 14, no. 14: 8880. https://doi.org/10.3390/su14148880

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