Next Article in Journal
Quantitative Assessment of Seasonal and Land-Use Impacts on Coastal Urban Sewage Systems with Seawater Intrusion Vulnerability Analysis
Previous Article in Journal
Hydrological Benefits of Green Roof Retrofitting Policies: A Case Study of an Urban Watershed in Brazil
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Water
Volume 17
Issue 13
10.3390/w17131937
water-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

The Influence of Coagulation on the Fertilizing Properties of Treated Wastewater

by
Justyna Czajkowska
,
Alicja Knap-Bałdyga
and
Monika Żubrowska-Sudoł
*
Department of Water Supply and Wastewater Disposal, Faculty of Environmental Engineering, Warsaw University of Technology, 20 Nowowiejska Street, 00-653 Warsaw, Poland
*
Author to whom correspondence should be addressed.
Water 2025, 17(13), 1937; https://doi.org/10.3390/w17131937 (registering DOI)
Submission received: 8 May 2025 / Revised: 25 June 2025 / Accepted: 26 June 2025 / Published: 28 June 2025
(This article belongs to the Section Wastewater Treatment and Reuse)
Browse Figures
Versions Notes

Abstract

Treated wastewater (TW) is a valuable source of water for plant irrigation, helping to protect water resources. However, to use it, a preliminary treatment is necessary, typically involving coagulation to reduce turbidity and then disinfection to ensure microbiological safety. The aim of this research was to determine changes in the concentrations of basic fertilizer components (N, P, and K) in TW after the coagulation process. The tests were carried out in three measurement series for volumetric and surface coagulation using three coagulants: Al2(SO4)3, PAX-XL 19F, and PAX-XL 1911. Four doses of aluminum were used for each coagulation method (volumetric coagulation: 1, 2, 4, and 8 mg Al/L; surface coagulation: 0.25, 0.5, 1, and 2 mg Al/L). Studies have shown that despite the reduction in the concentration of nutrients during the coagulation process, the reclaimed water used for grass irrigation would cover the entire K requirement of this plant. In the case of N and P, the demand would be covered by 14.34% and 8.55%, depending on the coagulant used and its dose. It was also documented that the type of coagulant significantly influences the reduction of fertilizing properties during wastewater treatment. PAX-XL19F was found to cause the least reduction in P and K concentrations, while Al2(SO4)3 had the least negative impact on N regardless of coagulation method or dose.

Graphical Abstract

1. Introduction

Recently, scientists have begun to pay attention to the problems related to depleting water resources and limited access to them for many people, while water consumption has increased by 600% in the last century [1,2]. This corresponds to an annual growth of 1.8%. The causes of water shortage include, among others, growing world population, climate change, and increasing demand for water. Problems related to water resources are therefore one of the most pressing challenges facing society in the 21st century [3,4].
According to the World Water Development Report [5], the amounts of water used for irrigation at any given time will vary depending on the type of crops and their different growing seasons. Lawns need 0.5–3 L/m2 per day during the entire growing season (lasting approximately 5 months from mid-April to mid-September) [6,7,8]. Cover crops have similar water requirements [9]. Ornamental flowers have higher water needs. The daily water needs of roses are 5–7 L/m2, while chrysanthemums require 4–4.5 L/m2, and lilies require 4–5 L/m2 [10]. The amount of water used for irrigation will also depend on farming practices and variability in local soil and climatic conditions, not to mention any changes in the area of land equipped for irrigation. The effectiveness of different irrigation techniques, such as drip or sprinkling systems, also directly affects overall water consumption.
The Food and Agriculture Organization of the United Nations forecasts an increase in irrigation water consumption by 5.5% between 2008 and 2050 [11]. Burek et al. [12] predict that the global demand for water for crop irrigation in 2050 will increase from 23 to 42% compared to the level in 2010. Global water demand will increase significantly over the next two decades in all three components: industry, households, and agriculture. Industrial and domestic demand will grow faster than the demand for agriculture, but the demand for agriculture will remain the largest [5]. Others estimate that global water demand for agriculture will increase by up to 60% by 2025 [13].
Given the increasing water demand, an alternative source to natural water resources for agricultural irrigation can be recovered water from wastewater [14,15,16]. According to Ramm and Smol [17], wastewater from municipal wastewater treatment plants is a viable source for meeting the growing demand for water in Europe. The potential for the reuse of treated municipal wastewater in the European Union is estimated to be up to six times greater than current reuse levels, and the countries with the largest potential for water recovery are Italy, Spain, Germany, the UK, and France. It should be noted that water reclamation is popular in Mediterranean countries, where there is a risk of water shortages in agriculture and drinking water supply [18]. Such solutions may bring economic benefits—reducing the need to draw water from the water supply network—and environmental benefits, such as a decrease in the extraction of water from natural resources. However, it is important that the recovered water does not pose a threat to the environment [19]. Reclaimed water may contain residues of chemicals such as pesticides, pharmaceuticals and heavy metals that can be harmful to plants, soil, and human health [20,21].
Using water recovered from treated wastewater for irrigation, it is possible to supplement it with fertilizing substances. Macronutrients are key elements needed by plants to grow and function. Their availability influences the quality and quantity of flowering in plants [22,23,24,25]. Nitrogen is the main factor determining the scale of plant growth, and it is also responsible for the proper color and density of turf [26]. Phosphorus plays a key role in the storage and transfer of energy and promotes winter survival and cold hardiness [26,27,28]. Potassium plays an essential role in turf quality, root growth, disease resistance, and cold hardiness. Its deficiency can significantly limit the growth of plants [28,29,30].
For example, the optimum N:P:K ratio for grasses should be 4:1:2, and the annual nitrogen dose should be within the range of 1.4–2.4 kg N per 100 m2, maintaining the ratio of 4:1:2 [6]. Assuming daily watering in the range of 0.5–3.0 L/m2, the seasonal water demand is from 75 to 450 L/m2 (5 months × 30 days × 0.5 L/day and 5 months × 30 days × 3.0 L/day). The permissible total nitrogen concentration in the treated wastewater from the medium-sized wastewater treatment plants (WWTPs) described in [31] is at the level of 10 mg/L, the seasonal nitrogen load introduced per m2 may range from 0.00075 to 0.0045 kg/m2. Therefore, by watering with treated reclaimed water, the nitrogen demand of grass can be covered by approximately 5% to even 19%. In the case of total phosphorus, the seasonal load introduced per m2 may range from 0.0001 to 0.0006 kg/m2. Given a phosphorus concentration of 0.7 mg/L, the current demand can be covered in the range of 1.5% to 5.3%. By fertilizing plants with the nutrient ingredients contained in irrigation water, costs can be reduced because the amount of fertilizers required is accordingly reduced. The above calculations show the maximum permissible concentrations in treated wastewater. However, it should be noted that these concentrations are being increasingly restricted under recent regulations, such as the new EU Urban Wastewater Treatment Directive. Nevertheless, reclaimed water from WWTPs can be a valuable source of water for irrigation, not only reducing the demand for freshwater but also partially satisfying plant nutrient needs and also reducing the consumption of synthetic fertilizers for plants [32].
Reclaimed water reuse standards vary significantly among countries, depending on local climate, crop type, and risk perception. Zhao et al. [33] present a comprehensive comparison of international (e.g., WHO, EU, China, USA, Australia, Russia, Israel, Jordan, etc.) standards and highlight differences in parameters such as microbial quality, salinity, and nutrient limits. Due to the broad and policy-oriented scope of this topic, a full discussion of these standards is beyond the focus of this study, which focuses on nutrient retention in treated wastewater following coagulation.
To ensure that reclaimed water meets the required standards, an effective disinfection process is essential to ensure microbiological safety. Among the necessary steps is an effective disinfection process, which is preceded by physicochemical treatment such as coagulation. One of the key functions of coagulation is to reduce turbidity, which otherwise impairs disinfection efficiency—especially in UV-based or ozonation systems. However, coagulation can also affect the fertilizing properties of the reclaimed water. Despite the significance of this impact, there is a lack of research in the literature addressing this aspect. This gap prompted an investigation into the effects of volumetric and surface coagulation on the fertilizing properties of reclaimed water. The study focused on three aluminum-based coagulants—Al2(SO4)3, PAX-XL 19F, and PAX-XL 1911, which are commonly used in wastewater treatment plants mainly for organic compounds and phosphorus removal. This study presents a novel approach by systematically comparing multiple aluminum-based coagulants and application methods to assess their effects on the fertilizing potential of reclaimed wastewater. However, other coagulants—such as calcium, magnesium, or lanthanum salts—have also shown promise with the added benefit of potentially lower environmental impact [34]. These alternatives were not the focus of this study but should be considered in future work.
Unlike most existing research, which focuses primarily on pollutant removal, this work evaluates how coagulation influences the concentrations of key macronutrients (N, P, K) critical for plant growth, using grasses (e.g., sports fields, urban greenery) as a model for seasonal nutrient demand. The findings provide valuable insights into the balance between effective wastewater treatment and the preservation of the fertilizing properties of reclaimed water, filling an important gap in the existing literature and offering practical implications for water reclamation processes. Therefore, it supports the development of reuse practices where nutrient recovery is desired, particularly in grass irrigation and urban landscaping.

2. Materials and Methods

2.1. Material

Coagulation studies were performed on a laboratory scale. The treated wastewater undergoing the process came from a wastewater treatment plant (WWTP) with a design capacity of 580,000 PE. The characteristics of the treated wastewater from the WWTP are presented in Table 1.
Three types of aluminum-based coagulants were used in the research. The first one was inorganic aluminum sulfate (Al2(SO4)3). The rest are an aqueous solution of polyaluminum chloride: PAX—XL 19 F (Al—8.7%; Cl—5.7%; pH—4.1; d = 1.22 g/cm3) and PAX—XL 1911 (Al—11.45 %; Cl—7.61%; pH—3.92; d = 1.302 g/cm3). These coagulants were selected based on preliminary screening tests conducted prior to the main experiment. In the initial phase, a wide range of commercial coagulants were evaluated, including pDADMAC, PAX-XL 19H, PAX-XL 1910, PAX-XL 10, PAX-18, PAX-16, and PAX-XL 60. This preliminary study aimed to identify which coagulants, when applied at the lowest possible dose, could effectively reduce the turbidity of treated wastewater to below 1 NTU (see explanation in Section 2.2).
The final selection of Al2(SO4)3, PAX-XL 19F, and PAX-XL 1911 was guided not only by their turbidity reduction performance, but also by their practical relevance in municipal wastewater treatment systems and economical aspects. Their widespread use makes them representative of solutions already applied or easily adaptable in real-life facilities, increasing the applicability of the findings.

2.2. Methods

The treated wastewater was subjected to two types of coagulation: volumetric coagulation (VC) and surface coagulation (SC). These methods were selected due to their widespread application in water and wastewater management facilities and their documented effectiveness in removing, among other things, turbidity from water and treated wastewater. Each process was performed in triplicate with a different portion of treated wastewater used for each experiment (experiment 1, experiment 2, experiment 3). The volumetric coagulation process was carried out on a four-station coagulator, whose diagram is shown in Figure 1. The device is equipped with a system for regulating the rotational speed of the stirrers. Coagulation was carried out in beakers with an active volume of 2 L. At the beginning of the test, coagulant was added to the beakers in an amount corresponding to the following doses of Al: 1, 2, 4, and 8 mg/L. The fast (180 rpm) and slow (30 rpm) mixing times were 1 min and 30 min, respectively. After the coagulation process, the samples were subjected to sedimentation for 30 min. Then, the samples were filtered at a speed of 15 m/h through sand filters (filter diameter: 15 mm, filling height: 0.3 m). The sand used in the filter bed had a grain size in the range of 0.8–1.4 mm, and HRT was about 30 s. The first portion of the filtrate, corresponding to two volumes of the filtration column, was discarded. Samples obtained after discarding the filtrate were used for chemical analysis.
The surface coagulation process was carried out at a laboratory station (identical for each coagulant), the schematic diagram of which is shown in Figure 2. The main element of the station is a filter filled with a sand bed (filter diameter: 30 mm, filling height: 1.1 m) and a tank located above the filtration column. The sand used in the filter bed had a grain size in the range of 0.8–1.4 mm, and HRT was about 528 s. Before starting the filtration, coagulants were added to the wastewater in quantities corresponding to the following doses: 0.25, 0.50, 1.0, and 2.0 mg Al/L. Then, rapid mixing was carried out for 30 s. After this step, filtration was started immediately at a speed of 3 m/h. The first portion of the filtrate, corresponding to two volumes of the filtration column, was discarded. Samples obtained after discarding the initial filtrate were used for chemical analysis.
It was assumed that coagulation should allow achieving turbidity values below 1 NTU. This is important for effective disinfection because suspended particles in water act as a protective shield for microorganisms and provide substrate for bacteria growth. It is acknowledged that disinfection technologies such as ozonation, hydrogen peroxide, or hypochlorite can tolerate higher turbidity levels (up to 5–10 NTU), and even UV systems can function effectively at values around 5 NTU in some WWTPs. However, our study adopted a conservative threshold of 1 NTU, based on literature indicating that lower turbidity improves disinfection reliability, especially in variable wastewater conditions and when microbial risk is high [35].

2.3. Analytics

Samples of treated wastewater from the WWTP and those after coagulation processes were analyzed for content of the fertilizer components N, P, K and in terms of the content of organic (COD). P, K, and COD were determined using Hach Lange cuvette tests LCK 349, LCK 228 and LCI 500. Measurements were performed in a spectrophotometer DR3900 (Hach Lange, Loveland, CO, USA). N was measured on a Shimadzu TOC-L CSN total organic carbon analyzer (Kyoto, Japan) with a TNM-L total nitrogen determination device. Each determination was repeated three times. Turbidity of the samples was measured using a HACH Turbidimeter 2100P (Hach Lange, Loveland, CO, USA). The measurements of pH and conductivity were taken using an ELMETRON pH-meter CP-411 (Elmetron Sp. J., Zabrze, Poland) and an ELMETRON Conductivity-meter CPC-411 (Elmetron Sp. J., Zabrze, Poland), respectively.
N and P concentrations were determined for each of the analyzed doses of coagulants. The K concentration was determined for the lowest dose of coagulants that would provide a reduction in turbidity to 1 NTU.
The measurement errors for the applied analytical methods were ±2% for phosphorus and potassium using Hach cuvette tests and ±5% for total nitrogen using the TNM-L analyzer.

3. Results and Discussion

3.1. Changes in the Content of Fertilizer Ingredients, Salinity, and pH as a Result of Coagulation Processes

The characteristics of treated wastewater before and after coagulation processes in all three experiments are presented in the Supplementary Materials. Based on these results, reductions in N, P, and K were calculated for the analyzed coagulants and coagulation types, as shown in Figure 3, Figure 4, Figure 5 and Figure 6. In the case of potassium, as mentioned in Section 2.3. (Analytics), the studies were conducted only for the lowest doses, where a reduction in turbidity to the level of 1 NTU was achieved.
In both cases of volumetric coagulation and surface coagulation, a decrease in the concentration of the analyzed fertilizer components was observed with an increase in the coagulant dose.
Regardless of the type of coagulation and used dose, the highest reduction for nitrogen was caused by coagulants from the PAX group and the lowest by Al2(SO4)3 (Figure 3 and Figure 4). Furthermore, it was observed that higher reductions were achieved for surface coagulation. In the case of this coagulation, for PAX-type coagulants, the same dose resulted in comparable nitrogen reduction efficiencies (Figure 4). However, in the case of volumetric coagulation, a higher nitrogen reduction was achieved for PAX-XL 1911 (Figure 3). For example, at a dose of 1 mg Al/L, the reduction for Al2(SO4)3 was 4.9%, for PAX-XL 19F it was 3.5% higher, and for PAX-XL 1911 it was 8.7% higher. Moreover, observed reductions in total nitrogen concentrations in the case of Al2(SO4)3 were relatively small—below 10%. It can be considered that this coagulant does not significantly influence this indicator in both coagulation methods.
In contrast to nitrogen, for phosphorus, the greatest reduction in concentration for each analyzed dose was achieved by Al2(SO4)3, regardless of the coagulation type (Figure 5 and Figure 6), and higher reduction values were observed for volumetric coagulation. For example, at a dose of 1 mg Al/L (volumetric coagulation; Figure 5), the phosphorus reduction for PAX-XL 19F was 27.5%, for PAX-XL 1911 it was 3.5% higher, and for Al2(SO4)3 it was 13.6% higher. Furthermore, it can be observed that for the highest analyzed dose, 8 mg Al/L, the reduction values are similar, which may indicate that the type of coagulant has no significant effect on phosphorus reduction when higher coagulant doses are used.
As mentioned in the Methods section, effective disinfection aims to reduce turbidity to a level of 1 NTU. Taking this into account, potassium was analyzed in the samples where the turbidity was below 1 NTU. In all cases, this was noted for the lowest coagulant doses. For volumetric coagulation, this reduction was 5.31%, 1.01%, and 3.73% for Al2(SO4)3, PAX-XL 19F, and PAX-XL 1911, respectively. For surface coagulation, it was 16.41%, 8.59%, and 12.81%, respectively. Reductions in surface coagulation were greater, while the trend related to the amount of reduction was maintained in both types of coagulation; i.e., the largest reduction was observed for Al2(SO4)3 and the smallest for PAX-XL 19F.
The removal of soluble N and K compounds could be caused by adsorption [36]. However, it should be emphasized that when the removal efficiency is below 10%, such low reductions may fall within the limits of measurement error. An important factor determining the reduction of fertilizing properties was the type of coagulant. With the same dose of Al introduced using different types of coagulants, a wide range of percentage reductions in N, P, and K content was achieved. Regardless of the type of coagulation, in the case of P and K, the coagulant that caused the least reduction in the concentration of these nutrients was PAX-XL19F (volumetric coagulation at 1 mg Al/L: 27.5% for P, 1.0% for K, and at 0.25 mg Al/L for surface coagulation: 37.2% for P, 8.6% for K)—see Figure 5 and Figure 6 and results for K. In the case of N, the least reduction was observed for Al2(SO4)3 (volumetric coagulation at 1 mg Al/L—4.9%, and for surface coagulation at 0.25 mg Al/l—11.4%)—see Figure 3 and Figure 4. These studies indicate the validity of conducting such tests, which will take into account not only different doses of coagulants but also different types of them.
Another important factor in determining the use of reclaimed water for irrigation is its salinity (as indicated by electrical conductivity (EC)). Coagulation processes can affect salinity. In the case of perennial ryegrass (Lolium perenne), the salinity limit is 3700 µS/cm [37]. Salinity after coagulation processes changed only slightly, and in all the studies conducted, the range was between 1115 and 1354 µS/cm (depending on EC in treated wastewater; Supplementary Materials).
The addition of coagulant can change the pH of the recovered water. In our studies, even for the highest doses of Al, no significant decreases in this indicator were observed, and the lowest pH value was 7.23 (Table S1a in Supplementary Materials).

3.2. Analysis of Changes in Proportions and Coverage of Fertilizer Demand

Analysis of changes in proportions and coverage in fertilizer demand was carried out only for variants that, at the minimum coagulant dose, ensured the removal of turbidity below 1 NTU, as shown in Table 1 and Table 2.
It is worth noting that as a result of coagulation processes, the proportion of fertilizer ingredients N:P:K, expressed as a mass–volume concentration ratio, changes. According to the literature, in the case of grasses, the ideal proportion of these ingredients is 4:1:2. In the wastewater before the coagulation process, the ratio was 7:1:31. As a result of volumetric coagulation for Al2(SO4)3, PAX-XL 19F, and PAX-XL 1911, the ratios were 11:1:50, 8:1:40 and 8:1:41, respectively. As a result of surface coagulation, for analogous conditions, these ratios were 11:1:47, 9:1:45, and 9:1:48, respectively. The presented results of the N:P:K ratio coincide with the obtained reductions in the analyzed components; i.e., after the coagulation process, the share of potassium increases, which is reduced to the smallest extent as a result of the coagulation processes.
Another important aspect is the analysis of changes in coverage of the fertilizer demand for plants (using the example of grass) as a result of coagulation processes. Table 2 shows the coverage of the demand for fertilizer components for grass in the analyzed treated wastewater before and after coagulation processes for all analyzed coagulants. The calculations assumed water demand of 0.5–3.0 L/m2 and seasonal demand for nitrogen, phosphorus, and potassium of 2.4, 0.6, and 1.2 kg/100 m2, respectively, in accordance with the N:P:K ratio of 4:1:2. In Table 2, the smaller value in the range applies to calculations for demand of 0.5 L/m2, and the larger one applies to calculations for demand of 3.0 L/m2.
The calculations presented in Table 2 prove that treated wastewater can be a valuable source of fertilizer ingredients. In the case of nitrogen, the coverage of the annual nitrogen demand may range from 2.39–14.34%. As a result of preliminary processes (lowering concentrations), the nitrogen demand coverage decreased but remained at the level of 1.95–13.65%. Regarding phosphorus, the annual demand coverage in treated wastewater may amount to 1.43–8.55%. However, after coagulation processes, it can be expected to meet the demand within the range of 0.78–6.63%. The highest demand coverage was observed in the case of potassium.
There is no reference in the literature regarding the coverage of fertilization requirements for grasses. To compare the results of our own study with those of other researchers, considering the concentrations of N, P, and K obtained by other authors, the coverage of nutrient requirements for grass was calculated. The results are presented in Table 3.
It can be seen that the determined coverage of the demand for fertilizer components is very diverse. Nevertheless, similar to the authors’ results, the greatest coverage of the demand is observed for potassium. In the case of nitrogen and phosphorus, the demand depends on the quality of the reclaimed water. It is worth considering the possibility of changing the technological process of wastewater treatment in order to reduce the efficiency of removing biogenic compounds. In addition to increasing the fertilizing properties of the reclaimed water, this would have a beneficial effect on reducing the costs of wastewater treatment. However, this aspect requires further research.

4. Conclusions

  • The analyzed treated wastewater is characterized by low concentrations of fertilizing components. However, it can cover up to 14% of the N demand, 9% of the P demand, and even 133% of the K demand for grass irrigation.
  • Coagulation processes reduce the coverage of the fertilizing component demand. However, in the case of K, the recovered reclaimed water after the coagulation process can still fully meet the seasonal requirement for this macronutrient. Studies have shown that this coverage is, on average, 123%. In the case of N, the average coverage of the demand after coagulation is 13%. The lowest coverage of the demand, amounting to an average of 6%, was observed for P, which corresponds with its highest removal efficiency during coagulation.
  • A significant factor determining the decrease in fertilizing properties was the type of coagulant. In the case of P and K, the coagulant that caused the least reduction in the concentration of these nutrients was PAX-XL19F, and in the case of N, it was Al2(SO4)3, regardless of the type of coagulation and coagulant doses. This highlights the importance of selecting appropriate coagulants when nutrient retention is a priority in reclaimed water use.
  • The nutrient concentrations observed, particularly for potassium, could help reduce the need for synthetic fertilizers in grass irrigation. However, a detailed cost–benefit analysis was beyond the scope of this work and would require site-specific economic data, fertilizer pricing, and operational costs. Nonetheless, the findings demonstrate that aluminum-based coagulation—if carefully optimized—can improve effluent clarity while maintaining a degree of fertilizing potential.
  • Further research is needed to integrate coagulation with disinfection steps and assess their combined effects on both safety and nutrient content. Additionally, the possible use of alternative, less nutrient-binding coagulants (e.g., calcium, magnesium, iron, lanthanum-based) should be investigated in future work to optimize both treatment efficiency and fertilizing potential.
The presented study offers new insights into the relationship between coagulation strategy and nutrient retention in treated wastewater. By comparing different coagulants and their application modes, the research contributes to optimizing water reuse practices where preserving fertilizing value is a priority. The results may serve as a foundation for developing more sustainable approaches to wastewater reclamation in landscape and grass irrigation.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/w17131937/s1, File: Supplementary Materials-results of three experiments. Table S1a. The results of the volumetric coagulation—Experiment 1. Table S1b. The results of the surface coagulation—Experiment 1. Table S2a. The results of the volumetric coagulation—Experiment 2. Table S2b. The results of the surface coagulation—Experiment 2. Table S3a. The results of the volumetric coagulation—Experiment 3. Table S3b. The results of the surface coagulation—Experiment 3.

Author Contributions

Conceptualization, M.Ż.-S., J.C. and A.K.-B.; methodology, M.Ż.-S.; validation, M.Ż.-S., J.C. and A.K.-B.; formal analysis, J.C.; investigation, J.C. and A.K.-B.; data curation, J.C.; writing—original draft preparation, J.C.; writing—review and editing, M.Ż.-S.; visualization, J.C.; supervision, M.Ż.-S.; project administration, M.Ż.-S. All authors have read and agreed to the published version of the manuscript.

Funding

The paper was prepared as a part of the “ReNutriWater—Closing local water circuits by recirculation of nutrients and water and using them in nature” project financed by the European Regional Development Fund (ERDF), project no. #C016.

Data Availability Statement

I have shared my research data in the Supplementary Materials.

Acknowledgments

The research was carried out on devices cofunded by the Warsaw University of Technology within the Excellence Initiative: Research University (IDUB) program.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Gupta, A.D.; Pandey, P.; Feijóo, A.; Yaseen, Z.M.; Bokde, N.D. Smart Water Technology for Efficient Water Resource Management: A Review. Energies 2020, 13, 6268. [Google Scholar] [CrossRef]
  2. Wada, Y.; Flörke, M.; Hanasaki, N.; Eisner, S.; Fischer, G.; Tramberend, S.; Satoh, Y.; van Vliet, M.T.H.; Yillia, P.; Ringler, C.; et al. Modeling global water use for the 21st century: The Water Futures and Solutions (WFaS) initiative and its approaches. Geosci. Model Dev. 2016, 9, 175–222. [Google Scholar] [CrossRef]
  3. Rosegrant, M.W.; Cai, X.; Cline, S.A. World Water and Food to 2025: Dealing with Scarcity; International Food Policy Research Institute: Washington, DC, USA, 2022. [Google Scholar]
  4. Vörösmarty, C.J.; Green, P.; Salisbury, J.; Lammers, R.B. Global water resources: Vulnerability from climate change and population growth. Science 2000, 289, 284–288. [Google Scholar] [CrossRef] [PubMed]
  5. WWAP (World Water Assessment Programme). The United Nations World Water Development Report 2018: Nature-Based Solutions for Water (United Nations Educational, Scientific and Cultural Organization, New York, United States). Available online: www.unwater.org/publications/world-water-development-report-2018/ (accessed on 4 April 2025).
  6. Gospodarczyk, F.; Popów-Nowicka, A. Powierzchnie trawiaste w architekturze ogrodów. Archit. Kraj. 2006, 3-4, 70–73. (In Polish) [Google Scholar]
  7. Wagner, I.; Krauze, K.; Zalewski, M. Błękitne aspekty zielonej infrastruktury. Zrównoważony Rozw. –Zastos. 2013, 4, 145–155. (In Polish) [Google Scholar]
  8. Staniak, M.; Fariaszewska, A. STUDIA I RAPORTY IUNG-PIB. In Produktywność Traw Pastewnych w Warunkach Suszy. Instytut Uprawy Nawożenia i Gleboznawstawa; Państwowy Instytut Badawczy w Puławach: Puławy, Poland, 2014. (In Polish) [Google Scholar]
  9. Ntshidi, Z.; Dzikiti, S.; Mazvimavi, D.; Mobe, N.T.; Mkunyana, Y.P. Water use of selected cover crop species commonly grown in South African fruit orchards and their response to drought stress. Phys. Chem. Earth 2021, 124, 103070. [Google Scholar] [CrossRef]
  10. Kombo, O.; Sahare, H. Micro-irrigation of Lowering Crops in Protected Condition. IJCR. 2020, Volume 8. Available online: https://ijcrt.org/papers/IJCRT2012047.pdf (accessed on 22 April 2025).
  11. FAO (Food and Agriculture Organization of the United Nations). Save and Grow: A Policy Maker’s Guide to the Sustainable Intensification of the Smallholder Crop Production; FAO: Rome, Italiy, 2011; Available online: https://www.fao.org/family-farming/detail/en/c/328012/ (accessed on 15 April 2025).
  12. Burek, P.; Satoh, Y.; Fischer, G.; Kahil, M.T.; Scherzer, A.; Tramberend, S.; Nava, L.F.; Wada, Y.; Eisner, S.; Flörke, M.; et al. Water Futures and Solution-Fast Track Initiative (Final Report); IIASA: Laxenburg, Austria, 2016; Available online: https://pure.iiasa.ac.at/id/eprint/13008/ (accessed on 22 April 2025).
  13. Alexandratos, N.; Bruinsma, J. World Agriculture Towards 2030/2050: The 2012 Revision; ESA Working paper No. 12-03; Food and Agriculture Organization of the United Nations (FAO): Rome, Italiy, 2012; Available online: www.fao.org/docrep/016/ap106e/ap106e.pdf (accessed on 10 April 2025).
  14. Zhang, D.; Guo, P. Integrated agriculture water management optimization model for water saving potential analysis. Agric. Water Manag. 2016, 170, 5–19. [Google Scholar] [CrossRef]
  15. Smol, M.; Adam, C.; Kugler, S.A. Inventory of Polish municipal sewage sludge ash (SSA)–Mass flows, chemical composition, and phosphorus recovery potential. Waste Manag. 2020, 116, 31–39. [Google Scholar] [CrossRef]
  16. Bauer, S.; Linke, H.J.; Wagner, M. Combining industrial and urban water-reuse concepts for increasing the water resources in water-scarce regions. Water Environ. Res. 2020, 92, 1027–1041. [Google Scholar] [CrossRef]
  17. Ramm, K.; Smol, M. Water Reuse—Analysis of the Possibility of Using Reclaimed Water Depending on the Quality Class in the European Countries. Sustainability 2023, 15, 12781. [Google Scholar] [CrossRef]
  18. Smol, M. Circular Economy in Wastewater Treatment Plant—Water, Energy and Raw Materials Recovery. Energies 2023, 16, 3911. [Google Scholar] [CrossRef]
  19. Ramm, K. Considerations Related to the Application of the EU Water Reuse Regulation to the Production of Snow from Reclaimed Water. Circ. Econ. Sustain. 2021, 2, 569–587. [Google Scholar] [CrossRef]
  20. Toze, S. Resue of effluent water–benefits and risks. Agric. Water Manag. 2005, 80, 147–159. [Google Scholar] [CrossRef]
  21. Kesari, K.K.; Soni, R.; Jamal, Q.M.S.; Tripathi, P.; Lal, J.A.; Jha, N.K.; Siddiqui, M.H.; Kumar, P.; Tripathi, V.; Ruokolainen, J. Wastewater treatment and reuse: A review of its applications and health implications. Water Air Soil Pollut. 2021, 232, 1–28. [Google Scholar] [CrossRef]
  22. Patel, S.; Sahu, T.L.; Netam, N.; Paikra, M.S.; Nishad, D. Effect of macronutrients on establishment of Korean lawn grass (Zoysia japonica Steud.). Pharma Innov. 2022, 11, 2238–2241. [Google Scholar]
  23. Maathuis, F.J. Physiological functions of mineral macronutrients. Curr. Opin. Plant Biol. 2009, 12, 250–258. [Google Scholar] [CrossRef]
  24. Ahmad, I.; Asif, M.; Amjad, A.; Ahmad, S. Fertilization enhances growth, yield, and xanthophyll contents of marigold. Turk. J. Agric. For. 2011, 35, 641–648. [Google Scholar] [CrossRef]
  25. Fayaz, K.; Singh, D.; Singh, V.K.; Bashir, D.; Kuller, L.R. Effect of NPK on plant growth, flower quality and yield of gerbera (Gerbera jamesonii). Res. Environ. Life Sci. 2016, 9, 1361–1363. [Google Scholar]
  26. Rowland, J.H.; Cisar, J.L.; Snyder, G.H.; Sartain, J.B.; Wright, A.L. USGA ultradwarf bermudagrass putting green properties as affected by cultural practices. Agron. J. 2009, 101, 1565–1572. [Google Scholar] [CrossRef]
  27. Fahad, S.; Hussain, S.; Saud, S.; Hassan, S.; Tanveer, M.; Ihsan, M.Z.; Shah, A.N.; Ullah, A.; Nasrullah, K.F.; Ullah, S.; et al. A combined application of biochar and phosphorus alleviates heat-induced adversities on physiological, agronomical and quality attributes of rice. Plant Physiol. Biochem. 2016, 103, 191–198. [Google Scholar] [CrossRef]
  28. Ihtisham, M.; Fahad, S.; Luo, T.; Larkin, R.M.; Yin, S.; Chen, L. Optimization of nitrogen, phosphorus, and potassium fertilization rates for overseeded perennial ryegrass turf on dormant bermudagrass in a transitional climate. Front. Plant Sci. 2018, 9, 487. [Google Scholar] [CrossRef] [PubMed]
  29. Snyder, G.H.; Cisar, J.L. Nitrogen/potassium fertilization ratios for bermudagrass turf. Crop Sci. 2000, 40, 1719–1723. [Google Scholar] [CrossRef]
  30. Turner, T.R.; Hummel, N.W., Jr. Nutritional requirements and fertilization. Turfgrass 1992, 32, 385–439. [Google Scholar]
  31. Directive (EU) 2024/3019 of 27 November 2024 Concerning Urban Waste-Water Treatment. Available online: https://eur-lex.europa.eu/eli/dir/2024/3019/oj/eng (accessed on 15 April 2025).
  32. Gómez-Lucena, I.; Poyato, E.C.; García, I.M.; Draissi, K.F.; Rodríguez-Díaz, J.A. NITRINET: A predictive model for nitrification in reclaimed water distribution in pressurised irrigation networks. Agric. Water Manag. 2024, 302, 108982. [Google Scholar] [CrossRef]
  33. Zhao, P.; Ma, M.; Hu, Y.; Wu, W.; Xiao, J. Comparison of international standards for irrigation with reclaimed water. Agric. Water Manag. 2022, 274, 107974. [Google Scholar] [CrossRef]
  34. Rajendran, S.; Sai Bharadwaj, A.V.S.L.; Barmavatu, P.; Palani, G.; Trilaksanna, H.; Kannan, K.; Meenakshisundaram, N. A Review on Lanthanum-Based Materials for Phosphate Removal. ChemEngineering 2024, 8, 23. [Google Scholar] [CrossRef]
  35. Léziart, T.; Dutheil de la Rochere, P.M.; Cheswick, R.; Jarvis, P.; Nocker, A. Effect of turbidity on water disinfection by chlorination with the emphasis on humic acids and chalk. Environ. Technol. 2019, 40, 1734–1743. [Google Scholar] [CrossRef]
  36. Jathan, Y.; Marchand, E.A. Enhanced coagulation for removal of dissolved organic nitrogen in water: A review. Chemosphere 2024, 366, 143429. [Google Scholar] [CrossRef]
  37. FAO (Food and Agriculture Organization of the United Nations). Water Quality in Agriculture, 29 Rev 1. 1985. Available online: https://www.fao.org/4/t0234e/t0234e00.htm (accessed on 8 April 2025).
  38. Evanylo, G.; Ervin, E.; Zhang, X. Reclaimed Water for Turfgrass Irrigation. Water 2010, 2, 685–701. [Google Scholar] [CrossRef]
  39. Zalacain, D.; Martinez-Perez, S.; Bienes, R.; Garcia-Diaz, A.; Sastre-Merlin, A. Turfgrass biomass production and nutrient balance of an urban park irrigated with reclaimed water. Chemosphere 2019, 237, 124481. [Google Scholar] [CrossRef]
  40. Fan, J.; Hochmuth, G.; Kruse, J.; Sartain, J. Effects of Reclaimed Water Irrigation on Growth and Nitrogen Uptake of Turfgrass. HortTechnology 2014, 24, 565–574. [Google Scholar] [CrossRef]
  41. Chen, W.; Lu, S.; Pan, N.; Wang, Y.; Wu, L. Impact of reclaimed water irrigation on soil health in urban green areas. Chemosphere 2014, 119, 654–661. [Google Scholar] [CrossRef] [PubMed]
  42. Vergine, P.; Lonigro, A.; Salerno, C.; Rubino, P.; Berardi, G.; Pollice, A. Nutrient recovery and crop yield enhancement in irrigation with reclaimed wastewater: A case study. Urban Water J. 2017, 14, 325–330. [Google Scholar] [CrossRef]
  43. Gori, R.; Lubello, C.; Ferrini, F.; Nicese, F. Reclaimed municipal wastewater as source of water and nutrients for plant nurseries. Water Sci. Technol. 2004, 50, 69–75. [Google Scholar] [CrossRef]
Water 17 01937 g001
Figure 1. Diagram of a laboratory research stand and technological diagram for volumetric coagulation.
Figure 1. Diagram of a laboratory research stand and technological diagram for volumetric coagulation.
Water 17 01937 g001
Water 17 01937 g002
Figure 2. Laboratory research stand and technological diagram for surface coagulation.
Figure 2. Laboratory research stand and technological diagram for surface coagulation.
Water 17 01937 g002
Water 17 01937 g003
Figure 3. Nitrogen reduction in the volumetric coagulation process.
Figure 3. Nitrogen reduction in the volumetric coagulation process.
Water 17 01937 g003
Water 17 01937 g004
Figure 4. Nitrogen reduction in the surface coagulation process.
Figure 4. Nitrogen reduction in the surface coagulation process.
Water 17 01937 g004
Water 17 01937 g005
Figure 5. Phosphorus reduction in the volumetric coagulation process.
Figure 5. Phosphorus reduction in the volumetric coagulation process.
Water 17 01937 g005
Water 17 01937 g006
Figure 6. Phosphorus reduction in the surface coagulation process.
Figure 6. Phosphorus reduction in the surface coagulation process.
Water 17 01937 g006
Table 1. Characteristics of treated wastewater used in the research.
Table 1. Characteristics of treated wastewater used in the research.
ParameterUnitRange
TurbidityNTU2.07–2.31
Nitrogenmg/L6.51- 8.56
Phosphorus mg/L0.47–1.99
Potassiummg/L33.9–38.1
CODmg/L20.3–24.7
pH-7.35–7.43
Electrical conductivityµS/cm1160–1342
Table 2. Covering the demand for fertilizer ingredients designated for grass.
Table 2. Covering the demand for fertilizer ingredients designated for grass.
DesignationWWTP-Treated WastewaterWastewater After Coagulation
Al2(SO4)3PAX-XL 19 FPAX-XL 1911
VCSCVCSCVCSC
The amount of N supplied with water [kg/100m2]0.06–0.340.05–0.330.05–0.300.05–0.310.05–0.280.05–0.300.05–0.28
Covering the demand for N [%]2.39–14.342.27–13.652.11–12.652.19–13.111.95–11.672.06–12.371.93–11.57
The amount of P supplied with water [kg/100m2]0.01–0.050.01–0.030.00–0.030.01–0.040.01–0.030.01–0.040.00–0.03
Covering the demand for P [%]1.43–8.550.84–5.030.78–4.701.10–6.630.90–5.421.05–6.320.82–4.89
The amount of K supplied with water [kg/100m2]0.27–1.600.25–1.520.22–1.340.26–1.580.24–1.470.26–1.540.23–1.40
Covering the demand for K [%]22.23–133.3821.04–126.2518.56–111.3822.00–132.0020.35–122.1321.40–128.3819.40–116.38
Table 3. Estimated coverage of fertilizer ingredients for grass determined based on the quality of reclaimed water in studies by other authors.
Table 3. Estimated coverage of fertilizer ingredients for grass determined based on the quality of reclaimed water in studies by other authors.
No.Concentration in Reclaimed Water Based on the LiteratureReclaimed MethodSourceCovering the Demand Calculated by Authors *
N [mg/L]P [mg/L]K [mg/L]N [%]P [%]K [%]
120.37ndchlorination[38]0.63–3.750.46–2.78nd
215.000.9022.00nd[39]4.69–28.131.13–6.7513.75–82.50
33.311.9812.14nd[40]1.03–6.212.47–14.817.59–45.53
422.232.17ndnd[41]6.95–41.682.71–16.28nd
5nd4.60ndcoagulation + filtration + chlorination[42]nd5.75–34.50nd
6nd5.00ndgravity disk filter + UV radiation[42]nd6.25–37.50nd
7ndnd38.60sand filter + UV[43]ndnd24.13–144.75
Note: * The calculations were made based on the same assumptions used in our own research, as presented in Table 2. nd—no data.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Czajkowska, J.; Knap-Bałdyga, A.; Żubrowska-Sudoł, M. The Influence of Coagulation on the Fertilizing Properties of Treated Wastewater. Water 2025, 17, 1937. https://doi.org/10.3390/w17131937

AMA Style

Czajkowska J, Knap-Bałdyga A, Żubrowska-Sudoł M. The Influence of Coagulation on the Fertilizing Properties of Treated Wastewater. Water. 2025; 17(13):1937. https://doi.org/10.3390/w17131937

Chicago/Turabian Style

Czajkowska, Justyna, Alicja Knap-Bałdyga, and Monika Żubrowska-Sudoł. 2025. "The Influence of Coagulation on the Fertilizing Properties of Treated Wastewater" Water 17, no. 13: 1937. https://doi.org/10.3390/w17131937

APA Style

Czajkowska, J., Knap-Bałdyga, A., & Żubrowska-Sudoł, M. (2025). The Influence of Coagulation on the Fertilizing Properties of Treated Wastewater. Water, 17(13), 1937. https://doi.org/10.3390/w17131937

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop