Irrigation water quality from wastewater reuse or groundwater sources: bridging the water–nutrient–food nexus

Water scarcity is one of the significant global issues, affecting most countries and gradually steering some of them to ‘Day Zero’. It arises due to many reasons such as population explosion, urbanization and industrial development, climate crisis, inadequate preparedness, and improper management of resources. Many countries are unable to cope with the rising water demand due to these factors and the persistence of resource-intensive economic development (UN Water 2021). Water scarcity and climate change are intertwined, resulting in extreme weather events and making freshwater availability highly unpredictable. Improper planning and management of water resources indeed results in economic water scarcity and impedes the developmental activities of a nation (Liu & Liu 2021). It is necessary to have an inclusive and integrated water resources management strategy to forestall this finite resource leaving only its footprint for the future.

Sustainable agriculture is essential to address the present and future needs of the communities in terms of food security, livelihood and living standards (FAO). Under water-scarce conditions, agricultural activities and their sustainability are challenging as this sector uses more than 70% of available freshwater (Urbano et al. 2017). In a developing country like India, agriculture is the central pillar of the nation's economy. Moreover, it is vital to ensure the food and nutrition security of the entire population, 1.428 billion, of the nation. Hence, it is necessary to develop a priority axis to search and categorize alternate adaptations to ensure sustainable agriculture (Baanu et al. 2022).

Various adaptations have been identified to reduce the pressure on freshwater resources and to improve agricultural practices (Haghi et al. 2020). Among them, water reuse, i.e., the use of treated wastewater (TWW) or reclaimed water can be seen as a sustainable as well as potential adaptation. It can not only conserve freshwater resources but also prevent environmental pollution by minimizing untreated wastewater discharge. Indeed, TWW can be seen as a source of nutrient supplements (Pereira et al. 2012; Kesari et al. 2021). In a nutshell, water reuse can revitalize agriculture (Djillali et al. 2020; Poustie et al. 2020).

Several literature works related to water reuse for irrigation and its effects on crop growth and yield (Tsadilas & Vakalis 2003; Kang et al. 2007; Libutti et al. 2018; Djillali et al. 2020; Hashmat et al. 2021), physicochemical and microbial properties (Balkhair et al. 2014; Helaly et al. 2018; Petousi et al. 2019; Perulli et al. 2021), and heavy metal accumulation (Gupta et al. 2010; Ghosh et al. 2012; Yaseen et al. 2017; Aftab et al. 2023) were reported. Fortunately, most of the earlier studies were concluded by highlighting the benefits of water reuse: a raise in soil fertility; improvement in crop growth and yield; reduction in energy utilization; and decrease in greenhouse gas emission. Unfortunately, a few studies were concluded with the following paradoxical effects: an increase in soil salinity and consequent reduction in fertility; microbial contamination of soil and its presence in crops; accumulation of heavy metals in soil and crop.

The quality of TWW primarily depends on treatment methods and for this purpose several methods have been developed. These methods include primary and secondary units, and an optional tertiary treatment unit. Primary and secondary treatment processes use physical forces, chemical reactions or microbial actions to treat wastewater, but they produce lower-quality effluent than the methods which include tertiary units (Halakarni et al. 2021). Tertiary treatment methods such as adsorption (El-Bassi et al. 2021; Kim et al. 2022) and membrane processes (Samage et al. 2022; Halakarni et al. 2023a, 2023b) are proven to be more efficient (Mallige et al. 2021).

The research gaps identified in the domain of water reuse for agriculture are: (i) no disquisition on the effect of reclaimed water on seed germination; (ii) no report on dilution of TWW by blending it with freshwater and analysing the effect on crop growth and yield; (iii) only a very few studies on the nutritive analysis of vegetables or fruits when water reuse is adapted; (iv) no studies on quantitative analysis on nutrients supplement by TWW; and (v) no documentation on economic analysis of yield considering the fertilizer reduction cost and augmented benefits of water reuse.

The research objective of the study presented in this paper is to address the above-mentioned grey areas in the domain so as to foster water reuse for agriculture. Considering GW irrigation as the benchmark, the study focused on analysing the effect of reclaimed water irrigation on (i) seed germination; (ii) crop morphological characteristics; (iii) crop yield; (iv) nutritional values of the edible parts; (v) fertilizer reduction; and (vi) benefit–cost (B–C) analysis.

The study was conducted in Sivakasi taluk of Tamil Nadu state, India for a period of 9 months, from June 2022 to March 2023. The study area is located to the East of the Western ghats and is characterized as a flat terrain. Black soil and red soil are the predominant soil groups in the taluk. The taluk experiences a hot and dry climate throughout the year with low rainfall and a low degree of humidity. The chief irrigation source is groundwater (GW) and is under a critical zone due to overexploitation and scanty rainfall. The area is being chosen as it is straggling with water scarcity and decreased agricultural practices. It is gradually transforming into a drought-prone zone primarily due to the climate crisis. Before implementing a potential sustainable adaptation to curb the impact on agriculture, it is imperative to perform a detailed study to know the facts behind closed doors.

In the present study, water reuse is adapted as a supplement as well as a replacement for freshwater irrigation with a focus on the water–food–nutrient nexus approach. An experimental field is prepared and Lablab bean, tomato, and chilli are grown on it. These crops are selected because of their: (i) high intake in the daily diet; (ii) cultivation over a considerable percentage of the gross crop area of the taluk; and (iii) promising return monetary benefits. Each crop type is irrigated separately with GW, diluted treated wastewater (DTWW), and TWW in individual plots separately. The TWW for irrigation is taken from the decentralized sewage treatment plant (D-STP) of the institute, which is located in the Sivakasi taluk. The effects of different irrigation water quality on seed germination, crop morphological characteristics and nutritive values of the edible parts, reduction in fertilizer application and monetary benefits are analyzed. The outcome of the study brings to light that the irrigation water quality has a significant influence on seed germination, crop growth and yield, nutritional values of the edible parts and monetary benefits.

Rabi is the primary agricultural cropping season, in which cultivation spawns from late August to the mid of January. The major crops cultivated in the taluk are rain-fed crops – including maize, cotton, red gram, black gram, Bengal gram, cowpea and millet. In addition, horticultural crops – including mango, guava, banana, amla, beans, tomato, chilli, brinjal, okra, onion and coriander – and flowers – including jasmine, oleander, and tuberose – are also cultivated significantly.

Daily rainfall data and daily minimum and maximum temperature data of the Sivakasi taluk are collected from the Public Works Department (PWD) of Tamil Nadu state for a period of 30 years (1991–2021). These daily data values are summed and averaged to obtain monthly data.

Soil sampling and testing are essential to ascertain the presence of macro and micro nutrients in the soil. In that way, it is an important diagnostic tool for identifying suitable crops for cultivation as well as assessing the fertility of soil (Nguemezi et al. 2020; Suchitra & Pai 2020). Soil samples from the experimental field are collected as per the standard procedure and tested in the soil laboratory for its physicochemical characteristics: electrical conductivity (EC), pH, organic carbon, nitrogen (N), phosphorous (P), potassium (K), nitrate (⁠⁠), nitrite (⁠⁠), ammonia (⁠⁠), calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), manganese (Mg), zinc (Zn), copper (Cu), boron (B), lead (Pb), mercury (Hg), cadmium (Cd), nickel (Ni), and arsenic (As) (Klimkowicz-Pawlas et al. 2019; Du et al. 2022; Koné et al. 2022; Sdiri et al. 2023).

The physicochemical and microbial characteristics of water are required to quantify the macro and micronutrients available in it and to verify its suitability for irrigation. Thus, the characteristics of the GW, DTWW, and TWW are also analyzed. The physiochemical parameters – including EC, pH, total nitrogen, ⁠, ⁠, phosphate (⁠⁠), K, Ca, Mg, Na, chloride (⁠⁠), Fe, Mg, Zn, Cu, borate (⁠⁠), Pb, Hg, Cd, Ni, and As – are analyzed (Perulli et al. 2019; Djillali et al. 2020; Biswas et al. 2021; Appiah-Brempong et al. 2022; Licata et al. 2022). The presence of microbes, including Escherichia coli, Coliform and Salmonella, are considered for microbial characterization (Hajji et al. 2022; Ma et al. 2022). In order to verify the suitability of the GW, DTWW, and TWW for irrigation, the laboratory test results are compared against the Food and Agriculture Organization standards (FAO 1985).

The life of a plant begins with its successful seed germination and is followed by the growth of the seedling (Nonogaki et al. 2010; Rajjou et al. 2012). The physiological process – including imbibition of water, cell elongation, and increase in cell number – of seed germination primarily depends on favourable environmental conditions such as light, temperature, soil, and water (Wolny et al. 2018; Xue et al. 2021).

Water is a core element for seed germination; as a matter of fact, the process begins with water imbibition (Luna & Chamorro 2016). Also, water is essential for the enzymatic activities, transportation of the biological macromolecules and antioxidant defence system (Szczerba et al. 2021). Sluggish water could affect seed germination and subsequent crop growth and yield (Sghaier et al. 2022). Therefore, optimal quality as well as desired quantification of water is essential for successful seed germination. To address this, a comparative study is conducted to analyze the influence of the GW, DTWW, and TWW on seed germination of the crops considered for the study, Lablab bean, tomato, and chilli.

Crop morphology analysis encompasses the study of external features of a plant such as root length, stem diameter at the base, stem height, number of leaves, leaf area, number of fruits, and fruit size (Djillali et al. 2020). The stem diameter at the base, and pod and fruit diameter at the middle are measured using a digital slide vernier calipre (Hassan et al. 2022). The stem height, from the base to the tip of the stem, is measured using a measuring tape. Leaf area is measured using the graphical grid counting method (Datta & Chakroboarty 2018). Randomly five plants are selected from each experimental plot; their morphological characteristics are measured and averaged for comparison.

The crop edible parts are hand-harvested periodically. After a harvest, the number of bean pods/fruits and their mass are recorded for every experimental plot. Randomly chosen representative pods/fruits are analyzed in the laboratory for their nutritional values, anti-diabetic and antioxidant capacities, heavy metal accumulation, and microbial quality. The nutritional values include carbohydrates, protein, fat, energy, fibre, cholesterol, and vitamins and minerals (FSSAI 2016).

TWW is a rich source of plant nutrients and would be an incentive to farmers. It contains many macro and micronutrients required for crop growth and development (Hussain et al. 2002).

The efficiency of any project can be assessed by the B–C analysis. B–C analysis is useful to find a way to use limited resources with the most benefits out of them (Palmer & Torgerson 1999). B–C ratio (⁠⁠) (Equation (4)), a profitability index expressed in terms of monetary values, has been used for the B–C analysis (Zangeneh et al. 2008). The project is economically efficient if the benefit outweighs the cost (⁠⁠).

The topsoil layer is removed and the soil samples at the depth of 0–15 cm are taken from six different locations in the experimental field. The collected samples are thoroughly mixed and foreign materials like debris and stones are removed. Quartering and compartmentalization are done to obtain the desired quantity of representative soil samples for testing.

The test results reveal that the soil is fertile and suitable for agriculture (Table 1). The presence of heavy metals is within the permissible limits (Chary et al. 2008; Pramanik & Chakraborty 2014; Mawari et al. 2022). Lead content is relatively higher but still, its availability is within the permissible limit.

The GW, DTWW, and TWW which have been used for the irrigation of the experimental plots are sampled and tested; results are compared against the irrigation water standards and found that all are suitable for agriculture (Table 2). The concentrations of macro and micronutrients in the DTWW and TWW are higher than in the GW. They can be considered a good source of nutrients for crop growth and yield. The presence of sodium and chloride is significantly higher in the TWW. This can accelerate the salt accumulation in mains and laterals besides promoting microbial growth, so it is not suitable for micro-irrigation (Zaman et al. 2018; Zhangzhong et al. 2018). The availability of heavy metals and microbes is in trace amounts yet below their threshold limits.

For Lablab bean, root length and leaf area are lower for the crops irrigated with the DTWW than the GW; however, the stem height and number of leaves are greater for the DTWW. In case of tomato, all four parameters – root length, stem height, number of leaves, and leaf area – are higher for the crops irrigated with the DTWW than the GW. The growth rate of chilli more or less resembles the pattern of Lablab beans. However, chilli is more sensitive to the thermal stress induced by the polyhouse. Stunted growth, poor pollination, very little flowering, and drying and falling of flower buds are the results of the thermal stress and it remains unproductive until the end.

When compared to the GW and DTWW, the TWW has higher micronutrients as well as macronutrients. In fact, the presence of iron, zinc, copper, and boron in the TWW can eliminate the foliar spray application for feeding the micronutrients. The crop morphological characteristics lead to the conclusion that TWW irrigation provides more vital nutrients for crop growth and development; thereby considerably improving their morphological characteristics. Fortunately, plants irrigated with TWW are in good health condition; this is ensured by the absence of leaf and root diseases.

The harvesting started after 3 months of the sowing and planting for Lablab bean and tomato, respectively, and thereafter lasted for a period of 5 months, from October 2022 to February 2023. More than 20 pod/fruit pickings are done at an average interval of 3–5 days. For the Lablab bean, the total number of pods and cumulative mass yielded are significantly higher for the TWW irrigation than the other two (Table 3). On the other hand, for tomatoes, the crops irrigated with the DTWW produced a higher yield than the other two. This proves that the presence of higher macro and micronutrients in the reclaimed water significantly improves crop yield. Unfortunately, the yield from the TWW-irrigated tomato is even lower than the GW-irrigated crops. This manifests that TWW has some detrimental effects on yield in some types of crops. Interestingly, dilution works in a better way for this case. More importantly, crops irrigated with DTWW and TWW are able to produce higher yields than the GW irrigation in most cases, even when reduced quantities of fertilizers are applied for these fields.

There is no yield from the chilli plants grown in the polyhouse, hence, only the edible parts of Lablab bean and tomato are analyzed for their quality: nutrient values, vitamins and minerals, anti-diabetic and antioxidant capacities, and lycopene content in tomato (Table 4); heavy metal accumulation (Table 5); microbial quality (Table 6).

The majority of the vitamins and minerals are available in relatively higher levels in the edible parts of the crops, both Lablab bean and tomato, irrigated with the GW (Table 4). However, the availability of potassium is higher in the TWW-irrigated Lablab bean; magnesium is slightly higher in the TWW-irrigated tomato; copper is higher in the DTWW- and TWW-irrigated tomatoes (Figure 8). Like major nutrients, the reduction in vitamins and minerals, especially vitamins, is also relatively more in Lablab beans.

The anti-diabetic and antioxidant capacities are generally expressed in terms of Inhibitory Concentration (IC₅₀) values. IC₅₀ refers to the amount of drug required to suppress the biological process by half (Aykul & Hackert 2016). Anti-diabetic property is assessed using α-glucosidase inhibition activity and antioxidant capacity is assessed using α, α-diphenyl-β-picryl hydrazyl (DPPH) assay (Kedare & Singh 2011; Baliyan et al. 2022). A higher value of IC₅₀ represents a lower capacity and vice versa. The anti-diabetic and antioxidant capacities are more for the Lablab bean and tomato crops irrigated with the GW. When comparing the DTWW- and TWW-irrigated crops of Lablab bean and tomato, the capacities are more for the TWW-irrigated crops. Lycopene content, one of the potential natural antioxidants of tomato, is the primary reason for the brightest red colour and all of its positive health effects (Imran et al. 2020). It is assessed using the UV-Vis spectrophotometric method (Barba et al. 2006; FAO 2006; Alda et al. 2009). Tomato irrigated with the GW has the highest level of lycopene, followed by TWW and DTWW.

Accumulation of heavy metals except lead (only for the crops irrigated with TWW) is within the permissible limits of Indian standards for vegetables and fruits (Table 5). Lead content is significantly higher in Lablab beans and slightly higher in tomatoes than the allowable limit. Accumulation of heavy metals is higher in reclaimed water irrigation and the results are in agreement with the earlier studies (Gupta et al. 2010; Hussain & Qureshi 2020; Othman et al. 2021). In a nutshell, heavy metal accumulation is higher in TWW irrigation, followed by DTWW and GWW.

The microbial quality analysis reveals that the edible parts of the GW-irrigated crops are germ-free (Table 6). Whereas, Escherichia coli and Coliform make their presence in the TWW- and DTWW-irrigated Lablab bean and tomato. Unfortunately, their presence is more on DTWW-irrigated crops than the TWW-irrigated crops for both Lablab bean and tomato. This demands further research to bring out the logical reason. Fortunately, none of the crops contains Salmonella bacteria, a highly infectious disease-causing pathogen that affects human health.

The prime factor for the reduced nutritive values could be biotic stress resulting from the excess microbial activities. The microorganisms affect metabolic activities and induce physiological stress, ultimately impacting plant development (Perulli et al. 2021). Again, the presence of microorganisms in an edible part breaks down the components such as protein, carbohydrate, amino-acid, and sugar by excreting lytic enzymes, thereby altering the biochemical reactions (Tournas 2005). Also, the microorganisms break the plant cell wall by softening it and utilizing the starch, carbon sources, lipids, vitamins, and minerals for their survival development, which in turn reduces the nutritive values of the vegetables or fruits (Alegbeleye et al. 2018).

The physiochemical characteristics of the DTWW and TWW make it clear that they have more potential for supplementing the soil nutrient requirements when compared to the GW as they have relatively higher concentrations of macro and micronutrients (Table 2). When compared to the GW, excess N, P, and K available in DTWW are 14.7, 100 and 72.7%, respectively; TWW are 25.0, 400, and 100%, respectively. Iron is available in the DTWW and TWW but its availability is below the detectable limit in the GW. It is noteworthy that zinc, copper, and borates are available only in TWW.

The conventional fertilizer dose estimated for Lablab bean, tomato, and chilli are 10.0:15.0:7.5, 60.0:30.0:15.0, and 66.0:16.0:25.0, respectively. To meet these requirements, fertilizers, namely urea, Single Super Phosphate (SSP), and Muriate of Potash (MOP), are applied in the experimental field. The crops irrigated with GW are applied with a conventional dose of fertilization, and the dosage for the crops irrigated with the DTWW and TWW are curtained after accounting for the supplemental fertilizer availability (Baanu et al. 2022) in the reclaimed water (Table 7). The reduction in the requirement of N is significant, followed by a considerable reduction in K and a marginal reduction in P for all the crops.

When compared to GW irrigation, the use of DTWW and TWW for irrigation reduces the fertilizer cost significantly (Table 8). The reduction in fertilizer application not only reduces its cost but also could bring down the magnitude of fertilizer production and associated energy requirements and greenhouse gas emissions. Also, the use of reclaimed water for agriculture curtails the GW pumping and thereby conserves freshwater resources.

For the B–C analysis, income is calculated for the typical minimum (₹20 per kg) and maximum (₹40 per kg) market prices of Lablab bean and tomato (Table 9). The B–C analysis brings out that the ratio is highest for the TWW-irrigated Lablab bean, followed by the DTWW irrigation. The ratio for the maximum selling price is 1.5 times the value corresponding to the minimum selling price for Lablab bean. On the other hand, the yield is higher for the DTWW-irrigated tomato and thereby the ratio is also highest for it. The ratio for the maximum selling price is twofold the value of the minimum selling price for tomatoes. Relatively, tomatoes yield better monetary benefits than the Lablab beans.

Table 9

Benefit–cost analysis

Cost of cultivation per hectare .	Lablab beans .			Tomato .
	GW .	DTWW .	TWW .	GW .	DTWW .	TWW .
	₹ .	₹ .	₹ .	₹ .	₹ .	₹ .
Field preparation	6,000	6,000	6,000	6,000	6,000	6,000
Sowing/Nursery	7,000	7,000	7,000	7,000	7,000	7,000
Weeding	10,000	10,000	10,000	10,000	10,000	10,000
Plant protection	12,000	12,000	12,000	12,000	12,000	12,000
Fertilizers	6,000	4,500	4,320	8,000	4,800	4,640
Wages	5,000	5,000	5,000	13,000	13,000	13,000
Miscellaneous	5,000	5,000	5,000	5,000	5,000	5,000
Total	51,000	49,500	49,320	61,000	57,800	57,640
Benefit (per hectare)
Yield from experimental plot (g)	2,673	2,727	7,098	12,999	14,073	10,064
Projected yield per hectare (kg)	3,605	3,678	9,573	17,531	18,980	13,573
Selling price @ ₹ 40/kg	108,150	110,334	287,185	701,253	759,191	542,919
Selling price @ ₹ 20/kg	72,100	73,556	191,457	350,626	379,596	271,460
for maximum market price	2.12	2.23	5.82	11.50	13.13	9.42
for minimum market price	1.41	1.49	3.88	5.75	6.57	4.71

Cost of cultivation per hectare .	Lablab beans .			Tomato .
	GW .	DTWW .	TWW .	GW .	DTWW .	TWW .
	₹ .	₹ .	₹ .	₹ .	₹ .	₹ .
Field preparation	6,000	6,000	6,000	6,000	6,000	6,000
Sowing/Nursery	7,000	7,000	7,000	7,000	7,000	7,000
Weeding	10,000	10,000	10,000	10,000	10,000	10,000
Plant protection	12,000	12,000	12,000	12,000	12,000	12,000
Fertilizers	6,000	4,500	4,320	8,000	4,800	4,640
Wages	5,000	5,000	5,000	13,000	13,000	13,000
Miscellaneous	5,000	5,000	5,000	5,000	5,000	5,000
Total	51,000	49,500	49,320	61,000	57,800	57,640
Benefit (per hectare)
Yield from experimental plot (g)	2,673	2,727	7,098	12,999	14,073	10,064
Projected yield per hectare (kg)	3,605	3,678	9,573	17,531	18,980	13,573
Selling price @ ₹ 40/kg	108,150	110,334	287,185	701,253	759,191	542,919
Selling price @ ₹ 20/kg	72,100	73,556	191,457	350,626	379,596	271,460
for maximum market price	2.12	2.23	5.82	11.50	13.13	9.42
for minimum market price	1.41	1.49	3.88	5.75	6.57	4.71

₹, Indian rupees.

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In fact, even if the ratio for TWW irrigation is less than freshwater irrigation, its value is greater than one, so water reuse for irrigation can be considered as a successful adaptation. This is because water reuse reduces the existing pressure on freshwater resources; water reuse makes agriculture possible in an area where otherwise it would be abandoned due to the unavailability of water.

This paper presented an experimental field study focusing on the effect of water reuse, i.e., the use of reclaimed water on three crops, namely Lablab bean, tomato, and chilli in a polyhouse experimental field. For the study, three types of irrigation were used: GW, TWW, and DTWW (50% GW and 50% TWW). The specific outcomes of the research objective are as follows:

• The seed germination is fastest when it is watered with the DTWW, followed by the TWW and GW watering. The high salinity of the TWW and the low nutrient concentration of the GW would be the reason for the slower germination. Thus, DTWW is recommended for seed germination; however, the optimal mixing ratio of GW and TWW for dilution may vary for different crop types and soil conditions. Further study shall be devoted to this area to arrive at the optimal blending ratio for a particular scenario.

• The crop morphological characteristics – root length, stem height, number of leaves, and leaf area – were maximum for the crops – Lablab bean, tomato, and chilli – irrigated with the TWW. However, the size of the Lablab bean pods and tomato fruits neither increased nor decreased when using the reclaimed water, both DTWW and TWW irrigation.

• The TWW-irrigated Lablab bean was able to produce about 2.7 times the yield of the GW-irrigated crops but the increase is meagre in the DTWW-irrigated crops. On the other hand, DTWW-irrigated tomatoes produced about 1.1 times the yield of the GW-irrigated crops and indeed the TWW-irrigated crop yield is the least. This output highlights the need for optimal blending of GW and TWW for higher yields of certain crops. Further study shall be devoted to addressing this issue as well.

• Concerning the nutritive values of the edible parts of the crops, both DTWW and TWW irrigation could not reach the corresponding values associated with the GW-irrigated crops. This would be due to the biotic stressors, the presence of microorganisms, in the edible parts. The marginal presence of microorganisms in the pods and fruits of the DTWW- and TWW-irrigated crops would not pose any serious health risk to the consumers, but it is necessary to prevent the raw consumption of such edible parts and is required to be boiled.

Analyses on crop yield and nutritional values of the edible parts lead to a conclusion that a greater number of studies have to be done with different – including crop types, soil types and TWW quality – conditions with a prime focus on nutritional values as well as yield. One has to choose crops that can produce high yields without losing the nutrient values much when using reclaimed water for irrigation. The farmers may be interested in the crops which yield more when using the reclaimed water but the government has to take initiatives to develop frameworks in order to ensure the nutritional security of the people.

• The reduction in fertilizer quantity for the DTWW- and TWW-irrigated crops was done after accounting for the N, P, and K values available in the reclaimed water. The N fertilizer reduction is the maximum while the reduction in P is the minimum. Thus, reduced dosage of fertilizer application by careful accounting of the fertilizer supplement available in the reclaimed water is recommended for water reuse agriculture.

• The B–C analysis brought out that the use of TWW for the irrigation of crops would be an alternative and sustainable adaptation to combat climate crises in water-scarce regions with a high B–C ratio neglecting the associated energy cost.

This research throws light on the fact that the quality of irrigation water plays a pivotal role in agricultural productivity in terms of food and nutritional values. This water–nutrient–food nexus approach shall be disseminated by highlighting the need for resource recovery, promoting food security, and creating awareness of nutrient availability to mitigate the climate crisis. These three factors ultimately contribute towards the achievement of Sustainable Development Goals (SDGs), especially SDGs 2 and 6. However, it is imperative that water reuse for agriculture must be subjected to varietal assessments as well as periodic monitoring in order to avoid any possible health hazards. Furthermore, good agronomic practices are also essential, to ensure the triple bottom line of sustainability: social, environmental, and economic development.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.