Treated Wastewater Irrigation Research Articles

Influence of decades-long irrigation with secondary treated wastewater on soil microbial diversity, resistome dynamics, and antibiotrophy development

In arid and semi-arid regions, the use of treated wastewater (TWW) for irrigation is gaining ground to alleviate pressure on natural water sources. Despite said treatment, the existing methods fail to eliminate potentially dangerous contaminants. As such, this study assessed the impact of long-term TWW irrigation (5 and 25 years) on soil physicochemical properties and bacterial resistance to heavy metals (Pb, Cu, Cd) and antibiotics (tetracycline and amoxicillin). The results revealed heightened salinity and conductivity and reduced pH in irrigated soils. TWW induces harmful effects by reducing microbial density and size, leading to the disappearance of sensitive populations. Conversely, resilient populations, which mainly utilize antibiotics as a carbon source, have adapted. Metagenomic 16S amplicon sequencing analysis demonstrated a shift, notably reducing Actinobacteria, Bacteroidetes, and Firmicutes while increasing Acidobacteriota and Patescibacteria in treated soils. Operational Taxonomic Units affiliated with either Halomonadacea, or Saccharimonadacea and Vicinamibacteracea, were defined as indicators of the absence or presence of TWW contamination, respectively. We conclude that TWW irrigation significantly increases bacterial resistance to heavy metals, whereas the impact of antibiotics is nuanced, with antibiotrophy leveraging lower concentrations in treated soils.

Comparative High-Throughput Sequencing Analysis of the Bacterial Community Associated with the Rhizosphere of Date Palm (Phoenix dactyllifera L.) Irrigated with Treated Wastewater and Groundwater

Water scarcity is a major agricultural issue in most arid and semi-arid regions of the world. Alternative water supplies, such as the reuse of wastewater for agricultural irrigation, have been introduced. However, little is known about their impact on the soil and rhizosphere microbiomes that receive irrigation. Therefore, this work evaluates the impact of treated wastewater (TWW) irrigation on the soil and rhizosphere bacterial communities of date palms in Al Madinah, Saudi Arabia. In this study, metagenomic DNA from the rhizosphere of the date palm was sequenced using Illumina high-throughput sequencing. According to the observed OTUs, Chao1 richness estimations, and Shannon diversity values, soils from groundwater-irrigated date palms showed higher microbial diversity than did soils from TWW-irrigated date palms. A total of 569 OTUs were generated; most of them (97.3%) were assigned into 15 different phyla, whereas 2.7% were marked as unclassified. DNA sequence analysis of the WWT-irrigated rhizosphere showed that the most abundant phyla were Firmicutes (43.6%), Bacteroidetes (17.3%), Proteobacteria (15.2%), and Actinobacteria (14.6%), representing more than 90.7% of the total community, while the soil of the rhizosphere irrigated with GW was dominated by Actinobacteria (44.1%), Proteobacteria (23.4%), Firmicutes (15.5%), and Gemmatimonadetes (4.9%). The most frequently observed species in the two soils were also different. The dominant species in TWW-irrigated soil was Planococcus plakortidis, which is prevalent in saline and moderately saline habitats and can play an important ecological role. The GW-irrigated rhizosphere exhibited higher levels of biocontrol bacteria, particularly Nocardioides mesophilus. These results provide a comprehensive understanding and insights into the population dynamics and microbiome of date palm rhizosphere. The findings show that the irrigation water quality has a significant impact on the microbiome composition. Identifying the microbial diversity is the first step toward determining the best way to use TWW in irrigation.

Cost-benefit analysis of an irrigation unit with treated wastewater in Chihuahua, Mexico

The reuse of water in agriculture is an alternative to guarantee food security in Mexico and efficient management of this resource. The objective was to conduct an economic evaluation by benefit-cost analysis in an irrigation district of treated wastewater (TWW) in Tabalaopa-Aldama, Chihuahua, Mexico. The cost-benefit methodology was used to estimate the economic assessment of public projects. The results indicated that the project operation would obtain a net social value of $1,054.4 million, a social return intern fee of 31.19 %, and a cost-benefit relation of 2.48. Even if the costs and benefits increase by up to 30 %, the project would still be economically viable and provide social benefits. The start-up of a TWW irrigation district will generate economic benefits for society and promote the reduction of environmental impact on the agricultural land in Tabalaopa, Aldama, Chihuahua, Mexico.

Biofertilizer development for wheat growth improvement under drought stress and treated wastewater irrigation

Biofertilizer development for wheat growth improvement under drought stress and treated wastewater irrigation

Impact of Drip Irrigation with Recycled Wastewater on Aromatic Compound Composition in Capia Pepper (Capsicum annum L.)

In recent years, treating and reusing polluted water for agricultural irrigation has become essential to ensuring water and food sustainability. In addition to the factors affecting human health in vegetables and fruits irrigated with treated wastewater, factors affecting consumer preferences, such as flavor and phenolic compounds, should also be examined. This study investigates the effect of treated wastewater irrigation on the aromatic compounds and phenolic composition of capia pepper, which holds a significant position and is extensively used in various food products in the food industry. Drip irrigation with treated and untreated wastewater from the Kalecik Wastewater Treatment Plant was applied to two pepper varieties in the Kalecik district of Ankara, Türkiye. This research found that wastewater irrigation impacted certain aroma components, including para-dichlorobenzene, alpha-cubebene, hexanoate, alpha-farnesene, limonene, isoamyl butyrate, squalene, and alpha-copaene, which contribute to the distinct aroma and fragrance of capia peppers. Total phenolic content, pH, and soluble solids were found to be high in peppers irrigated with wastewater, and it was observed that these parameters increased as the treatment levels of the wastewater decreased. The highest results were obtained in capia peppers irrigated with wastewater. Results indicate that heavy metal levels in peppers align with permissible limits, confirming the usability of both water sources. In the face of global water scarcity and the challenge of feeding an ever-growing population, studies like this offer valuable insights into sustainable and well-informed agricultural practices.

Phytoremediation ability of Panicum maximum and Salicornia europaea irrigated with treated wastewater for salt elements in the soil

Soil salinity is one of the major problems that threaten the soils in Jordan, which led to a decrease in the percentage of arable land in Jordan. The phytoremediation process is concerned with the restoration of contaminated soils using tolerant plants, such as halophyte plants. In this context, the potential short-term phytoremediation ability of Panicum Mombasa and Salicornia Europaea was evaluated and measured. A field experiment was conducted over two consecutive years to study the ability of these previous two crops for the phytoremediation of saline soils induced by treated wastewater irrigation. Both crops with bare soil as a control were irrigated together from the effluent of the Ramtha Wastewater Treatment Plant at the same time. Soil electrical conductivity was identified as the main parameter for measuring the plant’s ability for salt absorption. The results for both seasons show a higher accumulation of salts in bare soil significantly as expected since no plants were present to absorb these salts and no leaching requirements were added with irrigation water. The absorption rate for each crop was measured at the 1st season for comparison. It is measured for each crop depending on the length of the growing season. Salicornia’s absorption rate was greater than Panicum, and it reached 36 ppm/day for salicornia, whereas it reached 33 ppm/day for panicum. In the 2nd season, both crops are planted and harvested together. Salt absorbed percentage from the soil under Salicornia was greater than Panicum and it reached 73 % as compared to bare soil. However, in the soils under Panicum, the amount of salts absorbed reached 37 % as compared to bare soil. Plant analysis for both crops shows higher salt ions accumulation in Salicornia tissues than Panicum, and this explains the higher absorption rate for Salicornia than Panicum. Microbiological analysis for Panicum shows some contamination, whereas no contamination occurs in Salicornia. This is explained by the high salinity environment in Salicornia which is not favorable for e-coil, total, and fecal coliform to grow. The obtained Results from this research state that both crops have the ability for phytoremediation, with greater ability for Salicornia.

Suitability of treated wastewater for irrigation and its impact on groundwater resources in arid coastal regions: Insights for water resources sustainability

Water scarcity threatens agriculture and food security in arid regions like Saudi Arabia. The nation produces significant quantities of municipal wastewater, which, with adequate treatment, could serve as an alternative water source for irrigation, thereby reducing reliance on fossil and non-renewable groundwater. This study assessed the appropriateness of using treated wastewater (TWW) for irrigation in a dry coastal agricultural region in Eastern Saudi Arabia and its impact on groundwater resources. Field investigations were conducted in Qatif to collect water samples and field measurements. A multi-criteria approach was applied to evaluate the TWW's suitability for irrigation, including complying with Saudi Standards, the Irrigation Water Quality Index (IWQI), the National Sanitation Foundation water quality index (NSFWQI), and the individual irrigation indices. In addition, the impact of TWW on groundwater was assessed through hydrogeological and isotope approaches. The results indicate that the use of TWW in the study area complied with the Saudi reuse guidelines except for nitrate, aluminum, and molybdenum. However, irrigation water quality indices classify TWW as having limitations that necessitate the use for salt-tolerant crops on permeable and well-drained soils. Stable isotopic analysis (δ2H, δ18O) revealed that long-term irrigation with TWW affected the shallow aquifer, while deep aquifers were minimally impacted due to the presence of aquitard layer. The application of TWW irrigation has successfully maintained groundwater sustainability in the study area, as evidenced by increased groundwater levels up to 2.3 m. Although TWW contributes to crop productivity, long term agricultural sustainability could be enhanced by improving effluent quality, regulating irrigation practices, implementing buffer zones, and monitoring shallow groundwater. An integrated approach that combines advanced wastewater treatment methods, community involvement, regulatory oversight, and targeted monitoring is recommended to be implemented.

Alternating water sources to minimize contaminant accumulation in food plants from treated wastewater irrigation

The use of treated wastewater (TWW) for agricultural irrigation is a critical measure in advancing sustainable water management and agricultural production. However, TWW irrigation in agriculture serves as a conduit to introduce many contaminants of emerging concern (CECs) into the soil-plant-food continuum, posing potential environmental and human health risks. Currently, there are few practical options to mitigate the potential risk while promoting the safe reuse of TWW. In this greenhouse study, the accumulation of 11 commonly occurring CECs was evaluated in three vegetables (radish, lettuce, and tomato) subjected to two different irrigation schemes: whole-season irrigation with CEC-spiked water (FULL), and half-season irrigation with CEC-spiked water, followed by irrigation with clean water for the remaining season (HALF). Significant decreases (57.0–99.8 %, p < 0.05) in the accumulation of meprobamate, carbamazepine, PFBS, PFBA, and PFHxA in edible tissues were found for the HALF treatment with the alternating irrigation scheme. The CEC accumulation reduction was attributed to reduced chemical input, soil degradation, plant metabolism, and plant growth dilution. The structural equation modeling showed that this mitigation strategy was particularly effective for CECs with a high bioaccumulation potential and short half-life in soil, while less effective for those that are more persistent. The study findings demonstrate the effectiveness of this simple and on-farm applicable management strategy that can be used to minimize the potential contamination of food crops from the use of TWW and other marginal water sources in agriculture, while promoting safe reuse and contributing to environmental sustainability.

Changes in soil hydraulic and physio-chemical properties under treated wastewater irrigation: A meta-analysis

Treated wastewater (TWW) is increasingly used for irrigation, but its higher salt content compared to conventional water sources can induce soil salinization and sodification. This, in turn, may result in structural degradation and deterioration of soil hydraulic properties. The practice of using TWW for irrigation is not new, and it has long been applied in arid countries, with limited other water resources, while in recent years it is also getting used elsewhere given the worldwide influence on water resources. However, comparing and extrapolating results from existing studies on the use of TWW for irrigation is challenging due to the heterogeneity between experimental setups in terms of water quality, irrigation techniques applied, and pedo-climatic conditions. To explore the effect of TWW quality on soil hydraulic and physio-chemical following TWW irrigation and to examine to what extent these effects are soil type dependent, we compiled a database with results from 24 peer-reviewed studies across different soil types containing information on the link between TWW irrigation, and hydraulic and physio-chemical properties through various measurements. The meta-analysis revealed that application of TWW significantly increases sodium adsorption ratio (on average 71 ± 6%) and electrical conductivity (on average 51 ± 5%) of soil as compared to the use of conventional water source. Overall, there were no significant effects on the soil pore space (bulk density, soil total porosity) or pH. Interestingly, the application of TWW significantly increased soil organic carbon and aggregate stability, potentially even benefiting soil structure. In addition, the organic compounds in TWW also might lead to hydrophobicity. Yet, the effects of TWW on soil hydraulic and physio-chemical properties are not consistent across different TWW types and soil classes. A larger number of studies is required to draw sound conclusions on this topic. Anyway, this analysis already indicated that different soil textures might react differently to TWW irrigation. While in medium-textured soils, salt accumulation was observed and TWW significantly increased soil organic carbon and saturated hydraulic conductivity, fine-textured soils are more prone to clogging and reduced in saturated hydraulic conductivity. We also noticed an impact of the type of TWW, since the degree of treatment has a big impact on the remaining components added to the soils together with the water. Primary TWW, from which settleable and floatable solids are removed, resulted in the highest accumulation of salts and significantly increased soil organic carbon and improved soil aggregate stability. However, the elevated biochemical oxygen demand or chemical oxygen demand in this type of TWW leads to an accumulation of organic materials in the soil, negatively affecting its permeability and reducing soil saturated hydraulic conductivity. This study stresses the need for more standardized experiments quantifying the effect of TWW not only in terms of transfer of contaminants and biosafety, but also an effect on soil quality, and more specifically soil physical quality, especially at the longer term.

The impact of treated wastewater irrigation on strawberry development, fruit quality parameters, and microbial and chemical contaminant transfer: A health risk assessment

The reuse of treated wastewater (TWW) in agriculture is an important alternative technology for reducing freshwater demand and improving soil physicochemical and biological properties. According to the Jordanian national water policy for 2023–2040, freshwater allocated for irrigation in Jordan's agriculture will be decreased and replaced with TWW. The purpose of this study was to investigate how irrigation with TWW influenced strawberry performance as a model for annual plants, namely, the impact on soil, plants, productivity, heavy metals and microbial contamination. Strawberry plants were irrigated with TWW, surface water (SW), and blended water (BW), as contrasted to domestic tap water (DW). Irrigation with TWW, SW, and BW raised the electrical conductivity, total organic compounds%, total nitrogen%, P, and K in the substrate; the rise in salinity, which is one of the most important abiotic stresses, was related to Cl buildup in the substrates, which has a detrimental influence on plant growth, development, and productivity. The heavy metal hazard index values in strawberry fruits were less than one in all treatments, suggesting that the heavy metal level in strawberry fruits did not exceed the requirement for health protection from serious risk. However, microbial contamination by fecal bacteria such as Escherichia coli and Enterococci spp. and human pathogens such as Pseudomonas aeruginosa, Salmonella spp., and Staphylococcus spp. increased by TWW irrigation, for example E. coli population increased from 1.8 × 102 in DW-irrigated fruits to 2.8 × 103 colony forming unit per gram in TWW-irrigated fruits, which may pose health risks. Accordingly, it is possible to conclude that TWW, SW, and BW can be used to irrigate strawberries, but it must be washed before consumption.

Utilizing treated wastewater for pasture irrigation: Effects on productivity, plant community structure and soil properties

AbstractSurplus wastewater accumulates in winter and requires a discharging solution. In our study we examined the effects of using treated wastewater (TWW) as supplemental pasture irrigation in winter. To test the effect of TWW irrigation on the vegetation and soil, 10 grazing prevention exclosures were established at Ramat‐Hanadiv Park, Israel, with half of them irrigated with TWW. Soil and vegetation were sampled during 2 years of irrigation and 1 year after cessation of irrigation. Vegetation composition, species richness, and productivity were sampled at the peak of the growing season and various indices of herbage quality were measured. Our results show that irrigation with wastewater increased herbage production by an average of 38% and total pasture protein production by 9% relative to the control subplots. Conversely, TWW irrigation decreased plant protein content while increasing herbage fibre content and lowering its digestibility. Over a period of 2 years, species richness decreased in the irrigated subplots. Most of the soil indices examined were not affected by irrigation, but in the irrigation subplots, sodium values and the sodium adsorption‐ratio were higher than in areas without irrigation. Additional resources in winter enabled the plants to grow rapidly and increased interplant competition. Changes in vegetation composition were revealed through functional group reshuffling and species richness decline. The results of our study show that wastewater irrigation causes an increase in productivity but a decrease in forage quality. At the pastoral system level, the significant increase in productivity leads to increased availability of protein and herbage for animals.

Effect of treated wastewater irrigation on ornamental plants: Case study of Lantana and Hibiscus, Morocco

AbstractIn water stressed countries such as Morocco, the use of treated wastewater represents a strategic perspective for sustainable agricultural development. However, technological and management innovations are needed to make it feasible and effective. The main objective of this work is to evaluate the effect of irrigation with treated wastewater compared with fresh water on the growth of two ornamental plants: Rosa Sinensis hibiscus and Lantana Camara. The study also aimed to examine the impact of treated wastewater on the hydraulic performance of different irrigation systems. To carry out this study, irrigation was applied by two irrigation systems: subsurface drip irrigation and surface drip irrigation. Also, two sources of water were compared: treated wastewater from the WWTP of M'zar (tertiary treatment) and well water, each for a duration of 2 months. The results obtained showed that the treated wastewater generally promoted a better development of agronomic parameters such as height, number of branches, leaves, and flowers for both plants. The same observation was also made regarding the esthetical parameter. For the irrigation system effect, the results obtained showed a better development under the subsurface drip irrigation system; thus, the combination of treated wastewater and subsurface drip irrigation provided the best results for both plants. Regarding the hydraulic performance of the irrigation system, no risk of clogging of the distributors was observed in relation to the water quality; the uniformity coefficient and distribution uniformity remained above 90%. It can therefore be deduced that the use of treated wastewater for irrigation of green spaces should be at the heart of water resource mobilization policies. in fact, it represents an excellent alternative for promoting national water management strategies.

Optimizing nutrients from fly ash-amended soil through microbial-assisted phytoremediation using response surface methodology.

Nutrients are vital ingredients to boost plant health. The availability of nutrients is limited in fly ash (FA) waste to properly implement phytoremediation. The research explored the integration of microbes and treated wastewater irrigation in phytoremediation to provide the necessary nutrients for plant growth in fly ash-amended soils. The Box-Behnken method was used to design the experimental layout for the pot study. Response surface methodology (RSM) was applied as the optimization approach to model predictions for nutrient accumulation. The implemented pot study attained the highest morphological indicators with a plastochron index of 33.40, an absolute growth rate of 2.63 cm/day, and a leaf area of 2681.68 cm2 and attained maximum biomass of 24.91 g for the treatments that included a mid-range of the variables. The combination of FA 14.98%, microbial dose 4.07 mL, and treated wastewater as the irrigation source was found to be the optimized combination for nitrogen and phosphorus accumulation of 212.4 and 8.867 mg/L.

Growers' irrigation practices, knowledge, trust, and attitudes toward wastewater reuse in Lebanon, Jordan, and Tunisia through a food safety lens

Abstract Maximizing water reuse requires addressing legal and regulatory frameworks, but growers’ understanding of water as a vehicle for pollutants and safe practices is vital in this process. A cross-sectional survey of 85 growers in Lebanon, Jordan, and Tunisia explored these factors. Results showed that 70.6% of growers had limited knowledge about the transmission of pathogens, pesticides, and pharmaceuticals to food crops via treated wastewater (TWW). Additionally, 55% of farmers used TWW for irrigation, while 65.9% believed that it poses health risks to consumers when applied to crops eaten raw. A positive attitude toward TWW was a determining factor for maximizing water reuse applications. However, the limited access and unavailability of treatment plants were the primary reasons for not using TWW (32.9%). More concerning, less than half controlled the quality of irrigation water using microbiological tests (32.9%), chemical tests (37.6%), and turbidity tests (29.4%). Meanwhile, only 40% trusted local authorities’ control of TWW quality and 69.4% had no access to regulatory information. The present study showed the importance of prioritizing growers’ awareness of potential risks and establishing the practice of monitoring of water quality indicators and contaminants. These should be at the forefront of water reuse expansion strategies to mitigate associated risks.

Combination of intercropping maize and soybean with root exudate additions reduces metal mobility in soil-plant system under wastewater irrigation

The effects of root exudates and irrigation with treated wastewater on heavy metal mobility and soil bacterial composition under intercropping remain poorly understood. We conducted a pot experiment with maize and soybean grown in monocultures or intercultures, irrigated with either groundwater or treated wastewater. In addition, the pre-collected root exudates from hydroponic culture with mono- or inter-cropped maize and soybean were applied to the soil at four levels (0 %, 16 %, 32 % and 64 %). The results showed that application of root exudates increased plant growth and soil nutrient content. The analysis of “Technique for Order of Preference by Similarity to Ideal Solution” for higher plant biomass and lower soil Cd and Pb concentrations indicated that the best performance of soybean under treated wastewater irrigation was recorded under intercropping applied with 64 % of exudates, with a performance score of 0.926 and 0.953 for Cd and Pb, respectively. The second-best performance of maize under treated wastewater irrigation was also observed under intercropping applied with 64 % of exudates. Root exudate application reduced heavy metals migration in the soil-plant system, with a greater impact in intercropping than in monocropping. In addition, certain soil microorganisms were also increased with root exudate application, regardless of irrigation water. This study suggests that appropriate application of root exudates could potentially improve plant growth and soil health, and reduce toxic heavy metal concentrations in soils and plants irrigated with treated wastewater.

Mitigating risks and maximizing sustainability of treated wastewater reuse for irrigation

Scarcity of freshwater for agriculture has led to increased utilization of treated wastewater (TWW), establishing it as a significant and reliable source of irrigation water. However, years of research indicate that if not managed adequately, TWW may deleteriously affect soil functioning and plant productivity, and pose a hazard to human and environmental health. This review leverages the experience of researchers, stakeholders, and policymakers from Israel, the United-States, and Europe to present a holistic, multidisciplinary perspective on maximizing the benefits from municipal TWW use for irrigation. We specifically draw on the extensive knowledge gained in Israel, a world leader in agricultural TWW implementation. The first two sections of the work set the foundation for understanding current challenges involved with the use of TWW, detailing known and emerging agronomic and environmental issues (such as salinity and phytotoxicity) and public health risks (such as contaminants of emerging concern and pathogens). The work then presents solutions to address these challenges, including technological and agronomic management-based solutions as well as source control policies. The concluding section presents suggestions for the path forward, emphasizing the importance of improving links between research and policy, and better outreach to the public and agricultural practitioners. We use this platform as a call for action, to form a global harmonized data system that will centralize scientific findings on agronomic, environmental and public health effects of TWW irrigation. Insights from such global collaboration will help to mitigate risks, and facilitate more sustainable use of TWW for food production in the future.

Accumulation and Toxicity of Polycyclic Aromatic Hydrocarbons in Long-Term Soil Irrigated with Treated Wastewater

Our study focuses on examining the effects of treated wastewater irrigation (TWWI) on agricultural soils in water-scarce regions, with a specific emphasis on the presence and accumulation of polycyclic aromatic hydrocarbons (PAHs). This issue is particularly significant due to its potential threats to environmental security. During our research, we discovered the existence of 16 different PAHs in these soils, which are known to have harmful impacts on ecosystems and human health. The concentration of total PAHs ranged from 163.9 ng g−1 to 9177.4 ng g−1, with 4- and 5-ring PAHs being the most dominant contributors. The PAHs Fluoranthene and Pyrene were found to be the most prevalent in all soil samples. Comparing the PAH concentrations in our research area to those reported in other studies, we observed that the agricultural areas in our study were more contaminated. Through positive matrix factorization (PMF) and diagnostic ratios (DRs) analyses, we identified petroleum combustion, vehicular emissions, as well as coal, grass, or wood combustion as the primary sources of PAH contamination. We also noted a negative correlation between clay, silt, pH, and PAH concentrations, while a significant positive relationship was observed between total organic carbon (TOC), sand, and PAHs. Based on the computed environmental risk index value, the presence of PAHs in the area poses a moderate to high level of ecological risk. TWWI was identified as the main contributor to PAHs in the agricultural soils we studied. Therefore, it is crucial to establish and enforce standards for wastewater reuse in agricultural fields before irrigation takes place.

Assessing Soil Dynamics and Improving Long-Standing Irrigation Management with Treated Wastewater: A Case Study on Citrus Trees in Palestine

Irrigation with Treated Wastewater (TWW) is a well-known agricultural practice in Palestine. The long-term use of irrigation with TWW, a source of water and nutrients, can affect plant development, soil, and groundwater quality. Consequently, the frequency and the intervals of irrigation events should be adequately scheduled, especially when nutrients (TWW-N) cannot be separated from the water. Achieving good water quality implies its immediate reuse in irrigated agriculture. In contrast, long-term soil and groundwater quality conservation is marked by the complex mechanisms that correlate the soil, water, plant, and atmosphere. Therefore, monitoring and modeling (MMA) are combined to retrieve the soil water and nitrate fluxes and identify a proper irrigation management plan in a case study in Beit Dajan-Palestine, where a schedule adapted to conventional water was applied to a 6-year-old citrus orchard continuously irrigated with TWW. Soil nitrogen concentration and water content data were collected from March to August 2021 to calibrate the Hydrus-1D model under the (1) farmer demand (F) scenario, where irrigation volumes are delivered according to the farmer experience, and to define an optimal irrigation management strategy with TWW according to the (2) model demand (M) scenario, based on the irrigation frequency. The latter respects the allowable thresholds of soil solution electrical conductivity, σe, assuming an average soil salinity profile and estimated leaf nitrogen concentrations tolerance as reference; 2021 was taken as a calibration year to retrieve water and nitrate fluxes for 2019 and 2020. In 2021, the measured soil electrical conductivity, σe, showed no salinity risk with an average value of 1.07 dS m−1 (low salinity &lt; 2 dS m−1) but with a leaf nitrogen deficit. Although an acceptable level of available soil nitrogen was observed (ranging between 10 and 35 mg kg−1, whereas the standard value is 10–40 mg kg−1), critical concentrations were observed in the leaves (below 1%) in scenario (F) compared to scenario (M) (ranging between 1.7 and 1.9%). The latter also showed a decrease in nitrate leaching by 33% compared to the former. Overall, the comparison between the simulated and measured soil variables shows that the 1D-Hydrus model could follow the temporal variation in the monitored data, with some overestimation of the measured data during the simulation period. The simulations demonstrate that by modulating the salt tolerance threshold, the M scenario achieved better results in terms of root water and N uptake despite the stress inevitably experienced by citrus with long-term TWW irrigation. Moreover, the optimum threshold values used to assess the soil quality and citrus response under conventional water irrigation were inadequate for TWW practices. Therefore, MMA could be an alternative strategy to schedule proper TWW irrigation.

The nutritional composition of six plant species after irrigation with treated wastewater and possible hazards by heavy metal accumulation.

A field experiment was conducted investigating the possibility of using treated wastewater (TWW) on sites affected by water scarcity in summer, waterlogging during the wet season, and salinity. A corresponding pot experiment was conducted comparable to the field experiment in Kalaât Landelous. The same plant species (Atriplex nummularia Lindl., Eucalyptus gomphocephala DC., Acacia cyanophylla Lindl., Casuarina glauca Sieber ex Spreng., Cupressus sempervirens L., and Pinus halepensis Mill.) were grown with the same treatments. While, in the field the plants, elemental composition cannot be linked to inputs by TWW, this was studied under controlled conditions. Additionally, a control was established lower in salinity receiving tap water. The effect of TWW irrigation on macro- and microelement uptake by the six plant species was studied. The treatments were high soil salinity under drained saline (DS) conditions, high salinity under waterlogged saline (WS), and a drained non-saline control (DNS: EC = 3.0 dS/m, pH = 8.4). TWW application under DS treatment increased Na, Cl, Ca, Mg, N, P, and K in most plant tissues compared to the control. TWW application in WS treatment resulted in an increase in heavy metals. Cu and Zn showed the highest bioaccumulation factor (BAF). The BAF in different plant tissues followed the order: Cu > Zn > Mn > Cd > Ni > Co > Pb. The plants accumulated significant amounts of metals in their roots.

Effect of Alternating Well Water with Treated Wastewater Irrigation on Soil and Koroneiki Olive Trees

The use of treated wastewater (TWW) in irrigation has a positive impact by bringing fertilizers and organics. However, increases in the soil’s sodium adsorption ratio (SAR) creates a barrier to long-term TWW irrigation. Alternating well water with wastewater irrigation is one practical solution that could be used to address the problem. This work aims to study the effect of alternating two years of well water with two years of treated wastewater irrigation on the soil characteristics of a Koroneiki olive tree mesocosm. Urban and agri-food wastewater treated using various technologies, such as lagooning, activated sludge, multi-soil-layering, and constructed wetlands, were used for irrigation. The results showed that an increase in salinity (SAR and ESP) in soil and olive tree leaves are the main negative effects of continuous irrigation with TWW on soil and tree performance. Several chemical and biochemical parameters, such as SAR and Na+ concentration, demonstrated that alternating well water with treated wastewater irrigation can reverse these negative effects. This recovery effect occurs in a relatively short period of time, implying that such a management practice is viable. However, long-term well water application reduces soil fertility due to the leaching of organics and exchangeable ions.