Occurrence of parasites in waters used for crops irrigation and vegetables from the Savannah of Bogotá, Colombia

The World Health Organization (WHO) has established as a criterion of parasitological quality for irrigation water, ≤ 1 helminth egg/liter, which guarantees the safety in agricultural products. In this study, the presence of parasites in surface water used for irrigation of crops (n = 96) and vegetables (celery and lettuce) (n = 120), from the Former La Ramada irrigation district, was evaluated using conventional and molecular parasitological methods. Our findings showed contamination of irrigation systems in the study area with domestic wastewater, demonstrated by the presence of Ancylostomatidae eggs, Ascaris spp., Hymenolepis spp., Trichuris spp., Capillaria spp., Giardia spp. cysts, and oocysts of Toxoplasma gondii and Cryptosporidium spp. A prevalence of 33% and 23.3% was calculated for helminths and protozoa, respectively in vegetables, representing a possible risk to human and animal health in relation to these parasites. These findings show the need for continuous monitoring of the water quality used for crop irrigation, as well as the safety of food, taking into account the values established in national and international regulations.

Metagenomics-assembled analysis revealed the characteristics of antibiotic resistome and community coalescence in the soils irrigated with different irrigation materials

Antibiotic resistance has received widespread attention in recent years. Soil irrigation and fertilization are routine agricultural practices, but also lead to the spread of antibiotic resistance genes (ARGs) in soil-crop system such as via resistome coalescence. Despite community coalescence being ubiquitous and important in natural ecosystems, little research has been done to investigate resistome coalescence during soil irrigation activities. In this study, the characteristics of antibiotic resistome and community coalescence in the soils irrigated with different irrigation materials (wastewater, wastewater-river water, and wastewater-manure) have been revealed by utilizing microcosm experiments and high-throughput sequencing-based metagenomic assembly approaches. Results showed irrigation and coalescence changed soil quality and resistome. Totally, 789 unique ARGs were identified in the irrigation system, including some emerging ARGs. The abundance and diversity of ARGs increased in the coalesced soils, mainly due to the newly imported ARGs from irrigation materials. Relatively, the soils irrigated with wastewater and manure showed higher level of ARGs. Irrigation with the mixtures containing river water caused greater loss of indigenous taxa, while the community structure of mixing treatment with manure changed more dramatically. Interestingly, the succession of community in coalesced soils was influenced by transient competition for resources and ecological niche width, and the highest abundance and diversity of microorganisms and ARGs were found in the initial phase of coalescence, followed by a gradual succession towards the original community. With increasement of wastewater in the irrigation materials, the soil community showed a stepwise change rather than linear change. Notably, natural deposit of irrigation materials reduced their impacts on the ARGs in the coalesced soils. Findings provide new insights into the resistome coalescence during agricultural practices for reducing the spread risks of ARGs.

Performance of lagoon and constructed wetland systems for tertiary wastewater treatment and potential of reclaimed water in agricultural irrigation

Climate change poses challenges to agricultural water resources, both in terms of quantity and quality. As an adaptation measure, the new European Regulation (EU) 2020/741 establishes different water quality classes for the use of reclaimed water in agricultural irrigation. Italy is also working on the definition of a new regulation on reclaimed water reuse for agricultural irrigation (in substitution of the current one) that will also include the specific requirements imposed by the European one. Nature-based Solutions (NBS) can be a cost-effective and environmentally friendly way to facilitate water reclamation and reuse. The present study reports the outcomes of a long-term monitoring campaign of two NBS (e.g., a constructed wetland (CW) and a lagoon system (LS)) comparing influent and effluent concentrations of different contaminants (e.g., E. coli, BOD5, TSS, TN and TP) with the threshold values imposed by the new regulations. The results showed that in both the case studies, E. coli (about 100 CFU 100 mL-1) and BOD5 (lower than 25 mg L-1) mean effluent concentration need to be further reduced in reclaimed water to be suitable for unlimited reuse. As a negative aspect, in both the monitored NBS, an increase in TSS mean concentration in the effluent was observed, up to 40 mg L-1 in the case of the LS, making reclaimed water unsuitable for agricultural reuse. The CW has proven to be more effective in nitrogen removal (the effluent mean concentration was 3.4 mg L-1), whereas the LS was better at phosphorus removal (with an effluent mean concentration of 0.4 mg L-1). Based on the results, recommendations were made to further improve the performance of both systems in order to have adequate water quality, even for class A. Furthermore, the capacity of reclaimed water to meet crop water and nutrient needs was analyzed, and total nitrogen removal rate coefficients were calculated for the design of future LSs.

Wastewater reuse in agriculture: Prospects and challenges

Sustainable water recycling and wastewater reuse are urgent nowadays considering water scarcity and increased water consumption through human activities. In 2015, United Nations Sustainable Development Goal 6 (UN SDG6) highlighted the necessity of recycling wastewater to guarantee water availability for individuals. Currently, wastewater irrigation (WWI) of crops and agricultural land appears essential. The present work overviews the quality of treated wastewater in terms of soil microbial activities, and discusses challenges and benefits of WWI in line with wastewater reuse in agriculture and aquaculture irrigation. Combined conventional-advanced wastewater treatment processes are specifically deliberated, considering the harmful impacts on human health arising from WWI originating from reuse of contaminated water (salts, organic pollutants, toxic metals, and microbial pathogens i.e., viruses and bacteria). The comprehensive literature survey revealed that, in addition to the increased levels of pathogen and microbial threats to human wellbeing, poorly-treated wastewater results in plant and soil contamination with toxic organic/inorganic chemicals, and microbial pathogens. The impact of long-term emerging pollutants like plastic nanoparticles should also be established in further studies, with the development of standardized analytical techniques for such hazardous chemicals. Likewise, the reliable, long-term and extensive judgment on heavy metals threat to human beings's health should be explored in future investigations.

Dissemination of nonsteroidal anti-inflammatory drugs (NSAIDs) and metabolites from wastewater treatment plant to soils and agricultural crops via real-scale different agronomic practices

One of the most consumed pharmaceutical subgroups across the world is nonsteroidal anti-inflammatory drugs (NSAIDs). However, the dissemination of these compounds to the natural environments through agronomic practices is a serious global problem. The hypothesis of this study is to reveal the transition of selected NSAIDs, paracetamol (PAR), diclofenac (DCF), ibuprofen (IBU), and naproxen (NAP) together with six main metabolites, detected in raw/treated wastewater (RWW/TWW) and sewage sludge generated in an urban wastewater treatment plant (WWTP) to soils and agricultural crops (corn, barley, sunflower, and sugar beet) through two widely applied agronomic practices, irrigation with TWW and application of sewage sludge as soil amendment. In other words, the cycles of 10 NSAIDs have been evaluated by simultaneously monitoring their concentrations in RWW/TWW, sewage sludge, soils, and crops. It was determined that the parent compounds and detected metabolites were treated at quite higher removal efficiencies (93.4 - >99.9%) in the studied WWTP, while DCF was eliminated poorly (7.9-52.2%). However, although it changes seasonally for some compounds, it was determined that the concentrations of almost all investigated NSAIDs increased at the determined irrigation points in the discharge channel (DC) where agricultural irrigations were performed. Apart from that, DCF, NAP, and 2-hydroxyibuprofen (2-OH-IBU) were always detected in sewage sludge seasonally up to about 20.5, 11.3, and 3.7 ng/g, respectively. While 2-OH-IBU was determined as the dominant metabolite in RWW, TWW, and sewage sludge, the metabolite of 1-hydroxyibuprofen (1-OH-IBU) was determined as the dominant compound in soils. Although 1-OH-IBU was not detected in TWW and sewage sludge in any season, detecting this metabolite as a common compound in all investigated soils (up to 60.1 ng/kg) reveals that this compound is the primary transformation product of IBU in soils. It was observed that at least one of the metabolites of IBU (1-OH-IBU and/or 2-OH-IBU) was detected in all plants grown (up to 0.75 ng/g), especially during the periods when both agricultural practices were applied. In addition, the detection of 1-OH-IBU with increasing concentrations from root to shoots in corn grown as a result of both agronomic practices shows that this compound has a high translocation potential in the corn plant. Apart from this, it was determined that PAR was detected in corn (up to 43.3 ng/kg) and barley (up to 16.8 ng/kg) within the scope of irrigation with TWW, and NAP was detected in sugar beet (up to 11.2 ng/kg) through sewage sludge application.

Peracetic acid as a disinfectant for wastewater reuse - Regulation (EU) 2020/741 application on a pilot-scale

Water scarcity affects already a large part of the world's population. To overcome this situation, water management is needed, and wastewater reuse must be implemented and included as a new approach. To achieve that objective water quality must comply with the parameters established in the Regulation (EU) 2020/741 of the European Parliament and the Council of the European Union and new treatment solutions have to be developed. The main goal of this pilot study was to evaluate the peracetic acid (PAA) disinfection efficiency in a real wastewater treatment plant (WWTP) in order to accomplish the wastewater reuse objective. To this end, six disinfection conditions were studied, three PAA doses (5, 10, and 15) and three contact times (5, 10, and 15) based on the commonly used disinfection operational conditions in real WWTP. Comparing the Total Suspended Solids (TSS), turbidity, Biological Oxygen Demand (BOD5) and Escherichia coli content, after and before the disinfection step, was possible to conclude that PAA ensures the Regulation (EU) 2020/741 requirements and that the disinfected effluent can be reused for several uses. All the conditions in which the PAA dose was 15 mg/L and the condition with 10 mg/L of PAA with a contact time of 15 min were the most promising, presenting the second highest water quality class achieved. The results of this study illustrate the potential of PAA as an alternative disinfectant for wastewater treatment and, bring it closer to the water reuse objective by presenting several possibilities for water uses.

Health risks of Cryptosporidium and Giardia in the application of surface water and septic tank effluent in Chinese agriculture: Impact on cancer patients identified by quantitative microbial risk assessment

The protozoa Cryptosporidium and Giardia are major causes of diarrhea and are commonly found on vegetables in China. They pose a health risk, particularly to immunocompromised individuals, including cancer patients. A quantitative microbial risk assessment of Chinese data evaluated the risks of Cryptosporidium and Giardia exposure arising from the application of surface water and septic tank effluent to agricultural land. Exposure via agricultural produce consumption (consumers) and agricultural practices (farmers) was considered for subpopulations of cancer patients and immunocompetent people in urban and rural areas, and risk mitigation scenarios were modelled. The cumulative disease burdens attributable to cryptosporidiosis and giardiasis were, respectively, 9.68×10^-6 and 5.57×10^-5 disability-adjusted life years per person per year (DALYs pppy) for immunocompetent people, and 3.14×10^-5 and 1.51×10^-4 DALYs pppy for cancer patients. Cancer patients were approximately three times more likely to have an individual disease burden than immunocompetent people. The disease burden was higher for consumers than farmers, and higher in rural areas than urban areas (all exceeding the maximum recommended by the World Health Organization). The highest burdens were in provinces of high population, such as Henan, Guangdong, and Sichuan, while the burden associated with human and livestock fecal effluent application was higher than with surface water irrigation. Of the three vegetables studied, lettuce posed the greatest risk, followed by bok choy, while cucumber posed the least risk. Risk mitigation scenario analysis showed that pre-treatment of surface water and feces, and appropriate post-harvest handling of vegetables, including disinfection, cooking, and adequate surface heat treatment (75 °C for 60 s), should be considered when attempting to reduce disease burdens. The methodology and findings of this study are useful for evaluating and reducing the burden of Cryptosporidium and Giardia infections associated with agricultural irrigation and fertilization practices, particularly on cancer patients.

Microplastics contamination and characteristics of agricultural groundwater in Haean Basin of Korea

The quality of groundwater is critical to human health. MPs have access to groundwater from the soil, polluted by various agricultural activities. However, to date, there have been no studies on the occurrence of MP in groundwater from an agriculture field without any adjacent sources of contamination, such as nearby landfills. In this study, the occurrence and distribution of MPs in groundwater of an agricultural area in the Haean Basin, Korea, without any definite source of pollution, was examined. MP and groundwater samplings were conducted in the dry season in 2020, the wet and dry seasons in 2021, respectively. In this study, the reliability of MP analysis was improved through good practices from laboratory to field campaigns, collecting large groundwater samples (300-500 L) volumes. Any involvement of plastic materials was avoided during the full procedures as possible and. Detailed investigation was conducted for the distribution of potential plastics sources like mulching, plastic covers, dripping pipes and shading nets, and hydrogeological properties affecting MPs occurrence. Groundwater MP concentrations of 0.02-0.15 particles/L (median = 0.06 particles/L), 0.02-2.56 particles/L (median = 0.43 particles/L) and 0.20-3.48 particles/L (median = 0.83 particles/L) were found in three rounds of sampling that comprised of the exploratory investigation in 2020, the wet season, and the dry season in 2021, respectively. The identified polymer types were polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS) and polyamide (PA). The MPs concentrations showed no statistically significant seasonal variation but revealed an apparent strong positive correlation (r = 0.71) of MPs with the amount of groundwater use. Findings of this study need more clarification from repeated samplings for multiple years. This study reveals the occurrence of MPs in groundwater in Korea for the first time to the best of our knowledge.

Distribution of legacy and novel per- and polyfluoroalkyl substances in surface and groundwater affected by irrigation in an arid region

Frequent exchange of surface water and groundwater occurs in arid/semi-arid areas due to high evaporation and intensive irrigation activities, affecting the migration and transformation of per- and polyfluoroalkyl substances (PFASs) and threatening drinking water safety. This study analyzed legacy PFASs and potential precursors in surface water, groundwater, soil, and aquifer solid samples collected from a typical arid area, the Hetao Irrigation District of Northern China, to explore PFASs distribution and transformation between surface and ground. Total PFASs (ΣPFASs) in surface water was 29-232 ng/L, higher than 2-77 ng/L in groundwater. ΣPFASs in soil were 0.29-0.59 ng/g, higher than 0.09-0.27 in the aquifer solids. Regarding horizontal distribution, the concentration of PFASs in groundwater increased in downtowns and the areas recharged with lake water. In terms of vertical distribution, ΣPFASs decreased with the increase of depth, and more PFASs adsorbed on clay particles in the aquifer. The total oxidable precursor analysis showed that 8:2 FT and 4:2 FT were the dominant precursors of PFASs, resulting in an increment of 0.1-4 ng/L PFASs. Hydrogen and oxygen stable isotope compositions suggest similar sources between surface water and groundwater in the study area, while principal component analysis and Bayesian inference also indicate that surface water is an important source of groundwater PFASs. The annual infiltration PFASs to groundwater from Ulansuhai was estimated by the water balance approach to be 9.39 kg. Results highlight the influence of agricultural irrigation activities and lake infiltration on groundwater PFASs in the arid region.

Environmental implications of land use change on the fate of Zn in agricultural soils: A case study of Puding karst soils, southwest China

Land use change threatens food security because it may cause the depletion and/or low bioavailability of micronutrients in agricultural soils. Therefore, it is significant to investigate the fate of micronutrients and predict the potential environmental problems. The zinc isotope technique is of particular interest in interpreting soil processes. In this study, Zn isotopic data of soil samples in five profiles based on different land uses were provided, and Zn behavior in different soils was discussed. The isotopic ratios of soil samples in the abandoned orchard, secondary forest, abandoned cropland, and cropland are similar, with the δ⁶⁶Zn varying from 0.15 to 0.29‰. However, the samples in shrub grassland show a lower δ⁶⁶Zn of 0-0.20‰, which may be affected by anthropogenic sources. For the vertical patterns, the non-cultivated long-rooted plants (i.e., abandoned orchard and secondary forest) show no significant difference in the distribution of δ⁶⁶Zn, but the patterns of cropland and abandoned cropland samples are reversed. The cropland samples show positive correlations between δ⁶⁶Zn and Fe₂O₃ (R² = 0.90) and MnO (R² = 0.75), indicating that Fe and Mn oxides preferentially adsorb heavy Zn isotopes on the mineral surfaces. The high affinity between Zn and oxides indicated that the concentration of bio-available Zn in cropland soils was getting lower. As a result, the supplies of micronutrients may be deficient and urged from fertilizer. This study provides a better understanding of Zn cycling in agricultural systems and gives improvements in soil management.

Translating wastewater reuse for irrigation from OECD Guidelines: Tramadol sorption and desorption in soil-water matrices

Treated and untreated wastewater is often used for agricultural irrigation and, despite the many benefits of this practice, it poses the risk of biologically active chemical pollutants (such as pharmaceuticals, like tramadol) entering the environment. The partitioning of tramadol between soil/water at environmentally relevant concentrations is important to understand its environmental toxicity. Kinetics and isotherm sorption studies based on the Organisation for Economic Cooperation and Development (OECD) 106 Guideline were undertaken, ensuring comparability to previous studies. Studies were undertaken in three soils of different characteristics using aqueous concentrations of tramadol from 500 ng L^-1 (environmentally relevant) to 100 μg L^-1 (comparable to previous studies). Two of the soils presented a significantly (p < 0.05) higher sorption at a lower initial tramadol concentration (5000 ng L^-1), compared to 20,000 ng L^-1. Hysteresis was observed in all studied soils, indicating the accumulation of tramadol. Higher sorption to soils correlated with higher clay content, with soil/water partitioning coefficients (K_d) of 5.5 ± 13.3, 2.5 ± 3.8 and 0.9 ± 3.0 L kg¹ for soils with clay contents of 41.9%, 24.5% and 7.4%, respectively. Cation exchange was proposed as the main sorption mechanism for tramadol to soils when the pH was below tramadol's pK_a values (9.41 and 13.08). A comparative kinetics study between tramadol in soil/calcium chloride buffer and soil/wastewater effluent demonstrated significantly higher (p < 0.05) tramadol sorption to soil from wastewater effluent. This has the environmental implication that clay soils will be able to retain tramadol from irrigation water, despite the organic content of the irrigation water. Therefore, our studies show that tramadol soil sorption is likely to be higher in agricultural environments reusing wastewater than that predicted from experiments using the OECD 106 Guideline calcium chloride buffer.

A fixed-mix stochastic fractional programming method for optimizing agricultural irrigation and hydropower generation in Central Asia

In this study, a fixed-mix stochastic fractional programming (FSFP) method is developed for balancing the water-allocation conflict between upstream hydropower generation and downstream agricultural irrigation. FSFP has advantages in dealing with ratio-objective problem under uncertainty, reflecting the dynamic and stochastic characteristics over a long-term planning context, as well as analyzing interrelationships between system efficiency and violation risk of water-allocation target. Then, FSFP is firstly applied to Tuyamuyun reservoir in the lower reach of Amu Darya River basin (Central Asia), where multiple scenarios based on different hydropower-generation targets and inflow levels are examined for identifying the complex relationship between hydropower generation and crop irrigation. Major findings and managerial insights can be summarized as: (i) with the reduction of reservoir inflow, water allocation for downstream agricultural irrigation would decrease by 30.4% once the minimum demand is satisfied, and hydropower generation should be higher priority for pursuing higher marginal benefit; (ii) with the shrinking water supply and rising hydropower-generation target, cotton planting should be firstly restrained due to its high water demand and grape planting is encouraged; (iii) under extreme water scarcity (i.e., low and very-low inflow levels), low-level hydropower generation target (i.e., α = 0.45) is desired for meeting the food requirement in the study basin; (iv) for alleviating the water shortage during dry seasons, it is recommended that water storage should be conducted in autumn and winter, and water release for crop irrigation should be implemented during spring and summer. These findings can help managers identify sustainable water-allocation schemes for agricultural irrigation and hydropower generation against water shortage, environmental destruction and energy insecurity in arid regions.

Source and enrichment mechanism of fluoride in groundwater of the Hotan Oasis within the Tarim Basin, Northwestern China

In arid inland irrigated areas, the role of human activities on fluoride enrichment in groundwater is not fully understood. There is an extremely arid climate, high-intensity irrigation, and severe soil salinization in the Hotan Oasis within the Tarim Basin, Northwestern China. In this study, hydrogeochemistry and environmental isotope methods were combined to explore the distribution characteristics and controlling processes of fluoride enrichment in groundwater. The F^- concentration in groundwater had a range of 1.12-9.4 mg/L. F^- concentrations of all the groundwater samples were higher than 1.0 mg/L (Chinese Standards for Drinking Water Quality), and about 89% were higher than 1.5 mg/L (WHO Guidelines for Drinking Water Quality). High fluoride groundwater was mainly distributed downstream of the river and in the middle of the interfluvial zone. Vertically, the fluoride concentration was higher when the sampling depth was less than 15 m. There was a significant positive correlation between F^- concentration and salinity in groundwater. F^- in groundwater was mainly derived from river water fluoride, which could be imported to groundwater with infiltration of rivers and irrigation canals as well as irrigation return flow. Anthropogenic inputs may be partly responsible for fluoride enrichment in groundwater. Fluoride accumulated in the vadose zone by strong evapotranspiration and then leached into groundwater with irrigation return flow was the main mechanism of F^- enrichment in groundwater in the study area. This work is a clear example of how human activities together with natural processes can affect the chemical quality of groundwater, which is essential to safeguard the sustainable management of water and soil resources inland arid oasis areas.

Perceptions on the use of recycled water for produce irrigation and household tasks: A comparison between Israeli and Palestinian consumers

Water scarcity has resulted in extensive wastewater recycling for agricultural irrigation in both Israel and the Palestinian Territories. However, minimal data have been collected regarding perceptions about wastewater recycling between the populations in these two areas. While geographically close and economically linked, these two populations differ in terms of governance, income, and access to technology for wastewater recycling. To address the data gap pertaining to perceptions of wastewater recycling, a survey was administered among a convenience sample of subjects (n = 236) recruited from Eilat, Israel and Bethlehem, West Bank, from May to November 2018. The survey included questions addressing knowledge of water sources, water scarcity, and recycled water; willingness to use recycled water for produce irrigation and household tasks; and demographics. Israeli willingness to use recycled water for various purposes ranged from 8.3% to 55.1%, and more than half of Israeli respondents were willing to serve both raw and cooked produce irrigated with recycled water. Willingness to use recycled water ranged from 28.9% to 41.7% among the Palestinian respondents, and Palestinian respondents were more willing to engage in high-contact uses (i.e. drinking and cooking) than Israeli respondents. Among the Israeli respondents, experience or familiarity with wastewater recycling and water contamination were frequently significantly associated with willingness to use recycled water. In contrast, among Palestinian respondents, personal water contamination experience, home water safety testing, and trust in authorities to monitor recycled wastewater reuse were frequently significantly associated with willingness to use recycled water. Given the likely increasing water stress in both Israel and the Palestinian Territories, as well as the continued evolution of wastewater treatment technologies and the substantial amount of agricultural trade ongoing between Israel and the Palestinian Territories, it is important to identify effective and appropriate outreach and communication strategies to enable successful and acceptable water recycling.

Using an unmanned aerial system to monitor and assess irrigation water channels susceptible to sediment deposition

The irrigation channel of the Qishan River is among the most crucial agricultural water resource facilities in Qishan District, Kaohsiung City, Taiwan. The channel was blocked by debris due to flood events caused by Typhoon Morakot in 2009. This study analyzed images captured by an unmanned aerial system to identify channel areas susceptible to sediment deposition and propose measures for reducing the effects of natural hazards on irrigation water resources. The analysis results revealed that the channel was located downstream of the Qishan River; however, debris flows, riverbank landslides, and natural dam breaches deposited sediment in the downstream section, preventing the flow of water. Furthermore, the sediment and driftwood blocked the channel. The channel was also blocked due to a hyperconcentrated flow. Sediment deposition areas and volumes were estimated. On the basis of these results, we suggest that the damaged riverbed groundsills and river tributary banks be restored to inhibit erosion. In addition, subsurface water collection and transfer structures should be constructed to maintain the flow of water during the dry season. The study findings are expected to increase the efficiency of agricultural irrigation water management and prevent natural hazards from affecting water resources.

Development of a qualitative approach to assessing risks associated with the use of treated wastewater in agricultural irrigation

The European Commission's draft regulation for minimum requirements for water reuse in agriculture addresses microbial and basic water quality parameters but does not consider the potential impacts of chemicals of emerging concern (CECs) on human and environmental health. Because insufficient data prevents the quantitative characterisation of risks posed by CECs in treated wastewater (TWW), this paper presents a framework, which combines data and expert judgement to assess likelihood of occurrence and magnitude of impact. An increasing relative scale is applied where numeric values are pre-defined to represent comparative levels of importance. Subsequently, an overall assessment of the level of risk is characterised by multiplying together allocated scores, to obtain a single discrete overall score per CEC. Guidelines to support implementation of the framework as far as soil (the initial receiving compartment and pathway to further protected targets) are developed and applied. The approach is demonstrated through its application to clarithromycin, where results indicate that - under the considered scenario - there is limited possibility of its occurrence in soil in a bioavailable form. The role of a qualitative risk assessment approach is considered and the opportunity for its outputs to inform future research agendas described.

Assessment of contamination by anthropogenic dissolved organic matter in the aquifer that underlies the agricultural area

The use of wastewater for agricultural irrigation is a common practice worldwide; long-term use of wastewater can have adverse effects, such as the migration of the anthropogenic dissolved organic matter into the aquifer. Three-dimensional fluorescence spectroscopy (EEM) was used to investigate the characteristics of dissolved organic matter (DOM) in groundwater and irrigation wastewater, to establish the effect of intensive irrigation on the water quality from the aquifer that underlies the area. The fluorescence spectra showed the presence of humic and fulvic acids and anthropogenic organic compounds similar to aromatic proteins and soluble microbial products in wastewater resources. The significant fraction of DOM in groundwater samples are aromatic proteins and soluble microbial products, identical to wastewater. Chlorides and nitrate ion concentrations suggest a local flow system. High levels of TDS are associated with intensive irrigation with residual water and the return irrigation associated with a gradual increase in salts of CO₃^2-, NO₃^-, HCO₃^-, Cl^-, and SO₄^2-. The anthropogenic DOM is a useful indicator of water quality management in groundwater based on origin tracking of DOM and changes in organic pollutants. Fluorescence spectroscopy can be used to investigate groundwater pollution characteristics and monitor DOM dynamics in groundwater.

Seasonal dynamics in taxonomy and function within bacterial and viral metagenomic assemblages recovered from a freshwater agricultural pond

BACKGROUND

Ponds are important freshwater habitats that support both human and environmental activities. However, relative to their larger counterparts (e.g. rivers, lakes), ponds are understudied, especially with regard to their microbial communities. Our study aimed to fill this knowledge gap by using culture-independent, high-throughput sequencing to assess the dynamics, taxonomy, and functionality of bacterial and viral communities in a freshwater agricultural pond.

RESULTS

Water samples (n = 14) were collected from a Mid-Atlantic agricultural pond between June 2017 and May 2018 and filtered sequentially through 1 and 0.2 μm filter membranes. Total DNA was then extracted from each filter, pooled, and subjected to 16S rRNA gene and shotgun sequencing on the Illumina HiSeq 2500 platform. Additionally, on eight occasions water filtrates were processed for viral metagenomes (viromes) using chemical concentration and then shotgun sequenced. A ubiquitous freshwater phylum, Proteobacteria was abundant at all sampling dates throughout the year. However, environmental characteristics appeared to drive the structure of the community. For instance, the abundance of Cyanobacteria (e.g. Nostoc) increased with rising water temperatures, while a storm event appeared to trigger an increase in overall bacterial diversity, as well as the relative abundance of Bacteroidetes. This event was also associated with an increase in the number of antibiotic resistance genes. The viral fractions were dominated by dsDNA of the order Caudovirales, namely Siphoviridae and Myovirdae.

CONCLUSIONS

Overall, this study provides one of the largest datasets on pond water microbial ecology to date, revealing seasonal trends in the microbial taxonomic composition and functional potential.

Reusing oil and gas produced water for agricultural irrigation: Effects on soil health and the soil microbiome

Produced water (PW) is a major waste-product of oil and gas production that some consider a viable agricultural irrigation water source. However, the presence of petroleum hydrocarbons, toxic metals and potentially high salinity of PW may be deleterious for soil health. Thus, we irrigated wheat with minimally treated PW to investigate effects on soil health, wheat growth, and the soil microbiome. Irrigation treatments included control irrigation water (IW), 1% and 5% PW dilutions (1% PW, 5% PW), and a saltwater solution with salinity equivalent to the 5% PW dilution (SW). Wheat was irrigated three times a week, for a total of 2.1 L per pot by harvest. During wheat growth, we measured plant physiological parameters, soil electrical conductivity, as well as profiled soil microbial diversity by performing 16S ribosomal ribonucleic acid (rRNA) gene analysis. Soil health parameters were measured after harvest, including chemical, biological, physical, and nutrient properties that were used to calculate an overall soil health index (SQI). SQI analysis revealed that the SW and 5% PW treatments had significantly reduced soil health as compared to the control. Furthermore, the 16S rRNA gene analysis showed that the microbial community membership and structure was significantly different between irrigation treatments, highlighting shifts in the soil microbiome which may impact soil biochemical cycling. Both the SW- and 5% PW-treated wheat had reduced yields as compared to the control. Our results indicate that irrigating wheat with minimally treated PW may result in yield decreases, as well as reducing both overall soil health and soil microbial community diversity. Future large-scale field studies are needed to determine the long-term soil health effects of PW on different soil types and crops.

Metagenomic analysis of bacterial and viral assemblages from a freshwater creek and irrigated field reveals temporal and spatial dynamics

Lotic surface water sites (e.g. creeks) are important resources for localized agricultural irrigation. However, there is concern that microbial contaminants within untreated surface water may be transferred onto irrigated soil and crops. To evaluate this issue, water samples were collected between January 2017 and August 2018 from a freshwater creek used to irrigate kale and radish plants on a small farm in the Mid-Atlantic, United States. In addition, on one sampling date, a field survey was conducted in which additional water (creek source and point-of-use) and soil samples were collected to assess the viral and bacterial communities pre- and post- irrigation. All samples were processed for DNA extracts and shotgun sequenced on the Illumina HiSeq platform. The resulting metagenomic libraries were assembled de novo and taxonomic and functional features were assigned at the contig and peptide level. From these data, we observed that Betaproteobacteria (e.g. Variovorax) dominated the water, both at the source and point-of-use, and Alphaproteobacteria (e.g. Streptomyces) dominated both pre- and post-irrigated soil. Additionally, in the creek source water there were variations in the abundance of the dominant bacterial genera and functional annotations associated with seasonal characteristics (e.g. water temperature). Antibiotic resistance genes and virulence factors were also identified in the creek water and soil, with the majority specific to their respective habitat. Moreover, an analysis of clustered regularly interspaced short palindromic repeat (CRISPR) arrays showed the persistence of certain spacers through time in the creek water, as well as specific interactions between creek bacteriophages and their hosts. Overall, these findings provide a more holistic picture of bacterial and viral composition, dynamics, and interactions within a freshwater creek that can be utilized to further our knowledge on its suitability and safety for irrigation.

Recommendations to derive quality standards for chemical pollutants in reclaimed water intended for reuse in agricultural irrigation

The reuse of treated municipal wastewater (herein referred to as reclaimed water) in agricultural irrigation (RWAI) as a means to alleviate water scarcity is gaining increasing policy attention, particularly in areas where water demand mitigation measures have proved insufficient. However, reclaimed water reuse in practice is lagging behind policy ambition, with <2.5% of it reused in a European context. A key barrier identified as limiting its full valorisation is concern over its impact on human and environmental health. To address this concern, and to meet further objectives including achieving parity between current reclaimed water reuse guidelines operational in various Member States, the European Commission has proposed a regulation which identifies minimum quality requirements (MQR) for a range of microbiological and physico-chemical parameters but the inclusion of compounds of emerging concern (CECs) in terms of the determination of quality standards (QS) is missing. This paper reviews the existing pertinent EU legislation in terms of identifying the need for CEC QS for RWAI, considering the scope and remit of on-going pan-European chemicals prioritisation schemes. It also evaluates opportunities to link in with the existing EQS derivation methodology under the EU WFD to address all protection targets in the environmental compartments exposed via potential pathways of RWAI. Finally, it identifies the main data gaps and research needs for terrestrial ecosystems, the removal efficiency of CECs by WWTPs and transformation products generated during the wastewater reuse cycle.

Comparative metagenomic analysis of microbial taxonomic and functional variations in untreated surface and reclaimed waters used in irrigation applications

The use of irrigation water sourced from reclamation facilities and untreated surface water bodies may be a practical solution to attenuate the burden on diminishing groundwater aquifers. However, comprehensive microbial characterizations of these water sources are generally lacking, especially with regard to variations through time and across multiple water types. To address this knowledge gap we used a shotgun metagenomic approach to characterize the taxonomic and functional variations of microbial communities within two agricultural ponds, two freshwater creeks, two brackish rivers, and three water reclamation facilities located in the Mid-Atlantic, United States. Water samples (n = 24) were collected from all sites between October and November 2016, and filtered onto 0.2 μm membrane filters. Filters were then subjected to total DNA extraction and shotgun sequencing on the Illumina HiSeq platform. From these data, we found that Betaproteobacteria dominated the majority of freshwater sites, while Alphaproteobacteria were abundant at times in the brackish waters. One of these brackish sites was also host to a greater abundance of the bacterial genera Gimesia and Microcystis. Furthermore, predicted microbial features (e.g. antibiotic resistance genes (ARGs) and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) arrays) varied based on specific site and sampling date. ARGs were found across samples, with the diversity and abundance highest in those from a reclamation facility and a wastewater-impacted freshwater creek. Additionally, we identified over 600 CRISPR arrays, containing ∼2600 unique spacers, suggestive of a diverse and often site-specific phage community. Overall, these results provide a better understanding of the complex microbial community in untreated surface and reclaimed waters, while highlighting possible environmental and human health impacts associated with their use in agriculture.

Environmental impacts of an advanced oxidation process as tertiary treatment in a wastewater treatment plant

Due to global water scarcity, the use of reclaimed wastewater for crop irrigation is required; however, if the wastewater treatment is inadequate, it can be a source of environmental pollution. In order to improve wastewater reclamation, advanced oxidation processes (AOPs) have been tested. At full scale, ozonation is one such process that effectively removes micropollutants, despite its high-energy consumption. At pilot scale, other technologies such as the solar photo-Fenton process are being developed. This process is under consideration as a sustainable technology because it uses sunlight as a source of radiation. However, there is little information available on its environmental performance. In this work, we perform a comparative analysis between the ozonation and the photo-Fenton process as tertiary wastewater treatment processes used to reclaim wastewater for agricultural irrigation. We apply the Life Cycle Assessment (LCA) methodology for quantifying environmental impacts with ReCiPe and USEtox as life cycle impact assessment (LCIA) methods. The results show that both tertiary treatment options reduce water stress locally. Ozonation has a better overall environmental performance compared to the photo-Fenton process because the environmental impact of the required ozone is smaller than of the reactants involved in the solar photo-Fenton. Moreover, the first can be operated both day and night, and therefore needs no additional storage for collecting the nightly secondary effluent, and thus has lower infrastructure related impacts. Additionally, when the solar photo-Fenton process operates at an acidic pH, there are environmental drawbacks related to the pH adjustment, which consumes a large amount of acid thus liberating CO₂. Finally, the environmental impacts associated with the discharge of micropollutants to soil through the use of reclaimed water are very small compared to the other impacts generated by the treatment. However, due to the current LCIA method limitations of micropollutant impact assessment, these are subject to major uncertainty.

Characterization of implementation limits and identification of optimization strategies for sustainable water resource recovery through life cycle impact analysis

How we manage alternative freshwater resources to close the gap between water supply and demand is pivotal to the future of the environment and human well-being. Increased scarcity of water for agricultural irrigation in semi-arid and arid regions has resulted in a growing interest in water reuse practices. However, insight into the life cycle impacts and potential trade-offs of these emerging practices are still limited by the paucity of systematic evaluations of different water reuse implementations. In this study, a host of environmental and human health impacts at three implementation levels of allowing water reclamation for crop irrigation was comparatively evaluated across the operational landscape via a combination of scenario modelling, life-cycle impact analyses and Monte Carlo simulations. Net harvesting of reclaimed water for irrigation was found to be dependent upon the sophistication of the treatment processes, since multistage and complex configurations can cause greater direct water consumption during processing. Further, the direct benefits of water resource recovery can be essentially offset by indirect adverse impacts, such as mineral depletion, global warming, ozone depletion, ecotoxicity, and human health risks, which are associated with increased usage of energy and chemicals for rigorous removal of contaminants, such as heavy metals and contaminants of emerging concern. Nonetheless, expanded simulations suggest the significance of concurrently implementing energy recovery, nutrient recycling, and/or nature-based, chemical-free water technologies to reduce the magnitude of negative impacts from engineered water reclamation processes.

Potential for Beneficial Reuse of Oil and Gas-Derived Produced Water in Agriculture: Physiological and Morphological Responses in Spring Wheat (Triticum aestivum)

Produced water (PW) from oil and gas operations is considered a potential resource for food crop irrigation because of increasing water scarcity in dryland agriculture. However, efforts to employ PW for agriculture have been met with limited success. A greenhouse study was performed to evaluate the effects of PW on physiological and morphological traits of spring wheat (Triticum aestivum). Plants were irrigated with water treatments containing 10 and 50% PW (PW10 and PW50, respectively) and compared to a matching 50% salinity (NaCl50) and 100% tap water controls. Compared to controls, plants watered with PW10 and PW50 exhibited developmental arrest and reductions in aboveground and belowground biomass, photosynthetic efficiency, and reproductive growth. Decreases in grain yield ranged from 70 to 100% in plants irrigated with PW compared to the tap water control. Importantly, the PW10 and NaCl50 treatments were comparable for morphophysiological effects, even though NaCl50 contained 5 times the total dissolved solids, suggesting that constituents other than NaCl in PW contributed to plant stress. These findings indicate that despite discharge and reuse requirements focused on total dissolved solids, salinity stress may not be the primary factor affecting crop health. The results of the present study are informative for developing guidelines for the use of PW in agriculture to ensure minimal effects on crop morphology and physiology. Environ Toxicol Chem 2019;38:1756-1769. © 2019 SETAC.

Anaerobic submerged membrane bioreactor (AnSMBR) treating municipal wastewater at ambient temperature: Operation and potential use for agricultural irrigation

A 496 L pilot scale anaerobic submerged membrane bioreactor (AnSMBR) for the treatment of municipal wastewater was evaluated during a year of stable operation at ambient (28-10 °C) temperature, and inoculated with mesophilic inoculum. The temperature was the main parameter affecting the process performance. The chemical oxygen demand (COD) of the effluent was around 150 mg O₂/L in the summer period, operating with a volumetric loading rate (VLR) of 5 kg COD/m³ d and hydraulic retention time (HRT) of 8-10 h, with a specific methane production between 0.09 and 0.14 Nm³/kg COD_removed. However, during the winter season, an important increase of effluent COD was observed, and therefore the VLR was decreased to values around 1 kg COD/m³ d in order to recover the quality of the effluent. Biogas production was negligible in this period. The effluent complies with the parameters stipulated by Spanish law regarding the use of treated wastewater for agricultural irrigation.

Utilization of reverse osmosis (RO) for reuse of MBR-treated wastewater in irrigation-preliminary tests and quality analysis of product water

Membrane bioreactor (MBR) effluent collected from a wastewater treatment plant installed at an industrial zone was used for reverse osmosis (RO) membrane tests in the laboratory. For this, two different GE Osmonics RO membranes (AK-BWRO and AD-SWRO) were employed. The results showed that AK-brackish water reverse osmosis (AK-BWRO) and AD-seawater reverse osmosis (AD-SWRO) membranes have almost similar rejection performances regarding analyzed parameters such as conductivity, salinity, color, chemical oxygen demand (COD), and total organic carbon (TOC). On the other hand, these membranes behaved quite differently considering their permeate water flux at the same applied pressure of 10 bar. AD-SWRO membrane was also tested at 20 bar. The results revealed that AD-SWRO membrane had almost the same rejections either at 10 or at 20 bar of applied pressure. Compared with irrigation water standards, AK-BWRO and AD-SWRO gave an effluent with low salinity value and sodium adsorption ratio (SAR) which makes it unsuitable for irrigation due to the infiltration problems risi0ng from unbalanced values of salinity and SAR. Combination of MBR effluent and RO effluent at respective proportions of 0.3:0.7 and 0.4:0.6 for AK-BWRO and AD-SWRO, respectively, are the optimum mixing ratios to overcome the infiltration hazard problem. Choice of less-sensitive crops to chloride and sodium ions is another strategy to overcome all hazards which may arise from above suggested mixing proportions.

Application of a nanofibrous composite membrane to the fertilizer-driven forward osmosis process for irrigation water use

In this study, we fabricated a nanofibrous composite (NFC) membrane as a substrate to produce forward osmosis (FO) membranes, and we also assessed the use of liquid fertilizer as a draw solution for the FO process in order to produce agricultural irrigation water. Commercial cellulose triacetate (CTA) and thin-film composite (TFC) FO membranes were included in this study. Under FO tests, the NFC, CTA, and TFC membranes achieved initial osmotic water flux values of 35.31, 6.85, and 3.31 L/m²·h and final osmotic water flux values of 12.62, 6.31, and 3.85 L/m² h, respectively. The reason for the high osmotic water flux of the NFC membrane is because its nanofiber layer has low tortuosity, high porosity, and a low thickness, resulting in a reduction in the internal concentration polarization phenomenon. When liquid fertilizer was used as the draw solution, the water flux values in the FO experiments for the NFC, CTA, and TFC membranes were 15.54, 5.46, and 2.54 L/m²h. Finally, our results revealed that the FO process using liquid fertilizer as a draw solution can be applied to produce agricultural irrigation water from brackish water and the newly fabricated NFC membrane can be applied to the FO process.

Causative impact of air pollution on evapotranspiration in the North China Plain

Atmospheric dispersion conditions strongly impact air pollution under identical surface emissions. The degree of air pollution in the Jing-Jin-Ji region is so severe that it may impose feedback on local climate. Reference evapotranspiration (ET₀) plays a significant role in the estimation of crop water requirements, as well as in studies on climate variation and change. Since the traditional correlation analysis cannot capture the causality, we apply the convergent cross mapping method (CCM) in this study to observationally investigate whether the air pollution impacts ET₀. The results indicate that southwest regions of Jing-Jin-Ji always suffer higher PM_2.5 concentration than north regions through the whole year, and correlation analysis suggests that PM_2.5 concentration has a significant negative effect on ET₀ in most cities. The causality detection with CCM quantitatively demonstrates the significantly causative influence of PM_2.5 concentration on ET₀, higher PM_2.5 concentration decreasing ET₀. However, CCM analysis suggests that PM_2.5 concentration has a relatively weak causal influence on ET₀ while the correlation analysis gives the near zero correlation coefficient in Zhangjiakou city, indicating that the causative influence of PM_2.5 concentration on ET₀ is better revealed with CCM method than the correlation analysis. Considering that ET₀ is strongly associated with crop water requirement, the amount of water for agricultural irrigation could be reduced at high PM_2.5 concentrations. These findings can be utilized to improve the efficiency of water resources utilization, and reduce the exploiting amount of groundwater in the Jing-Jin-Ji region, although PM_2.5 is detrimental to human health.