Does Irrigation with Treated and Untreated Wastewater Increase Antimicrobial Resistance in Soil and Water: A Systematic Review

Expanding the focus of the One Health concept: links between the Earth-system processes of the planetary boundaries framework and antibiotic resistance

The scientific community warns that our impact on planet Earth is so acute that we are crossing several of the planetary boundaries that demarcate the safe operating space for humankind. Besides, there is mounting evidence of serious effects on people's health derived from the ongoing environmental degradation. Regarding human health, the spread of antibiotic resistant bacteria is one of the most critical public health issues worldwide. Relevantly, antibiotic resistance has been claimed to be the quintessential One Health issue. The One Health concept links human, animal, and environmental health, but it is frequently only focused on the risk of zoonotic pathogens to public health or, to a lesser extent, the impact of contaminants on human health, i.e., adverse effects on human health coming from the other two One Health "compartments". It is recurrently claimed that antibiotic resistance must be approached from a One Health perspective, but such statement often only refers to the connection between the use of antibiotics in veterinary practice and the antibiotic resistance crisis, or the impact of contaminants (antibiotics, heavy metals, disinfectants, etc.) on antibiotic resistance. Nonetheless, the nine Earth-system processes considered in the planetary boundaries framework can be directly or indirectly linked to antibiotic resistance. Here, some of the main links between those processes and the dissemination of antibiotic resistance are described. The ultimate goal is to expand the focus of the One Health concept by pointing out the links between critical Earth-system processes and the One Health quintessential issue, i.e., antibiotic resistance.

Heterogeneous Antibiotic Resistance Gene Removal Impedes Evaluation of Constructed Wetlands for Effective Greywater Treatment

Microorganisms carrying antimicrobial resistance genes are often found in greywater. As the reuse of greywater becomes increasingly needed, it is imperative to determine how greywater treatment impacts antimicrobial resistance genes (ARGs). Using qPCR and SmartChip™ qPCR, we characterized ARG patterns in greywater microbial communities before, during, and after treatment by a recirculating vertical flow constructed wetland. In parallel, we examined the impact of greywater-treated irrigation on soil, including the occurrence of emerging micropollutants and the taxonomic and ARG compositions of microbial communities. Most ARGs in raw greywater are removed efficiently during the winter season, while some ARGs in the effluents increase in summer. SmartChip™ qPCR revealed the presence of ARGs, such as tetracycline and beta-lactam resistance genes, in both raw and treated greywater, but most abundantly in the filter bed. It also showed that aminoglycoside and vancomycin gene abundances significantly increased after treatment. In the irrigated soil, the type of water (potable or treated greywater) had no specific impact on the total bacterial abundance (16S rRNA gene). No overlapping ARGs were found between treated greywater and greywater-irrigated soil. This study indicates ARG abundance and richness increased after treatment, possibly due to the concentration effects of the filter beds.

Health risk assessment of heavy metals in saffron (Crocus sativus L.) cultivated in domestic wastewater and lake water irrigated soils

Irrigation of crops with domestic wastewater (DW) is a common practice in developing countries like India. However, domestic wastewater irrigation poses a risk of migration of toxic heavy metals to edible parts of crops, which requires serious measures to prevent their uptake. In this study, the effect of DW irrigation in comparison with Sarbal Lake water (SLW) and borewell water (BW) on soil characteristics and cultivated saffron (Crocus sativus L.) was investigated. For this purpose, samples of water, soil, and saffron (corm, petal, and stigma) were collected from the suburban area of Pampore, Srinagar district, Jammu and Kashmir, India. The results showed that DW irrigation had the maximum significant (p < 0.05) influence on the physico-chemical and nutrient characteristics of the soil, followed by SLW and BW irrigation, respectively. The growth and yield parameters of saffron were also significantly (p < 0.05) increased in the case of DW irrigation as compared to SLW and BW. The quality ranking of the cultivated saffron was found to be in accordance with the ISO standard (III: BW and II: DW and SLW). On the other hand, DW irrigation showed a significant increase in heavy metal contents (mg/kg) of saffron plant parts such as As (0.21-0.40), Cd (0.04-0.09), Cr (0.16-0.41), Cu (7.31-14. 75), Fe (142.38-303.15), Pb (0.18-0.31), Mn (15.26-22.81), Hg (0.18-0.25), Ni (0.74-1.18), Se (0.13-0.22), and Zn (3.44-4.59), followed by SLW and BW. However, the levels of heavy metals did not exceed the FAO/WHO safe limits. Bioaccumulation factor (BAF), dietary intake modeling (DIM<0.006496), health risk assessment (HRI<0.028571), and target hazard quotient (THQ<1) analyses showed no potential health hazard associated with the consumption of saffron irrigated with DW and SLW. Therefore, the results of this study provide valuable insights into the optimization of irrigation sources for saffron cultivation.

Assessment of the combined inputs of antimicrobials from top soil improvers and irrigation waters on green leafy vegetable fields

Sustainable food systems involve the recycling of biowaste and water. This study characterizes thirty-one top soil improvers of anthropogenic, animal, and green waste origin, along with eleven irrigation waters from rivers, channels, and civil wastewater treatment plants (cWWTPs) for the presence of antimicrobials. Liquid chromatography coupled with hybrid High-Resolution Mass Spectrometry (LC-HRMS/MS) was employed to identify forty-eight drugs belonging to the classes of sulfonamides (11), tetracyclines (7), fluoroquinolones (10), macrolides (12), amphenicols (3), pleuromutilins (2), diaminopyrimidines (1), rifamycins (1) and licosamides (1). Sludge from cWWTPs, animal manure, slurry, and poultry litter exhibited the highest loads for sulfonamides, tetracyclines, fluoroquinolones and macrolides (80, 470, 885, and 4,487 ng g-1 wet weight, respectively) with nor- and ciprofloxacin serving as markers for anthropogenic sources. In compost and digestate, antimicrobials were found to be almost always below the limits of quantification. Reused water from cWWTPs for irrigation in open-field lettuce production were contaminated in the range of 12-221 ng L-1 with sulfonamides, tetracyclines, and fluoroquinolones, compared to very few detected in channels and surface waters. The Antimicrobials Hazard Index (HI), based on the Predicted No Effect Concentration for Antimicrobial Resistance (PNECAMR), was significantly >100 in contaminated topsoil improvers from urban and animal sources. Accounting for worst-case inputs from topsoil improvers and irrigation water, as well as dilution factors in amended soil, fluoroquinolones only exhibited an HI around 1 in open fields for lettuce production. The origin of topsoil improvers plays a pivotal role in ensuring safe and sustainable leafy vegetable production, thereby mitigating the risk of Antimicrobial Resistance (AMR) onset in food-borne diseases and the transfer of AMR elements to the human gut flora.

Impacts of sulfamethoxazole stress on vegetable growth and rhizosphere bacteria and the corresponding mitigation mechanism

Antibiotics are an important pharmaceutical class excessively used by humans. Its presence in the soil can impact plant growth and induce antibiotic resistance. This research studies the effect of sulfamethoxazole (SMX) on plant growth, rhizosphere bacteria composition, and resistance genes. Two sets of vegetables (basil, cilantro, and spinach) were treated separately with water and SMX solution. The plant growth data and soil samples were collected and analyzed. The results revealed that SMX increased spinach leaf length (34.0%) while having no significant impacts on basil and cilantro. On the other hand, SMX improved the bacterial diversity in all samples. The shifts in the abundance of plant growth-promoting bacteria could indirectly affect vegetable stem and leaf length. SMX also significantly increased the abundance of resistance genes Sul1 and Sul2. A further study into the correlation between bacteria highlights the importance of Shingomonas and Alfipia for inhibiting the spread of key resistance gene hosts, namely, Pseudomonas, Stenotrophomonas, and Agrobacterium. This research provides insight into SMX's impact on vegetable growth and microbial diversity. It also points out important microbial interactions that could potentially be utilized to mitigate ARG proliferation.

Antibiotic resistance genes and bacterial diversity: A comparative molecular study of treated sewage from different origins and their impact on irrigated soils

Present study aims to investigate how is soil affected following irrigation with treated effluents of different origins by analysing the bacterial diversity, metabolic diversity and antibiotic resistance genes (ARGs). Comparative analysis with previously reported ARGs in effluents was performed to understand the mobility of ARGs from treated wastewater to the irrigated soil with respect to the control soil regimen. Acinetobacter, Burkholderia and Pseudomonas were observed as the most abundant genera in all the samples. The metabolic gene abundance of all the samples suggests a prominent contribution to natural mineral recycling. Most abundant ARGs observed encode resistance for clindamycin, kanamycin A, macrolides, paromomycin, spectinomycin and tetracycline. Treated effluent reuse did not appear to enhance the ARG levels in soils in most cases except for institutional treatment site (M), where the ARGs for aminoglycosides, β-lactams and sulfonamides were found to be abundantly present in both treated effluent and the irrigated soil. This study finds the importance of wastewater treatment from different origins and the impact of treated wastewater reuse in irrigation. This study also emphasises on the better understanding of ARGs mobility from water to soil.

Influence of Reclaimed Water Quality on Infiltration Characteristics of Typical Subtropical Zone Soils: A Case Study in South China

Irrigation with reclaimed water (RW) can alleviate water scarcity and improve the environmental and economic benefits. However, RW contains a large number of salts, suspended particles, organic matter, etc., which can affect soil infiltration. Previous studies focused on the examination of this effect in alkaline soils, but the infiltration change of acidic soils has seldom been investigated. This study selects four typical types of soil in the subtropical area in the south of China and designs experiments using different concentrations of RW to examine the influence of RW on the infiltration of various acid soils. The short-term impact is examined based on a one-dimensional horizontal method, and the long-term infiltration characteristics are measured by a Mini Disk infiltration meter with one year’s RW irrigation. Results show that RW irrigation can restrain the short-term infiltration of red soil while accelerating that of purple soil, aquic soil and paddy soil. Regarding the long-term effect, the cumulative infiltration of red soil increases with the decline of the concentration of RW, while there is no unique trend for the other soils. After one year’s RW irrigation, physical properties such as soil particle size distribution, texture and EC have changed. For red soil, EC increased significantly with RW irrigation, from 46.7 µS/cm to 101.07 µS/cm. However, regarding aquic soil, EC decreased from 157.05 µS/cm to 123.20 µS/cm. Moreover, the infiltration rate coefficient of red soil and aquic soil exhibits a significant positive correlation with RW concentration (p < 0.01), while the silt content shows a significantly negative correlation (p < 0.01). Furthermore, soil infiltration parameters c and S value of the purple soil, paddy soil, is significantly negative correlated with pH value (p < 0.01). The results reflected that appropriate RW quality for irrigation is different among various soil types, which will influence the sustainable application of RW. It can shed insights into solving the water scarcity issue and improving water sustainability in subtropical regions.

Comparison Study on Sonodirect and Sonoalternate Current Electrocoagulation Process for Domestic Wastewater Treatment

Nowadays, there is a problem related to wastewater handling which is released from different activities. The electrocoagulation method has been a dominant treatment method for wastewater treatment. There are different forms of electrocoagulation methods for wastewater treatment. Nevertheless, there was no comparison made for the removal efficiency of the sonoalternate current (SAC), alternate current (AC), sonodirect current (SDC), and direct current (DC) electrocoagulation process. The efficiency of electrocoagulation methods was compared for their removal of chemical oxygen demand (COD) from Jimma University domestic wastewater. Batch Reactor DC/AC electrocoagulation cell was used to determine the removal efficiency. During the comparison, the response surface methodology (RSM) was used to analyze and optimize the data taken from the laboratory. Besides, ANOVA was used to analyze the interaction effects of different parameters. The removal of COD from domestic wastewater was achieved with DCE, ACE, SDCE, and SACE which were 82.6%, 86.58%, 88.6%, and 92.5%, respectively, under optimal experimental conditions. From the finding, SACE was more successful at removing % COD than the DCE, ACE, and SDCE methods. For DCE and SDCE, the formation of an impermeable oxide layer at the cathode and the occurrence of corrosion at the anode due to oxidation made the COD removal process less efficient compared with SACE processes. From the experimental results it can be concluded that the SACE has the lowest power consumption and higher process efficiency than the other EC methods and can be a promising solution for removing pollutants from domestic wastewater.

Reclamation of Treated Wastewater for Irrigation in Chile: Perspectives of the Current State and Challenges

Reclamation of treated wastewater is considered a viable option for reducing the agricultural and national water deficit, especially in Mediterranean-type and arid climatic conditions. Given that Chile is a country around 40% of whose territory is classified as semi-arid and desert and 20% as Mediterranean, with serious water scarcity problems, and which uses a great deal of the resource in agricultural irrigation, the present paper offers perspectives on the current state of treated wastewater reuse and considers challenges to improving the development of water reclamation for irrigation in Chile as a case study. The methods followed included a systematic literature review to answer two important questions: (a) What is the state of reclamation of treated wastewater for irrigation in Chile? and (b) What criteria/parameters determine the feasibility of reclaiming treated wastewater for irrigation in Chile? The results showed that Chile has been affected by climate change in a short time: a megadrought has occurred over the last ten years, increasing the necessity for the country to secure alternative water sources for irrigation. The country has advanced greatly in wastewater treatment coverage, achieving almost 100% in urban areas, with technologies that can produce quality water as a new water source for irrigation. However, the lack of regulations and limited frameworks could explain the low direct reuse at present—below 1% of total flow. Regarding challenges, the necessity of updates to Chile’s institutional and legal frameworks, besides the inclusion of rural communities and the study of emerging contaminants, will be discussed. By these means, it will be possible to more efficiently utilize recycled wastewater as a new source for irrigation in this country.