Agricultural Wastewater Research Articles

Surface and electrochemical characteristics of S-scheme nanoheterostructured photocatalysts of AgIO3/Cu2SnS3 with enhanced solar energy driven photocatalytic activity

Wastewater treatment is regarded as one of the most challenges to overcome worldwide water threats. As a result, great efforts were devoted to find alterative solutions to maximize the usage of wastewater in industries or agriculture which consumes 70 % of water resources. Interestingly, the utilization of solar energy as a renewable, green and costless energy source is the ideal sustainable solution for wastewater treatment. In this context, Chalcogenides based nanoheterostructures such as AgIO3/Cu2SnS3 were prepared via simple, cost-effective and large-scale methods then utilized as visible light active photocatalysts for wastewater treatment. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), N2 sorpometry (BET), X-ray photoelectron spectroscopy (XPS), ultraviolet visible light spectrophotometry (UV–vis), and Isoelectric point (pHiep) were utilized to investigate the characteristics of nanoheterostructures. The produced nanoheterostructures were evaluated as photocatalysts for amoxicillin photodegradation using solar energy. The AgIO3/Cu2SnS3 (25ACS) demonstrated a superior photodegradation efficiency (93.5 %) after 60 min. Mot-Schottky plots and trapping experiments were carried out to have an extensive insight of the photodegradation mechanism.

Multilayered alginate–hydrogel-functionalized zeolite based on ionic cross-linking composed with a certain Ca2+ and Mg2+ ratio for ammonium adsorption

To enhance ammonium removal in wastewater treatment, a novel adsorbent, multilayered ionic cross–linked alginate–hydrogel–metal-coated zeolite (Al-H-M-Z), was synthesized. Essential divalent cations, 2.60 mmol of Ca2+ and Mg2+, were incorporated into Al-H-M-Z (10 g) in a Ca2+:Mg2+ ratio of 0.73:1.85, facilitating strong alginate–polymer interactions and significantly enhancing the adsorption efficiency. Langmuir and Freundlich isotherm analyses revealed that Al-H-M-Z had a maximum adsorption capacity of 56.5 ± 8.78 mg g−1 and an adsorption intensity of 0.703 ± 0.122, which were 7.24-fold and 1.59-fold higher than those of natural zeolite (7.80 ± 1.09 mg g−1 and 0.444 ± 0.254), respectively. These enhanced properties are attributed to the modified structural and surface chemistry. The Al-H-M-Z coating exhibited a 4.76-fold increase in surface area (3.91 m2 g−1), an 8.94-fold increase in micropore volume (17.8 × 10−3 cm3 g−1), and a 4.22-fold increase in pore diameter (4.14 nm) when compared to the traditional Al-only coating. For applicability, Al-H-M-Z and Z achieved ammonium removal rates of 7.94% and 5.61%, respectively, in actual fish farm wastewater, representing a 1.41-fold improvement in adsorption efficiency after the coating process.

Study the Utilization of Biochar Derived from Sugarcane Waste to Enhance the Biogas Efficiency During the Anaerobic Digestion Process for Treating Pig Farm Wastewater

This experiment aims to study the use of biochar (Biochar, BC) from sugarcane trash through the pyrolysis process at different temperatures of 300, 400, 500, 600 and 700°C. Then add BC to the Anaerobic Digestion (AD) system of wastewater from pig farms, then analyze the characteristics of wastewater and the amount of biogas obtained before and after treatment and to study the characteristics of decomposition, the generation of biogas (Biogas) to the reduction of organic matter in wastewater (COD). From this experiment, it can be concluded that all 6 systems are producing biogas, such as: the normal system and the system with BC filling at different burning temperatures: 300, 400, 500, 600 and 700℃ in the amount of 0.4g into the system. .64, 46.13, 51.90 and 65.98% respectively. From the experiments of all systems, it is observed that the system filled with BC at a temperature of 700℃ is able to produce biogas the best because the high heating temperature will cause the electrons of the charcoal to break easily and cause more holes to be a place for microbes to grow well. A comparison of the conventional system and adding biochar with the same amount but different temperature into the sewage treatment system without using air can be concluded that the conventional system is the generation of biogas is still low efficiency and the system of adding BC at the temperature of 300, 400, 500, 600℃ in the same amount. Notice that the generation of biogas is higher in order and the filling of BC at a temperature of 700℃ is able to produce biogas higher than other systems.

Molecular imprinting based sensor system developed using polymeric nanoparticles for detecting 17β‐estradiol in agricultural wastewater

AbstractMicro pollutants pose a significant issue in water ecosystems. Particularly high concentrations of 17β‐estradiol (E2) have been identified in agricultural wastewater, which poses harmful effects on aquatic organisms and disrupts ecosystem balance. Therefore, effective determination of E2 from water sources is crucial. This study developed a biosensor capable of detecting E2 in wastewater using specific polymer nanoparticle synthesis through molecular imprinting. Est‐imp‐poly(multi‐walled carbon nanotubes‐glycidyl methacrylate [MWCNT‐GMA]) polymer nanoparticles were synthesized using a surfactant‐free emulsion polymerization method, and their characterization was conducted using FTIR and scanning electron microscopy (SEM) technologies. The Qmax value for Est‐imp‐poly(MWCNT‐GMA) nanoparticles in a 1 mg/mL E2 solution was determined to be 140 ppm. Comparing adsorption capacities, the molecularly imprinted nanoparticles (MIP) showed nearly five times higher E2 adsorption compared to non‐imprinted polymers (NIP). The Est‐imp‐poly(MWCNT‐GMA)‐Nafion/screen‐printed electrode (SPE) system was employed for analyzing wastewater samples. The current measurements taken at various concentrations in the wastewater consistently matched the E2 concentration calibration curve. The limit of detection (LoD) and limit of quantification (LoQ) were determined to be 0.042 and 0.12 μM, respectively. The biosensor demonstrated a linear working range from 0.12 to 50 μM, with a high correlation coefficient (R2 = 0.9927). These results highlight the potential of the developed biosensor for detecting E2 in real samples.

Examining the efficacy of biological filters in the removal of agricultural pesticides and nutrient elements from agricultural drainage water

The high water consumption in agriculture has led to an obvious water crisis in this sector, and the use of unconventional water sources, especially agricultural drains, is considered necessary. For this purpose, the present study was carried out to evaluate the efficiency of biological filters with different types of substrates for treating agricultural wastewater in Khuzestan province, located in the south of Iran, to use receptive resources and reuse them in agriculture. Next, the efficiency of four types of biological filters for treating agricultural drainage water with different retention times was evaluated. Sawdust, cotton stalks, wheat straw, stubble, and rice husk were used as filters. Qualitative factors included agricultural pesticides (Atrazine, Randup, Paraquat, and 2, 4-D) and nutrients (nitrate, nitrogen, phosphate, and phosphorus). By examining the trend of increasing the retention time and the corresponding removal percentage, it was observed that the retention time has a direct relationship with the amount of removal efficiency of nutrients and agricultural toxins. As the residence time increases, the average amount of nutrient compounds in different filters decreases, and their removal percentage increases. The highest removal percentage of nitrate, total nitrogen, phosphate, and total phosphorus was 74.03, 71.66, 57.97, and 61.85% in the sawdust filter and was assigned to 10 days. The highest percentage of removal of Atrazine, Tofudi, Paraquat, and Roundup toxins with a removal efficiency of 91.73, 84.27, 89.81, and 88.46% was also observed in the treatment of sawdust for 10 days. The sawdust filter showed a good performance in removing the parameters of agricultural toxins and nutrient compounds in a retention time of 10 days compared to other filters and retention times. As a general result, the sawdust filter can be cited as a reliable substrate with acceptable efficiency compared to other filters.

Evaluation of the pollutant removal efficiency of swine wastewater through two configurations of hybrid wetlands with tropical ornamental plants

The pig farming industry in Mexico is an important economic activity that is growing significantly, generating large volumes of wastewater that negatively affect water bodies and human health. The lack of adequate treatment systems exacerbates this problem. Hybrid constructed wetlands that combine Vertical Flow Constructed Wetlands (VF-CWs) and Horizontal Flow Constructed Wetlands (HF-CWs) offer an economical and effective treatment using natural processes. The objective was to evaluate the removal of contaminants from pig farm wastewater using two configurations of hybrid systems with ornamental plants. Two configurations were established: System I: VF-CWs + HF-CWs and System II: HF-CWs + VF-CWs. The VF-CWs were planted with Canna hybrids and the HF-CWs with Heliconia latispatha. The results indicated higher removal efficiencies of organic matter, nitrogen, and phosphorus in System I (BOD5: 72.99 %, COD: 71.41 %, TN: 79 %, NH4+: 84.31 %, NO3-: 74.29 %, TP: 59.54 %, FC: 99.88 %) compared to System II (BOD5: 66.80 %, COD: 67.01 %, TN: 77.90 %, NH4+: 82.31 %, NO3-: 70.48 %, TP: 55.81 %, FC: 99.89 %), regarding FC, the same results were obtained in both systems. Both plant species showed vigorous development, although the growth of Heliconia latispatha was more notable. In conclusion, the results suggest that the VF-CWs + HF-CWs configuration in hybrid wetlands could be a suitable option for treating this type of effluent.

Microbial strategies for lead remediation in agricultural soils and wastewater: mechanisms, applications, and future directions.

High lead (Pb) levels in agricultural soil and wastewater threaten ecosystems and organism health. Microbial remediation is a cost-effective, efficient, and eco-friendly alternative to traditional physical or chemical methods for Pb remediation. Previous research indicates that micro-organisms employ various strategies to combat Pb pollution, including biosorption, bioprecipitation, biomineralization, and bioaccumulation. This study delves into recent advancements in Pb-remediation techniques utilizing bacteria, fungi, and microalgae, elucidating their detoxification pathways and the factors that influence Pb removal through specific case studies. It investigates how bacteria immobilize Pb by generating nanoparticles that convert dissolved lead (Pb-II) into less harmful forms to mitigate its adverse impacts. Furthermore, the current review explores the molecular-level mechanisms and genetic engineering techniques through which microbes develop resistance to Pb. We outline the challenges and potential avenues for research in microbial remediation of Pb-polluted habitats, exploring the interplay between Pb and micro-organisms and their potential in Pb removal.

Application of microbubble air flotation to harvest Microcystis sp. from agriculture wastewater: The regulation and mechanisms.

The harvesting of microalgae is the main bottleneck of its large-scale biomass production, and seeking an efficient, green, and low-cost microalgae harvesting technology is one of the urgent problems to be solved. Microbubble air flotation has been proven to be an effective measure, but the mechanisms of microbubbles-algal cell attachment are still unclear. In this study, microbubble air flotation was used as a harvesting method for Microcystis cultured in agricultural wastewater. The process mechanism of microbubble air flotation harvesting microalgae in wastewater was fully revealed from three aspects (the design of bubble formation, the adhesion law, and the recovery rate of microalgae under different working conditions). The results show that the length of the release pipe is the main factor affecting the proportion of microbubbles with a particle size of less than 50 μm. In the process of adhesion, when the particle size of microbubbles is 0.6-1.7 times the size of Microcystis, the adhesion efficiency of microbubbles to Microcystis is the highest. Under the conditions of pressure 0.45 MPa, gas-liquid ratio 5%, and release pipe length 100 cm, the harvesting performance of Microcystis was the best. Microbubble air flotation has better harvesting performance (63.5%, collection rate) of Microcystis with higher density. By understanding the mechanism of microbubble flotation, the technical parameters of microbubble flotation for harvesting energy microalgae are optimized to provide support for the development of efficient and low-cost devices and equipment for collecting microalgae.

Performance evaluation of integrated Upflow Anaerobic Sludge Blanket reactor with trickling filter used for municipal wastewater treatment and effluent reuse potential for agriculture

Effluent reuse is a rapidly growing field of research where assessing the quality of effluent is one of the focus areas. This research examines the viability of using wastewater in agriculture by testing an integrated Upflow Anaerobic Sludge Blanket (UASB) reactor with a trickling filter (TF) system during the dry season. Compliance monitoring was conducted for 30 days from May 11 to June 9 of 2021. Samples were collected, handled, and analyzed following standard wastewater analysis procedures for biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), volatile suspended solids (VSS), cations, anions, heavy metals, E. coli, and helminth egg. The UASB-TF system in Kality wastewater treatment performed well in removing COD, BOD5, and TSS with average removal rates of 80.5%, 82.9%, and 80.9%, respectively, compared well with similar treatment configurations. The effluent quality satisfied the national inland discharge limit with a residual concentration of 125.1 mg/L for COD, 61.7 mg/L for BOD5 and 85.8 mg/L for TSS. On the other hand, high concentrations of chromium, nitrate-nitrogen, and helminth egg count restricted effluent reuse for agricultural purposes due to high health risks and environmental contamination. We found out that discharging industrial sewage into the domestic sewer network could inhibit microbial growth and affect the biological treatment processes. Furthermore, adopting integrated treatment systems in developing countries might face operational challenges and monitoring nitrate, helminth egg, and heavy metals would help provide timely operational feedback. An appropriate tertiary treatment unit—constructed wetlands or polishing ponds—is therefore needed to be introduced to ensure effluent reuse for agricultural purposes.

МИКРОВОДОРОСЛИ ХЛОРЕЛЛА ДЛЯ ОЧИСТКИ СТОКОВ В СЕЛЬСКОМ ХОЗЯЙСТВЕ

A promising way to solve current problems of energy saving and reducing environmental pollution may be the use of microalgae. These simple microorganisms are capable of purifying contaminated wastewater in agriculture. Wastewater contains nitrogen, phosphorus, sulfate and other contaminants. In order to optimize the technology of obtaining biodiesel fuel from lipid components in the conditions of small agricultural producers, the possibility of using Chlorella vulgaris in cleaning from ammonium ions and phosphate ions was studied. Chlorella was cultivated in a photobioreactor on a standard Tamiya medium and wastewater for 10 days at a temperature of 30 ° C and an illumination of 14 kLx in the red (620-740 nm), blue (430-500 nm) and green (500-565 nm) wavelength ranges. The filtrate of the microalgae suspension was collected over several days and assessed for the content of phosphate and nitrate ions using a photometric method. The greatest increase was observed with illumination in the red range (2 times higher), the minimum value in the green. The studies found that cell growth occurs both in synthetic, standard nutrient media and in wastewater, the latter being more costeffective. It was found that when adding chlorella to wastewater, the maximum decrease in the content of ammonium ions and phosphate anions is observed on the 6-7th day (by 19-59% and 5-29%, respectively), which is most likely due to the use of these elements by microalgae for nutrition and maintenance of life. A scheme for growing Chlorella vulgaris on wastewater for further production of lipid components of biodiesel fuel is proposed.

Electrochemical membrane systems for remediating ammonium-containing wastewater via coupling capacitance adsorption and oxygen reduction

As the main nitrogen-containing pollutant of industrial and agricultural wastewater, ammonium (NH4+) is obtainable from the natural nitrogen cycle and industrial emission. Electrochemical recovering nitrogen (N) from nitrate-polluted wastewater to produce ammonia (NH3) is a promising route to mitigate pollution risks and create economic values. Since side reactions at the electrodes are inevitable, and the competition mechanism between electric double layer capacitance (EDLC) behavior and side reactions is still unclear. Herein, electrochemical selective NH4+ recovery from wastewater was achieved by coupling NH4+ adsorption and side oxygen reduction reaction (ORR) in a novel electrochemical membrane extraction system using Ti3C2TX-based gas-diffusion cathodes. Batch experiments showcase simultaneous NH4+ removal and recovery, with TiOX/TiC-C exhibiting the highest removal capability of 408 mgN g−1. In situ Raman spectroscopy revealed the critical role of the four-electron transfer ORR reaction in the conversion of NH4+ to NH3. Density functional theory (DFT) showed that excellent electron-donating ability for NH4+ of TiOX/TiC-C electrode (1.97 eV) facilitated NH4+ diffusion onto electrode interface. The study sheds light on the intricate interplay between NH4+ adsorption and ORR, highlighting the significance of tailored support and vacancy engineering in advancing wastewater treatment and resource recovery.

Electrocoagulation process for phosphate recovery of agricultural wastewater: effect of calcium adding, voltage, and time.

Recovery of valuable resources, such as phosphate recovery from wastewater, can help close the nutrient cycle and is interesting to investigate. This study aims to evaluate phosphate recovery and set aside TOC, OC, and IC in agricultural wastewater using electrocoagulation with a helix electrode configuration. This study employed the Response Surface Methodology (RSM) for statistical analysis and modeling, utilizing a central composite design (CCD). Variation of calcium concentration (2-7mg/L), voltage (15-45V), and electrocoagulation time (5-15min) was applied in an electrocoagulation reactor with a helix-shaped stainless steel cathode and a solid cylindrical Mg anode. Based on RSM analysis, electrocoagulation with a helical electrode configuration significantly affects phosphate recovery and the removal of TOC, OC, and IC when treating agricultural wastewater. Under operating conditions of 15V, 15min time, and 2mg/L calcium concentration, we achieved the lowest phosphate concentration of 0.003mg/L (99.74% reduction). The highest TOC allowance is > 100% of the initial concentration, the TC allowance is 55.79%, and the IC allowance is 30.91%. The formation of metal hydroxides affects the efficiency of TOC removal in the electrocoagulation process, and higher electrolysis times lead to higher TOC removal efficiency. Higher voltages also improve the coagulation and flotation processes in the reactor. Calcium concentration plays a role in enhancing the flocculation process and binding phosphonates from wastewater.

Wastewater and agriculture in Mezquital valley (Mexico): analyzing alternatives from circular economy and ecological economy using bibliometric review

Given the water crisis worldwide, using wastewater in agriculture is an alternative because it employs around 70% of the planet’s freshwater despite the fact the implications of its use without prior treatment are diverse. The Mezquital Valley in Mexico is the second largest region in the World to use this type of water, and various disciplines have studied it for decades. Still, it has not been systematized to analyze the evolution of the impacts of its use in the region, nor has it been analyzed from a theoretical perspective. This work aim is analyzing the contributions of the Circular Economy and the Ecological Economy in order to provide an explanation of the problem and possible alternatives for using this vital resource. The theoretical analysis is supported by a schematic review of scientific articles published from 1990 to 2022 in the Scopus database, using bibliometric analysis.

The impact of shade net use on total nitrogen removal by duckweed (Lemna perpusilla) at different levels of catfish farming effluent

Duckweed (Lemna perpusilla) has been shown to reduce nutrient levels in aquaculture effluent, particularly total nitrogen, which can be caused by a variety of organic contaminants in water. Duckweed biomass is an important source of bioenergy and phytoremediation in aquaculture. This aspect makes it a viable solution for sustainable integrated aquaculture, although appropriate duckweed biomass development is critical to its success and long-term survival. Duckweed growth, as an autotroph, is controlled by two factors: nutrition and sunlight. The aquaculture production cycle changes nutrient content in medium culture based on feed, fish age, and density, while weather influences solar radiation. The study aims to investigate duckweed growth response and phytoremediation capacity by analyzing changes in catfish farming waste-water quality grouped by fish age (L1: 2 months, L2: 3 months, and L3: 4 months) and shade net treatment at 25 % sunlight blocking (N25), 50 % (N50), and no shade net (N0). The experiment was carried out in triplicate in a semi-outdoor growth system placed in a greenhouse. It comprised of three series of duckweed culture containers filled with catfish farming wastewater, each with a working volume of 50 L. A total of 48 duckweed culture containers were floated inside a series of Recirculating Aquaculture System (RAS) tanks. Biomass harvesting and water quality monitoring were done every three days for a period of 18 days. N25 had the highest biomass weight, productivity, and average TN elimination efficiency, with values of 225.21 ± 140.04 g, 50.05 ± 10.06 g/(m2.d), and 61.94 ± 8.01 %, respectively (P < 0.05). The N0 values were 190.80 ± 117.52 g, 42.40 ± 9.29 g/(m2.d), and 55.61 ± 6.85 % (P < 0.05). The lowest values observed in N50 were 72.27 ± 55.70 g, 16.06 ± 4.90 g/(m2.d), and 51.67 ± 4.10 % (P < 0.05). This study proved the optimal duckweed growth and TN removal effectiveness with N25 under varying light intensity, allowing for the long-term use of duckweed in waste management and integrated aquaculture.

Occurrence, Bioaccumulation, and Risk Assessment of Organophosphate Esters in Rivers Receiving Different Effluents.

Organophosphate esters (OPEs), as alternatives to brominated flame retardants, are extensively used in both production and daily life, with their environmental contamination and toxic effects being a concern. This study investigated the concentration levels, bioaccumulation, and ecological effects of OPEs in five different effluent-receiving rivers. The results demonstrate that the concentration range of Σ13OPEs across the five rivers was between 142.23 and 304.56 ng/L (mean: 193.50 ng/L). The highest pollution levels of OPEs were found in rivers receiving airport and industrial wastewater, followed by agricultural wastewater, mixed wastewater, and domestic wastewater. Tris(2-chloroisopropyl) phosphate (TCPP), triethyl phosphate (TEP), and tricresyl phosphate (TCrP) were identified as the main pollutants. The accumulation concentrations of OPEs in fish ranged from 54.0 to 1080.88 ng/g dw, with the highest bioaccumulation found in Pelteobagrus fulvidraco, followed by Carassius auratus and Misgurnus anguillicaudatus. The brain was the primary organ of accumulation, followed by the liver, gills, intestine, and muscle. Tri-n-propyl phosphate (TPeP) and TEP exhibited the highest bioconcentration, with log BAF values exceeding three. The bioaccumulation of OPEs was influenced by pollutant concentration levels, hydrophobic properties, and biological metabolism. Ecological risk assessment revealed that the cumulative risk values of Σ13OPEs ranged from 0.025 to 16.76, with TCrP being the major contributor. It posed a medium-low risk to algae but a high risk to crustaceans and fish.

Distribution characteristics and risk assessment of fluoride in surface water of urban typical rivers

Recent research on fluoride in water primarily focuses on groundwater; however, the potential environmental risks of fluoride in urban rivers should not be overlooked. In 2023, this study collected 135 surface water samples from the Ershibu River in Hefei, China, during various flood periods. Through descriptive statistical analysis, correlation analysis, principal component analysis-multiple linear regression (PCA-MLR) modeling, hazard quotient (HQ) assessment, and Monte Carlo simulation analysis, the spatial and temporal distribution, potential sources, and health risks of fluoride were investigated. The results showed that fluoride concentrations in the Ershibu River ranged from 0 to 1.38 mg/L. According to the PCA-MLR calculations, industrial pollution (73.92 %) was identified as the main source, followed by hydrogeochemical evolution (16.10 %) and agricultural activities (9.98 %). The HQ analysis revealed that the average exceedance rates of HQ for the five exposed populations were as follows: infants (64.45 %) > young children (2.22 %) = adults (2.22 %) > children (0) = teenagers (0). Therefore, relevant authorities should improve defluoridation facilities to reduce fluoride levels in industrial and agricultural wastewater and implement measures to protect public health. Future research should investigate the migration processes and toxicity mechanisms of fluoride more thoroughly.

Modeling Bibb Lettuce Nitrogen Uptake and Biomass Productivity in Vertical Hydroponic Agriculture

Global fertilizer production and mismanagement significantly contribute to many harmful environmental impacts, revealing the need for a greater understanding of crop growth and nutrient uptake, which can be used to optimize fertilizer management. This study experimentally adapts first-principles microbial modeling techniques to the hydroponic cultivation of Bibb lettuce (Lactuca sativa) under nitrogen-limited conditions. Monod and Michaelis–Menten’s approaches are applied to predict biomass productivity and nutrient uptake and to evaluate the feasibility of reclaimed wastewater as a nutrient source of nitrogen. Experimental and modeling results reveal significantly different kinetic saturation constants (Ks = 1.331 and Km = 17.887 mg L−1) and a corresponding cell yield strongly dependent on nutrient concentration, producing visually and compositionally distinct tissue between treatments receiving ≤26.2 and ≥41.7 mgN L−1. The resulting Monod model overestimates dry mass predictions during low nutrient conditions, and the collective results support the development of a dynamic Monod curve that is temporally dependent during the plants’ lifecycle. Despite this shortcoming, these results support the feasibility of reclaiming nitrogen from wastewater in hydroponic agriculture, expecting to produce lesser biomass lettuce exhibiting healthy tissue. Furthermore, this study provides a mathematical foundation for agricultural simulations and nutrient management.

Growth of complete ammonia oxidizers on guanidine

Guanidine is a chemically stable nitrogen compound that is excreted in human urine and is widely used in manufacturing of plastics, as a flame retardant and as a component of propellants, and is well known as a protein denaturant in biochemistry1–3. Guanidine occurs widely in nature and is used by several microorganisms as a nitrogen source, but microorganisms growing on guanidine as the only substrate have not yet been identified. Here we show that the complete ammonia oxidizer (comammox) Nitrospira inopinata and probably most other comammox microorganisms can grow on guanidine as the sole source of energy, reductant and nitrogen. Proteomics, enzyme kinetics and the crystal structure of a N. inopinata guanidinase homologue demonstrated that it is a bona fide guanidinase. Incubation experiments with comammox-containing agricultural soil and wastewater treatment plant microbiomes suggested that guanidine serves as substrate for nitrification in the environment. The identification of guanidine as a growth substrate for comammox shows an unexpected niche of these globally important nitrifiers and offers opportunities for their isolation.

Agricultural Runoff Effects on Leaf Litter Decomposition: A Comparative Study in Natural and Constructed Deltaic Mediterranean Wetlands

Wetlands, widely distributed and hotspots of biodiversity, play a crucial role in global biogeochemical cycles and human well-being. However, despite their ecological importance, wetlands worldwide are under threat due to widespread conversion into agricultural fields, leading to changes in hydrology, increased salinity, and more frequent eutrophication. In response to these challenges, constructed wetlands are created to treat agricultural wastewater and mitigate eutrophication. This study aims to assess the effect of natural vs. constructed wetlands on ecosystem functioning (organic matter decomposition of the dominant vegetation: Phragmites australis and Typha angustifolia). We conducted this study in the Ebro River Delta (NE Spain), which represents a deltaic wetland affected by agricultural land-use changes, examining two constructed and two natural wetlands. Our findings indicate that the influence of agricultural runoff on the decomposition process was similar in both types of wetlands, suggesting that freshwater agricultural runoff has a consistent effect on ecosystem functioning, regardless of its origin, natural vs. constructed. Differences in macroinvertebrate communities associated with leaf litter were likely due to specific conductivity but did not impact decomposition rates. The estimated time required to decompose 95% of the T. angustifolia litter produced annually in the studied wetlands ranged from 288 to 856 days. In constructed wetland, this decomposition time exceeded one year, contributing to soil formation and carbon sequestration in wetland ecosystems. Our study suggests that the utilization of constructed wetlands for treating agricultural runoff can aid in mitigating the impacts of agricultural land use in these areas.

Laccase Immobilized on Arginine-Functionalized Boron Nitride Nanosheets for Enhanced Atrazine Degradation.

Enzyme-mediated systems have been widely employed for the biotransformation of environmental contaminants. However, the catalytic performance of free enzymes is restricted by the rapid loss of their catalytic activity, stability, and reusability. In this work, we developed an enzyme immobilization platform by elaborately anchoring fungal laccase onto arginine-functionalized boron nitride nanosheets (BNNS-Arg@Lac). BNNS-Arg@Lac showcased ∼75% immobilization yield and enhanced stability against fluctuating pH values and temperatures, along with remarkable reusability across six consecutive cycles, outperforming free natural laccase (nlaccase). A model pollutant, atrazine, was selected for a proof-of-concept demonstration, given the substantial environmental and public health concerns in agriculture runoff. BNNS-Arg@Lac-catalyzed atrazine degradation rate was nearly twice that of nlaccase. Moreover, BNNS-Arg@Lac consistently demonstrated superior atrazine degradation in synthetic agricultural wastewater and various mediator systems compared to nlaccase. Comprehensive product analysis unraveled distinct degradation pathways for BNNS-Arg@Lac and nlaccase. Overall, this research provides a foundation for the future development of enzyme-nanomaterial hybrids for degrading environmental chemicals and may unlock new potential for green and efficient resource recovery and waste management strategies.