- Integrating electrochemical, biological, physical, and thermochemical process units to expand the applicability of anaerobic digestion
- An evaluation of anaerobic co-digestion implementation on New York State dairy farms using an environmental and economic life-cycle framework
- Combining anaerobic digestion and hydrothermal liquefaction in the conversion of dairy waste into energy: A techno economic model for New York state
- Hydrothermal carbonization of anaerobic digestate and manure from a dairy farm on energy recovery and the fate of nutrients
- Repurposing anaerobic digestate for economical biomanufacturing and water recovery
- Insights from Intensive Stream Monitoring in an Eastern Mediterranean Agricultural Catchment Illuminate Anthropogenic Impact on Water Quality
- Assessing the weed infestation potential of dredged streambed sediments targeted for reuse in agricultural fields
- The fuzzy effect of soil conservation practices on runoff and sediment yield from agricultural lands at the catchment scale
- Pesticide load dynamics during stormwater flow events in Mediterranean coastal streams: Alexander stream case study
- Benefits of growing potatoes under cover crops in a Mediterranean climate
- Enhancing Nitrate Removal With Industrial Wine Residue: Insights From Laboratory Batch and Column Experiments Using Chemical, Isotopic and Numerical Modeling Tools
- Hydrosaline balance evolution of an irrigated zone: The case of Lerma basin (Spain, 2004–2020)
- Geochemical modeling of systems affected by irrigation: The case of Lerma basin (Spain, 2004–2020)
- Feasibility of using rural waste products to increase the denitrification efficiency in a surface flow constructed wetland
- Evaluating the potential use of a dairy industry residue to induce denitrification in polluted water bodies: A flow-through experiment
- Main sources and processes affecting dissolved sulphates and nitrates in a small irrigated basin (Lerma Basin, Zaragoza, Spain): Isotopic characterization
- Geochemical processes controlling water salinization in an irrigated basin in Spain: Identification of natural and anthropogenic influence
- Assessment of a newly implemented irrigated area (Lerma Basin, Spain) over a 10-year period. I: Water balances and irrigation performance
- Assessment of a newly implemented irrigated area (Lerma Basin, Spain) over a 10-year period. II: Salts and nitrate exported
- Source and fate of nitrate in contaminated groundwater systems: Assessing spatial and temporal variations by hydrogeochemistry and multiple stable isotope tools
- Three-dimensional hydrogeological reconstruction based on geological depositional model: A case study from the coastal plain of Arborea (Sardinia, Italy)
- Assessment of the Impacts of Phyto-Remediation on Water Quality of the Litani River by Means of Two Wetland Plants (Sparganium erectum and Phragmites australis)
- Comparative study on the performance of Typha latifolia and Cyperus Papyrus on the removal of heavy metals and enteric bacteria from wastewater by surface constructed wetlands
- Nitrogen and phosphorus removal efficiency of three helophytes in constructed surface flow wetlands for urban wastewater treatment
- A novel horizontal subsurface flow constructed wetland planted with Typha angustifolia for treatment of polluted water
Integrating electrochemical, biological, physical, and thermochemical process units to expand the applicability of anaerobic digestion
Anaerobic digestion (AD) is a mature biotechnology-production platform with millions of installations at homes, farms, and industrial/municipal settings. Large-scale industrial, agricultural, and municipal waste-treatment systems may observe novel integration with electrochemical, biological, physical, and thermochemical process units to make AD more attractive. Without governmental subsidies, AD has often only a relatively low economic return or none at all. Diversification of products besides methane in biogas may help to change this. Here, several sections discuss different process units to: 1) upgrade biogas into biomethane; 2) convert carbon dioxide in biogas to more biomethane; 3) generate cooling power from process heat; 4) produce bio-crude oil (bio-oil) from organic matter; and 5) produce a liquid biochemical product from organic matter. This is not meant to be an exhaustive list, but rather a selection of particularly promising process units from a technological view, which are already integrated with AD or close to full-scale integration.
An evaluation of anaerobic co-digestion implementation on New York State dairy farms using an environmental and economic life-cycle framework
Anaerobic digestion systems on dairy farms in New York State rely on gate-fee revenues from co-digestion to ensure economic viability. Yet, because gate fees are paid on a volumetric (or weight) basis, farmers have been compelled to accept large waste volumes. When these wastes are co-digested at rates exceeding the design capacity of the digester, potentially significant technical, environmental, and economic consequences may arise. To better understand these trade-offs, we performed a combined environmental life-cycle and economic assessment with uncertainty analysis. We used the Anaerobic Digestion Model #1 to simulate the co-digestion process for 10 potential co-substrates that were hypothetically mixed with dairy manure throughout a range of loading rates. These simulation results demonstrated the need to include a robust anaerobic digestion model to capture complex process dynamics and loading limits. Results also showed that while higher loading rates were more economically favorable, they caused considerable reductions in the degree of waste stabilization during the digestion process, which dramatically increased downstream methane emissions (e.g., >450%) on the farm compared to manure-only digestion. Regardless, most co-digestion scenarios led to a net reduction in total life-cycle emissions compared to manure only and not digesting the co-substrate due mainly to greater electric power production and synthetic fertilizer replacement. Economically, gate-fee revenue was the most important contributor to profitability, substantially outweighing the revenue from electric power production, while also compensating for the increased handling costs of the added waste volume. Ultimately, the model clearly demonstrated the important environmental and economic implications arising from current anaerobic digestion implementation practices and policy in New York State. In addition, the model highlighted key stages in the system life-cycle, which was used to instruct and recommend immediately actionable policy changes.
Combining anaerobic digestion and hydrothermal liquefaction in the conversion of dairy waste into energy: A techno economic model for New York state
There is increasing global interest and policies being enacted to lower greenhouse gas emissions, especially from the agricultural sector. In the U.S. for example, states with large dairy operations may combine proven manure valorization technologies, such as anaerobic digestion and hydrothermal liquefaction. Sustainable manure treatment would increase the recovery of energy and other useful co-products, namely biogas, biocrude oil and hydro-char as well as lower the environmental impacts. In this study, the economic feasibility of implementing a centralized bioenergy system in New York State was investigated. The feasibility of this transformation depends on many factors, including capital costs, discount rates, and other financing arrangements, electricity selling prices, incentives and farm sizes and locations. For a large-scale implementation in New York State accounting for nearly 50% of the state’s dairy farms, our model of a distributed, hybrid anaerobic/hydrothermal system was shown to treat 590 million liters of wet manure per day, producing 607 million kWh of electricity, 162,000 L of biocrude oil and 117,000 kg of hydro-char per day. Electricity selling price is a critical factor. Increasing the electricity selling price from wholesale ($0.06/kWh) to retail ($0.18/kWh) increased the net present value from $395 million to $1.5 billion (considering a 40-year project lifetime).
Hydrothermal carbonization of anaerobic digestate and manure from a dairy farm on energy recovery and the fate of nutrients
Hydrothermal carbonization (HTC) of raw and anaerobically digested (AD) manure with either water or whey was studied, with the goal of recovering energy and nutrients. Specifically, the impacts of HTC reaction temperature (180–240 °C), solid feedstock, and type of liquid on hydrochar quality and aqueous phase properties were tested. Of the hydrochars produced, the calorific value of whey-based hydrochar was the highest, (19.4 and 16.0 MJ/kg for manure and digestate, respectively). Overall, the net energy gain was higher for HTC of manure with whey (7.4–8.3 MJ/kg dry feedstock) and water (4.4–5.1 MJ/kg) compared to the combined AD-HTC process with whey (4.4–5.3 MJ/kg) and water (2.3–2.9 MJ/kg). Digestate-derived hydrochar contained up to 1.8% P, higher than manure-derived hydrochar (≤1.5%). Using whey as a liquid for HTC increased the aqueous-phase N-P-K concentrations up to 3,200, 410, and 7,900 mg/L, respectively, suggesting its potential use as a liquid fertilizer.
Repurposing anaerobic digestate for economical biomanufacturing and water recovery
Due to mounting impacts of climate change, particularly increased incidence of drought, hence water scarcity, it has become imperative to develop new technologies for recovering water from nutrient-rich, water-replete effluents other than sewage. Notably, anaerobic digestate could be harnessed for the purpose of water recovery by repurposing digestate-borne minerals as nutrients in fermentative processes. The high concentrations of ammonium, phosphate, sulfate, and metals in anaerobic digestate are veritable microbial nutrients that could be harnessed for bio-production of bulk and specialty chemicals. Tethering nutrient sequestration from anaerobic digestate to bio-product accumulation offers promise for concomitant water recovery, bio-chemical production, and possible phosphate recovery. In this review, we explore the potential of anaerobic digestate as a nutrient source and as a buffering agent in fermentative production of glutamine, glutamate, fumarate, lactate, and succinate. Additionally, we discuss the potential of synthetic biology as a tool for enhancing nutrient removal from anaerobic digestate and for expanding the range of products derivable from digestate-based fermentations. Strategies that harness the nutrients in anaerobic digestate with bio-product accumulation and water recovery could have far-reaching implications on sustainable management of nutrient-rich manure, tannery, and fish processing effluents that also contain high amounts of water.
Insights from Intensive Stream Monitoring in an Eastern Mediterranean Agricultural Catchment Illuminate Anthropogenic Impact on Water Quality
Degraded water quality is a well-known impact of intensive agriculture on riverine environments, stemming from nutrient leaching, stream flow harvesting, and other factors. This study analyzes water quality in the Nahalal Stream, focusing on pH, electrical conductivity, and macro-nutrients under varying conditions: upstream vs. downstream, base flow vs. flood, and open vs. closed sluice gates. Contrary to expectations, higher nitrate concentrations were found upstream near the spring, while phosphorus levels were higher downstream. Results indicate that multiple stressors, including riparian vegetation, soil erosion, and water management, significantly influence water quality dynamics, highlighting the necessity of comprehensive restoration efforts.
Assessing the weed infestation potential of dredged streambed sediments targeted for reuse in agricultural fields
Soil erosion causes sedimentation in streams adjacent to agricultural areas, negatively impacting water quality and aquatic ecosystems. Dredged sediments are often dumped into riparian zones, disrupting the eco-hydrological balance and harming stream health. While reusing these sediments as amendments in agriculture may offer a solution, farmers hesitate due to the risk of weed infestations and potential crop losses. This study explores the weed risks associated with using dredged sediments, confirming that their use can lead to increased weed proliferation. We provide a protocol for assessing weed management needs, aiming to mitigate the adverse effects on both crops and water quality.
The fuzzy effect of soil conservation practices on runoff and sediment yield from agricultural lands at the catchment scale
Intensive soil degradation in the Harod Catchment, northern Israel, prompted local authorities to implement soil and water conservation practices. This study, the first of its kind in Israel, quantifies the impact of these practices on water discharge, runoff, and sediment yields across two tributaries of the Harod River: Shkedim and Shunem. Despite similarities in soil and rainfall, the Shkedim catchment, with abundant conservation efforts, showed lower runoff and sediment yields compared to Shunem. However, high soil loss in Shkedim persists due to riparian cultivation and inadequate maintenance of conservation structures, undermining the effectiveness of these practices at the catchment scale.
Pesticide load dynamics during stormwater flow events in Mediterranean coastal streams: Alexander stream case study
Cultivated land significantly contributes to pesticide pollution in riverine and estuarine environments through runoff and soil erosion during rainfall. Traditional ecotoxicological assessments often focus solely on dissolved pesticide concentrations, disregarding the synergistic effects of pesticide mixtures in both dissolved and adsorbed phases. This study characterized and quantified pesticide levels in suspended sediments and water during storm events in the Alexander stream, Israel. Over seven flood events, 63 pesticides were detected, with varying transport dynamics: only 7% of herbicide, 20% of fungicide, and 42% of insecticide loads moved with suspended sediments. Findings highlight the need for comprehensive monitoring in water quality projects.
Benefits of growing potatoes under cover crops in a Mediterranean climate
This 3-year study evaluated the incorporation of cover crops (CC) in commercial potato production to combat severe soil erosion in Mediterranean agriculture. We developed comprehensive agronomic practices for growing potatoes in CC-covered soil, adjusting management and machinery accordingly. Our findings demonstrate that using CC results in no yield reduction or nutrient deficiencies, a 95% decrease in soil erosion, and over a 60% reduction in runoff. Additionally, CC effectively suppresses weed species and biomass. The direct economic benefit for growers is estimated at a 1.3% savings in variable production costs, highlighting the need for public support in adopting these practices.
Enhancing Nitrate Removal With Industrial Wine Residue: Insights From Laboratory Batch and Column Experiments Using Chemical, Isotopic and Numerical Modeling Tools
Groundwater nitrate pollution is a significant global concern resulting from excessive fertilizer use in agriculture. This pollution poses health risks to humans and ecosystems by contaminating drinking water supplies and aquatic ecosystems. Sustainable remediation of nitrate is necessary to safeguard human health and the environment. Successful field‐scale remediation requires laboratory feasibility studies to find the appropriate compounds to reduce nitrate (electron donors) and the best application measures to remove nitrate at a minimum cost. In our research, laboratory experiments were carried out using two industrial wine wastes as electron donors to evaluate their potential to remove nitrate from nitrate‐polluted water. Chemical, isotopic, and numerical modeling tools have been used to quantify the amount of nitrate removed. The results indicate that one product successfully removed nitrate and can be implemented in the field as a mitigation strategy, while the other was ineffective and cannot be used. The isotopic fractionation from the laboratory experiments and the numerical model would be subsequently applied in the field to quantify the efficiency of nitrate removal.
Hydrosaline balance evolution of an irrigated zone: The case of Lerma basin (Spain, 2004–2020)
Geologically saline zones with scarce pluviometry are areas susceptible to salinization of their natural drainage. However, the salinization of the receiving water systems can be accelerated with the implementation of irrigation. This work aims to analyze the effects of irrigation on some zones transformed into irrigation land, from the beginning of the process until its complete consolidation. To this end, salt balances are evaluated as a whole and for each significant chemical element. The study zone is the irrigable area of the Lerma basin (Spain), where hydrosaline balances have been carried out since the hydrological year 2004 (before the implementation of irrigation) until 2020 (after the consolidation of irrigation). The implementation of irrigation in the area has doubled the mass of exported salts up to an average of 3177 kg/ha irrigable·year, for the entire study period. 55 % of that amount results from a global mineral dissolution, although this process seems to decrease with time as these minerals are being flushed from the soil. Before irrigation was implemented, the general global dissolution pattern produced more concentration of most ions (SO42−, Cl−, Mg2+, Na+, and K+) in the water outputs than in the water inputs. After the implementation of irrigation, there were more water inputs than outputs in the balance and that was shown by the decrease in the dissolved HCO3− and Ca2+.These results indicate that the consolidation of irrigation progressively decreases the induced salinization in the water systems that receive the irrigation return flows. Further studies are required to expand the general understanding of the process and its effects, quantify the different geochemical processes involved, and identify possible additional environmental issues induced by irrigation.
Geochemical modeling of systems affected by irrigation: The case of Lerma basin (Spain, 2004–2020)
Geologically “saline” zones with scarce pluviometry, which are already susceptible to the salinization of natural drainage, can experience the acceleration of the salinization of the receiving water systems with the implementation of irrigation. The main objective of this paper is to analyze the geochemical processes that control the variations of the hydrosaline balance due to the implementation of irrigation of the Lerma basin (Spain) from the beginning of its transformation into irrigation land (2004) until the consolidation of irrigation (2020). The results of this study evidence the dissolution of some mineral phases, such as halite, gypsum, and dolomite, and the precipitation of others, such as calcite. Additionally, the final composition of the irrigation return flows cannot be explained without consideration of the Na–Ca exchange. Part of the dissolved Ca2+ is deposited in the soil, which, in turn, contributes with Na+ to the solution. These natural processes are accelerated with irrigation but progressively slow down as the soil salts are washed with time. Although less evident, there is an additional negative agroenvironmental effect associated with the precipitation of calcite and the possible formation of petrocalcic horizons in the soil. The results obtained herein indicate that studies focusing on the salinity of irrigated zones should go a step further and include the geochemical processes in quantifying the global mass of exported salts.
Feasibility of using rural waste products to increase the denitrification efficiency in a surface flow constructed wetland
A surface flow constructed wetland (CW) was set in the Lerma gully to decrease nitrate (NO3−) pollution from agricultural runoff water. The water flow rate and NO3− concentration were monitored at the inlet and the outlet, and sampling campaigns were performed which consisted of collecting six water samples along the CW flow line. After two years of operation, the NO3− attenuation was limited at a flow rate of ~2.5 L/s and became negligible at ~5.5 L/s. The present work aimed to assess the feasibility of using rural waste products (wheat hay, corn stubble, and animal compost) to induce denitrification in the CW, to assess the effect of temperature on this process, and to trace the efficiency of the treatment by using isotopic tools. In the first stage, microcosm experiments were performed. Afterwards, the selected waste material was applied in the CW, and the treatment efficiency was evaluated by means of a chemical and isotopic characterization and using the isotopic fractionation (ε) values calculated from laboratory experiments to avoid field-scale interference. The microcosms results showed that the stubble was the most appropriate material for application in the CW, but the denitrification rate was found to decrease with temperature. In the CW, biostimulation in autumn-winter promoted NO3− attenuation between two weeks and one month (a reduction in NO3− between 1.2 and 1.5 mM was achieved). After the biostimulation in spring-summer, the attenuation was maintained for approximately three months (NO3− reduction between 0.1 and 1.5 mM).
Evaluating the potential use of a dairy industry residue to induce denitrification in polluted water bodies: A flow-through experiment
Improving the effectiveness and economics of strategies to remediate groundwater nitrate pollution is a matter of concern. In this context, the addition of whey into aquifers could provide a feasible solution to attenuate nitrate contamination by inducing heterotrophic denitrification, while recycling an industry residue. Before its application, the efficacy of the treatment must be studied at laboratory-scale to optimize the application strategy in order to avoid the generation of harmful intermediate compounds. To do this, a flow-through denitrification experiment using whey as organic C source was performed, and different C/N ratios and injection periodicities were tested. The collected samples were analyzed to determine the chemical and isotopic composition of N and C compounds. The results proved that whey could promote denitrification. Nitrate was completely removed when using either a 3.0 or 2.0 C/N ratio. However, daily injection with C/N ratios from 1.25 to 1.5 seemed advantageous, since this strategy decreased nitrate concentration to values below the threshold for water consumption while avoiding nitrite accumulation and whey release with the outflow. The isotopic results confirmed that nitrate attenuation was due to denitrification and that the production of DIC was related to bacterial whey oxidation. Furthermore, the isotopic data suggested that when denitrification was not complete, the outflow could present a mix of denitrified and nondenitrified water. The calculated isotopic fractionation values (ε15NNO3/N2 and ε18ONO3/N2) might be applied in the future to quantify the efficiency of the bioremediation treatments by whey application at field-scale.
Main sources and processes affecting dissolved sulphates and nitrates in a small irrigated basin (Lerma Basin, Zaragoza, Spain): Isotopic characterization
Irrigated agriculture affects the quality of water bodies receiving irrigation return flows by both salinization and nitrate pollution, which are controlled by site-specific factors such as geology or agriculture management. In this work, coupled hydrogeochemistry and isotopic data are used to determine the factors controlling water salinization and nitrate pollution in a small irrigated basin in Northeast Spain. This basin is representative of a large irrigated surface in the Middle Ebro Valley, presenting perched aquifers developed over Quaternary glacis and half of its surface under pressurized irrigation. Identification of the controlling factors and the differences between both environmental problems (salinization and nitrate pollution) were established through chemical composition and stable isotope analyses (δD and δ18O-[H2O]; δ34S and δ18O-[SO42]; δ15N and δ18O-[NO3−]) of collected samples in groundwater, springs and surface water during the irrigated and the non-irrigated season. The isotopic composition of water indicated no significant evapoconcentration and a higher influence of irrigation water (rather than precipitation water) on the hydrology of the basin. Sulphate was used as a tracer for salinization. There was no positive correlation between nitrate and sulphate, indicating differences in the controlling factors for each compound. Sulphate content was significantly higher in surface water than in groundwater, and a mixture of soil and local gypsum sulphates explained the isotopic composition of most of the collected samples. One sampling location presented samples affected by fertilizers. Nitrate concentration was significantly lower in surface water than in groundwater, with synthetic fertilizers being the main source, especially the ammonia/urea components. The isotopic composition of surface water suggested a low degree of denitrification while circulating in a diffuse pathway over a low permeability substrate. All water quality information was incorporated into a conceptual model of the study site.
Geochemical processes controlling water salinization in an irrigated basin in Spain: Identification of natural and anthropogenic influence
Salinization of water bodies represents a significant risk in water systems. The salinization of waters in a small irrigated hydrological basin is studied herein through an integrated hydrogeochemical study including multivariate statistical analyses and geochemical modeling. The study zone has two well differentiated geologic materials: (i) Quaternary sediments of low salinity and high permeability and (ii) Tertiary sediments of high salinity and very low permeability. In this work, soil samples were collected and leaching experiments conducted on them in the laboratory. In addition, water samples were collected from precipitation, irrigation, groundwater, spring and surface waters. The waters show an increase in salinity from precipitation and irrigation water to ground- and, finally, surface water. The enrichment in salinity is related to the dissolution of soluble mineral present mainly in the Tertiary materials. Cation exchange, precipitation of calcite and, probably, incongruent dissolution of dolomite, have been inferred from the hydrochemical data set. Multivariate statistical analysis provided information about the structure of the data, differentiating the group of surface waters from the groundwaters and the salinization from the nitrate pollution processes. The available information was included in geochemical models in which hypothesis of consistency and thermodynamic feasibility were checked. The assessment of the collected information pointed to a natural control on salinization processes in the Lerma Basin with minimal influence of anthropogenic factors.
Assessment of a newly implemented irrigated area (Lerma Basin, Spain) over a 10-year period. I: Water balances and irrigation performance
Implementation of irrigated agriculture is common in semi-arid areas around the world. An assessment of irrigation performance is presented herein for a hydrological basin with an area of 7.38 km2, representative of pressurized irrigated areas within the Ebro Basin (Spain). The study covers ten hydrological years, comprehending periods before (2004–2005), during (2006–2008) and after (2009–2013) transformation to irrigated land. Water balances were carried out for each of the 55 agricultural plots and for the totality of irrigable area. Once the water balance for the basin is validated, indicators of irrigation performance were obtained from the soil water balances for the vegetative cycle of the crops in each plot. Water balances presented good results, with balance errors below 10.0% for most of the studied years and an error of 1.2% across the entire study period. After implementation of irrigation, irrigation became the main water input to the basin (approximately 60%) whereas actual evapotranspiration accounted for the major output (approximately 70%). Irrigation efficiency reached 76.1%, while the losses of efficiency were due to evaporation and wind drift of sprinkler irrigation (13.5%) and drainage fraction (10.4%). A water deficit of 17.8% was estimated. The irrigation efficiency increased (1.05% year−1), while the irrigation drainage fraction decreased (0.95% year−1). However, improvements in irrigation performance were not guaranteed as water deficits also increased (0.95% year−1). Optimal water use could be achieved through adequate design of irrigation schedules, i.e., irrigation rates adjusted to the requirements of crops and minimization of evaporation and wind drift losses.
Assessment of a newly implemented irrigated area (Lerma Basin, Spain) over a 10-year period. II: Salts and nitrate exported
Irrigated agriculture impacts the quality of water bodies receiving irrigation return flows. The leaching of salts and nitrate from Lerma Basin (7.38 km2), a newly-implemented pressurized irrigated area in the Ebro Basin (Spain), was assessed in this study for the hydrological years 2004–2013, covering years before (2004–2005), during (2006–2008) and after (2009–2013) the implementation of irrigation. The concentration of salts and nitrate were measured for all the components of the water balance and the amounts of these pollutants coming from the irrigated surface (352 ha) were estimated. Besides, salt and nitrate contamination indices were computed. Under unirrigated conditions, the studied area exported 1.89 Mg ha−1 year−1 and 11.4 kg ha−1 year−1 of salts and nitrate-nitrogen, respectively. These amounts increased to 3.51 Mg ha−1 year−1 for salts and 30.8 kg ha−1 year−1 for nitrate-nitrogen after the implementation of irrigation. Salt and nitrate contamination indices (SCI and NCI, respectively) increased by a factor of three from unirrigated to irrigated conditions, reaching values of 0.96 [Mg ha−1 year−1]/[dS m−1] and 0.12, respectively. Despite these values being well under the threshold considered for more sustainable irrigated areas (SCI < 2.0 [Mg ha−1 year−1]/[dS m−1] and NCI < 0.2), it would be advisable to improve irrigation management to increase water use and decrease leaching. Complementary measures such as adjusting fertilization rates to temporal crop necessities or the use of catch crops may prove to be useful.
Source and fate of nitrate in contaminated groundwater systems: Assessing spatial and temporal variations by hydrogeochemistry and multiple stable isotope tools
Intensive farming often degrades groundwater resources globally, with nitrate concentrations exceeding the 50 mg/L limit for drinking water, posing health risks. Assessing farming’s impact on groundwater spatially and temporally is crucial for policymakers and land managers. This study evaluates nitrate sources and fate in groundwater using hydrogeochemical and isotopic tools in Arborea, Italy, a nitrate vulnerable zone (NVZ) due to intensive farming and livestock. Six hydrogeochemical surveys were conducted bimonthly at 13 sites over 6 km², totaling 82 water samples. Physical-chemical parameters, nitrogen species concentrations, major and minor components, and isotopic values (boron, hydrogen, oxygen, nitrogen, and sulfur) were determined. Groundwater samples, of meteoric origin, showed near-neutral pH (6.8–7.9), variable redox potential, dissolved oxygen, electrical conductivity, and chemical composition. Nitrate levels varied widely (<1 to 162 mg/L), reflecting groundwater interaction with sediments. Shallow wells (5 m depth) showed nitrate peaks during fertilization and irrigation, while deeper wells (15–37 m) had high nitrate in sandy aquifers but low nitrate and high ammonium in clay layers. δ15N and δ18ONO3 values indicated manure or sewage as nitrate sources, with δ11B confirming manure as the predominant source. No seawater mixing was detected, but local mixing between shallow and deep groundwater occurred. Natural nitrate attenuation was observed in deep groundwater with lagoon clays, indicated by specific isotopic values and molar ratios. This study highlights the need for site-specific investigations and adequate groundwater monitoring to design best practices for preserving groundwater under Mediterranean conditions. Animal waste spreading significantly affects groundwater, necessitating thorough monitoring in intensive farming areas.
Three-dimensional hydrogeological reconstruction based on geological depositional model: A case study from the coastal plain of Arborea (Sardinia, Italy)
This study presents a novel approach for the hydrogeological assessment of sedimentary coastal aquifers. Specifically, the methodology is tailored for modeling groundwater flow and nitrates contamination in typical Mediterranean coastal plains with high anthropogenic pressures, as exemplified by the Arborea plain (central western Sardinia, Italy). The study started with development of an updated geological–depositional model based on sequential stratigraphy. Geological and geophysical data, processed in a geographic information system (GIS) environment, supported the definition of a 3D hydrogeological conceptual model and provided a solid basis for the interpretation of groundwater flow directions. The 3D hydrogeological model allowed constraining groundwater circulation, flow paths and distribution of nitrate concentrations in the aquifers. The methodology appears as a valid tool applicable in other coastal areas to determine geological and hydrogeological settings. The definition of a quantitative hydrogeological framework will support the effective management of local water resources.
Assessment of the Impacts of Phyto-Remediation on Water Quality of the Litani River by Means of Two Wetland Plants (Sparganium erectum and Phragmites australis)
This study assesses the effectiveness of a constructed wetland using two aquatic plants, Phragmites australis and Sparganium erectum, in removing pollutants from the polluted waters of the Litani River in Lebanon. Results showed significant improvements in water quality downstream of the wetland, with average pollutant removal efficiencies of 41% for chemical oxygen demand (COD), 54% for biological oxygen demand (BOD5), and 97% for nitrate (NO3−). However, there was an increase in sulfate (SO42−) content by 62%. Despite this, most effluent parameters were within the discharge limits set by the Ministry of Environment (MoE) and the FAO’s wastewater reuse guidelines. Statistical analyses confirmed significant variations between upstream and downstream water samples, highlighting the effectiveness of phytoremediation. The study concludes that constructed wetlands are a viable solution for improving water quality and removing contaminants, with potential for application in other locations.
Comparative study on the performance of Typha latifolia and Cyperus Papyrus on the removal of heavy metals and enteric bacteria from wastewater by surface constructed wetlands
Water scarcity remains a critical issue in semi-arid countries, particularly in Egypt, where agriculture consumes over 85% of water resources. Urbanization, industrialization, and the high cost of advanced water treatment exacerbate this problem, leading to the use of untreated wastewater for irrigation. This study investigates an eco-friendly solution using constructed wetlands planted with Typha latifolia and Cyperus papyrus, supported by a zeolite substrate, to treat wastewater. Results demonstrated that Typha latifolia achieved removal efficiencies of 68.5% for COD, 71% for BOD, 70% for TSS, and 82.3% for ammonia. Cyperus papyrus performed even better, with removal efficiencies of 85.5%, 86.2%, 83.9%, and 92.3%, respectively. Bacteriological parameters decreased by 99.9%, and Salmonella sp was completely removed in three days. Using the Box–Behnken design, the optimal conditions for removing heavy metals like copper and zinc were identified as 72 hours of contact time, with removal rates of 72% for Cu and 84% for Zn.
Nitrogen and phosphorus removal efficiency of three helophytes in constructed surface flow wetlands for urban wastewater treatment
This study compares the effectiveness of three macrophytes (Typha angustifolia, Phragmites australis, and Sparganium erectum) in the secondary and tertiary treatment of urban wastewater in a Mediterranean climate. Over multiple years, Phragmites demonstrated superior growth in height and density, with an aerial biomass of 52.2-54.3 t dw.ha-1, outperforming Typha and Sparganium. The underground biomass was also highest for Phragmites in tertiary treatment. In terms of nutrient absorption, Phragmites and Typha showed significant nitrogen (N) and phosphorus (P) uptake, with Phragmites accumulating more N and P in its underground parts and Typha capturing higher percentages of N (14.8%) and P (33.6%) in its aerial parts. Overall, the study highlights Phragmites australis as the most effective species for nutrient absorption, particularly for nitrogen, in wastewater treatment.
A novel horizontal subsurface flow constructed wetland planted with Typha angustifolia for treatment of polluted water
The study focuses on improving water quality in the Marriott Lake, Egypt, using three constructed wetland configurations: one with Typha angustifolia and an aeration system (CWA), one with Typha angustifolia but no aeration (CWR), and a control system without plants or aeration. These wetlands were tested over four seasons and various hydraulic loading rates (HLR). The CWA system, with perforated pipes for aeration, achieved the highest pollutant removal efficiency. It removed 98.4% of turbidity, 83.3% of BOD5, 95.8% of COD, 99.9% of ammonia, and 94.7% of total nitrogen. It also removed 100% of Vibrio sp. and Escherichia coli, and reduced total bacteria by 92.3% and anaerobic bacteria by 97.5%. Seasonal changes and HLR significantly impacted performance. The study shows that the aerated planted system (CWA) effectively enhances water purification and offers a cost-effective alternative to artificial aeration in constructed wetlands.