Nitrate-contaminated Water Research Articles

Single Atom Catalyst for Nitrate-to-Ammonia Electrochemistry.

Various life forms suffer from the negative effects of nitrate when it accumulates in water bodies, which is a major concern in the present day. The removal of nitrate from water bodies is a critical challenge, and the most effective method to achieve that is to change it into ammonia. Ammonia is a clean energy source and a vital input for the fertilizer industry. The Haber-Bosch process, which dominates the industrial production of ammonia, requires a lot of energy. A more sustainable way to produce ammonia is to use nitrate-contaminated water and reduce it to ammonia through electrocatalysis. This review is constituted of amalgamated articles featuring unique conditions that affect the productivity and activity of the transition metal single atom catalyst (TNMSAC) for the electrocatalytic nitrate reduction to ammonia (NRA) reaction. It explores factors such as nitrate ion adsorption, the characteristics of the central electroactive transition metal, the type of coordinating atoms, the impact of potential on stability, and the interplay among single atoms on the selectivity and yield of ammonia gas. In addition, this review also covers advanced concepts such as dual-atom catalysts, dual single atom catalysts, and single atom alloys. The review will provide valuable guidance for enhanced comprehension and strategic designing of TNMSAC for the electrocatalytic conversion of NRA, which will contribute to achieving a green ammonia economy.

Electrocatalytic nitrate reduction on Fe, Fe3O4, and Fe@Fe3O4 cathodes: Elucidating structure-sensitive mechanisms of direct electron versus hydrogen atom transfer

Electrochemical nitrate reduction (NO3RR) offers a promising avenue for treating nitrate-contaminated water and recovering ammonia (NH3), yet the complexities of direct electron transfer (DET) and hydrogen atom transfer (HAT) mechanisms crucial for efficiency remain elusive. This study bridges the gap with a combined experimental and theoretical approach, elucidating the impact of catalyst structure on NO3RR pathways. We discover that catalysts favoring strong NO3− adsorption and efficient water dissociation were more inclined towards DET, enhancing denitrification. The Fe@Fe3O4/FF cathode, leveraging the synergistic interplay between metallic Fe and Fe3O4, excelled in NO3RR via DET, achieving an NH3 yield of 0.28 mmol h−1 cm−2 and a Faradaic efficiency of 95.7% for NH3 at -1.6 V (vs. SCE), with minimal nitrite accumulation at 100 mmol/L nitrate. Conversely, the Fe/FF and Fe3O4/CC cathodes showed reduced NH3 production and increased nitrite levels, attributed to the lack of Fe3O4 and metallic Fe, respectively, resulting in a dominant HAT mechanism. Moreover, Fe@Fe3O4/FF facilitated complete denitrification in real wastewater treatment by harnessing Cl− for electrochemically mediated breakpoint chlorination. This research not only deepens our understanding of NO3RR mechanisms but also paves the way for designing superior nitrate reduction catalysts.

Efficient electrocatalytic nitrate reduction on molecular catalyst with electron-deficient single-atom Cuδ+ sites

Electrocatalytic nitrate (NO3−-N) reduction to ammonia (NH3-N) (ENRR) coupled with NH3-N separation represents a sustainable process for nitrate pollution mitigation. The −(Cuδ+-N4)- moiety-bearing carbon materials (SCMs) are robust ENRR catalysts but suffer from energy-intensive synthetic process. Furthermore, the complexity in altering the coordination environment of Cuδ+ raises the difficulty in optimizing its electron-deficiency for an enhanced ENRR. Herein the copper phthalocyanine (CuPc) and copper perfluorocyanine (CuF16Pc) molecular catalysts, which share the same −(Cuδ+-N4)- moiety with SCMs but are commercially available, are attempted for ENRR. The CuF16Pc, which differs from CuPc by the substitution of the H in Pc with F, shows alleviated intermolecular agglomeration and increased electron-deficiency of.the Cuδ+ center, owing to the electron-withdrawing effect of F. The alleviated intermolecular agglomeration exposes more Cuδ+, which makes CuF16Pc outperform CuPc (2254.9 vs. 1979.3 mg-NH3 h−1 gCu−1) and most of the reported catalysts in the mass activity of ENRR. However, the Cuδ+ with a larger electron-deficiency in CuF16Pc is less active than that in CuPc for ENRR, owing to the higher energy barrier for NO* hydrogenation to NOH* on it. It reminds us that the CuPc is more ideal for ENRR if its agglomeration issue can be addressed. Finally, an integrated continuous-flow system composed of the CuF16Pc-driven ENRR and PVDF fibers-mediated NH3 separation is customized, which enables a steady NO3−-N removal efficiency of 96.4 % and NH3-N recovery efficiency of 97.2 % from simulated nitrate-contaminated water.

Nitrate Sensor with a Wide Detection Range and High Stability Based on a Cu-Modified Boron-Doped Diamond Electrode.

This paper describes an electrochemical sensor based on a Cu-modified boron-doped diamond (BDD) electrode for the detection of nitrate-contaminated water. The sensor utilizes the catalytic effect of copper on nitrate and the stability of the BDD electrode. By optimizing the electrolyte system, the linear detection range was expanded, allowing the sensor to detect highly concentrated nitrate samples up to 100 mg/L with a low detection limit of 0.065 mg/L. Additionally, the stability of the sensor was improved. The relative standard deviation of the current responses during 25 consecutive tests was only 1.03%. The wide detection range and high stability of the sensor makes it suitable for field applications and the on-site monitoring of nitrate-contaminated waters.

Boosting nitrate electroreduction reactivity with a 3D Cu-Pd bimetallic flow-through electrode

NO3− pollution in water and wastewater is a pressing global environmental issue, leading to the deterioration of water quality and an increased risk to human health. Herein, we present a three-dimensional (3D) flow-through electrode composed of electrodeposited Cu-Pd bimetallic catalysts on a nickel foam. The Cu-Pd bimetallic particles exhibited cluster-like shapes on the surface of the nickel foam. This electrode design enhanced the electrochemical activity of the NF/Cu63Pd37 electrode for NO3− reduction, as evidenced by linear sweep voltammetry (LSV) measurements. By tailoring the Cu-Pd ratio (Cu:Pd 0.63:0.37), the NF/Cu63Pd37 electrode showed the highest reactivity of NO3− reduction and selectivity (43.1 %) toward N2. Importantly, the NF/Cu63Pd37 electrode not only achieved over 99 % NO3− removal but also exhibited a higher kinetic rate constant of 1.44 h−1 in the flow-through mode. In contrast, in the flow-by mode, NO3− removal was 67.5 % with a lower reaction rate constant of 0.30 h−1. Furthermore, the NF/Cu63Pd37 electrode exhibited a reduced energy consumption (EEO) of 6.86 kWh m−3 order−1 in the flow-through mode, contrasting with 13.66 kWh m−3 order−1 in the flow-by mode. Moreover, the results also demonstrated successful NO3− remediation across various initial pH values (pH 3, 6, 9, and 11) and NO3− concentrations (100, 200, and 300 mg L−1). The results of this study highlight that the 3D Cu-Pd bimetallic flow-through electrode, with its high reactivity in reducing NO3−, marks a significant advancement in efficiently treating nitrate-contaminated water.

Factors Affecting Nitrogen Use Efficiency (NUE): Meta Analysis

Nitrogen (N) is an essential and limiting nutrient for crop production, as it is a structural part of plants and is involved in various processes. Worldwide, agricultural soils lack one or more essential nutrients, and nitrogen is one of them. Adding a sufficient amount of N will increase production. However, the overuse of N and loss of N from the soil-plant system is detrimental to the environment and results in economic losses. Nitrogen has reactive forms like ammonia, ammonium, nitrate, nitrite, nitric oxide, and nitrous oxide. Some reactive forms of N are harmful to humans, animals, plants, and microbial ecology. Nitrate can cause the eutrophication of surface water and contamination of groundwater. Drinking nitrate-contaminated water can cause methemoglobinemia and other health issues. Nitrous oxide emission depletes the ozone layer and contributes to climate change. Ammonia emissions contribute to acid rain and are also responsible for nitrous oxide emissions. This review addresses different factors/pathways/circumstances that contribute to the loss of N from the soil-plant system and reduce nitrogen use efficiency (NUE). Different factors influence NUE like ammonia volatilization, nitrification, denitrification, immobilization, leaching, runoff, temperature, soil pH, soil texture, rainfall and irrigation, soil salinity, tillage, weeds, pests, diseases, N loss from plants, fires, crop rotation, crop nutrition, crop varieties, and nitrogen management (right time, right source, right place, and right rate/amount).

Electronic Structure Optimization and Proton-Transfer Enhancement on Titanium Oxide-Supported Copper Nanoparticles for Enhanced Nitrogen Recycling from Nitrate-Contaminated Water.

Electrocatalytic reduction of nitrate to NH3 (NO3RR) on Cu offers sustainable NH3 production and nitrogen recycling from nitrate-contaminated water. However, Cu affords limited NO3RR activity owing to its unfavorable electronic state and the slow proton transfer on its surface, especially in neutral/alkaline media. Furthermore, although a synchronous "NO3RR and NH3 collection" system has been developed for nitrogen recycling from nitrate-laden water, no system is designed for natural water that generally contains low-concentration nitrate. Herein, we demonstrate that depositing Cu nanoparticles on a TiO2 support enables the formation of electron-deficient Cuδ+ species (0 < δ ≤ 2), which are more active than Cu0 in NO3RR. Furthermore, TiO2-Cu coupling induces local electric-field enhancement that intensifies water adsorption/dissociation at the interface, accelerating proton transfer for NO3RR on Cu. With the dual enhancements, TiO2-Cu delivers an NH3-N selectivity of 90.5%, mass activity of 41.4 mg-N h gCu-1, specific activity of 377.8 mg-N h-1 m-2, and minimal Cu leaching (<25.4 μg L-1) when treating 22.5 mg L-1 of NO3--N at -0.40 V, outperforming most of the reported Cu-based catalysts. A sequential NO3RR and NH3 collection system based on TiO2-Cu was then proposed, which could recycle nitrogen from nitrate-contaminated water under a wide concentration window of 22.5-112.5 mg L-1 at a rate of 209-630 mgN m-2 h-1. We also demonstrated this system could collect 83.9% of nitrogen from NO3--N (19.3 mg L-1) in natural lake water.

Life strategies and metabolic interactions of core microbes during thiosulphate-based denitrification.

Sulphur-driven denitrification is a low-cost process for the treatment of nitrate-contaminated water. However, a comprehensive understanding of core populations and microbial interactions of a sulphur-based denitrifying system is lacking. This study presents results from three replicated denitrifying systems amended with thiosulphate and operated under a low C/N ratio. Amplicon sequencing revealed gradual enrichments of a few abundant denitrifiers. Based on genome-centred metagenomics and metatranscriptomics, a core set of microbes was identified in the systems, with Pseudomonas 1 and Thauera 2 being the most abundant ones. Although the replicates showed different enrichments, generalized observations were summarized. Most core populations conserved energy from denitrification coupled with sulphur. Pseudomonas 1 and Thauera 2 were able to finish complete denitrification. Surprisingly, they were also able to synthesize almost all amino acids and vitamins. In contrast, less abundant members, including Pseudomonas 2, were relatively auxotrophic and required an exogenous supply of amino acids and vitamins. The high expression of enzymes involved in biosynthesis and transport systems indicated their syntrophic relationships. The genomic findings suggested life strategies and interactions of the core thiosulphate-based denitrifying microbiome, with implications for nitrate-polluted water remediation.

Extent of anthropogenic influence on groundwater quality and human health-related risks: an integrated assessment based on selected physicochemical characteristics

Majority of people living on earth rely on groundwater as their primary supply of water for daily needs. However, human activities continuously threaten this natural resource. In an attempt to unravel the extent of impact of human-related activities on groundwater physicochemical characteristics in Nnewi and Awka urban clusters (Nigeria), several techniques were integrated in this study. Groundwater samples were warm and acidic in nature. Concentrations of SO4 2-, NO3 -, PO4 3-, Cl-, HCO3 -, Ca2+, Mg2+, Na+, and K+ were within set benchmarks. Water nutrient pollution index (ranging from 0.060-0.745), nitrate pollution index (varying between -0.999 and -0.790), and water pollution index (ranging from 0.057-0.630) estimated the extent of anthropogenic contamination and showed low anthropogenic impact on the groundwater physicochemical characteristics. The health risks due to the ingestion and skin absorption of the nitrate-contaminated water computed for six age groups (6-12 months, 5-10 years, 10-15 years, 15-20 years, 20-60 years, and > 60 years) showed health risk values that were < 1, implying low chronic health risks to humans. The cumulative total health hazard index ranged between 0.006 and 0.787 with a mean value of 0.167. Chemometric analyses and geochemical plots revealed the relationships between the variables and contamination sources. Chadha’s plot showed that 55% of the samples were Ca2+-Mg2+-Cl- waters, predominating over Na+-Cl- and Ca2+-Mg2+-HCO3 - waters. Bivariate and multivariate geochemical plots also indicated low anthropogenic impact. Furthermore, principal component analysis and R-type hierarchical clustering confirmed that the groundwater chemistry and quality were mostly influenced by geogenic processes than human-related acts. Conclusively, the extent of anthropogenic influence on the groundwater physicochemical characteristics is low. These findings would be useful in future monitoring of groundwater in both urban clusters.

Fluoride and nitrate in groundwater: a comprehensive analysis of health risk and potability of groundwater of Jhunjhunu district of Rajasthan, India.

Groundwater contamination is a major concern in front of the scientific community because it is directly related to human health, especially in arid and semi-arid regions. Therefore, a comprehensive study was engaged to evaluate the water quality, potability, and human health risk assessment due to the consumption of fluoride- and nitrate-contaminated water in Jhunjhunu district of Rajasthan. In order to assess the water quality, samples were collected from 87 locations in the study region, and a total of 16 parameters were analyzed as per the standard methods. The results showed that the value of the number of quality parameters consisting of pH, EC, TDS, fluoride, chloride, nitrate, sulfate, total hardness, calcium, magnesium, and total alkalinity was higher than the recommended limit of BIS and WHO. The fluoride in 11% and nitrate in 6% of samples were observed to exceed the permissible limit of WHO. The results of risk assessment due to fluoride and nitrate revealed that hazard index values of 71% of groundwater samples for males, 78% of groundwater samples for females, and 75% of groundwater samples for children were greater than 1, indicating the significant health hazard due to consumption of groundwater. The water quality index (WQI) found that 39% of groundwater samples belong to categories that cannot be used for drinking purposes. Principal component analysis (PCA) reduced the large number of variables affecting the overall quality and chemistry of groundwater and determined four major components which account for 69.50% variance in the data. PCA concluded that both geogenic and anthropogenic sources of contamination influenced the groundwater of the study area.

Electrochemical Denitrification of Synthetic Aqueous Solution and Actual Contaminated Well Water: RSM Modeling, Kinetic Study, Monte Carlo Optimization, and Sensitivity Analysis

The process of electrochemical denitrification is applied with the aim of converting nitrate ( NO 3 − ) to N2 gas by reducing nitrate and oxidizing by-products such as ammonia ( NH 4 + ). In this study, Ti/RuO2 and graphite were used as anode and cathode electrodes, respectively, to treat synthetic aqueous solutions containing different concentrations of nitrate ions. Nitrate initial concentration (2.75–55 mg NO3-N/lit), voltage (2.5–30 V), pH (3–13), electrode distance (ED = 0.5–3.5 cm), and reaction time (10–180 min) were the main studied operating parameters for the electrochemical denitrification (ECD) reactor. The experiments were designed using the central composite design (CCD) method. The experimental results were modeled with the response surface methodology (RSM) technique. Scanning electron microscope (SEM), X-ray diffraction analyzer (XRD), and Fourier transform infrared spectroscopy (FTIR) characterized electrodes were performed before and after all experiments. Optimization and sensitivity analysis was performed using the Monte Carlo simulation (MSC) approach. The energy consumption and current efficiency were calculated for the ECD reactor. Kinetic models of zero, first, and second order were evaluated, and the second-order model was selected as the best kinetic model. Also, the effect of adding monovalent, divalent salts, and organic compounds to the process was evaluated. Finally, three nitrate-contaminated water wells were selected near agricultural lands as real samples and investigated the performance of the ECD process on the samples. The performance of the ECD reactor for the real samples showed some decrease compared to the synthetic samples.

PSXVI-5 Rumen Parameters and Microbial Population Changes in Fattening Holstein Heifers fed with Nitrate-Contaminated Water

Abstract The aim of this study was to evaluate the effect of drinking water nitrate concentration on rumen parameters and its microbial population that may affect greenhouse gases in fattening cattle. Holstein heifers (n = 24; 161 ± 19.9 kg of initial BW, and 183 ± 25.3 d of age) were housed individually and fed ad libitum. Animals were assigned to 4 treatments according to nitrate concentration in drinking water: 1) Control (n=6), without NO3-; 2) Low (n=6), with 44 mg/L of NO3-; 3) Moderate (n=6), with 110 mg/L of NO3-, and 4) High (n=6), with 220 mg/L of NO3-. After 14 and 168 days the ruminal content was sampled to determine pH, volatile fatty acids (VFA), nitrate and nitrite concentration, and rumen microbiota (except for Moderate). To assess the rumen microbiota, DNA-based qPCR of total bacterial population (16S rRNA), dissimilatory sulfate-reducing prokaryotes (aprA), ammonia-oxidizing bacteria and archaea (amoA-AOB and amoA-AOA), typical complete denitrifiers (nosZ-clade I linked to the transformation of N2O to N2), and anammox bacteria (hzo) was determined. Rumen pH, VFA, nitrate and nitrite were analyzed with a mixed effects model. Rumen microbial populations were statistically treated by analysis of variance applying pairwise comparisons (Fisher's least). Rumen pH, VFA, nitrate and nitrite were not affected by nitrate concentration in drinking water; however, rumen nitrite concentrations were greater (P &amp;lt; 0.01) in d 14 than in d 168 (32.1 vs. 6.3 ± 4.20 mg/L, respectively). Nitrate drinking water concentration did not affect rumen microbial populations, except for complete-denitrifying population (nosZ-clade I) which were slightly greater (P=0.01) in High than in Control in d 168. In conclusion, nitrate-contaminated water did not show a significant impact on rumen parameters and microbial populations but increased the bacterial denitrifying potential after a long term, which could decrease ruminal N2O emissions and nitrite ruminal accumulation in fattening heifers.

(Invited) Electrocatalytic Reduction of Nitrate: Insight from Manipulating Adsorbate Affinity

Fertilizer use and fossil-fuel combustion has increased nitrate concentrations in many wastewaters and watersheds to levels that threaten environmental and human health. Consequently, treatment of nitrate-contaminated water is a growing area of energy consumption. Electrocatalytic nitrate reduction offers a distributable treatment solution also capable of producing value-added products (e.g. ammonium), using electrons as a reducing agent at ambient temperatures and pressures. However, nitrate reduction occurs at similar electrochemical potentials to water reduction, reducing the Faradaic efficiency particularly in dilute nitrate concentrations characteristic of wastewater. Here we consider how changing a catalysts’ affinity for nitrate (via oxide supports) or its relative affinity for protons (via electronic structure) impact activity and selectivity of the electrocatalytic nitrate reduction reaction in neutral media.

Subclinical Hypothyroidism in Families Due to Chronic Consumption of Nitrate-Contaminated Water in Rural Areas with Intensive Livestock and Agricultural Practices in Durango, Mexico

Nitrate is a widely disseminated water pollutant and has been linked to health disorders, including hypothyroidism. Here, we evaluated the relationship between thyroid function and chronic exposure to nitrates in rural zone families, in addition to the genetic and autoimmune factors. Exposure and effect biomarkers, thyroid hormones, and autoantibodies of tiroperoxidase were measured, as well the presence of two FOXE1 polymorphisms (rs965513, rs1867277). Pearson’s correlation, principal component analysis, Kruskal–Wallis, and chi-squared tests were used for statistical analysis. A total of 102 individuals were analyzed; 45% presented subclinical hypothyroidism, a negative correlation was observed between methemoglobin and the total T3 (r = −0.43, p = 0.001) and free T3 levels (r = −0.34, p = 0.001), as well as between TSH and the free T4 (r = −0.41, p = 0.0001) and total T4 (r = −0.36, p = 0.0001). A total of 15.7% had positive antithyroid ab-TPO, while the polymorphic genotype (AA) represented only 3% (rs965513) and 4% (rs1867277) among subjects with subclinical hypothyroidism. The high frequency of subclinical hypothyroidism in the population under study could be related, mainly, to chronic exposure through the consumption of nitrate-contaminated water.

Performances and mechanisms of microbial nitrate removal coupling sediment-based biochar and nanoscale zero-valent iron

Immobilized microorganism technology has attracted increasing attention for high concentration of microbes, low cell loss and high resistance to impact of environment. The microbial reduction of nitrate in the presence of sediment-based biochar (SBC) and nanoscale zero-valent iron (nZVI) was investigated in four different free systems. NZVI-SBC/bacteria system realized the best nitrate removal of 97.61% within 3 days through the synergistic effect of SBC and nZVI on denitrifying bacteria. Accumulation of nitrite and ammonium in nZVI-SBC/bacteria system also decreased. High-throughput sequencing results showed that the proportion of denitrifying bacteria in microbial community structure increased after adding nZVI-SBC. The performance of nitrate removal was then studied through PVA/SA-immobilization. Immobilized active pellets performed better nitrate removal (98.89%) and stronger tolerance under different conditions than the free bacterial cells. Overall, this study provided a promising approach by utilizing SBC and nZVI for the bio-remediation of nitrate-contaminated water in practical application.

Water denitrification by displacement biofiltration

This work was aimed creating a simple and reliable submersed biofilter for the decentralized treatment of nitrate-contaminated water. Denitrification of water was studied by the method of displacement (piston) bio-filtration in specially designed devices intended for home application. At certain sizes of grains of bio-filtration bed and filtration flow directions in it, the change in operating mode of denitrifying biofilter from direct flow to displacement mode offers the following advantages. There is no need to maintain a continuous and slow flow of water through the biofilter. The consumers have the opportunity to feed big portions of water into the bio-filter in one gulp (pulse) and nevertheless get the same quantity of denitrified water. The design of created biofilters is simple. Assembling these bio-filters implies the use of materials with a minimum carbon footprint.

Water denitrification by displacement biofiltration: transition of designed biofilter to the stationary mode

This work was aimed at creating a simple and reliable submersed biofilter for the decentralized treatment of nitrate-contaminated water. Denitrification of water was performed by the method of displacement (piston) biofiltration in specially designed U-shaped devices intended for residential use. The efficiency of biofiltration in these devices was evaluated under the conditions of their continuous service. The biofilter exhibited an essential increase in the rate of denitrification when transferring to the stationary mode. Hence, the consumer will have the opportunity of supplying big portions of nitrate-contaminated water into the biofilter in one gulp (pulse) and simultaneously getting the same amount of deeply denitrified water. This mode of biofilters exploitation prevents the clogging of the filtration bed and the channeling in it. The design of the created biofilters is rather simple. Materials with a minimum carbon footprint can be used to fabricate these devices.

Phytodepuration of Nitrate Contaminated Water Using Four Different Tree Species.

Water pollution by excessive amounts of nitrate (NO3−) has become a global issue. Technologies to clean up nitrate-contaminated water bodies include phytoremediation. In this context, this research aimed to evaluate four tree species (Salix alba L., Populus alba L., Corylus avellana L. and Sambucus nigra L.) to remediate nitrate-contaminated waters (100 and 300 mg L−1). Some physiological parameters showed that S. alba L. and P. alba L. increased particularly photosynthetic activity, chlorophyll content, dry weight, and transpired water, following the treatments with the above NO3− concentrations. Furthermore, these species were more efficient than the others studied in the phytodepuration of water contaminated by the two NO3− levels. In particular, within 15 days of treatment, S. alba L. and P. alba L. removed nitrate quantities ranging from 39 to 78%. Differently, C. avellana L. and S. nigra L. did not show particular responses regarding the physiological traits studied. Nonetheless, these species removed up to 30% of nitrate from water. In conclusion, these data provide exciting indications on the chance of using S. alba L. and P. alba L. to populate buffer strips to avoid NO3− environmental dispersion in agricultural areas.

Evaluation of South African Sand/Zero-Valent Iron Combinations for the Treatment of Nitrate-Contaminated Water: Kinetic and Effect of Competitive Ions

This study aimed to define the optimum weight ratio between Berea Red sand (BRS)/zero-valent iron (ZVI) combinations to be used in the treatment of nitrate contaminated water. The effect of competing ions (phosphate and sulfate) on the nitrate removal efficiency of the best performing BRS-ZVI w/w ratio was also assessed. To achieve this objective, batch tests were performed under anoxic and acidic conditions (pHi = 4.5), using two combinations: 50%BRS-50%ZVI (w/w) and 25%BRS-75%ZVI (w/w), as well as 100%ZVI as a control. BRS and ZVI had 1 to 2-mm grain size. pH and nitrogen species were tested during these batch tests. Kinetic analysis was also carried out. While the removal efficiencies of 100%ZVI and 25%BRS-75%ZVI (w/w) were 70.2% and 83.1%, respectively, the experimental results showed that the combination of 50%BRS-50%ZVI (w/w) had the highest nitrate removal efficiency (99.5%), implying a synergistic effect between BRS and ZVI. Likewise, the kinetic analysis showed that the nitrate removal rate (k) increased as the BRS mass in the BRS-ZVI combination increased. Furthermore, the presence of phosphate and sulfate negatively affected the nitrate removal performance of the 50%BRS-50%ZVI combination, which was the best performing weight ratio. However, this weight ratio still showed high nitrate removal capacities in the presence of phosphate and sulfate, respectively. The 50%BRS-50%ZVI combination demonstrated to be the optimum among the used ones. However, further investigation in a large-scale reactor on this combination is recommended for further optimization of its performance.

Медично-гіґієнічна оцінка впливу нітратів джерел децентралізованого водопостачання на захворюваність систем серцево-судинної та кровообігу

Aim. To analyze the levels of nitrate pollution of decentralized water supply sources in the settlements of Lviv region, and to investigate their influence on the formation of morbidity of the cardiovascular and circulation system among the adult population of the region. Materials and Methods. The study was conducted according to the results of monitoring the nitrate content (mg / dm3) in the decentralized water supply sources for the period of 2012-2018 and the morbidity of the cardiovascular and circulation system of the adult population of 20 districts of Lviv region during 2012-2016. The assessment of health hazards for the adult population of Lviv region from consumption of nitrate-contaminated drinking water was carried out in accordance with the risk assessment methodology based on the calculated hazard coefficients (HQ). The results were processed by traditional methods of variation statistics using licensed computer programs Microsoft Excel and Statistica 10.0. Results and Discussion. The laboratory survey covered 2212 (2012) - 2468 (2018) sources of decentralized water supply in Lviv region. There is a clear tendency of increase in the level of nitrate contamination of the drinking water. Excessive nitrate content was found in 18.6-21.7% of individual sources, 9.9-10.5% of public wells and 12.6-13.3% of public captures. The highest concentrations and the highest percentage of excesses were registered in Mykolaiv, Zhovkva, Zolochiv, and Pustomyty districts, and the smallest of excess nitrates was recorded in Turka, Sambir and Staro-Sambir districts. The average excess nitrate content in the most polluted areas was in the range of 3.3-8.0 MAC, which corresponds to concentrations at 165-400 mg/dm3. The highest rates of cardiovascular morbidity and circulatory system were registered in areas where the population uses mainly decentralized water sources and cases were recorded of significant excess of nitrates in drinking water. The statistical analysis found positive correlation connections between the development of ischemia (moderate, r=0.49, p&lt;0.05), angina pectoris (average, r=0.77, p&lt;0.05), and hypertension (severe, r=0.99, p &lt;0.05) and nitrate content in the drinking water. The determination coefficients were 23.08%, 59.58% and 98.01%, respectively. According to the results of the regression analysis, an adequate mathematical model was constructed to predict the probable development of this pathology among the adult population of the region. An assessment of the health hazard for adults consuming drinking water contaminated with nitrates indicates a threat of increased non-infection morbidity, including that of cardiovascular and circulation system, namely an increase in the average (HQ 1-5) risk of nitrates at 1.8-5.0 MAC to high (HQ 5-10) - at their concentration of 5.9-8.0 MAC. Conclusions. The solution to the problem of reducing nitrate pollution of drinking water should be included amongthe most important issues not only in the field of environmental protection, but also the protection of public health. Improving the environment will help reduce the load on the healthcare system in terms of preventing and treating cardiovascular disease. Keywords: nitrates, drinking water, cardiovascular diseases, diseases of the circulatory system