A review of analytical procedures for the simultaneous determination of medically important veterinary antibiotics in environmental water: Sample preparation, liquid chromatography, and mass spectrometry.

Medically important (MI) antibiotics are defined by the United States Food and Drug Administration as drugs containing certain active antimicrobial ingredients that are used for the treatment of human diseases or enteric pathogens causing food-borne diseases. The presence of MI antibiotic residues in environmental water is a major concern for both aquatic ecosystems and public health, particularly because of their potential to contribute to the development of antimicrobial-resistant microorganisms. In this article, we present a review of global trends in the sales of veterinary MI antibiotics and the analytical methodologies used for the simultaneous determination of antibiotic residues in environmental water. According to recently published government reports, sales volumes have increased steadily, despite many countries having adopted strategies for reducing the consumption of antibiotics. Global attention needs to be directed urgently at establishing new management strategies for reducing the use of MI antimicrobial products in the livestock industry. The development of standardized analytical methods for the detection of multiple residues is required to monitor and understand the fate of antibiotics in the environment. Simultaneous analyses of antibiotics have mostly been conducted using high-performance liquid chromatography-tandem mass spectrometry with a solid-phase extraction (SPE) pretreatment step. Currently, on-line SPE protocols are used for the rapid and sensitive detection of antibiotics in water samples. On-line detection protocols must be established for the monitoring and screening of unknown metabolites and transformation products of antibiotics in environmental water.

Novel techniques to determine dilution ratios of raw wastewater and wastewater treatment plant effluent in the 5-day biochemical oxygen demand test.

The current 5-day biochemical oxygen demand (BOD5) test methods lack detailed information on sample dilution, which typically leads to an incorrect dilution ratio of samples and failed BOD5 testing. This study proposed an improved dilution technique that effectively determines the dilution ratios for raw wastewater and wastewater treatment plants (WWTPs) effluent. The numbers of raw wastewater and WWTPs effluent samples used in the BOD5 tests were 201 and 61, respectively. The experimental results demonstrated that both the raw wastewater and WWTPs effluent varied in BOD5 values with the sample dilution ratio, and these changes were more noticeable when the dissolved oxygen consumption ratio (DOCR) was less than 20% or when the dilution ratio was large. Assuming that the BOD5 value over the DOCR range of 40%-70% was true, the optimal DOCR range was 40%-90% for the raw wastewater and 40%-70% and 80%-90% for the WWTPs effluent, where the relative error of BOD5 values in these DOCR ranges was less than 10% depending on the dilution ratio. The correlation between the sample dilution ratio and the BOD5 value over the optimal DOCR range was considerably higher than that over the entire DOCR range. This was combined with the correlation equation between BOD5 and chemical oxygen demand to propose an equation that could determine more accurate sample dilution ratios for raw wastewater and WWTPs effluent compared to the conventional sample dilution methods for the BOD5 test.

New insights into the occurrence and removal of 36 pesticides in pesticide wastewater treatment plants in Korea.

This study investigates the occurrence of 36 pesticides-including 33 that were monitored from 2007 to 2019 in Korean rivers-in wastewaters from pesticide manufacturing facilities (PMFs) and in 13 pesticide wastewater treatment plants (PWWTPs). Furthermore, an approach for the effective removal of these pesticides from pesticide wastewater (PW) is proposed. Among the 36 pesticides investigated, 32 were found to be present in the PMF wastewater and PWWTP influents (at concentrations ≤466.8 mg/L). In addition, 24 of the 36 pesticides were detected in PWWTP effluents, indicating that effluents are discharged without the complete removal of many pesticides. Moreover, the PWWTP effluent influences the presence of pesticides in river (confidence interval: ≥ 95%; p < 0.05). Although the chemical oxidation-activated sludge process is frequently recommended for the treatment of PWs, the findings from the current study indicate that an activated sludge-activated carbon adsorption process is more suitable for PW treatment due to its superior removal efficiency, treatment stability, and economic feasibility. Consequently, its application for the treatment of PWs can markedly decrease the levels of pesticides discharged into rivers.

Concentrations and Risk Assessments of Antibiotics in an Urban-Rural Complex Watershed with Intensive Livestock Farming.

Antibiotics used for the treatment of humans and livestock are released into the environment, whereby they pose a grave threat to biota (including humans) as they can cause the emergence of various strains of resistant bacteria. An improved understanding of antibiotics in the environment is thus vital for appropriate management and mitigation. Herein, surface water and groundwater samples containing antibiotics were analyzed in an urban-rural complex watershed (Cheongmi Stream) comprising intensive livestock farms by collecting samples across different time points and locations. The spatiotemporal trends of the residual antibiotics were analyzed, and ecological and antibiotic resistance-based risk assessments were performed considering their concentrations. The results showed that the concentrations and detection frequencies of the residual antibiotics in the surface water were affected by various factors such as agricultural activities and point sources, and were higher than those found in groundwater; however, frequent detection of antibiotics in groundwater showed that residual antibiotics were influenced by factors such as usage pattern and sewage runoff. Furthermore, few antibiotics posed ecological risks. The risk assessment methods adopted in this study can be applied elsewhere, and the results can be considered in the environmental management of residual antibiotics in the Cheongmi Stream watershed.

Identifying nitrogen sources in intensive livestock farming watershed with swine excreta treatment facility using dual ammonium (δ15NNH4) and nitrate (δ15NNO3) nitrogen isotope ratios axes.

We proposed a novel approach based on dual ammonium and nitrate nitrogen isotope ratios (δ15NNH4 and δ15NNO3, respectively) axes to identify nitrogen sources in intensive livestock farming watersheds, especially those with swine excreta treatment facilities. The δ15NNH4 and δ15NNO3 values in water samples were measured monthly in 2016-2017. Soil and mineral fertilizers, sewage, sewage effluent, manure, and swine effluents were the five sources considered to identify nitrogen sources. The results showed that nitrogen pollution from agricultural activities was well reflected by the seasonal δ15NNH4 and δ15NNO3 patterns in the river, and microbial nitrification was suggested as the dominant nitrogen transformation process in the river. This study revealed that δ15NNH4 and δ15NNO3 axes provided better results than the traditionally used nitrate oxygen (δ18ONO3) and δ15NNO3 axes for identifying nitrogen sources in agricultural watersheds with swine excreta treatment facilities. The mixing model results showed that stream water was severely contaminated with swine effluents (e.g., a mean minimum contribution of 31%), thus affecting the quality of the mainstream (p = 0.068 < 0.10). This study was the first successful application of dual δ15NNH4 and δ15NNO3 axes to better understand nitrogen sources in intensive livestock farming watersheds with swine excreta treatment facilities.

Characteristics of veterinary antibiotics in intensive livestock farming watersheds with different liquid manure application programs using UHPLC-q-orbitrap HRMS combined with on-line SPE.

Composted livestock manures, in both solid and liquid form, are used as fertilizers in cropland. However, excess solid and liquid manures in agricultural watersheds are considered as nonpoint pollution sources because of their high nutrient and heavy metal contents of, as well as their antibiotic contents, especially veterinary antibiotics (VAs). In this study, 21 VAs under nine classes (i.e., cephems, ionophores, lincosamides, penicillins, pleuromutilins, quinolones, streptogramins, sulfonamides, and tetracyclines) found in agricultural watersheds were simultaneously analyzed via UHPLC-q-orbitrap high-resolution mass spectrometry using an on-line solid-phase extraction system. The residues of VAs in the surface water of two intensive livestock rearing watersheds (Cheongmi and Gwangcheon streams) in Korea were successfully quantified, and the values were found to range from 1.84 ± 0.42 ng L-1 to 835.6 ± 31.9 ng L-1. Time lags of 2-3 months were observed between the periods of liquid manure application and the periods with the maximum concentrations of VAs. In both watersheds, samples from points close to areas with extensive application of liquid manure exhibited high concentrations of most of the 21 VAs. Between the watersheds, the one with heavier application of liquid manure showed higher concentrations of the target VAs. To the best of our knowledge, this study represents the first attempt at evaluating the correlation between liquid manure application and environmental occurrence of VAs in surface water. The findings reveal that liquid manure application plays an important role in introducing VAs into aquatic environments.

Application of struvite precipitation in treating ammonium nitrogen from semiconductor wastewater.

Struvite precipitation was applied to the removal of NH(4)-N in semiconductor wastewater. Batch experiments were conducted to examine the effects of final pH, magnesium and orthophosphate dosages and the initial influent concentrations of NH(4)-N and F on the removals of NH(4)-N and PO(4)-P by forming struvite deposits. pH was an important parameter in the simultaneous removals of ammonium nitrogen and orthophosphate. In struvite precipitation, the amount of orthophosphate in the solution affected NH(4)-N removal much more than that of magnesium ions in some cases. It was revealed that the low and high initial concentrations of NH(4)-N and F inhibited NH(4)-N and PO(4)-P removal efficiencies in struvite precipitation, respectively. We also evaluated field-scale treatment plant incorporated by struvite precipitation process. On semiconductor wastewater with an NH(4)-N concentration of 155 mg/L, the results obtained showed that the incorporation of the struvite precipitation process brought about a high NH(4)-N removal efficiency of over 89% on average.

Determination of 18 veterinary antibiotics in environmental water using high-performance liquid chromatography-q-orbitrap combined with on-line solid-phase extraction.

The use of antibiotics and their occurrence in the environment have received significant attention in recent years owing to the generation of antibiotic-resistant bacteria. Antibiotic residues in water near livestock farming areas should be monitored to establish effective strategies for reducing the use of veterinary antibiotics. However, environmental water contamination resulting from veterinary antibiotics has not been studied extensively. In this work, we developed an analytical method for the simultaneous determination of multiple classes of veterinary antibiotic residues in environmental water using on-line solid-phase extraction (SPE)-high performance liquid chromatography (HPLC)-high resolution mass spectrometry (HRMS). Eighteen popular antibiotics (eight classes) were selected as target analytes based on veterinary antibiotics sales in South Korea in 2015. The developed method was validated by calibration-curve linearities, precisions, relative recoveries, and method detection limits (MDLs)/limits of quantification (LOQs) of the selected antibiotics, and applied to the analysis of environmental water samples (groundwater, river water, and wastewater-treatment-plant effluent). All calibration curves exhibited r2 > 0.995 with MDLs ranging from 0.2 to 11.9 ng/L. Relative recoveries were between 50 and 150% with coefficients of variation below 20% for all analytes (spiked at 500 ng/L) in groundwater and river water samples. Relative standard deviations (RSDs) of standard-spiked samples were lower than 7% for all antibiotics. The on-line SPE system eliminates human-based SPE errors and affords excellent method reproducibility. Amoxicillin, ampicillin, clopidol, fenbendazole, flumequine, lincomycin, sulfadiazine, and trimethoprim were detected in environmental water samples in concentrations ranging from 1.26 to 127.49 ng/L. The developed method is a reliable analytical technique for the potential routine monitoring of veterinary antibiotics.

Assessment and identification of nitrogen pollution sources in the Cheongmi River with intensive livestock farming areas, Korea.

This study aimed to develop methods for assessing and identifying nitrogen sources in the Cheongmi River, Korea, that has intensive livestock farming areas (ILFA) in its watershed. The assessment focused on the feasibility of the simultaneous use of stable isotopic compositions of ammonium (δ15NNH4) and nitrate (δ15NNO3) for identifying the main nitrogen pollution sources in the Cheongmi River watershed. Our results suggested that the organic nitrogen (Org-N) to total nitrogen (T-N) ratio could be used as an indicator for assessing the effect of livestock excreta on waterways in ILFA. We observed that the T-N concentration was much more strongly affected by livestock excreta than the T-P concentration in the mainstream of the Cheongmi River. The positive correlation was more significant between δ15NNH4 and NH4-N than that between δ15NNO3 and NO3-N for river water samples. Furthermore, the use of δ15NNH4 was more effective than that of δ15NNO3 in evaluating nitrogen variations between May and August in the Cheongmi River because the differences in δ15NNH4 between May and August were more remarkable compared to those in δ15NNO3. Finally, the simultaneous use of δ15NNH4 and δ15NNO3 showed that the dominant nitrogen source at sites M3, M4, M5, and M6, specifically in May, was livestock excreta in the Cheongmi River. The results of this study could be used for sustainable water quality management in the Cheongmi River watershed.

Enhancing struvite precipitation potential for ammonia nitrogen removal in municipal landfill leachate.

This study was conducted to improve struvite precipitation for NH4-N removal purpose in landfill leachate. For this purpose, we evaluated the effect of the feeding sequence of precipitating reagents (magnesium, orthophosphate, and buffering reagent) on NH4-N removal by forming struvite deposits. Struvite precipitation effectively proceeded by an addition of excess magnesium and phosphate sources followed by an addition of the buffering reagent, in which condition the local formation of inappropriate deposits or the contamination of the desired struvite was minimized. We also tested the effect of struvite addition as the seeding materials on NH4-N removal. Seed addition would increase the potential for the struvite crystal growth, which enhanced NH4-N removal performance in landfill leachate treatment.

Evaluation of struvite obtained from semiconductor wastewater as a fertilizer in cultivating Chinese cabbage.

The present work evaluated the fertilizing value of struvite deposit recovered from semiconductor wastewater in cultivating Chinese cabbage. The fertilizing effect of struvite deposit was compared with that of commercial fertilizers: complex, organic and compost. Laboratory pot test results clearly showed that the growth of Chinese cabbage was better promoted when the struvite deposit was used than with organic and compost fertilizers even though complex fertilizer was the most effective in growing Chinese cabbage. It was revealed that potassium (K) was a key element in the determination of growth rate of Chinese cabbage. Also, the abundant nutrients such as nitrogen (N), phosphorus (P), K, calcium (Ca) and magnesium (Mg) were observed in the vegetable tissue of struvite pot. Specifically, P was the most-founded component in the vegetable tissue of struvite pot. Meanwhile, the utilization of struvite as a fertilizer led to the lowest accumulation of copper (Cu) and no detection of cadmium (Cd), arsenic (As), lead (Pb) and nickel (Ni) in the Chinese cabbage. It was found that the optimum struvite dosage for the cultivation of Chinese cabbage was 1.6 g struvite/kg soil. Based on these findings, it was concluded that the struvite deposits recovered from semiconductor wastewater were effective as a multi-nutrient fertilizer for Chinese cabbage cultivation.

Effect of mixing on spontaneous struvite precipitation from semiconductor wastewater.

The objective of this study was to investigate on the effect of mixing intensity (G) and mixing duration (t(d)) on struvite precipitation in the chemical mechanical polishing (CMP) wastewater generated from the semiconductor manufacturing process. Batch-scale experiments revealed that struvite crystallization was affected by both G and t(d). The mixing effect was to enhance the mass transfer of solute to the crystals in the process, resulting in the improvement of struvite crystallization and growth. By forming struvite, removal efficiencies of N and P increased logarithmic with the multiple values of G and t(d), i.e., Gt(d). Insufficient mixing energy with the Gt(d) value less than 10(5) caused an increase in the formation potential of unexpected precipitate unlike to pure struvite, causing a decrease in removal efficiencies of N and P in the process. At the Gt(d) value over 10(6), struvite precipitation was not restricted by fluoride, of which high level inherently contained in the CMP wastewater. The study results can be taken into consideration in the design and operation of the struvite precipitation process for both nutrient (N and P) removal and recovery.

Long term operation of pilot-scale biological nutrient removal process in treating municipal wastewater.

The performance of a pilot-scale biological nutrient removal process has been evaluated for 336 days, receiving the real municipal wastewater with a flowrate of 6.8m(3)/d. The process incorporated an intermittent aeration reactor for enhancing the effluent quality, and a nitrification reactor packed with the porous polyurethane foam media for supporting the attached-growth of microorganism responsible for nitrification. The observation shows that the process enabled a relatively stable and high performance in both organics and nutrient removals. When the SRT was maintained at 12 days, COD, nitrogen, and phosphorus removals averaged as high as 89% at a loading rate of 0.42-3.95 kg COD/m(3)d (corresponding to average influent concentration of 304 mg COD/L), 76% at the loading rate of 0.03-0.27 kg N/m(3)d (with 37.1mg TN/L on average), and 95% at the loading rate of 0.01-0.07 kg TP/m(3)d (with 5.4 mg TP/L on average), respectively.