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Organophosphate pesticides (OPs) are highly toxic; their presence in surface waters is a matter of great concern. To the best of our knowledge, OPs in wastewater from agrochemical manufacturing facilities (AMFs) and influents and effluents from agrochemical wastewater treatment plants (AWWTPs) have not been previously investigated. Therefore, we investigated the presence of 8 OPs (5 of which are regulated under the Water Environment Conservation Act (WECA)) in 15 AMFs and 13 AWWTPs detected through surface water monitoring and proposed measures for effectively regulating these OPs in AWWTPs. Five OPs (chlorpyrifos, diazinon, dichlorvos, EPN, and fenitrothion) were detected in the AMF and AWWTP influents; three (methyldemeton, parathion, and phenthoate) were not. Of the five detected OPs, chlorpyrifos, dichlorvos, and fenitrothion are not currently regulated via effluent limitations for WWTPs under WECA; thus, additional regulations are required. The most effective process configuration for the removal of these OPs was biological treatment through activated sludge processes, followed by activated carbon adsorption. In the system, 100% OP removal from the AWWTP influents was observed. This treatment technology can be implemented in AWWTPs to minimize the presence of OPs in surface waters, thereby protecting human health and aquatic life.

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.

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.

Swine wastewater effluent is a key source of water contamination since it contains high levels of nutrients, including nitrogen and phosphorus, as well as nitrates and refractory organic matter (ROM). ROM refers to organic compounds that are usually resistant to microbial degradation. When swine wastewater effluent containing high levels of ROM is subsequently discharged into rivers and streams without being adequately treated, purification costs for drinking water increase and there remains a possibility for harmful substances to enter the human body. In this study, we introduce new methods for setting total organic carbon (TOC) water quality standards for discharging swine wastewater effluent containing high levels of ROM after treatment. To set the TOC water quality standards, various analysis methods based on statistics, technology, and experience based on operational data of livestock-manure treatment facilities were applied. In addition, the achievability of the proposed TOC standards in livestock-manure treatment facilities and the financial burden of their implementation on livestock farms were also reviewed. Here, we set tentative values that include all of our results derived from each methodology and set the TOC standards to levels that can be achieved through the normal operation of swine-wastewater treatment facilities (60 mg/L for public treatment facilities and 140 mg/L for treatment facilities operated by individual farms). When setting TOC standards, both single and combined methodologies should be considered and employed after comprehensively assessing livestock management policies, regional conditions, and the burden on stakeholders.

In this study, we propose the application of struvite precipitation for the sustainable recovery of nitrogen (N) and phosphorus (P) from anaerobic digestion (AD) effluents derived from swine manure. The optimal conditions for four major factors that affect the recovery of N and P were derived by conducting batch experiments on AD effluents obtained from four AD facilities. The optimal conditions were a pH of 10.0, NH4-N:Mg:PO4-P molar ratio of 1:1.4:1, mixing intensity of 240 s&minus, 1, and mixing duration of 2 min. Under these optimal conditions, the removal efficiencies of NH4-N and PO4-P were approximately 74% and 83%, respectively, whereas those of Cu and Zn were approximately 74% and 79%, respectively. Herein, a model for swine manure treatment that incorporates AD, struvite precipitation, and biological treatment processes is proposed. We applied this model to 85 public biological treatment facilities in South Korea and recovered 4722 and 51 tons/yr of NH4-N and PO4-P, respectively. The economic analysis of the proposed model&rsquo, s performance predicts a lack of profitability due to the high cost of chemicals, however, this analysis does not consider the resulting protection of the hydrological environment. Field-scale studies should be conducted in future to prove the effectiveness of the model.

We proposed a novel approach based on dual ammonium and nitrate nitrogen isotope ratios (δ

Pesticides and veterinary pharmaceuticals are used for effective crop production and prevention of livestock diseases, these chemicals are released into the environment via various pathways. Although the chemicals are typically present in trace amounts post-release, they could disturb aquatic ecosystems and public health through resistance development toward drugs or diseases, e.g., reproductive disorders. Thus, the residues of pesticides and veterinary pharmaceuticals in the environment must be managed and monitored. To that end, we developed a simultaneous analysis method for 41 target chemicals in environmental water samples using ultra-high-performance liquid chromatography (UHPLC)&ndash, quadrupole-orbitrap high-resolution mass spectrometry (HRMS) coupled with an on-line solid-phase extraction system. Calibration curves for determining linearity were constructed for 10&ndash, 750 ng∙L&minus, 1, and the coefficient of determination for each chemical exceeded 0.99. The method&rsquo, s detection and quantitation limits were 0.32&ndash, 1.72 ng∙L&minus, 1 and 1.02&ndash, 5.47 ng∙L&minus, 1, respectively. The on-line solid-phase extraction system exhibited excellent method reproducibility and reduced experimental error. As the proposed method is applicable to the monitoring of pesticides and veterinary pharmaceuticals in surface water and groundwater samples acquired near agricultural areas, it allows for the management of chemicals released into the environment.

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

This study evaluated the feasibility of recovering and recycling nitrogen (N) and phosphorus (P) from livestock excreta as struvite ( $MgNH_4PO_4{\cdot}6H_2O$ ) in South Korea. Our experimental results showed that struvite precipitation was a very effective way to recover N and P from livestock ex...

Nutrient budget is one of the Organization for Economic Co-operation and Development (OECD) agri-environmental indicators. A model was developed for regional nutrient management in Korea. In this study, a sensitivity analysis of parameters of a nutrient budget model was performed for two regions with intensive livestock farming in Korea. In the nitrogen budget, gross nitrogen surplus (GNS) and hydrospheric nitrogen surplus (hNS) were analyzed separately. For GNS, the most influential parameters were excreta production per swine in Hongseong and excreta production per beef cattle in Anseong. For hNS, N content of solid manure in swine and beef cattle were the most influential. For GNS and phosphorus surplus (PS), excreta production per livestock and the N(P) in the excreta of livestock were the predominant parameters. Livestock excreta showed a high sensitivity in both areas because the livestock headcount was high, thus, the excreta accounted for a large share of the input parameters for the model. Therefore, calculating reliable regional nutrient budgets would require further research on excreta production per livestock and the N(P) excretion in livestock. The nutrient budget model could be implemented for agri-environmental policy e.g., environment friendly regional livestock farming and sustainable integrated crop livestock systems.

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.

Fine nano-sized magnetite particles were synthesized and then used to treat backside grinding (BG) wastewater for the removal of silica nanoparticles (SiO 2 ). Batch experiments were conducted to examine the effects of the magnetite dosage, pH, stirring intensity (G) and duration (t d ), magnetic field strength and sedimentation time on the removal of SiO 2 . The optimum dosage of magnetite was determined as 16 mg/L, which had the best SiO 2 removal of about 97%, under the conditions of initial pH 5.9, stirring intensity 900 S −1 , stirring duration 30 min, sedimentation time 30 min and magnetic field strength 317 mT. The synthesis of nano-sized magnetite particles 10 nm in diameter led to a reduction in the magnetite dosage needed for the removal of SiO 2 . The pH was maintained at less than 10 to obtain the high SiO 2 removal mentioned above. When the pH was over 10, the Fe detached from magnetite particles which subsequently led to a decrease in SiO 2 removal. Magnetite aggregation was affected by both G and t d . Increasing the values of G and t d enhanced the removal of SiO 2 . When the multiple values of G and t d , i.e., Gt d reached 12,000, a SiO 2 removal of 95% was achieved. The relationship between the magnetic field strength and sedimentation time was also evaluated. An increase in the magnetic field strength improved the removal of SiO 2 . Specifically, the SiO 2 removal was greatly dependent on the sedimentation time when the magnetic field strength was weak. The results of this study can be used in the design and operation of a magnetite aggregation process to treat BG wastewater for the removal of SiO 2 .

This study evaluated the fertilizing value of struvite deposit recovered from swine wastewater in cultivating lettuce. Struvite deposit was compared to complex fertilizer, organic fertilizer and compost to evaluate the fertilizing effect of struvite deposit. Laboratory pot test showed that the struvite deposit better enhanced lettuce growth in comparison to commercial fertilizers. It was revealed that the growth rate of lettuce was simultaneously controlled by phosphorus (P) and magnesium (Mg). Moreover, nutrients such as nitrogen (N), P, K, calcium (Ca) and magnesium (Mg) were abundantly observed in the vegetable tissue of struvite pot. Meanwhile, struvite application led to the lower accumulation of mercury (Hg), lead (Pb), chromium (Cr 6+ ) and nickel (Ni). In addition, no detection of cadmium (Cd), arsenic (As) and nickel (Ni) in the lettuce tissue was observed in struvite application pots. The experimental results proved that the optimum struvite dosage for lettuce cultivation was 0.5 g struvite/kg soil. The column experiments clearly showed that ammonia nitrogen was more slowly released from struvite deposit than from complex fertilizer. Consequently, it was concluded that the struvite deposits recovered from swine wastewater were effective as a multi-nutrient fertilizer for lettuce cultivation.

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.

The purposes of this study were to suggest the methodology to select prior areas in the environmental pollution survey for livestock excreta (EPSLE) as well as to elucidate the validity of the methodology. In this study, the prior areas in the EPSLE were determined by examining the number of compost facilities categorized according to the three levels of size including the basin, the sub-basin and the watershed, respectively, based on the data from "Annual Nation-wide Pollution Sources Survey (2012)". The results suggested that the list of prior basins were Nakdong, Geum, Youngsan and Han river basins in order. Also, it was examined that the prior sub-basins in the four river basins including Nakdong, Geum, Youngsan and Han rivers were Naesung Stream, Geumgang Gongju, Juam Dam and Namhan Downstream, respectively. The prior watersheds in the sub-basins of Naesung stream, Geumgang Gongju, Juam Dam and Namhan Downstream were Seocheon Downstream, Geum Stream, Gyeombaek Suwipyo and Yanghwa Stream, respectively. The validity of the methodology used in this study was elucidated by analyzing the correlation of the number of compost facilities with the concentrations of T-N and T-P observed in the end-points of sub-basins. The results of correlation analysis showed that the concentrations of T-N and T-P increased with the number of compost facilities. Specifically, there was the stronger correlation between the number of compost facilities and the concentrations of T-N than that for T-P. Consequently, it was proved that the methodology used in this work was valid and rational for the selection of prior areas in environmental pollution survey for EPSLE.

In this work, a 3-stage biological aerated filter (BAF) system was proposed for the enhancement of nitrification at short hydraulic retention time (HRT). This was done by incorporating an intermittent aeration reactor, as an organic polishing reactor, into a conventional 2-stage pre-denitrification/nitrification BAF system. Laboratory experiments were performed at three different HRTs (i.e., 3, 2 and 1 h). Experimental results clearly showed that NH 4 -N removal of a conventional BAF system severely deteriorated in the presence of even a very small amount of organic matter at the short HRT of 1 h. Moreover, nitrite accumulation was observed at this HRT. This means that organic matter could be a limiting factor in nitrification at short HRTs. These problems were effectively controlled in the 3-stage BAF system. When the HRT of a conventional BAF system was reduced from 2 to 1 h, NH 4 -N removal decreased in from 96.6% to 74.0%. In contrast, for the experimental 3-stage BAF system, NH 4 -N removal remained high over 94% at the HRT of 1 h. This was because the polishing reactor eliminated organic matter before it could enter the nitrification reactor. Finally, this organic polishing reactor contributed to the higher removal of T-N and T-P.

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.

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.

This study evaluated the feasibility of using struvite deposit recovered from semiconductor wastewater as a slow-release fertilizer for cultivating Lactuca sativa (lettuce). To the best of our knowledge, the plant availability and fertilizer value of the recovered struvite precipitate have never been studied before. In an assessment, the fertilizing value of struvite deposit was compared with that of commercial fertilizers: complex, organic, and compost. Laboratory pot test results clearly showed that lettuce growth was better facilitated with struvite deposit than with commercial fertilizers. In addition, the fixed amounts of nitrogen, phosphorus, potassium, and magnesium were the highest in the lettuce tissue grown in the struvite pots. At the same time, less mercury, lead, chromium, and nickel accumulated in the lettuce tissue grown in the struvite pots than in commercial fertilizer pots. The optimum struvite dosage for the cultivation of lettuce was found to be 0.938 g struvite/kg soil. The c...

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.

Recently, auto-thermal thermophilic aerobic digestion (ATAD) has a great attention for destruction of wasted sludge biomass in wastewater treatment plant. Reduction of sludge concentration has been successfully achieved with pilot scale ATAD and ceramic filtration process in field condition. However, high concentration of COD, total nitrogen (TN) and total phosphorus (TP) was observed in filtrate, which should be treated before recirculation of filtrate to biological wastewater treatment plant. This study was focused on removal of nitrogen and phosphorus contained in the filtrate of ATAD, using struvite crystallization method. The effect of operational and environmental parameters (such as, N, P and Mg ion concentration and molar ratio, pH, reaction time, agitation strength, seed dosage, and reaction temperature) on the treatment of TN and TP with struvite crystallization were evaluated. Magnesium (as MgCl26H2O) and phosphorus (as K2HPO4) ions were, if necessary, added to increase nitrogen removal efficiency by the crystal formation. Average concentration of NH4-N and PO4-P of the filtrate were 1716.5 mg/L and 325.5 mg/L, respectively. Relationship between removal efficiencies of nitrogen and phosphorus and molar ratios of Mg and PO4-P to NH4-N was examined. Crystal formation and nitrogen removal efficiencies were significantly increased as increasing molar ratios of magnesium and phosphorus to nitrogen. As molar ratio of Mg : PO4-P : NH4-N were maintained to 2 : 1 : 1 and 2 : 2 : 1, removal efficiencies of nitrogen and phosphorus were 71.6% and 99.9%, and 93.8% and 98.6%, respectively. However, the effect of reaction time, mixing intensity, seed dose and temperature on the struvite crystallization reaction was not significant, comparing to those of molar ratios. Settled sludge volume after struvite crystallization was observed to be reduced with increase of seed dose and to be increased at high temperature.

As production of LCD increases, it has become necessary to find an economically efficient way of treating LCD wastewater with high concentration of fluoride. This study focuses on the calcium sources : CaCl2, Ca(OH)2 and CaCO3 for the treatment of the LCD wastewater including high concentration of fluoride. Of course considering removal efficiency and economical aspect, study is continued. Then this study have objective giving aid to field. Consequently, each calcium source's removal efficiency was measured in various pH, calcium dosage, reaction time, and mixing intensity. The optimum operational conditions for CaCl2 were found to be pH of 7, calcium dosage of 0.4[Ca] / [F] (mol / mol), 1 hr of operation and 200 rpm of mixing intensity. For Ca(OH)2, they were pH of 7, calcium dosage of 30 mL/L, 1 hr of operation, and 200 rpm of mixing intensity. While CaCO3 had operational conditions of pH of 4, calcium dosage of 30 mL/L, 1 hr operation and 200 rpm of mixing intensity. But it is recommended to use calcium sources according to various field conditions.

In this work, a composite formed by adding loess with lanthanium ("La-Loess") was proposed for effective removal of phosphate found in confined water bodies such as lake and reservoir. It was found that the theoretical maximum amount of lanthanum that can be attached to Loess was 2.68 mg La/g Loess. The phosphate removal was enhanced as an added amount of La-Loess composite increased. Furthermore, there was a noticeable difference in phosphate removal between Loess and La-Loess as the latter required 1.5 to 10 times less Loess than the former. Both Isotherm equations of Freundlich and Langmuir can be used to explain the phosphate adsorption characteristics in using La-Loess composites. The phosphate removal was very effective in the pH range of 5~8, which means that the proposed adsorbent can be directly applied to natural water without adjusting pH. Also, the La-Loess composites were well settled within 30 min without causing turbidity in water. Consequently, the proposed La-Loess can be strongly recommended for phosphate removal in confined water bodies.

In this study, the effect of the pretreatment of NH 4 -N by struvite precipitation on biological nitrogen removal was investigated in treating swine wastewater. Evaluation was mainly focused on nitrification which occurred in the activated sludge system after struvite precipitation. Laboratory experiments were performed at four different hydraulic retention times (HRT), i.e., 48, 32, 24 and 16 h. Results of the long-term operation of systems showed that the struvite precipitation used as the pretreatment of raw swine wastewater enhanced the nitrification performance in activated sludge system by reducing the applied loading rates of NH 4 -N and TCOD in all operating conditions. The reduction of the applied NH 4 -N loading rate kept the levels of free ammonia (FA) concentration in biological reactors low and it prevented nitrite accumulation. In addition, the struvite precipitation elicited the biological denitrification reaction and PO 4 -P removal by increasing the ratios of carbon-to-nitrogen and carbon-to-phosphorus of wastewater after struvite precipitation. The struvite precipitation also enhanced the biological TCOD removal performance by reducing the toxic effect of FA. Triplicate INT-dehydrogenase tests clearly showed that FA inhibited the degradation of organic matter in activated sludge system. Finally, the struvite precipitation contributed to high TCOD, T-N and PO 4 -P removals of 83, 90, and 97% by facilitating biological reaction at a short HRT of 16 h.

Effects of ferrous ion coagulation in treating coke wastewater were examined through tests. In addition, nitrification tests using coagulated coke wastewater were carried out to evaluate t...

In this study, a three-stage biological aerated filter (BAF) system was proposed to enhance nitrogen removal in the treatment of low carbon-to-nitrogen ratio (C/N ratio) municipal wastewater. Laboratory experiments were conducted at three different recirculation ratios of 1, 2, and 3. Effects of dynamic flow were also evaluated in this study. Results of the long-term operation of the three-stage BAF system in dynamic flow showed nitrogen removal was affected by the both recirculation ratio and C/N ratio in dynamic flow. Dynamic flow enabled the nitrogen removal efficiency of the system to be higher than that of nondynamic flow system in treating low C/N ratio wastewater due to the more efficient use of organic substrates. Overall NH4-N removal performance was stable with a removal efficiency of 99% on average during the operational period due to the unique system configuration where independent nitrification occurred. It was concluded that the three-stage BAF system proposed in this study provide...

Performance of a 4-stage biological aerated filter (BAF) system was evaluated with low TCOD/TKN ratio municipal wastewater, focusing on nitrogen removal. To evaluate the BAF system, a modified Ludzack-Ettinger (MLE) process was set up and compared to the BAF system. Laboratory experiments were conducted to examine the effect of hydraulic retention time (HRT). Results of the long-term operation of both systems showed that overall NH4 -N removal efficiency of the MLE was drastically reduced (from 98% to 17%) as hydraulic retention time decreased from 6 h to 3 h, whereas that of the BAF was stable with the removal efficiency of 95–96% on average, regardless of HRT applied. The effectiveness of the proposed BAF was observed in denitrification performance. Effluent NOx-N concentrations of the BAF system were lower than MLE (average of 5 mg/L) within 95% confidence level at the HRT of 6 h. At a total chemical oxygen demand (TCOD) to total kjeldahl nitrogen (TKN) ratio of 3.6, the effluent NO3-N concentration of...

This study was initiated to elucidate the relation between the toxicity of , , and and sludge age (Solids retention time, SRT). The effect of SRT on the toxicity of , , and in activated sludge system was investigated with INT-dehydrogenase assay. Experimental results showed that the inhibitory effects of , , and were reduced as the sludge age increased from SRT 5 d to SRT 25 d. It is noteworthy that the experimental results enabled to determine the relative toxicity of the tested metals depending on the sludge age. At the SRT of 5 and 9 days, the order of toxicity of the three metals to the activated sludge was > > (the value of , , and was 16.15, 25.90, and 32.49 mg/L, respectively) and > > (the value of , , and was 39.12, 27.93, and 42.31 mg/L, respectively), respectively. However, the toxicity of three metals was almost same at the SRT of 14 and 25 days (the range of in SRT 14 and 25 days was from 49.80 mg/ L to 53.44 mg/L among three heavy metals). This results would be explained by that the quantity of biopolymer formed in short SRT was small, whereas that in long SRT was large. Consequently, it is recommended that sludge age be maintained at long SRT in order to avoid the toxicity inhibition of heavy metals such as , , and .

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.

A conventional DEPHANOX process was modified in order to improve the nitrogen removal efficiency. The modified-DEPHANOX was created by adding an extra intermittent aeration reactor in the process while reducing the size of the reaeration reactor. With respect to nitrification, it was observed that the nitrification performances of both processes were significantly affected by the nitrification efficiency in its respective nitrification reactors. Also, the increase of organic matters and ammonia loading rates in the nitrification reactors decreased the ammonia removal efficiency. In nitrification reactors, when the hydraulic retention times (HRT) were set at 8 and 6 h, and the temperature was set at 25°C, the increase in organic matter did not significantly affect nitrification. However, when they were set at 6 and 5 h and the temperature was set at 16 and 17°C, respectively, the increase in organic matter had a significant effect on nitrification. A comparative study of denitrification performance between...

Two-stage sequencing batch reactor (SBR) with independent nitrification was evaluated for simultaneous removal of COD, nitrogen, and phosphorus from a low carbon-to-nitrogen wastewater (C/N ratio ranged from 1.1 to 7.4). Independent nitrification proceeded by incorporating the contact period within the system and the nitrification period in the external reactor, which was an outsourcing resource dedicated to enhancing nitrification activity. The contact period enabled the fraction of organic substrate in the influent. Ammonia nitrogen was then able to be decanted to the external nitrification reactor, in which ammonia nitrogen was nitrified as much as 70%. During the nitrification period, dominate microbial group was an ammonia oxidizing bacteria such as Nitrosomonas sp. JL21, Nitrosomonas sp. JL2, and Nitrosolobus multiformis . During the react period, the nitrogen nitrified was not only denitrified, but organic matters were also biodegraded. It was revealed that the effective and preferential use of organic substrate enhanced the overall performance of the system without the supplement of any external carbon sources. Removal efficiencies of COD, nitrogen, and phosphorus were as high as 87% at the loading rate of 0.06–4.79 kg COD/m 3 day, 81% at the loading rate of 0.05–0.84 kg N/m 3 day, and 60% at the loading rate of 0.01–0.09 kg P/m 3 day, respectively.

The SBR treatment of domestic wastewater with the fermented food waste (FFW) as an external carbon source and its three feeding methods (i.e., the slug, intermittent, and continuous feeding methods) were evaluated in this study. The use of FFW as an external carbon source was as effective as acetate for nutrient removal. It was observed that the removal efficiency of TN and TP, when the FFW was used as external carbon source, was 89.2 and 73.9%, respectively, at the SCOD/NO3−-N ratio of 10. The feeding method of FFW was an important factor on nutrient removal depending on the SCOD/NO3−-N ratio, especially P-release. It was observed that the denitrification rate was the quickest in order of the slug, intermittent, and continuous feeding in all of the SCOD/NO3−-N ratios investigated. However, the optimal feeding method in the P-release rate was changed according to SCOD/NO3−-N ratio. In the low SCOD/NO3−-N ratio, such as SCOD/NO 3− -N ratios of 7.5 and 10, the continuous feeding was the best of three feedin...

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.

Seawater-induced flocculation of alkaline tannery wastewater can increase the removal efficiency of organic compounds, such as particulate, colloids, colored compound, and other dissolved organic compounds. Evaluation of the potential biological treatment was performed by the activated sludge system of suspended micro-organisms using seawater flocculated tannery wastewater. The pH adjustment of the influent wastewater and PO4-P addition after seawater flocculation were the most important operational parameters to enhance the removal efficiency of chemical oxygen demand (COD) in the activated sludge process. Removal efficiency of COD was also increased as the sludge retention time (SRT) was increased. With the pH adjustment and PO4-P addition after seawater flocculation, 75% of COD was removed at the SRT of 15 days. Flocculation through the use of seawater was used as the primary treatment in the onsite tannery wastewater treatment plant. Experimental results demonstrated that seawater flocculation was mor...

Toxicants, which may cause the inhibition to the biological process in sewage/wastewater treatment plant, need to be monitored within short time to prevent from serious damage. A new method, Temperature-based rapid toxicity test (TempTox test) using Ceriodaphnia dubia, was developed and compared with the standard 48 hr acute bioassay (Std. 48-hr test). Inorganic toxicants of cadmium, zinc, copper, cyanide, chromium (III), chromium (VI) and organic toxicants of phenol, PCP and pesticides of BPMC, Diazinon, Fenitrothion were tested for TempTox test and Std. 48-hr test. Because the TempTox test is based on just temperature control, C. dubia neonates were exposed to toxicants under high temperature (35.5 °C) condition without any complicated pretreatment. After given exposure time of 1, 1.25, 1.5 hours, the number of the live (no toxic effect) or the dead (toxic effect) was counted with eye without the aid of any microscope and median effective concentrations (EC50 values) were determined. From the results for all toxicants, the TempTox test was proved to be as sensitive as the Std. 48-hr test with shorter-time of just 1.25–1.5 hours. Moreover, the TempTox test was further much more sensitive than alternative bioassays such as the 1-hour I.Q. test and 30-minute Microtox. The TempTox test showed a high applicability of toxicity bioassay for real sewage/wastewater treatment plant by its easiness, rapidity and sensitivity. Finally, the prototype for short-term TempTox test was introduced.

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 6.8 m 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 37.1 mg 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.

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.