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The production of solid recovered fuel (SRF) from sewage sludge has been credited with facilitating Korea's waste management shift toward a resource circular economy. In this study, a novel pilot-scale wet electrostatic precipitator (WESP) was developed and installed in a bio-drying-assisted solid recovered fuel (SRF) generation plant for the first time. To investigate the performance of the novel WESP, various sizes of particulate matter, i.e., total particle matter (PM), particle matter smaller than 10 μm (PM10), and particle matter smaller than 0.1 μm (PM0.1), collection efficiencies were evaluated and demonstrated promising performances. Under optimal operating conditions (flow rate of 5 m3/min and an applied voltage of 30 kV), 99.76% PM and 91% PM10 collection efficiencies were achieved, and the PM concentration was 0.16 mg/m3, which met the exhaust emission standard. However, a dramatic increase in PM0.1 was observed and could be explained by the break-up theory, binary homogenous nucleation, and ion-induced nucleation. The experimental findings could serve as useful information to understand the WESP system. [ABSTRACT FROM AUTHOR]

The Ministry of Environment in Korea aims to reduce non-point source (NPS) pollution and improve soil water management by expanding NPS priority management areas. Six NPS priority management areas to reduce suspended solids (SS) according to soil loss were chosen as they either constitute serious hazards to the natural ecosystem due to NPS pollutants or they are areas with unusual geologic structure or strata. Although more comprehensive standards are required for effective NPS management, however, no detailed consideration factors and standards are available in the legal provisions. Therefore, in this study, based on the existing six priority NPS management areas and using results from previous studies, we present detailed legal designation standards. We found that the higher the altitude, slope, and field area ratio, the higher the effect of SS on water quality during rainfall. Additionally, there is a high correlation as R2 0.9813 between SS and the habitat and riparian index. These results are useful for establishing detailed standards for areas requiring an NPS management system, future expansion of the NPS priority management area designation, and policymaking and research for reducing NPS pollution in Korea. [ABSTRACT FROM AUTHOR]

Owing to urbanization, impervious areas within watersheds have continuously increased, distorting healthy water circulation systems by reducing soil infiltration and base flow; moreover, increases in surface runoff deteriorate water quality by increasing the inflow of nonpoint sources. In this study, we constructed a Hydrological Simulation Program—Fortran (HSPF) watershed model that applies the impervious area and can set medium- and long-term water circulation management goals for watershed sub-areas. The model was tested using a case study from the Yeongsan River watershed, Korea. The results show that impervious land-cover accounts for 18.47% of the upstream reach in which Gwangju City is located; approximately twice the average for the whole watershed. Depending on the impervious area reduction scenario, direct runoff and nonpoint source load could be reduced by up to 56% and 35%, respectively; the water circulation rate could be improved by up to 16%. Selecting management goals requires the consideration of both policy objectives and budget. For urban areas with large impervious cover, the designation of nonpoint source management areas is required. For new cities, it is necessary to introduce water circulation systems (e.g., low impact development techniques) to improve rainwater penetration and recharge and activate preemptive water circulation. [ABSTRACT FROM AUTHOR]

This study aimed to estimate pollutant unit loads for different landuses and pollutants that reflected long-term runoff characteristics of nonpoint source (NPS) pollutants and recent environmental changes. During 2008–2014, 2026 rainfall events were monitored. The average values of antecedent dry days, total rainfall, rainfall intensity, rainfall duration, runoff duration, and runoff coefficient for each landuse were 3.8–5.9 d, 35.2–65.0 mm, 2.9–4.1 mm/h, 12.5–20.4 h, 12.4–27.9 h, and 0.24–0.45, respectively. Uplands (UL) exhibited high suspended solids (SS, 606.2 mg/L), total nitrogen (TN, 7.38 mg/L), and total phosphorous (TP, 2.27 mg/L) levels, whereas the runoff coefficient was high in the building sites (BS), with a high impervious surface ratio. The event mean concentration (EMC) for biological oxygen demand (BOD) was the highest in BS (8.0 mg/L), while the EMC was the highest in BS (in the rainfall range <10 mm) and UL and forest land (in the rainfall range >50 mm). The unit loads for BOD (1.49–17.76 kg/km2·d), TN (1.462–10.147 kg/km2·d), TP (0.094–1.435 kg/km2·d), and SS (15.20–327.70 kg/km2·d) were calculated. The findings can be used to manage NPS pollutants and watershed environments and implement relevant associated management systems. [ABSTRACT FROM AUTHOR]

To determine the high-priority tributaries that require water quality improvement in the Nakdong River, which is an important drinking water resource for southeastern Korea, data collected at 28 tributaries between 2013 and 2017 were analyzed. To analyze the water quality characteristics of the tributary streams, principal component analysis and factor analysis were performed. COD (chemical oxygen demand), TOC (total organic carbon), TP (total phosphorus), SS (suspended solids), and BOD (biochemical oxygen demand) were classified as the primary factors. In the self-organizing maps analysis using the unsupervised learning neural network model, the first factor showed a highly relevant pattern. To perform the grade classification, 11 parameters were selected. Six parameters are concentrations of the main parameters for the water quality standard assessment in South Korea. We added the pollution load densities for the selected five primary factors. Joochungang showed the highest pollution load density despite its small watershed area. According to the results of the grade classification method, Joochungang, Topyeongcheon, Hwapocheon, Chacheon, Gwangyeocheon, and Geumhogang were selected as tributaries requiring high-priority water quality management measures. From this study, it was concluded that neural network models and grade classification methods could be utilized to identify the high-priority tributaries for more directed and effective water quality management. [ABSTRACT FROM AUTHOR]

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−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'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. [ABSTRACT FROM AUTHOR]