• Clean Technology
• /
• v.18 no.2
• /
• pp.209-215
• /
• 2012

The performance and removal efficiencies of a pilot scale biofilter were estimated by using ammonia and hydrogen sulfide as the odorous gases. Expanded polyurethane foam coated with powdered activated carbon and zeolite was used as a biofilm supporting medium in the biofilter. Odorous gases from the sludge thickener of a municipal wastewater treatment plant were treated in the biofilter for 10 months and the inlet ammonia and hydrogen sulfide concentrations were 0.1-1.5 and 2-20 ppmv, respectively. The removal efficiencies reached about 100% at the empty bed retention time (EBRT) of 3.6-5 seconds except for the adaptation periods. The pressure drop of the biofilter caused by the gas flow was also low that the maximum attained was 31 mm $H_2O$ during the operation. Its stability was confirmed in the long term due to the fact that the biofilter and the polyurethane medium had a minimum plugging and compression. The microbial community on the medium is critical for the performance of the biofilter especially the distribution of ammonia oxidizing bacteria (AOB) and sulfur oxidizing bacteria (SOB). The distribution of Nitrosomonas sp. (AOB) and Thiobacillus ferroxidans (SOB) was confirmed by FISH (fluorescence in situ hybridization) analysis. The longer the operation time, the more microbial population observed. Also, the medium close to the gas inlet had more microbial population than the medium at the gas outlet of the biofilter.

• Korean Chemical Engineering Research
• /
• v.43 no.2
• /
• pp.318-323
• /
• 2005

Supercritical water oxidation (SCWO, P>221 bar, T>$374^{\circ}C$) is a promising method for the decomposition of refractory organic compounds. In this study, the SCWO of Ethylenediaminetetraacetic acid (EDTA) was carried out in a tubular-type continusous reactor system with an $H_2O_2$ oxidant at $387-500^{\circ}C$, 250 bar and residence time (RT) of 15.9-88.9 s. The decomposition efficiencies increased with increasing temperature and oxidant amount, while it was inversely proportional to feed flow rate. The decomposition efficiency of 99.6% was obtained at $500^{\circ}C$, 250 bar, oxidant amount of 400% and residence time of 40.1 s. The effect of temperature on the decomposition efficiency was more significant than that of oxidant amount. In the case of the decomposition efficiency of 5,000 mg/L of EDTA (3,063 mg/L as $COD_{Cr}$), the decompostion of 99% or higher was obtained at the condition of over 40.1 s (RT) and 200 stoichiometric % of $H_2O_2$ in the supercritical water of $500^{\circ}C$ and 250 bar.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.47 no.1
• /
• pp.79-91
• /
• 2005

Wetland systems are widely accepted natural water purification systems around the world in nonpoint sources pollution control. Constructed wetlands have become a popular technology for treating contaminated surface and wastewater. In this study, the field experiment to reduce nonpoint source pollution loadings from polluted stream waters using wetland system was performed from June 2002 to March 2004, including winter performance using four newly constructed wetlands. The Dangjin stream water flowing into Seokmun estuarine lake was pumped into wetlands, and inflow and hydraulic residence time of the system was $500m^{3}{\~}1500m^{3}/day\;and\;2{\~}5$ days respectively. After 3 years operation plant-coverage was about $80~90\%$ from zero at initial stage even with no plantation. Average water quality of the influent in growing season was BOD_{5}\;3.96mg/L$, TSS 22.98 mg/L, T-N 3.29 mg/L, T-P 0.30 mg/L. The average removal rate of four wetlands for $BOD_{5},\;TSS,\;T-N\;and\;T-P$ in growing season was $24\%$, $62\%$, $54\%$, and $51\%$, respectively. And average water quality of the influent in winter season was $BOD_{5}$ 4.92 mg/L, TSS 12.47 mg/L, T-N 5.54 mg/L, and T-P 0.32 mg/L, respectively. The average removal rate of four wetlands for them was $-21\%$. $23\%$, $33\%$, and $53\%$, respectively. The reason of higher BOD_{5} effluent concentration in winter season might be that low temperature restrained microorganism activity and a organic body from the withered plant and algae was flown out. Except the result of $BOD_{5}$, the effectiveness of water quality improvement in winter season was satisfactory for treating polluted stream waters, and $BOD_{5}$ variation was within the range of background concentration. Performance of the experimental system was compared with existing data base (NADB), and it was within the range of general system performance. Overall, the wetland system was found to be satisfactory for NPS control such as improvement of polluted stream water.

• Journal of Korean Society of Disaster and Security
• /
• v.13 no.4
• /
• pp.75-92
• /
• 2020

In most cases of the water balance analysis, the return flow ratio for each water supply was uniformly determined and applied, so it has been contained a problem that the volume of available water would be incorrectly calculated. Therefore, sewage and wastewater among the return water were focused in this study and the data-driven model was developed to forecast the outflow from the sewage treatment plant. The forecasting results of LSTM (Long Short-Term Memory), GRU (Gated Recurrent Units), and SVR (Support Vector Regression) models, which are mainly used for forecasting the time series data in most fields, were compared with the observed data to determine the optimal model parameters for forecasting outflow. As a result of applying the model, the root mean square error (RMSE) of the GRU model was smaller than those of the LSTM and SVR models, and the Nash-Sutcliffe coefficient (NSE) was higher than those of others. Thus, it was judged that the GRU model could be the optimal model for forecasting the outflow in sewage treatment plants. However, the forecasting outflow tends to be underestimated and overestimated in extreme sections. Therefore, the additional data for extreme events and reducing the minimum time unit of input data were necessary to enhance the accuracy of forecasting. If the water use of the target site was reviewed and the additional parameters that could reflect seasonal effects were considered, more accurate outflow could be forecasted to be ready for climate variability in near future. And it is expected to use as fundamental resources for establishing a reasonable river water management system based on the forecasting results.

• The Journal of Engineering Geology
• /
• v.33 no.1
• /
• pp.51-59
• /
• 2023

The Nakdong river is both a natural resource crucial to underwater ecosystems and a water source for its basin's residents. Industrial wastewater and domestic sewage must meet the relevant standards for discharged water before they can flow into the river. The correlation between old and new measures of organic matter was examined using water quality data from 50 monitoring locations in the main stream of the Nakdong river. The coefficient of determination (R²) for total organic carbon (TOC), the new measure of organic matter, and chemical oxygen demand (COD), the old measure of organic matter, in the main stream of the Nakdong river was 0.6134, indicating high correlation. Water quality at each location assessed using TOC and COD showed disparities that cannot be ignored: quality appeared higher when evaluating the main stream of the Nakdong river using TOC instead of COD. Therefore, there remains a need to review water quality ratings based on TOC; continuous monitoring of COD is also required. In addition, the cause of the difference should be clearly identified to help assess artificial sources of pollution and natural factors affecting organic matter. Water management of the Nakdong river will then be possible using the water quality rating.

• Korean Journal of Environmental Agriculture
• /
• v.27 no.3
• /
• pp.217-224
• /
• 2008

To obtain optimum configuration, depth and load of constructed wetlands(CWs) for treating of hydroponic waste solution(HWS) which was produced in greenhouses, the study was conducted with 4 kinds of combined systems such as Vertical flow(VF)-Horizontal flow(HF), VF-VF, HF-VF and HF-HF CWs. In four configurations of CWs, the treatment efficiency of pollutants from HWS under depth of HF and VF beds, HWS loading and HWSs were investigated. Removal rate of pollutants under different depth of VF and HF in 2-stage hybrid CWs was in the order of 50 cm < 70 cm regardless of CWs configuration. Removal rate of pollutants under HWS loading in 2-stage hybrid CWs was in the order of $150L\;m^{-2}\;day^{-1}{\fallingdotseq}300L\;m^{-2}\;day^{-1}\;>\;450L\;m^{-2}\;day^{-1}$. The optimum depth and HWS loading were 70 cm and $300L\;m^{-2}\;day^{-1}$ in four configurations of CWs, respectively. Using this optimum condition, for various HWSs (cucumber, paprika and strawberry HWS), removal rate of pollutants in HF-HF CWs was higher than that in HF-VF CWs. Optimum configuration of 2-stage hybrid CWs for treating hydroponic waste solution in greenhouses was found out to be HF-HF CWs. Therefore, under the optimum conditions, removal rate of BOD, COD, SS, T-N and T-P in HF-HF CWs were 84, 81, 84, 51 and 93%, respectively.

• Journal of Wetlands Research
• /
• v.16 no.3
• /
• pp.431-440
• /
• 2014

To propose the improvement and management plans to strengthen the pollutant removal efficiency of dam reservoir's constructed wetlands(CWs), the operation status and configuration of CWs (including water depth, operational flow, water flow distribution, residence time, and pollutant removal efficiency, aspect ratio, open water/vegetation ratio etc.) were analyzed in 10 major wetlands constructed in dam reservoirs. The pollutant concentrations in the inflows of the studied CWs were lower than those of American and European constructed wetlands. Especially, organic matter concentrations in all of inflows were below 3 mg/L(as BOD) due to advanced treatment of sewage disposal plant and an intake of low concentration water during dry and normal seasons. The average removal efficiency of total nitrogen(TN) and total phosphorus(TP) for 10 CWs ranged from 7.6~67.6%(mean 24.9%) and -4.9~74.5%(mean 23.7%), respectively, showing high in wetlands treating municipal wastewater. On the other hand, the removal efficiency of BOD was generally low or negative with ranging from -133.3 to 41.7%. From the analysis of the operation status and configuration of CWs, it is suggested that the low removal efficiency of dam reservoir's CWs were caused by both structural (inappropriate aspect ratio, excessive open water area) and operational (neglecting water-level management, lack of facilities and operation for first flush treatment, lake of monitoring during rainy events) problems. Therefore, to enable to play a role as a reduction facility of non-point source(NPS) pollutants, an appropriate design and operation manuals for dam reservoir's CW is urgently needed. In addition, the monitoring during rainy events, when NPS runoff occur, must be included in operation manual of CW, and then the data obtained from the monitoring is considered in estimation of the pollutant removal efficiency by dam reservoir's CW.

• Journal of Wetlands Research
• /
• v.24 no.4
• /
• pp.345-353
• /
• 2022

A wastewater treatment plant (WWTP) is a major gateway for the engineered nano-particles (ENPs) entering the water bodies. However existing studies have reported that many WWTPs exceed the No Observed Effective Concentration (NOEC) for ENPs in the effluent and thus they need to be designed or operated to more effectively control ENPs. Understanding and predicting ENPs behaviors in the unit and \the whole process of a WWTP should be the key first step to develop strategies for controlling ENPs using a WWTP. This study aims to provide a modeling tool for predicting behaviors and removal efficiencies of ENPs in a WWTP associated with process characteristics and major operating conditions. In the developed model, four unit processes for water treatment (primary clarifier, bioreactor, secondary clarifier, and tertiary treatment unit) were considered. Additionally the model simulates the sludge treatment system as a single process that integrates multiple unit processes including thickeners, digesters, and dewatering units. The simulated ENP was nano-sized TiO₂, (nano-TiO₂) assuming that its behavior in a WWTP is dominated by the attachment with suspendid solids (SS), while dissolution and transformation are insignificant. The attachment mechanism of nano-TiO₂ to SS was incorporated into the model equations using the apparent solid-liquid partition coefficient (Kd) under the equilibrium assumption between solid and liquid phase, and a steady state condition of nano-TiO₂ was assumed. Furthermore, an MS Excel-based user interface was developed to provide user-friendly environment for the nano-TiO₂ removal efficiency calculations. Using the developed model, a preliminary simulation was conducted to examine how the solid retention time (SRT), a major operating variable affects the removal efficiency of nano-TiO₂ particles in a WWTP.

• Journal of Korea Water Resources Association
• /
• v.53 no.12
• /
• pp.1081-1095
• /
• 2020

This study is to evaluate stream flow and water quality changes of Yeongsan river basin (3,371.4 km2) by inter-basin water transfer (IBWT) from Juam dam of Seomjin river basin using SWAT (Soil and Water Assessment Tool). The SWAT was established using inlet function for IBWT between donor and receiving basins. The SWAT was calibrated and validated with 14 years (2005 ~ 2018) data of 1 stream (MR) and 2 multi-functional weir (SCW, JSW) water level gauging stations, and 3 water quality stations (GJ2, NJ, and HP) including data of IBWT and effluent from wastewater treatment plants of Yeongsan river basin. For streamflow and weir inflows (MR, SCW, and JSW), the coefficient of determination (R2), Nash-Sutcliffe efficiency (NSE), root mean square error (RMSE), and percent bias (PBIAS) were 0.69 ~ 0.81, 0.61 ~ 0.70, 1.34 ~ 2.60 mm/day, and -8.3% ~ +7.6% respectively. In case of water quality, the R2 of SS, T-N, and T-P were 0.69 ~ 0.81, 0.61 ~ 0.70, and 0.54 ~ 0.63 respectively. The Yeongsan river basin average streamflow was 12.0 m3/sec and the average SS, T-N, and T-P were 110.5 mg/L, 4.4 mg/L, 0.18 mg/L respectively. Under the 130% scenario of IBWT amount, the streamflow, SS increased to 12.94 m3/sec (+7.8%), 111.26 mg/L (+0.7%) and the T-N, T-P decreased to 4.17 mg/L (-5.2%), 0.165 mg/L (-8.3%) respectively. Under the 70% scenario of IBWT amount, the streamflow, SS decreased to 11.07 m3/sec (-7.8%), 109.74 mg/L (-0.7%) and the T-N, T-P increased to 4.68 mg/L (+6.4%), 0.199 mg/L (+10.6%) respectively.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.28 no.3
• /
• pp.279-293
• /
• 1995

The most obvious and easily recognizable sources of potential water pollution are point sources such as domestic and industrial wastes. But recently, the potential effects of nonpoint sources on water quality have been increased apparently. In order to evaluate the characteristics and the effects of nonpoint sources on water quality, this study was performed in Suyeong Bay from May, 1992 to July, 1992. The depth-averaged 2-dimensional numerical model, which consists of the hydrodynamic model and the diffusion model was applied to simulate the water quality in Suyeong Bay. When flowrate was $65.736m^3/s,$ the concentration of pollutants (COD, TSS and VSS) at Oncheon stream (Sebeong bridge) during second flush were very high as much as 121.4mg/l of COD, 1148.0mg/l of TSS and 262.0mg/1 of VSS. When flowrate was 4.686m^3/s, the concentration of pollutants $(TIN,\;NH_4\;^+-\;N,\;NO_2\;^--N\;and\;PO_4\;^{3-}-P)$ during the first flush were very high as much as 20.306mg/1 of TIN, 14.154mg/1 of $NH_4\;^+-N$, 9.571mg/l of $NO_2\;^--N$ and l.785mg/l of $PO_2\;^{3-}-P$ As results of the hydrodynamic model simulation, the computed maximum velocity of tidal currents in Suyeong Bay was 0.3m/s and their direction was clockwise flow for ebb tide and counter clockwise flow for Hood tide. Four different methods were applied for the diffusion simulation in Suyeong Bay. There were the effects for the water quality due to point loads, annual nonpoint loads and nonpoint loads during the wet weather and the investigation period, respectively. The efforts of annual nonpoint loads and nonpoint loads during the wet weather seem to be slightly deteriorated in comparison with the effects of point loads. However, the bay was significantly polluted by the nonpoint loads during the investigation period. In this case, COD and SS concentrations ranged 2.0-30.0mg/l, 7.0- 200.0mg/l in ebb tide, respectively. From these results, it can be emphasized that the large amount of pollutants caused by nonpoint sources during the wet weather were discharged into the bay, and affected significantly to both the water quality and the marine ecosystem. Therefore, it is necessary to consider the loadings of nonpoint pollutants to plan wastewater treatment plant.