A B S T R A C TThe objective of this study was to evaluate the ozone oxidation of dissolved Fe and Mn ions in abandoned neutral or alkaline mine drainage (NAMD) and the subsequent micro-sand filtration by conducting a pilot-scale operation with several ozone doses in an ozone reactor. The effects of the hydraulic retention time on the ozone oxidation were also investigated. The pH values were either neutral or slightly alkaline and the average Fe and Mn concentrations in the abandoned NAMD were 25.5 and 2.06 mg/L, respectively. The experiment results indicated that six-hour ozone oxidation with an ozone dose of 24.0 g O 3 /h (i.e. initial ozone concentration: 3.53 mg O 3 /L) and subsequent micro-sand filtration could meet the drinking water quality standard (less than 0.3 mg/L) for both Fe and Mn in the micro-sand filter effluent. The hydraulic retention time of the ozone reactor at this ozone dose was 106 s, and the media of sand grains were between 0.4 and 0.7 mm in diameter. The total dissolved solids, alkalinity, and SO 2À 4 concentrations of the influents were virtually unchanged in this pilot-scale operation. However, the oxidation-reduction potential of about 18 mV in influents increased rather gradually in effluents, and was recorded in the range of 185-210 mV during ozone oxidation. The ozone oxidation and subsequent micro-sand filtration under the operating conditions, in this study, appear to be among the desirable alternatives for the effective removal of dissolved Fe and Mn in the form of metal precipitates during ozone oxidation. This alternative could prevent metal precipitates from settling at the bottom of local water channels by removing them before they are discharged into streams.
The objective of this study was to evaluate the ozone oxidation of dissolved heavy metals in an abandoned mine drainage (AMD) by conducting a pilot-scale operation at two different ozone doses of 7.5 and 24.0 g O(3)/h into an ozone reactor. A portion of the abandoned mine drainage near the Jungam Mine in Samchuck, Korea was pumped into this pilot-scale plant and used as an influent for the ozone oxidation. Some possible precipitates of metal oxides and hydroxides that resulted from the pilot-scale ozone oxidation of the dissolved Fe and Mn ions in the AMD (with a hydraulic retention time of 106 seconds in the ozone reactor) were effectively removed via sand filtration. A six-hour ozone oxidation with an ozone dose of 24.0 g O(3)/h and subsequent sand filtration, before backwashing the sand filter bed, can meet Korean drinking water quality standards (less than 0.3 mg/L) for Fe and Mn in the sand filter effluent under the operating conditions that were used in this study. The SO(4)(-2) concentrations and alkalinities of the influents were not affected by the ozone oxidation. The pH values of the influents were neutral or slightly alkaline, and after the six-hour oxidation, increased very slightly. These experiment results show that the ozone oxidation of dissolved heavy metals and the subsequent sand filtration of metal precipitates are desirable alternatives to removing heavy metals in an abandoned mine drainage.
Objectives : This paper summarizes effective waste management and disposal methods for plastic and medical wastes during the prolonged COVID-19 pandemic.Methods : We reviewed the literatures reporting and identifying the current status and characteristics of wastes related to COVID-19, and the management and treatment guidelines for those wastes. We also investigated various technologies for waste treatment and disposal, and assessed the current status and future direction of the technologies in Korea.Results and Discussion : In the first half of 2020 in Korea, the amount of plastic waste produced had increased by 15.6% year-on-year, and medical waste production also increased significantly from 0.6 ton in January 2020 to 2,928 ton in August 2021. All of the infectious wastes are currently being incinerated in Korea, but there are concerns on air pollutant emissions and insufficient treatment facilities. Municipal solid waste also suffers from a lack of landfill capacity and low price competitiveness in the recycling industry.Conclusions : Policy and system need to be improved to reduce the infectious waste generation from the sources, and treatment and disposal technologies for produced wastes also need to be developed. Furthermore, hospitals and health care facilities should establish their own waste reducing systems which may include chemical treatment and sterilization units.
The field study was carried out to investigate runoff characteristics of non-point source (NPS) by cultivation activity in river district. Two sites were selected mainly as G region (paddy field, green house), located in Kwangju, Gyeonggi Province, and S region (ordinary field), located in Namyangju, Gyeonggi Province, those belong to Paldang reservoir watershed. The paddy field with water storage capacity showed a slow increase in runoff as rainfall intensity increases. Meanwhile, both green house and ordinary filed revealed a rapid increase. The average BOD runoff concentration of paddy field, green house, and ordinary field was 2.0 mg/L, 2.8 mg/L, 7.9 mg/L, respectively. It indicates that ordinary field shows the highest value in BOD, SS, T-N, and T-P concentration due to the soil loss during rainfall. As a result of runoff load estimation according to the field, a T-N runoff load of paddy field was 1,793.9 kg/year, higher than that of ordinary field. It was estimated that a SS runoff load of ordinary field was 69,704 kg/year and accounts for more than 70% of overall runoff load.
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