Assessment of characteristic distribution of PCDD/Fs and BFRs in sludge generated at municipal and industrial wastewater treatment plants

The presence of polychlorinated dibenzo-p-dioxins and furan (PCDD/Fs) and brominated flame retardants (BFRs) in sludge generated at municipal wastewater treatment plants (MWTPs) and industrial wastewater treatment plants (IWTPs) was investigated. The concentrations of these pollutants were in the following ranges: 5.38-7947 ng kg⁻¹ dw (0.02-49.9 ng WHO-TEQ kg⁻¹ dw) for 17 PCDD/Fs, 17.5-66 761 μg kg⁻¹ dw for 27 polybrominated diphenyl ethers (PBDEs), 1.55-29 604 μg kg⁻¹ dw for hexabromocyclododecanes (HBCDs) (α-, β-, and γ-diastereomers), and 4.01-618 μg kg⁻¹ dw for tetrabromobisphenol A (TBBPA). Generally, the levels of each compound in the sewage-sludge samples were higher than those in the industrial-sludge samples with some exceptions. The characteristic distribution profiles of target compounds were observed for different types of sludge and different sources of wastewater. High-chlorinated PCDD/Fs were dominant in all samples except those from the textile industry. The distribution of the BFRs in industrial-sludge samples varied, whereas that of the BFRs in sewage-sludge samples was consistent. The proportion of penta-BDEs in sewage sludge was higher than that in industrial sludge, even though BDE-209 was the most dominant congener in all the samples. For HBCDs, the distribution of diastereomers (α-, β-, and γ-HBCD) was similar across sludge samples that had the same source of wastewater and treatment processes.     

Analysis and evaluation of chlorinated persistent organic compounds and PAHs in sludge in Korea

The concentrations of 12 POPs listed in the Stockholm convention, chlorophenols (CPs) and PAHs were investigated in sludge samples from wastewater and sewage treatment plants (WWTPs and STPs). The concentrations of PCDD/Fs in the wastewater sludge ranged from 0.189 to 1092 ng-TEQkg(-1) dry wt., and most of the sludge samples had levels below the EU guideline for the land application of PCDD/Fs (<100 ng-TEQkg(-1) dry wt.) except one sample. Co-PCB congeners were analyzed from four WWTPs, with total concentrations ranging from 0.265 to 26.6 ng-TEQkg(-1) dry wt., which were similar to the results obtained from previous studies. The levels of PCDD/Fs and Co-PCBs varied according to the main source of the influent to each WWTP and the paper industry was the main source of these compounds in the sludge due to the chlorine bleaching process. In case of OCPs, HCB and p,p'-DDE were detected at relatively high levels in the sludge samples compared to other target compounds, ranging from 1.30 to 21.5 microg kg(-1) dry wt. and 0.758 to 14.8 microg kg(-1) dry wt., respectively. Different OCP distribution patterns were observed according to sludge types, with HCB and DDTs being dominant in the sludge from WWTPs and STPs, respectively. The total levels of PAHs and CPs ranged from 1.24 to 44.9 mg kg(-1) dry wt. and 0.340 to 3.85 mg kg(-1) dry wt., respectively. The PAHs and CPs were also shown to have various distribution patterns, possibly due to the different wastewater sources to the WWTPs.     

A feasibility study of thermal hydrolysis by-products as barrier layer materials in the final cover system for a landfill

Most sludge has historically been disposed of in landfills and by ocean dumping but, because of its heavy metal content, this will be totally banned in Korea starting in 2012, based on the London Dumping Convention. Therefore, treatment and disposal methods that are environmentally friendlily are urgently required. The recycling of sewage sludge is a good treatment method for solving sludge problems in an environmentally friendly way. In this study, physical and environmental tests were conducted to evaluate the feasibility of using the by-products of thermal hydrolysis of sewage sludge as barrier layer materials in the final cover systems for landfills. In addition, testing methods for freezing-thawing (KS F 2332) and wetting-drying (KS F 2330) cycles were conducted to assess the effects of cold and hot soil climates starting from pavement. These tests yielded positive results for alternative materials for the barrier layer in a final cover system for a landfill.     

Feasibility of phosphate fertilizer to immobilize cadmium in a field

To reduce effectively cadmium (Cd) phytoextractability by phosphate fertilizer in Cd contaminated soil, fused and superphosphate (FSP) was applied at the rate of 0, 33.5 (recommendation level), 167.5, and 335 kg P ha⁻¹ for radish (Raphanus sativa L.). Unlike from what we expected, soil Cd extractability and Cd concentration in radish increased with increasing FSP application in the field. To determine the effect of FSP on Cd immobilization, FSP was mixed with the selected soil at the rate of 0, 200, 400, 800, and 1600 mg P kg⁻¹ and then incubated for 8 weeks. As observed in the field study, NH₄OAc extractable Cd concentration increased slightly with FSP addition up to 400 mg P kg⁻¹ and thereafter dramatically decreased upon increasing its application rate. Soil pH and negative charge were decreased at low level of FSP application up to 400 mg P kg⁻¹, but thereafter continually increased with increasing application level. This could be indirect evidence that net soil negative charge was increased by the specific adsorption of phosphate at the high rate of FSP application over 400 mg P kg⁻¹. The labile Cd fraction (water soluble and exchangeable + acidic fraction) increased with increasing FSP application by 400 mg P kg⁻¹ and thereafter gradually decreased with corresponding increase in unlabile fraction (oxidizable and residual fraction). Based on these results, FSP might be applied with a very high rate over 800 mg P kg⁻¹ to decrease Cd extractability in the selected field. However, this level is equivalent to 1440 kg P ha⁻¹, which is about 43 times higher than the recommendation levels for radish production and resulted in a significant increase in water soluble P concentration creating a new environmental problem. Therefore, the feasibility of FSP to reduce Cd extractability in the field is very low.     

The status of flood wastes treatment and future tasks in South Korea

Natural disasters such as typhoon, flood, and heavy rainfall cause damage in South Korea every year during the summer season. After each rainy season, South Korea suffers not only from flood wastes but also from debris that pile up at dams and stagnate at the estuary of the river. Thus, it is very important to handle these types of wastes as quickly as possible to recover from flood damages and to prevent environmental contamination such as offensive odor and water contamination by the leachate from flood wastes. Other countries such as Japan or USA have established and implemented regulations and guidelines for flood waste. Note, however, that South Korea did not establish practical guidelines; hence, the urgency of establishing practical measures for flood waste. In this study, we suggested various ways of making environmentally sound guidelines including the method of reducing the amount of flood waste by environmentally sound treatment process for flood waste, and the method of setting up and operating the temporary storage site for purposes of efficient separation and treatment of flood waste.     

International comparative study of 3R and waste management policy developments

Reduce, reuse, and recycle (3R) policies form the basis of waste management and global warming countermeasures globally, so we conducted a comparative study of 3R and waste management policies in the European Union (EU), USA, Korea, Japan, China, and Vietnam. An international workshop for 3R and waste management policymakers was held in Kyoto, Japan, and a bibliographic survey was also conducted to collect data. 3R policies are clearly given priority in the hierarchy of waste management in every country studied. Thermal recovery, which includes power generation from waste heat and methane gas collected from organic waste, is also a priority; this is consistent with the increased use of countermeasures to reduce greenhouse gas (GHG) emissions. In the EU, waste management is characterized by practical and effective 3R policies through the development of realistic regulations and by the policymakers??desire to simplify management systems. The policy ideal in China, however, is the development of a circular economy that targets reductions in the amount and hazardousness of waste. Limits on the number of final disposal sites, strategies for procuring resources, and GHG emission countermeasures are closely linked with 3R policies, and further development of 3R policies in parallel with such issues is expected.     

Comparison of different disinfection processes in the effective removal of antibiotic-resistant bacteria and genes

This study compared three different disinfection processes(chlorination, E-beam, and ozone) and the efficacy of three oxidants(H2O2, S2O-8, and peroxymonosulfate(MPS)) in removing antibiotic resistant bacteria(ARB) and antibiotic resistance genes(ARGs) in a synthetic wastewater. More than30 mg/L of chlorine was needed to remove over 90% of ARB and ARG. For the E-beam method, only1 dose(kGy) was needed to remove ARB and ARG, and ozone could reduce ARB and ARG by more than 90% even at 3 mg/L ozone concentration. In the ozone process, CT values(concentration × time)were compared for ozone alone and combined with different catalysts based on the 2-log removal of ARB and ARG. Ozone treatment yielded a value of 31 and 33(mg·min)/L for ARB and ARGs respectively. On the other hand, ozone with persulfate yielded 15.9 and 18.5(mg·min)/L while ozone with monopersulfate yielded a value of 12 and 14.5(mg·min)/L. This implies that the addition of these catalysts significantly reduces the contact time to achieve a 2-log removal, thus enhancing the process in terms of its kinetics.     

Characteristics of Asian dust transport based on synoptic meteorological analysis over Korea

Classification of synoptic patterns and their correlation with dust events over East Asia were performed by means of cluster analysis. The average linkage and K-means clustering techniques were used to identify two major weather types during Asian dust events (ADEs; total 26 ADEs with 47 dusty days) of six spring seasons from 1996 to 2001. The first weather type mainly influenced neighboring Asian countries and frequently occurred with ADEs (approximately 23% of ADE cases). It mostly occurred under a surface high (low)-pressure system over the west (east) of the Korean peninsula coupled with an upper-level trough and cutoff low passage over the center of the Korean peninsula. It showed strong advection in the middle/ upper troposphere with both a high aerosol index and enhanced coarse particulate matter (PM) loading over Korea. In contrast, the second weather type was mostly associated with long distance or continental-scale transport and occurred less frequently with ADEs (approximately 15%). It appeared with an upper-level trough and a cutoff low vertically connected with a surface low system that was formed by a strong cyclonic vortex over the north of the Korean peninsula. There were weak advection, low aerosol index, and low coarse PM concentration over the Korean peninsula during the second weather type. In addition, it was found to be mostly associated with the trans-Pacific transport of Asian dust to the western coast of North America.     

Hydroxyl radical generation and oxidative stress in Carassius auratus liver as affected by 2,4,6-trichlorophenol

With Carassius auratus, one of the main economic fish species in Eastern China as test material, this paper studied the hydroxyl radical generation and oxidative stress in its liver under the effect of 2,4,6-trichlorophenol (2,4,6-TCP). Different doses of 2,4,6-TCP were injected intraperitoneally into the fishes, and the Electron paramagnetic resonance (EPR) spectra of hepatic free radicals, activities of superoxide dismutase (SOD), catalase (CAT) and glutathione-s-transferase (GST), levels of reduced glutathione (GSH) and oxidized glutathione (GSSG), and malondialdehyde (MDA) contents were determined 24h after injection. The results showed that under the effects of 2,4,6-TCP, the generation of free radical that was considered to be hydroxyl radical increased significantly, the activities of antioxidant enzymes decreased, with CAT most strongly affected and followed by SOD and GST, the GSH level decreased significantly while GSSG level had little difference, resulting in a decreased GSH/GSSG ratio, and the MDA content increased significantly. All the test parameters showed that C. auratus was subjected to oxidative stress and damage when exposed to 2,4,6-TCP.     

Organically modified low-grade kaolin as a secondary containment material for underground storage tanks

Batch scale reactions were conducted to evaluate the efficacy of modified low-grade kaolin for the treatment of petroleum contaminants. Low-grade kaolin, which has been unvalued as material in the mining process because of its low quality for commercial products, was modified with HDTMA (hexadecyl-trimethylammonium), and its efficiency was compared with that of HDTMA-modified bentonite, which is used as a secondary containment barrier for underground storage tanks. The sorption capacity and hydraulic conductivity of both the HDTMA-modified bentonite and low-grade kaolin were investigated and showed distribution coefficients in the sorption of benzene, toluene, ethylbenzene and xylene ranging between 45.7 and 583.7 and 57.0 and 525.1, respectively. The hydraulic conductivities were 2.53 × 10⁻⁸ and 5.62 × 10⁻⁸ cm/s for the HDTMA-modified bentonite and low-grade kaolin, respectively. These results suggest that HDTMA-modified low-grade kaolin could be used as a hydraulic barrier against advection migration of petroleum contaminants. Simulation of the one-dimensional transport of benzene through a liner made of either one of the compounds was also performed. These results also showed that HDTMA-modified kaolin more effectively retards the transport of benzene.