• Journal of the Mineralogical Society of Korea
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• v.19 no.4 s.50
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• pp.355-361
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• 2006

Artificially crushed sands occupy approximately 30 percent of the total consumption in South Korea. The demand for the crushed sands is expected to rise in the future. Most manufacturers use granitic rocks to produce the crushed sands. During the manufacturing process, fine fractions (i.e., sludges or particles smaller than 63 microns) are removed through the process of flocculation. The fine fraction occupies about 15% of the total weight. The sludges are comprised of quartz, feldspars, calcite, and various kinds of clay minerals. Non-clay minerals occupy more than 75 percent of the sluges weight, according to the XRD semi-quantification measurement. Micas, kaolinites, chlorite, vermiculite, and smectites occur as minor constituents. The sludges from Jurassic granites contain more kaolinites and $14{\AA}$-types than those from the Cretaceous ones. The chemical analysis clearly shows the difference between the parent rocks and the sludges in chemical compositions. Much of colored components in the sludges was accumulated as the weathering products. Particle size analysis results show that the sludges can be categorized as silt loam in a sand-silt-clay triangular diagram. This result was for her confirmed by the hydraulic conductivity data. In South Korea, the sludges remained after crushed sand production are classified as an industrial waste because of their impermeability, and which is caused by their high silt and clay fractions.

• Environmental Engineering Research
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• v.16 no.2
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• pp.103-109
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• 2011

This work experimentally determined the effect of thermal and microwave pretreatments on the anaerobic digestion of mixtures of municipal primary and secondary sludges in semi-continuous mesophilic digesters at hydraulic retention times (HRT) of 20, 15, 10, 7, and 5 days. The ratio of soluble chemical oxygen demand (COD) to total COD in thermally pretreated and microwaved sludges at $80^{\circ}C$ was 2.7 and 3.2 times higher than that of raw sludge, respectively. The volatile solids (VS) and COD removal efficiencies in all three digesters fed with raw (control), thermally pretreated (TM), and microwaved (MW) sludges decreased as the HRT was reduced. The highest relative improvement in VS removal compared to the control occurred at the HRT of 5 days in the TM and MW (29 and 41% higher than the control, respectively). At this HRT, improvement in the COD removal efficiencies in the TM and MW compared to the control was 28 and 53%, respectively. Improvements in biogas production compared with the control increased in both the TM and MW as the HRT was reduced to 5 days. The relative improvement in daily biogas production compared to the control from the TM and MW was 33 and 53% higher than the control at the HRT of 5 days, respectively. The results show that microwave pretreatment is more effective than thermal pretreatment in increasing the solubilization degree and mesophilic anaerobic biodegradability of sewage sludge.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.17 no.1
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• pp.41-47
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• 1981

The characteristics of septic tank sludges were investigated and the kinetic coefficients in the aerobic biodegradation were evaluated from bach treatability tests. Using an unbiased statistical method, the estimated values, k (substrate removal rate coefficient) =0. 0175hr-1 at 17\ulcornerC, K. (Michaelis Menten constant) = 248mg/ e, a (cell yield coefficient)=0.625, and Kd (cell decay coefficient:' =0. 00192hr-1 were obtained based on biodegradable COD(mg/ \ulcorner) and volatile suspended solids(mg/\ulcorner). The relationship between COD and BOD, COD (mg/\ulcorner) =2. 1 BOD(mg/\ulcorner) +250, also was established for the septic tank sludges. Dilution was inevitable for the grit removal because of the high viscosity of the sludges. An aerobic activated sludge process rather than anaerobic processes was recommended for the removal of soluble organics after the removal of grit and suspended solids. A multi-stage activated sludge process was adapted for this highly concentrated and not easily-degradable waste. It was estimated that a four-stage activated sludge process would require 40 hours retention time compared to 92 hours for a single-stage process, 52 hours for a double-stage process, and 46 hours for a three stage process in order to achieve an effluent quality of 84mg/ e COD( 40mg/ e BOD) with about 4, OOOmg/ \ulcorner MLSS from an influent quality of I, 500mg/ t COD(714mg/.e BOD), while multi-stages beyond four stage would not save the required retention time significantly.

• Journal of Environmental Science International
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• v.14 no.4
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• pp.413-425
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• 2005

The 16 priority PAHs (Polycyclic Aromatic Hydrocarbons) designated by US Environmental Protection Agency were analyzed for some digested sludges from wastewater treatment plants in Korea. PAHs are an important group of organic contaminants present in sewage sludge due to their persistence and toxic potential. PAHs were extracted from freeze-dried sludges using a methylene chloride-methanol (2:1) mixture in a soxhlet extractor. The extracts were cleaned-up by silica gel/alumina combination column and subsequently fed into gas chromatograph/mass spectrometer (GC/MS) for determining PAH contents. The sum of the 16 PAHs in the sewage sludge varied from 534.8 to $5754.5 {\cal}ug/{\cal}kg$, dry wt.. In the sewage sludge, phenanthrene appears as the most abundant PAHs, followed by naphthalene, pyrene, fluoranthene. Source of the investigated sewage sludges relatively predominated pyrogenic. PAHs levels of sewage sludges in Korea appeared to be lower than those in other countries.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.4
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• pp.66-78
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• 2003

The effects of several factors such as heavy metals, living microorganims, high molecular conglomerator in sewage sludge were analysed. And the effects of the sewage sludges which were mixed with other organic waste such as paper mill sludge or night soil sludge upon the feeding rate and biomass of earthworm population were also estimated. The earthworm populations could not survive when newly produced sewage sludges were fed without any pretreatment. The contents of heavy metals were under the levels that could inhibit earthworm's growth. The living microorganisms and the high molecular conglomerator in the sewage sludge had no relations with ecotoxicological effects of sewage sludge upon the earthworm population. Sewage sludge which had been mixed with paper mill sludge and aged for more than 21 days showed no ecotoxicological effects on tiger worm(Eisenia fetida) population. And the feeding rate of earthworm population and the turnover rate of earthworm biomass were higher in those sewage sludges than in the sewage sludges pretreated by other ways.

• Journal of Korean Society on Water Environment
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• v.18 no.2
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• pp.123-130
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• 2002

Bench scale experiments were carried out with two biological nutrient removal(BNR) units, A/O and $A^2O$ processes, to investigate the behavior of phosphorus in the system and to compare the characteristics of phosphorus removal in two BNR processes. To achieve this goal, COD/T-P and COD/TKN ratios of the influent was varied in the range of 23~64 and 5~24, respectively. In A/O process, influent COD/T-P ratio should be kept higher than 44mg/L to meet the final effluent T-P concentration lower than 1mg/L and in $A^2/O$ process, influent COD/T-P and COD/TKN ratios higher than 56 and 10, respectively, were required for good phosphorus release and uptake with no influence of nitrate nitrogen in return sludge. At this conditions, the rate of phosphorus release in the anaerobic basin should be kept higher than 0.1 kg S-P/kg MLVSS d In A/O process, the phosphorus content of anaerobic and aerobic sludges was increased as SRT of total system was becoming longer resulting in decreasing the difference of phosphorus content between two sludges while phosphorus release in anaerobic basin and phosphorus uptake in aerobic basin was not incident. In $A^2/O$ process, the phosphorus content of anaerobic and aerobic sludges were not increased with higher SRT of total system due to the relatively high nitrate concentration in return sludge. However, the difference of phosphorus content between anaerobic and aerobic sludges was incident when phosphorus release and uptake was observed.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2000.11a
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• pp.91-96
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• 2000

A commercial-scale Fluidized Bed Incinerator(FBI) to treat dewatered sludges has been developed by Jindo Corporation, Korea, as one of the governmental R&D project during 1990 to 1997. The FBI plant was constructed at Kunsan city and fully in operation after finishing the successful test-burn period since June 1998. The company now has a capability of the design, construction and operation of commercial FBI plants. This paper introduces the experiences of design and operation of Kunsan FBI plant, which has the capacity of 60 ton/day and incinerates various sludges from waste water treatment facilities and liquid waste such as waste oil or waste solvent.

• Economic and Environmental Geology
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• v.33 no.2
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• pp.139-146
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• 2000

Development of an effective liner by utilization of the tailings frm the Imcheon mine and polymer has been tried. The tailings piled in the Imcheon mine, whose true specific gravity is about 2.86, are composed mainly of quartz, alkali-feldspar, muscovite and pyrite, and mostly (93.7% in volume) coarser than sand grain size (50${\mu}{\textrm}{m}$). Strength, leaching and permeability tests have been performed on the test specimens of polymer concrete manufactured with various mixing proportions of tailings, unsaturated polyester resins(UPR), calcium carbonates, stone powder sludges and granite soils. Polymer concrete specimens with stone powder sludges or granite soils as fillers and aggregates indicate 2.5 to 3 fold higher flexural and compressive strengths and lower permeabilities than those with calcium carbonates, which shows their usability as a waterproof liner. Also, the polymer concrete liner with stone powder sludge fillers is more advisable in aspects of utilization of waste sludges than that with other fillers.

• Proceedings of the Microbiological Society of Korea Conference
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• 2003.05a
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• pp.111-114
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• 2003

The dynamics of microbial community structure of the various domestic wastewater treatment processes were examined using a novel approach of quinone profiles. The compositions of microbial quinone of 5 sites fer plant and lab-scale activated sludge were analyzed. More than 14 kinds of quinones were observed in the activated sludges tested in this study. The microbial community structure of the plant activated sludge processes a little differed from that of the lab-scale submerged MBR systems. The dominant quinones were UQ-8, UQ-10 followed $MK-8(H_4)$, MK-7 and MK-6. The molar ratio of ubiquinones to menaquinones (UQ/MK) changed from 0.81 to 1.9, indicating that aerobic bacteria dominated the microbial community of the activated sludge examined. The microbial diversity of the activated sludges calculated from the all quinone compositions was 9.5-11.9 and the microbial equability of the activated sludges was 0.64-0.79.

• Journal of Industrial Technology
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• v.16
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• pp.169-174
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• 1996

Microstructural analyses of synthetic arsenic-containing heavy metal sludges solidified with Portland cement were performed. Heavy metal sludges containing 0.04M of cadmium, chromium, copper, lead, and arsenic were prepared by sodium hydroxide precipitation and successive vacuum filtration. The sludges mixed with cement were cured for 14 days. The solidified sample was characterized by 1) leaching test, 2) scanning electron microscopy and 3) X-ray diffractometry. Of the metals tested, only Pb concentration in the leachate exceeded the Korean regulatory limit. The level of lead in the leachate was as high as 10 times the regulatory limit. X-ray analysis suggested that the metal hydroxides might be present in complex or impure crystalline phases.