• Journal of the Korean Wood Science and Technology
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• v.22 no.2
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• pp.37-45
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• 1994

The possibility of reusing the paper sludge as a raw material of composition board mixed with cement was investigated. For the measurement of physical and mechanical properties, wood coment board and sludge combinend cement boards were fabricated with the three weigh ratios of paper sludge 10 % (SI), 20 % (S II) and 30 % (S III) to cement weight. For adding the cement hardning, $CaCl_2$ was also added to each mixed paste with the ratio of 1 %, 3 % and 5 % to cement weight, respectively. Crystal formation in paper sludge-, wood-cement composites was observed by scanning electron microscope. The results were summarized as follows. 1. Density and partial compressive strength of each specimens were relatively high in the order of sludge I, sludge II, Korean pine, Italian poplar and sludge III, sludge I, Korean pine, sludge II, Italian poplar and sludge III. 2. The mechanical properties of sludge-cement boards (S I and II) were higher than that of wood-cement boards prepared with Korean pine and Italian poplar. But the mechanical properties of wood-cement boards were improved by the adding of $CaCl_2$. 3. Water absorption and thickness swelling were increased with increase of sludge content to cement weight. 4. In SEM observation, sludge-cement composites showed sufficiently formed crystals but wood-cement composites showed poorly formed crystals.

• Korean Journal of Microbiology
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• v.28 no.3
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• pp.243-248
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• 1990

Genetically engineered strains of Pseudomonas, which could degrade the various aromatic hydrocarbons, were acclimated to the synthetic wastewater with increasing substrate concentration. All of the tested strains except KUD101 showed 70-90% of the COD removal efficiencies. Acclimated strains, Pseudomonas putida KUD106, KUD107 and KUD108 were inoculated into the ordinary activated sludge and these sludges were used in the dyeing or alkylbenzene wastewater treatment system. In the case of the wastewater containing alkylbenzene compounds, COD removal efficiency was 12-14% higher than that of the ordinary activated sludge, while it was not effective for dyeing wastewater. On the other hand, the floc formation of the activated sludge inoculated with genetically engineered strains was more rapid in both wastewaters tested than that of the activated sludge by the ordinary natural strains.

• Membrane and Water Treatment
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• v.10 no.5
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• pp.331-338
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• 2019

This study aimed to investigate the membrane fouling and sludge characteristics in a pilot-scale submerged membrane bioreactor (MBR) operated under low temperature ($7^{\circ}C$). To elucidate the mechanisms of membrane fouling at low temperature, we studied the correlation between MBR performances and physicochemical properties of sludge including extracellular polymeric substance (EPS), relative hydrophobicity (RH) and floc size during long-term operation. The MBR was shown able to remove chemical oxygen demand (COD) stably and efficiently (>90 %) in the case of overgrowth of filamentous bacteria (bulking sludge) at low temperature. On the other hand, the occurrence of filamentous bulking greatly accelerated membrane fouling, as indicated by membrane filtration period of 14 days for filamentous bulking at $7^{\circ}C$, in comparison with that of 27 days for non-bulking sludge at $24^{\circ}C$ The overgrowth of filamentous bacteria resulting from low-temperature condition led to an increased release of EPS, higher RH, smaller floc size and lower fractal dimension of sludge. These factors accelerated the formation of compact cake layer on membrane surface in association with performance diminution in terms of increase in transmembrane pressure (TMP) of the membrane and thus the decrease in membrane permeability.

• Journal of Environmental Science International
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• v.28 no.7
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• pp.607-615
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• 2019

The purpose of this study is to biological treatment of high salinity wastewater using Aerobic Granular Sludge (AGS). In laboratory scale's experiments research was performed using a sequencing batch reactor, and evaluation of the denitrification reaction in accordance with the injection condition of salinity concentration, surface properties of microorganisms, and sludge precipitability was performed. The results showed that the salinity concentration increased up to 1.5%, and there was no significant difference in the nitrogen removal efficiency; however, it showed a tendency to decrease gradually from 2.0% onward. The specific denitrification rate (SDNR) was 0.052 - 0.134 mg $NO_3{^-}-N/mg$ MLVSS (mixed liquor volatile suspended solid)${\cdot}day$. The MLVSS/MLSS (mixed liquor suspended solid) ratio decreased to 76.2%, and sludge volume index ($SVI_{30}$) was finally lowered to 57 mL/g. Using an optical microscope, it was also observed that the initial size of the sludge was 0.2 mm, and finally it was formed to 0.8-1.0 mm. Therefore, salinity injection provides favorable conditions for the formation of an AGS, and it was possible to maintain stable granular sludge during long-term operation of the biological treatment system.

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.6
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• pp.460-464
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• 2000

Extracellular polymeric substances (EPS) are believed to play a role in the binding and formation of microbial flocs. However, the precise role is not well known. Sludge settling characteristics and the carbohydrate to protein ratio in EPS were tested with various airflow rates in this study. Sludge was collected from three modified sequencing batch reactors (SBRs), which were operated at 16$\^{C}$ with an airflow rate of 0.8L/min, 3L/min and 6L/min, respectively. During the operation, the reactor operated at an airflow rate of 0.8L/min showed sludge volume index (SVI) of 80 to 90ml/g and a constant ratio of carbohydrate to protein in the EPS, while a significant increase in the SVI was seen in the other reactors. Sludge bulking increased the amount of carbohydrate in the EPS, while kept protein almost constant in the airflow rate of 3L/min ad 6L/min. Surface charge also increased with increases in the carbohydrate to protein ratio in the EPS, which weakens the attraction between the EPS and multivalent cations. The ratio of carbohydrate to protein in the EPS was tween the EPS and multivalent cations. The ratio of carbohydrate to protein in the EPS was inferred to be essential for bioflocculation.

• Journal of Microbiology and Biotechnology
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• v.22 no.8
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• pp.1035-1043
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• 2012

The ammonia-oxidizing bacterial (AOB) communities in three membrane bioreactors (MBRs) were monitored for 2 months after an acclimation period in order to investigate the influence of sludge age and medium type on AOB changeability and its connection with nitrification effectiveness. One MBR with a sludge age of 4 days was fed with a synthetic medium, whereas the other two with sludge ages of 8 and 32 days were fed with landfill leachate. The research revealed that landfill leachate can be effectively treated in an MBR with a higher sludge age for longer periods of time and that this improvement in performance was correlated with an increase in AOB biodiversity. Interestingly, the medium type has a stronger influence on AOB biocenosis formation than the sludge age.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.6
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• pp.769-778
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• 2009

Performances and internal behaviors of the upflow hybrid anaerobic filters treating a dairy wastewater were analyzed to identify the functions and roles of the modular crossflow media and sludge bed layer and to discover their interrelationship in the filter. The media could perform independent biological and physical separation role without buildup of sludge bed, while the role of sludge bed was dependent on the function of the media. The filter packed with the crossflow media did not necessarily require the formation of sludge bed when treating a dairy wastewater. Biological contribution of the media was controlled by that of biologically active sludge bed complementing mutually each other. The gas-liquid-solid separation capability of the media was indispensible to ensure the active biological role of sludge bed, since sludge bed buildup without the media had no independently effective biological function. It was believed that the filter in itself could also function as a selector for physical gas-liquid-solid separation resulting in selectively concentrating particles with superior settleability in sludge bed. The sludge bed in the filter played a key role in the physical solids capture from influent as well as biological organics removal.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.448-452
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• 2001

An Experimental study was carried out to develop a simple method of processing copper waste sludge which is produced by PBC manufacturing. The procedure is based on leaching of wet sludge in 2N H$_2$SO$_4$, and the solid / liquid ratio is controlled approximately at 1/10. The recovery of copper is 85.4%, and pH of the leachate is 3.20. Adding ammonia solution into leachate forms ammine, and hydroxide compounds derived from other impurities in leachate at pH 10. The hydroxide compound can be treated by ferrite process, and the product is a stable oxide compound. Then the ammine solution is heated to evaporate ammonia, and the copper hydroxide is formed. Heating at 8$0^{\circ}C$by aeration, copper hydroxide is transformed into copper oxide with a purity of 98.4%. This process can recover most copper from sludge and the residue can be stabilized by the formation of a stable oxide compound which is not hazardous to environment.

• Journal of Korean Society on Water Environment
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• v.24 no.4
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• pp.458-464
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• 2008

Bulking phenomena and scum formation are common problem in suspended growth system like the activated sludge plants for wastewater treatment. Apart from wastewater composition, operating conditions, such as mechanical stress by insufficient oxygen supply, are often decisive for the occurrence of a bulking or scumming problem. There were the comparative aeration tanks in terms of sludge bulking caused by the difference of mechanical aeration facilities in the wastewater treatment plant of N paper mill company. In this study the cause of bulking was investigated through not only the biological isolation and identification but also a series of operational data consideration. On the basis of the investigation results for bulking cause, the operational criteria on dissolved oxygen concentration was derived to decrease the bulking problem.

• Journal of Korean Society on Water Environment
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• v.21 no.1
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• pp.29-33
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• 2005

In order to recycle the waste material and to develop the thickening unit of waste activated sludge from wastewater treatment facilities, the filtration bio-reactor equipped with a shadow mask filter module was employed for this work from which the operating properties and parameters were drawn. The sludge thickening and filtration unit is made of cylindrical acryl tank(12cm i.d. ${\times}$ 58cm height: working volume of 6L), where the flat-sheet type of shadow mask filter module(pore size: 220~250um, opening area: 34.8~39.6%) was installed and the effluent was withdrawn from the effluent port at the lowest point of the reactor, and the filtration was performed only by the hydraulic pressure. For evaluating the operating performance of this reactor, some parameters such as the solid-liquid separation of different biomass concentrations, the water quality of filtrate, the aeration cleaning time and the cleaning effect were investigated. Depending on the MLSS concentrations, the different time to withdraw 3L of filtrate was required in which the longer filtration time was necessary for the higher MLSS concentrations caused by the thicker formation of cake layer: 40 minutes for 5,000 mg/L, 70 minutes for 10,000 mg/L and 100 minutes for 15,000 mg/L, where the concentrations of SS were 8.9, 6.7 and 6.5 mg/L, respectively. Under the same operating conditions (the intensity of aeration cleaning: 80 L/min, MLSS: 10,000 mg/L), the proper aeration cleaning time was revealed 30 seconds, and the stable formation of cake layer was in the range of 10 to 15 minutes. Therefore, the shadow mask considered as a waste material can be of use as a filter material for the sludge thickening system.