• 상하수도학회지
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• 제19권2호
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• pp.149-154
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• 2005

Conventionally used flocculation tanks require large space and high energy requirement for mixing. Static flocculators using gravel bed filter operate at a lower flow rate ($5-10m^3/m^2{\cdot}h$). Further, the cleaning of this system is difficult. A novel high rate static flocculator/filter developed at UTS packed with buoyant media such as polystyrene, polypropylene has been found to operate at higher filtration rates (30-45 $5-10m^3/m^2{\cdot}h$). They can easily be cleaned with minimal energy. Detailed experiments conducted with an artificial kaolin clay solution show that buoyant media is an excellent static flocculator in producing uniform filterable microflocs (12-15 m) even when it is operated at a high rate of 30-40 m/h. Detailed filtration experiments were conducted in a wastewater treatment plant to treat the biologically treated effluent with a floating media of depth of 120 cm. This filter was able to remove majority of phosphorus and remaining solids. It reduced significantly the fecal coliforms and fecal streptoccoci, thus requiring less amount of chlorine for disinfection. The advantage of this system is the low energy and water requirement for cleaning of filter bed. The periodic backwash adopted 30 seconds air and water and 30 seconds water cleaning every 90 minutes filter operation. Thisis equivalent to 1-2% of filtered water production. Mechanical cleaning system on the other hand, requires very low energy requirement (<1% of filtered water production).

• 상하수도학회지
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• 제33권2호
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• pp.151-158
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• 2019

Objectives of this study were to identify the hotspot for displacement of the on-line water quality sensors, in order to detect illicit discharge of untreated wastewater. A total of twenty-six water quality parameters were measured in sewer networks of the industrial complex located in Daejeon city as a test-bed site of this study. For the water qualities measured on a daily basis by 2-hour interval, the self-organizing maps(SOMs), one of the artificial neural networks(ANNs), were applied to classify the catchments to the clusters in accordance with patterns of water qualities discharged, and to determine the hotspot for priority sensor allocation in the study. The results revealed that the catchments were classified into four clusters in terms of extent of water qualities, in which the grouping were validated by the Euclidean distance and Davies-Bouldin index. Of the on-line sensors, total organic carbon(TOC) sensor, selected to be suitable for organic pollutants monitoring, would be effective to be allocated in D and a part of E catchments. Pb sensor, of heavy metals, would be suitable to be displaced in A and a part of B catchments.

• 상하수도학회지
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• 제18권4호
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• pp.515-521
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• 2004

Anaerobic digestion has many advantages over the more conventional aerobic treatment processes such as low levels of excess sludge production, low space (area) requirements, and the production of valuable biogas. The purpose of this study was to evaluate the effect of organic loading rate of anaerobic digestion on thermophilic($55^{\circ}C$) and mesophilic($35^{\circ}C$) conditions. Fluorescent in situ hybridization (FISH) method was also used to study the microbial community in the reactors. The stabilizing time in mesophilic anaerobic reactors was shorter as approximately 20 days than 40 days in the thermophilic anaerobic reactors. The amount of methane production rate in anaerobic reactors was independent of the concentrations of supplied substrates and the amount of methanogens. When the microbial diversity in the mesophilic and thermophilic reactors, which had been treated with acetate-based artificial wastewater, were compared, it was found that methanogenesis was carried out by microbial consortia consisting of bacteria and archaea such as methanogens. To investigate the activity of bacterial and archaeal populations in all anaerobic reactors, the amount of acetate was measured. Archaea were predominant in all reactors. Interestingly, Methanothrix-like methanogens appeared in mesophilic anaerobic reactors with high feed substrate concentrations, whereas it was not observed in thermophilic anaerobic reactors.

• 환경위생공학
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• 제11권2호
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• pp.43-52
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• 1996

Using rotating biological contactor(RBC) with artificial endogenous stage and aerobic fixed biofilm reactor(AFBR), organic material removal and biological nitrification of piggery wastewater has been studied at a pilot plant. RBC was operated in the endogenous phase at a interval of every 25 days. The concentration of COD, BOD and TKN in influent wastewater were from 2,940 to 3,800 mg/L, from 1,190 to 1,850 mg/L and from 486 to 754 mg/L respectively. The maximum active biomass content represented as VSS per unit aera was $2.0mg/cm$^{2}$ and biofilm dry density of $17mg/cm^{3}$ was observed at biofilm thickness of $900{\;}{\mu}m$. It was observed that the pilot scale RBC/AFBR process exhibited 72 percentage to 93 percentage of BOD removal, In order to obtain more than 90 percentage of BOD removal, the organic loading rate to the RBC/AFBR process should be maintained less than $0.09{\;}m^{3}/m^{2}{\cdot}day(125.9g{;\}BOD/m^{3}{\cdot}d$. The TKN removal efficiencies was from 45.5 to 90.9 percentage according to vary influent loading rate, It was estimated that the RBC/AFBR process consumed approximately 6.2 mg/L(as $CaCO_{3}$) of alkalinity per 1 mg/L of $NH_{3}$-N oxidized as the nitrification took piace.

• Journal of Microbiology and Biotechnology
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• 제12권6호
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• pp.979-985
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• 2002

The possibility of microalgal nitrogen treatment was tested in wastewaters with a low carbon/nitrogen (C/N) ratio. Chlorella kessleri was cultured in the two different artificial wastewaters with nitrate as a nitrogen source: one contained glucose for an organic carbon source and the other without organic carbon sources. The growth rates of the two cultures were almost identical when the aeration rate was over 1 vvm. These results suggest that microalgae could successfully remove nitrogen from wastewater, as far as the mass transfer of $CO_2$, was not limited. Nitrate was successfully reduced to below 2 mg $NO_3^-$-N/ml from the initial nitrate concentration of 140 mg $NO_3^-$-N/ml in 10 days, even in the wastewater with no organic carbon source. Similar results were obtained when ammonium was used as the sole nitrogen source instead of nitrate. Higher concentrations of nitrogen of 140, 280, 560 and 1,400 mg/ml were also tested and similar amounts of nitrogen were removed by algal cultures without showing any substrate inhibition.

• Environmental Engineering Research
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• 제19권4호
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• pp.387-393
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• 2014

The purpose of this study is to evaluate integrated anaerobic hydrogen fermentation and membrane bioreactor (MBR) for on-site domestic wastewater treatment and resource recovery. A synthetic wastewater (COD 17,000 mg/L) was used as artificial brown water which will be discharged from urine diversion toilet and fed into a continuous stirred tank reactor (CSTR) type anaerobic reactor with inclined plate. The effluent of anaerobic reactor mixed with real household grey water (COD 700 mg/L) was further treated by MBR for reuse. An optimum condition maintained in anaerobic reactor was HRT of 8 hrs, pH 5.5, SRT of 5 days and temperature of $37^{\circ}C$. COD removal of 98% was achieved from the overall system. Total gas production rate and hydrogen content was 4.6 L/day and 52.4% respectively. COD mass balance described the COD distribution in the system via reactor byproducts and effluent COD concentration. The results of this study asserts that, anaerobic hydrogen fermentation combined with MBR is a potent system in stabilizing waste strength and clean hydrogen recovery which could be implemented for onsite domestic wastewater treatment and reuse.

• 한국환경과학회지
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• 제12권8호
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• pp.847-852
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• 2003

It was examined carefully that the bacterial die-off between Chlorella vulgaris and E. coli. W3110 was tested through adding TOC (total organic carbon) with the lab-scaled continuous river water flow system (CRWFS). Artificial synthetic wastewater was applied at two levels of organic carbon concentration; 1,335 mg/l in treatment type 1 and 267 mg/l in type 2. In both types, the population densities of Chlorella vulgaris were similar in a maximum 8.25 ${\times}$ 10$\^$6/ cells/ml (type 1) and 6.925 ${\times}$ 10$\^$6/ cells/ml (type 2). The maximum densities of E. coli. W3110 were 2.0 ${\times}$ 10$\^$8/ colony forming unit (CFU)/ml in type 1 and 3.9 ${\times}$ 10$\^$8/ CFU/ml in type 2. The densities increased for 11 days in type 1 and 4 days in type 2, then decreased rapidly till the 35th day, then slightly increased again. This trend was prominent in type 2. It implied that a wider range of nutrients was required in the growth of heterotrophic bacteria in type 2 than in type 1. We could not expect successful bacterial die-off if the wastewater retention time was not furnished sufficiently.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권3호
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• pp.194-199
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• 2001

Chlorella kessleri cultivated in artificial wastewater using diurnal illumination of 12h light/12h dark (L/D) cycles. The inoculum density was 10(sup)5 cells/mL and the irradiance in light cycle was 45$\mu$mol㎡s(sup)-1 at the culture surface. As a control culture, another set of flasks was cultivated under continuous illumination. Regardless of the illumination scheme, the total organic carbon (TOC) and chemical oxygen demand (COD) was reduced below 20% of the initial concentration within a day. However, cell concentration under the L/D lighting scheme was lower tan that under the continuous illuminating scheme. Thus the specific removal rate of organic carbon under L/D cycles was higher than that under continuous illumination. This result suggested that C. kessleri grew chemoorganotrophically in the dark periods. After 3 days, nitrate was reduced to 136.5 and 154.1mg NO$_3$-N/L from 168.1mg NO$_3$-N/L under continuous illumination and under diurnal cycles, respectively. These results indicate nitrate removal efficiency under continuous light was better than that under diurnal cycles. High-density algal cultures using optimized photobioreactors with diurnal cycles will save energy and improve organic carbon sources removal.

• Membrane and Water Treatment
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• 제8권1호
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• pp.1-18
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• 2017

In this study, reuse of biologically treated wastewater of denim washing and dyeing industry has been evaluated by membrane technologies. After that experiments were carried out at laboratory scale in textile dyeing unit by using obtained permeate water samples on 100% cotton based raw fabric belonging to examined industry. During membrane experiments, two different UF (UC100 and UC030) and two different NF (NP010 and NP030) were evaluated under alternative membrane pressures. In permeate water obtained on selected samples, conductivity at the range of $1860-2205{\mu}S/cm$, hardness at the range of 60 to 80 mg/L, total color at the range of 2.4 to 7.6 m-1 and COD at the range of 25-32 mg/L was determined. The following analyzes were performed for the dyed fabrics: perspiration fastness, rub fastness, wash fastness, color fastness to water, color fastness to artificial light, color measurement through the fabric. According to analysis results, selected permeate water have no negative impact on dyeing quality. The study showed that membrane filtration gave good performance for biologically treated textile wastewater, and NF treatment with UF pre-treatment was suitable option for reuse of the effluents.

• 한국미생물·생명공학회지
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• 제22권4호
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• pp.415-422
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• 1994

The biodegradation of aromatic compounds by a mixed culture GE1 was investigated in an artificial wastewater containing 250 mg/l of benzene, toluene, and phenol in semicontinuous culture. In the control group (no strains) with an aeration rate of 75 ml/l/min, 37% of phenol and 83% of benzene were volatilized during early 24 hrs and toluene was disappeared from the medium within 12 hrs. The biodegradation of benzene and toluene was effective in SB (strains + biofilm) treatment, while phenol was degraded more quickly in SG (strains + glucose) treatment including glucose as an additional carbon source. aromatic compounds added at a concentration of 250 mg/l were completely removed by SG treatment after 16 hrs or 32 hrs, respectively. The removal rate of COD was high as much as 80 mg/l/h in SG treatment during early period, but COD revealed a stable value of 116~140 mg/l after 12 hrs caused by increased biomass. Therefore, it is concluded that the mixed GE1 could be used for the wastewater treatment including aromatic compounds such as benzene, toluene, and phenol.