• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.215-221
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• 2004

Effluent of wastewater treatment plant is to be disinfected to protect drinking water sources. DOF (Dissolved Ozone Flotation) was developed to meet this purpose. DOF was developed by combining DAF system with ozone. DAF system has good floating power with numerous microbubbles, and ozone has strong oxidation capability. And DOF system has good floating power and strong oxidation capability simultaneously. When DOF was applied to secondary wastewater effluent, color of 11CU in raw water which was secondary effluent was reduced to 1CU by the DOF system. Removal rate of other water quality parameters treated by DOF were also higher than that by DAF, which were proved the strength of oxidation capability of ozone. When ozone concentration of 3.3mg/l were applied in DOF system, general aerobic bacteria were reduced to 5CFU/ml from TNTC (Too many Numbers To Count). With the same ozone concentration, total coliform were not detected at all. These figures are under the numbers of drinking water regulation. These microbes were the target parameters of DOF. It was proved that DOF was very effective in disinfection of wastewater treatment plant effluent as well as in removal of color, turbidity, and T-P.

• Microbiology and Biotechnology Letters
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• v.42 no.2
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• pp.131-138
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• 2014

While coupling wastewater treatment with microalgal bioenergy production is very promising, new approaches are needed to enhance microalgal growth and lipid accumulation in wastewater. Therefore, this study investigated the effect of iron on the growth, nutrient removal, and lipid accumulation of Scenedesmus sp. LX1 in both artificial wastewater and domestic secondary effluents. When increasing the iron concentration from 0 to 2 mg/l in the artificial wastewater, the biomass production of Scenedesmus sp. LX1 increased from 0.17 to 0.54 g/l; the nitrogen and phosphorus removal efficiency increased from 15.7% and 80.6% to 97.0% and 99.2%, respectively; and the lipid content was enhanced 84.2%. The relationship between the carrying capacity/maximal population growth rate of Scenedesmus sp. LX1 and the initial iron concentration were also in accordance with the Monod model. Furthermore, when increasing the iron concentration to 2 mg/l in four different domestic secondary effluent samples, the lipid content and lipid production of Scenedesmus sp. LX1 was improved by 17.4-33.7% and 21.5-41.8%, respectively.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.1
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• pp.73-81
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• 2014

One-dimensional flux theory (1DFT) is conventionally used for design of secondary clarifier of wastewater treatment plant. However, the 1DFT cannot describe turbulence, density current, shape parameters of the clarifier. In this study, we optimized the configurations of influent guide baffle and effluent baffle through the simulation using computational fluid dynamics (CFD) and its verification by particle image velocity (PIV) test. The energy dissipating inlet (EDI) without influent guide baffle ($0^{\circ}$) showed the best efficiency for minimizing downward velocity under the center well of the clarifier. The lowest velocity distribution around the effluent weir region could be obtained with the McKinney baffle (EB-2). The performances of the influent and effluent baffles were clearly verified by PIV test results.

• Journal of Korean Society on Water Environment
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• v.21 no.2
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• pp.158-168
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• 2005

In this study, the discharging effluents from have been 9 municipal wastewater treatment plants surveyed for 1 year-period. Statistics including probability distribution, cumulative occurrence concentration and other statistical parameters were presented. In addition, treatment performance and its stability were also discussed. Most of the plants, have an operational problem of high soluble organic content in the secondary effluent which may be associated with the integrated treatment of human and livestock manures. Nitrogen concentration in the effluents were usually higher during the period of summer and winter. It was found that this is mainly due to lack of the proper C/N ratio during the summer, or/and the effects of low temperature and less dilution by dry weather during the winter. Phosphorus concentration is sharply increased in June. Discussion with plant operators told that it is due to the dissolution of phosphate from the sludge accumulated in the primary settling tanks from the early spring to june. During this period, usually, sludge treatment line is highly overloaded with flush-outs of the sediments also stored in the bottom of combined sewer due to the low flow during winter season. Most of the plants can meet new effluent discharge limits of the nitrogen and phosphorus, and total coliform without further treatment.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.2
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• pp.131-137
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• 2016

The development of alternative water resources has emerged as an effective method for solving drought of water resources due to extreme weather and increase in water consumption. Recently, in Korea, there has been active research on reverse osmosis desalination technology, wastewater reuse using forward osmosis membranes, and the forward osmosis(FO)-reverse osmosis(RO) hybrid process combining these two technologies. In this study, the basic performance of FO membranes manufactured by three domestic and international manufactures such as Microfilter Co., Ltd., Toray Chemical Korea Inc., and Hydration Technologies Inc., were investigated for wastewater reuse. In addition, as an experiment to select feed solution, the selected membranes were operated 48 consecutive hours using three secondary effluents pretreated by the UF membrane with a pore size of $0.1{\mu}m$ and auto strainer with pore sizes of $1{\mu}m$ and $100{\mu}m$ as feed solution. Although there was not much difference in the operating performance. Thus, the treated water using the $100{\mu}m$ auto strainer was selected as feed solution applied to the assessment.

• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.38-43
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• 2013

ETA (ethanolamine), a pH control agent, has been used as an ammonia substitute in the secondary system of nuclear power plants since 2001. It is impossible to remove ETA from the wastewater treatment system in the nuclear power plant operating currently, because it is the non-biodegradable organics in terms of the environmental. The optimum process and chemicals for the removal of chemical oxygen demand (COD) & N with the field sample were investigated. More than 95% of Ammonium ions, contained much in wastewater, was removed with a diffused aeration system. COD could be removed over 90% through the process that includes the oxidation with mixed peroxidants (sodium persulfate/sodium percarbonate) followed by the physicochemical treatment with coagulants.

• Journal of Korean Society of Water and Wastewater
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• v.17 no.4
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• pp.542-549
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• 2003

In the present study, the feasibility of $UV/H_2O_2$ systems was investigated using low and medium-pressure lamps on biologically treated wastewater effluents for secondary effluent reclamation. Two types of UV lamps were used as the light sources (a 39-W low-pressure mercury lamp and a 350-W medium-pressure mercury lamp). The results from these UV systems showed that the removal of organic compounds could be achieved in the contact time of longer than 30min (i.e., low UV doses). Efficiencies of color removal and disinfection were far better than those of organic matters measured as TOC, DOC and $TCOD_{cr}$. In the low-pressure lamp UV system, it has been found that DOC and color removals were 60.9 and 86.2% with 50mg/L of $H_2O_2$ and contact times of 30 minute, respectively. Whereas, with the medium-pressure lamp UV system, TOC, DOC and color removal were 27.1, 5.6 and 95% with 14.3mg/L of $H_2O_2$ and 14 minute of contact times, respectively. Both systems could be applied for the reclamation of secondary effluent treated with biological treatment processes.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.2
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• pp.219-225
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• 2008

Evaluating and designing secondary clarifier require to define characteristics of influent MLSS (Mixed Liquor Suspended Solids). In this study, bioflocculation and settling characteristics for MLSS from a Biological Nutrient Removal (BNR) plant located in near Seoul were measured. MLSS concentrations in bioreactor were about 2,500mg/L in summer and about 4,000mg/L in winter, respectively. Tests showed that there was not much bioflocculation occurred in secondary clarifier. Average ESS/DSS (Effluent Suspended Solids/Dispersed Suspended Solids) was 100%. From the settling tests, ZSV (Zone Settling Velocity) and settling constant (n) in Vesilind equation were estimated at different MLSS temperatures. SVI (Sludge Volume Index) and SSVI (Stirred Sludge Volume Index) were also measured at different temperatures. It was found that ZSV was positively correlated with temperature and n was inversely proportional to temperature. SVI and SSVI had very similar values at about $25^{\circ}C$ of MLSS, However, SVI had more than 2 times higher values than SSVI at below $20^{\circ}C$ of MLSS. Temperature effect must be considered to design and evaluate secondary clarifier.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.3
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• pp.335-342
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• 2011

Secondary effluent contains particle compounds which are comprised of microorganisms that occurs membrane fouling when the water is reused. This study evaluates the characteristics of membrane fouling of secondary effluent reuse. Effects of chemical backwashing are analyzed to reduce membrane fouling by regular chemical backwashing. As the result, major membrane foulants are verified EPS materials which include protein and polysaccharide that cause biofilm cake layer on the membrane. Also, sodium hypochlorite is applied to chemical backwashing. The backwashing improves recover rate when injected chemical concentration is increased and chemical backwashing cycle is amplified. Chemical backwashing cycle affects more than injected chemical concentration yet idle time does not noticeably influence on reducing membrane fouling.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.40 no.5
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• pp.53-59
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• 2008

This study was carried out to investigate the effect of photocatalysis using $TiO_2$ and UV applied for the COD reduction of wastewater in linerboard mill. Trials were done to obtain the optimum addition amounts of $TiO_2$ and $H_2O_2$ to the wastewater and find an appropriate pH condition for photocatalysis on $TiO_2$ for degrading COD. The photocatalytic reaction was applied to the wastewater collected after secondary activated sludge treatment in WWTP of linerboard mill. The optimum application of photocatalysis reaction was obtained under the addition conditions of 2 g/L of $TiO_2$ and 200 mg/L of $H_2O_2$ at pH 3.0, respectively. The removal efficiency of $SCOD_{Cr}$ by photocatalytic treatment was 86.4 % and higher than Fenton treatment in which removal efficiency was 67.4 %. It was concluded that the photocatalytic process using $TiO_2$ and UV could be applied to the wastewater treatment in linerboard mill and also to the dramatic drop-off in NBDCOD load from wastewater of tertiary treatment in WWTP.