허인량In Ryang Huh,이건호Geon Ho Yi,최지용Ji Yong Choi,정의호Ui Ho Jeong,이용석Yong Seok Lee

DOI: Vol.15(No.3) 305-314, 1999

This study was performed to find out water quality characteristics and then to predict water quality of Pyongchang river and Juchon river, which are the major tributaries of the Han river, S. Korea. According to this study, BOD decay coefficient of the main stream of Pyongchang river was appeared to be 0.120∼0.250day^(-1), Juchon river 0.166∼0.225day^(-1) and the effect of BOD coefficient of K₃ was appeared to be higher than K₁. Based on survey data, BOD, Total nitrogen and Total Phosphrous calibration and verification result were in good agreement with measured value within mean coefficient variance(MSE) value, which were 6.0%, 3.4%, 13.6% and 6.3%, 9.0%, 16.3%, respectively. Sectional water quality predictions of the main stream of Pyongchang river are executed on the basis of the following cases 1) with sewage treatment of Pyongchang-eup 2) rain fall effect. As a result, BOD improvement rates of case 1) were appeared 10.6% in normal times, 25.6% in the dry season, and case 2) gave a serious impact on main stream.

최지용Ji Yong Choi,신은성Eun Sung Shin,이동훈Dong Hoon Lee

DOI: Vol.15(No.3) 315-323, 1999

Urban areas contribute the highest nan-point source pollutant loading per unit area and not only customary pollutants but hazardous materials as well, thus urban areas have a great impact on water quality. In this paper, in order to estimate the urban non-point source pollutant loading in the Han River watershed, the Kuui and the Noryangjin basins were selected as representative spots and equipped with the water quality automatic monitoring system. These basins are located in the up and down stream of the urban area (Seoul). In this study, analysis on non-point source pollutant loading in regards to precipitation, runoff and water duality were investigated COD and SS parameters were selected to calculate unit loading data because these entities have a close relationship with non-point source pollution The results revealed that annual non-point source pollutant COD loading was 2,004 tons/yr, which is approximately 15% of the total COD loading of 13,874 tons/yr and annual non-point source pollutant SS loading was 29,631 tons/yr, which is 28% of the total SS loading of 75,285 tons/yr.

김영철Young Chul Kim,김완중Wan Joong Kim

DOI: Vol.15(No.3) 325-333, 1999

In this paper, one dimensional steady-state biofilm model was used to predict the performance of organic matter reductions when domestic wastewater was treated by water hyacinth ponds (WHPs). For this purpose, a pilot-scale WHPs was built and operated during the period between July 1 and November 17, 1998. Reduction of the organic matters at the WHPs was found to be highly affected by the hydraulic retention time, water temperature and applied organic loading as well. A significant thickness of biofilm layer mainly consisting of the bacteria and algae, was observed from the surface of the roots under the microscope, which provides evidence that biofilms of the roots are primarily responsible for the reduction of organic matters, along with the suspended types of microorganisms at the WHPs. Results of the model validation show that this type of the model is useful for the scale-up and operation of the ponding systems using aquatic plants.

허우명Woo Myung Heo,김재옥Jae Ok Kim,김범철Bom Chul Kim

DOI: Vol.15(No.3) 335-343, 1999

The effect of aeration on the water quality was investigated in a reservoir, Lake Dalbang, which is utilized for the water supply to Donghae City. Water quality has been getting worse from the beginning of impoundment and recently it showed the indication of eutrophication, such as the increase of cyanobacterial density and odor problem in drinking water. Six aerators were installed to improve water quality in 1996. Phytoplankton community and the concentrations of chlorophyll a, total phosphorus, and total nitrogen were measured from April, 1995 to December, 1997. The thermal stratification was destroyed after the onset of aeration. DO of September and October increased from 4-6 ㎎O₂/L before aeration in 1995 to 7-8 ㎎O₂/L in 1996 and 1997 after the destratification. The whole lake became isothermal at 18-20℃. Total phosphorus concentration of the water column decreased slightly from 15-40 ㎎P/㎥ in 1995 to 15-30 ㎎P/㎥ in 1997. The total algal biomass of growing season increased from 178 ㎎Chl.a/㎡ in 1995 to 1150 ㎎Chl.a/㎡ in 1997. But cyanobacterial cell density decreased from 20,640 cells/mL in August 1995 to 20-50 cells/mL in August 1997. Blue-green and green algae showed rapid decreasing trend since 1995, while diatom increased in 1996 and 1997. The dominant species in warm seasons of 1995 was Anabaena macrospora(occasionally Microcystis sp.). It was replaced by Asterionella formosa and Melosira granulara in 1997. From the result it can be concluded that total phytoplankton biomass increased by aeration.

한승우Seung Woo Han,강임석Lim Seok Kang

DOI: Vol.15(No.3) 345-352, 1999

Various Al(Ⅲ) solutions having different r (OH_(added)/Al) values and chemical species compositions were prepared and physical arid chemical characteristics of PACls solutions were examined. Then, the prepared PACls were compared with other Al(Ⅲ) coagulants for coagulation characteristics in water treatment process. The addition of NaOH to the supersaturated AlCl₃ solutions made it possible to synthesize the different types of PACls useful for water treatment. The result of the analysis by timed spectrophotometer with a color developing reagent (ferron) showed that r (OH_(added)/Al), initial aluminum concentration, and base concentration significantly influenced the hydrolytic compositions of aluminum in PACls, but revealed that Al species distribution of PACls was little affected by the base injection rate ranging from 21.5 ㎖/hr to 60 ㎖/hr. Coagulation test of synthetic water showed that the effect of coagulation pH on turbidity removal was severer for low r ratio PACls, alum, and AlCl₃. Also, the effect of pH for coagulation of Nakdong river water showed that each Al(Ⅲ) coagulant had different effects on turbidity and TOC removal. Especially, PACls were least affected among other Al(Ⅲ) coagulants used.

김진호Jin Ho Kim,이종식Jong Sik Lee,안승구Seung Ku Ahn

DOI: Vol.15(No.3) 353-361, 1999

In order to find out major factors affecting ground water quality, 53 plastic house farms were surveyed at Hwasung, Yongin, Suwon and Pyimgtak in Kyonggi area from April to August in 1998. Ground water quality was suitable for irrigation purpose, but nitrate-nitrogen concentration in ground water of some sites in Pyungtak exceeded in water quality level for irrigation(20㎎/ℓ). Big differences among regions were shown(5.2∼26.9㎎/ℓ), but weren`t among periods(13.95∼14.65㎎/ℓ) in part of nitrate-nitrogen concentrations. It was found that ground water quality mainly depended on the numbers of years when cropping had been done. It was getting worse as that is increased Well depth was, too. The deeper well depth was, the better water quality was. And physiographic features made the ground water quality character different. Almost kinds of ions were high under fan. EC was high correlated with NO₃-N, COD_(cr), SO₄^(2-), and Cl^-.

Ihnsup Han

DOI: Vol.15(No.3) 363-381, 1999

The impacts of dissolved oxygen on the removal of phenolics (phenol, o-nitrophenol (ONP) , and 2, 4-dinitrophenol (DNP)) by granular activated carbon (GAC) from an artificial groundwater were investigated with isotherm, rate, and extraction experiments. The isotherm experiments were conducted at pH 4 and pH 7.5 under oxic and anoxic conditions. Pretreatment of GAC with a reductant (Fe(Ⅱ)) were conducted to determine whether sorption of target compounds by GAC could be improved. The removal of target compounds by virgin GAC was somewhat affected by the presence of dissolved oxygen, particularly phenol and DNP. Removal of phenol and DNP was enhanced by at least 200%. Pretreatment of GAC deteriorated the sorption of phenol but improved sorption of ONP and DNP, except for DNP at pH 7.5 under oxic condition. Sorption of these compounds with pretreated GAC was also affected by the presence of dissolved oxygen and solution pH. Sorption rate experiments were conducted at pH 4 under oxic and anoxic conditions followed by GAC extractions using a microscale Soxhlet extraction apparatus. Sorption rates of phenol and DNP were very similar: That is, the approach to equilibrium in the presence of dissolved oxygen was longer than in the absence of dissolved oxygen. However, the sorption of ONP was not changed greatly by the presence of dissolved oxygen. GAC extraction efficiencies for phenol sorbed under oxic conditions were decreased with increasing contact time whereas extraction efficiencies for anoxic conditions did not show such a considerable trend. Extraction efficiencies of ONP and DNP from GAC showed a trend that decreased with increasing contact times from the GACs sorbed under both oxic and anoxic conditions. A plausible explanation for the observed results in the experiments for sorption rate and extraction is that there were some chemical reactions other than oxidative coupling occurred on GAC surfaces in the presence/absence of dissolved oxygen.

Ihnsup Han

DOI: Vol.15(No.3) 383-394, 1999

The impacts of background dissolved organic matter (BOM) on the sorption of three phenolics (phenol, o-nitrophenol (ONP), and 2, 4-dinitrophenol (DNP)) were investigated with isotherm experiments. To investigate the effect of BOM, three different amounts of BOM per unit weight of GAC were preloaded. All the experiments were conducted in an artificial groundwater. Preloaded GAC shows decreased sorption capacity for phenol undue both oxic and anoxic conditions, increased for ONP at pH 4 in a certain range of equilibrium concentration, and increased for DNP at pH 4 under both oxic and anoxic conditions and at pH 7.5 under anoxic conditions. Sorption of these compounds with preloaded GAC was affected by the presence of dissolved oxygen and solution pH. The most plausible explanation for the changed sorption capacities of the GAC for ONP and DNP under certain conditions is that there were some chemical reactions other than oxidative coupling on GAC surfaces.

박승국Seung Kook Park,서인석In Seok Seo,연동석Dong Seok Yeon,이상일Sang Ill Lee

DOI: Vol.15(No.3) 395-403, 1999

Anaerobic reactor in BNR(Biological Nutrients Removal) process is very important for phosphorus removal. In this research, the effect of ARV(Anaerobic Reactor Volume) and biomass concentration on biological nutrients removal in dynamic state activated sludge processes was evaluated. IAAS(Intermittently Aerated Activated Sludge) and DynaFlow Dynamic Flow Intermittently Aerated Activated Sludge) process were operated as a dynamic state activated sludge process. ARV(Anaerobic Reactor Volume) and biomass concentration have not an great effect on total nitrogen and organic removal efficiencies, whereas, have a great effect on total phosphorus removal efficiencies, especially, at low biomass concentration. When ARVF(Anaerobic Reactor Volume Fraction) were 0, 7, 13% at SRT 5 day, phosphorus removal efficiency were <30, 64, 84%, respectively. At SRT 10 and 12 days, difference of phosphorus removal efficiency on ARVF were only 7%. As bulking was occurred, phosphorus removal were deteriorated, whereas organic and nitrogen removals were not. When biomass concentration was over 5,000 ㎎/liter, the effect of anaerobic reactor on phosphorus removal was not important in both systems.

황규대Gye Dae Whang,소용신Yong Sin So,조영무Young Mu Cho

DOI: Vol.15(No.3) 405-413, 1999

The dyeing wastewater contains considerable amounts of hardly biodegradable substances such as volatile organic compounds, surfactants, dyes, sizing agents. This work was carried out to investigate the feasibility and effectiveness of the MBR(Membrane Bio Reactor) process for treatment of dyeing wastewater. Ceramic membrane with pore size of 0.l ㎛ was selected due to the convenience of backwashing and higher flux. For 90 days operation of MBR, MLSS concentration in the bioreactor was increased from 4000㎎/L to 19,500㎎/L. At the beginning the permeation flux was about 45L/㎡-hr and reduced to 5.7L/㎡-hr after 90 days of operation. The permeation flux was recovered by backwashing at the beginning of operation, but, after long-term operation, permeate flux was not favorably recovered by backwashing only. Some elements such as Al, Si, Na, Cl, Fe, Sn and Cr which were mostly originated from influent might contribute membrane fouling. The removal efficiencies of SCOD_(cr) and color of MBR were 78.6% and 34.4% respectively. Despite of the increased MLSS concentration, removal efficiency of organic matters and color density was not significantly improved because microorganism which could utilize the organic matters did not fully developed. Thus in order to enhance the removal efficiency of MBR process, MLSS concentration in bioreactor is to be maintained in the range of 4000∼6000㎎/L and PACAS(Powdered Activated Carbon Activated Sludge) process is recommended.

신항식Hang Sik Shin,안현희Hyun Hee An,강석태Seok Tae Kang

DOI: Vol.15(No.3) 415-420, 1999

Among several factors related to the fouling of the submerged membrane bioreactor (SMBR) such as suction pressure, backwash cycle, MLSS, and ECP (exocellular polymer). ECP which is main component of activated sludge flocs has been reported as a major factor on fouling because it increases of viscosity in activated sludge and accumulates on the surface of membrane. In this study, the cake and plugging resistances caused by MLSS and ECP were measured to identify the influence of ECP on fouling quantitatively. It was found that the cake resistance by ECP occupied over 90% of total resistance. The ratio of protein-like ECP (ECPp) to carbohydrate-like ECP (ECPc) was an important fator to increase the cake resistance. In the operation of SMBR, it was needed to monitor the concentration of protein-like ECP and total ECP.

신항식Hang Sik Shin,안현희Hyun Hee An,강석태Seok Tae Kang,최광호Kwang Ho Choi,임성균Seong Gyun Lim

DOI: Vol.15(No.3) 421-428, 1999

Fouling characteristics were studied in the continuous operation of pilot-scale submerged membrane bioreactor (SMBR) for 120days. The ratio of flux decline (J/Jo) varied with suction pressure and backwash cycle. Fouling decreased significantly while flux increased when the reactor operated on suction at 300㎜Hg for 5 minutes followed by backwash for 1 minute. Fouling was affected by MLSS and SS in the influent seriously. In particular, influent SS such as cellulose material, hair and red pepper powder caused most of resistance in the beginning of operation, attaching the surface of membrane and blocking the pores. Therefore, pretreatment was required to remove SS. It was observed that SMBR was stable to high and shock loadings, as the removal efficiencies of COD and SS were maintained 97% and 100% when influent characteristics changed irregularly. Because the cake resistance caused by ECP was the major resistances caused by MLSS and resistance varied with the ratio of protein and carbohydrate even in constant ECP from previous study, total ECP and the ratio of ECPp to ECPc must be monitored to keep the flux stably in SMBR.

김병군Byong Goon Kim,서인석In Seok Seo,박승국Seung Kook Park,신익상Ik Sang Shin

DOI: Vol.15(No.3) 429-436, 1999

The KOMIAE process(KOWACO Modified Intermittent Aeration process) for nitrogen and phosphorus removal was investigated to find an optimum aerobic/anoxic time, optimum HRT and to evaluate the effect of temperature and influent C/N ratio. In this research, a 1.7㎥ pilot plant was used and fed with domestic wastewater which contained 100.8㎎/L of BOD, 22.3㎎/L of T-N and 2.11㎎/L of T-P on average. From the experimental results, the removal efficiency of COD_(mn), T-N and T-P were 75%, 75% and 90% respectively. The optimum aerobic/anoxic time and optimum HRT in KOMIAE process were 2/2hour and 8hour respectively. Nitrogen removal in KOMIAE process was influenced on temperature and influent C/N ratio. In the case of 20℃, the nitrogen removal efficiency was 78% but the nitrogen removal efficiency was lower than 46% at 15℃. For the purpose of 80% of nitrogen removal efficiency, the influent C/N ratio should be over 8.

임굉Going Yim

DOI: Vol.15(No.3) 437-448, 1999

Zeolites are crystalline aluminosilicate minerals that contain alkali and alkaline-earth metals, such as sodium, potassium, and calcium, as well as water, in their structural framework. The framework is porous, enclosing interconnected cavities in which the metal cations and water molecules are contained. The zeolites have reversible hydration properties in addition to their ration exchange properties. The adsorption effect of heavy meal ions - Cu(Ⅱ), Cd(Ⅱ), Ni(Ⅱ), Pb(Ⅱ), and Zn(Ⅱ) - in wastewater on zeolites by batch adsorption process is investigated. Besides the influence of NH₄^+ ion or CN^- ion coexisted with the heavy metal ions in the wastewater was discussed. The amount of adsorbed ions was variable by initial pH and ionic concentration, especially initial pH value of solution had an important effect on the adsorption. In case of low pH solution, e.g. below 3.0, clinoptilolite adsorbed Pb(Ⅱ), Cd(Ⅱ), Cu(Ⅱ), and Zn(Ⅱ) ions but mordenite almost did not adsorb except Pb(Ⅱ) ion. Under the same adsorption conditions, these ions were more adsorbed on clinoptilolite than on mordenite. Adsorptive rate of heavy metal ions creased equally in order of Pb(Ⅱ)>Cd(Ⅱ)>Cu(Ⅱ)>Zn(Ⅱ)>Ni(Ⅱ) ion on mordenite and clinoptilolite. This tendency was interpreted by the fact that the smaller the radius of hydrated metal ion is, the more is the heavy metal ion adsorbed on zeolites. The adsorption rate of heavy metal ions except Pb(Ⅱ) ion decreased in the presence of NH₄^+ ion in the solution. Especially, the absorptivity of Cu(Ⅱ) ion decreased with increasing CN^- ionic concentration due to the formation of complex anion with CN^- ion.

강호Ho Kang,신경숙Kyung Sook Shin,문서연Seo Yeon Moon

DOI: Vol.15(No.3) 449-458, 1999

This study was performed to optimize the anaerobic pretreatment of swine wastewater for the subsequent nitrogen and phosphorous removal. Step-wise decrease in hydraulic retention time(HRT) and increase in organic loading rate(OLR) were utilized in anaerobic filter reactor at mesophilic temperature(35℃). Total chemical oxygen demand(TCOD) removal efficiency of 36-45% at HRTs of 1-2days was observed with the OLR range of 6-12g TCOD/L-d. The suspended solids removal showed 30-39% at HRTs of 1-2days. The methane production rate appeared to be 1.45v/v-d at an HRT of 1 day and the methane content showed unusually high(ranged 71-82%) during the entire operational periods. The reactor alkalinity concentration over 2,000㎎/L as CaCO₃ during the operation could play an important role for compensating pH drop caused by nitrification. The COD/TKN ratio of 11-23, COD/TP ratio of 30-50 and higher buffering capacity of the effluent from the anaerobic filter could be adequate substrate condition for the subsequent biological nitrogen and phosphorous removal.

Sung Hyun Kwon,Dae Chul Cho

DOI: Vol.15(No.3) 459-464, 1999

The biodegradation of one popular nitramine energetics, Ammonium Dinitramide (ADN) by mixture of dentrifying bacterial species was investigated. ADN was observed to be effectively mineralized in the anaerobic mixed culture. The initial ADN concentration of 250㎎/L was reduced to non-detectable levels (>99% removal efficiency) in 5 days of incubation under anaerobic conditions. Final products generated from anaerobic degradation of nitramine energetics by anaerobic metabolism were NH₄^+, CH₄, and CO₂ that were released to the environment with the denitrifiers` growth. In addition, it was found that the activity of denitrifiers was inhibited by high concentration of ammonia generated through the degradation reactions of energetic nitrites.