최의소 Eui So Choi

DOI: Vol.12(No.4) 325-331, 1996

민경석 , 안영호 Kyung Sok Min , Young Ho Ahn

DOI: Vol.12(No.4) 333-341, 1996

Recycle effects on physicochemical and morphological characteristics of biopellets produced in enhanced UASB(EUASB) reactor were investigated and a simplified method for evaluation of pelletized degree and physical characteristics of biopellet was proposed. The pellets produced from the EUASB system operated with recycle ratio, R = 2 showed a better settleability and biomass holding capacity. Relationship between settleability and biomass holding capacity of pellets was little dependent with ash contents. As ultimate analysis, mass fractions of carbon, nitrogen and oxygen were shown a little different with regard to recycle ratio. And COD/VSS of pellets was affected mass fractions of carbon and nitrogen. The morphological characterization with SEM showed that the consortium of microorganisms was very dependent with hydrogen partial pressure and operational conditions.

민경석 , 안영호 Kyung Sok Min , Young Ho Ahn

DOI: Vol.12(No.4) 343-349, 1996

In this study, hydrogen partial pressure effects on formation of anaerobic biopellets were investigated. So, two-in-series UASB system with well defined biopellets was operated with acetic and propionic acid mixture( 1:1 as COD base) as substrate. As decrement of the hydrogen partial pressure in two-in-series UASB system, it could be observed a lot of biomass discharge from the first stage reactor, damaged biopellets in the second stage reactor, and dispersed sludges in settler. These were reflected in necessity of high hydrogen partial pressure as a key condition for pelletization process. Particularly, the evidence on growth of hydrogenotrophs and extracellular polymer excretions could not be found. And autolysis of microorganisms in declining growth or endogenous stage was observed in the second stage reactor with settler.

양재삼 , 정주영 , 강정원 , 황갑수 Jae Sam Yang , Ju Young Jeong , Jeong Won Khang , Gap Soo Whang

DOI: Vol.12(No.4) 351-358, 1996

Present status of five heavy metals(Ni, Cu, Cd, Co and Fe) and their geochemical behaviors were investigated with three environmental factors(salinity in seawater, organic contents and silt+clay fractions in sediments) in Ulsan Bay. The concentrations of the studied metals were normalized with those of Fe to compensate the effect of lithogeneous weathering materials. For surface seawater, the normalized Ni, Cu and Co were found to be high in the middle part of the bay and low in both sides of the head and the mouth parts of the bay. Such trend probably is due to the anthropogenic input from the adjacent industrial plants. A highly positive relationship was found between the organic contents and silt+clay fractions in the sediments. Such trends were found between the normalized metal contents and the organic portions in the sediments, and also similar phenomena were detected between the metals and the silt+clay fractions. Whereas Co showed somewhat different pattern of distribution and their possible explanation was intensively discussed.

이규훈 , 정은지 , 박태주 Kyou Hoon Lee , Eun Ji Jung , Tae Joo Park

DOI: Vol.12(No.4) 359-367, 1996

A fixed-film biological reactor(FFBR) packed with SAC(Synthetic Activated Ceramic) media was tested to investigate the removal efficiency of both organic matter and ammonia of raw sewage and final effluent of J municipal wastewater treatment plant in Pusan. The influent to the wastewater treatment plant of the city of Pusan consists of typical municipal wastewater and the discharges of industrial works and sanitary landfill leachate. Experiments were performed to evaluate the removal efficiencies of chemical oxygen demand(COD_(Cr)) and ammonia in two lab-scale FFBR by increasing COD_(Cr), loading rate from 0.85㎏/㎥/day to 1.24㎏/㎥/day and NH₄^+-N loading rate from 0.24㎏/㎥/day to 0.48㎏/㎥/day in case that raw sewage were used as substrate. In case of final effluent as substrate, the FFBR demonstrated of achieving 28.3∼33.4% removal efficiencies of COD_(Cr) at the COD_(Cr) loading rates of 0.28∼0.55㎏/㎥/day and 67.0∼85.3% removal efficiencies of NH₄^+-N at the NH₄^+-N loading rates of 0.13∼0.38㎏/㎥/day. The results of the research showed that a fixed-film biological reactor(FFBR) packed with SAC media could be applicable for treatment of raw sewage and final effluent since the process is, compared to the conventional activated sludge process, more effective at the sewage including high NH₄^+-N loading rates.

신성교 , 박청길 , 이수웅 Sung Kyo Shin , Chung Kil Park , Su Woong Lee

DOI: Vol.12(No.4) 369-375, 1996

The relationships between chlorophyll-a(Chl.a) and BOD were investigated through culture and degradation study of phytoplankton and field samples to determine the autochthonous BOD caused by the phytoplankton production in the eutrophic waters in the Nakdong River. The correlation coefficients between Chl.a and BOD, and Chl.a and COD were found to be 0.732 and 0.666 respectively. From the results of culture and degradation of phytoplankton in laboratory, the correlation coefficients between Chl.a and BOD were 0.876(mean value), and 0.968 respectively. Therefore, it was possible to express as TBOD = α. chl.a + allochthonous BOD, and to determine the contribution of autochthonous BOD to total BOD in the Nakdong River. It was found that the percentages of autochthonous BOD in total BOD were 51.7, 47.9, 65.2, 30.5 and 52.6 % at Mulgum, Namji, Jukpo, Koryong and Waekwan. The converting factor(α) for the calculation of autochthonous BOD was depended upon the biomass of phytoplankton as well as the activity, which was changed in accordance with waters conditions. It was found to be 0.042, 0.036, 0.047, 0.029 and 0.048 at Mulgum, Namji, Jukpo, Koryong and Waekwan.

조성렬 , 김충래 , 김학성 Sung Yul Jo , Chung Rae Kim , Hag Seong Kim

DOI: Vol.12(No.4) 377-382, 1996

The purpose of this study is to survey the phosphorus behavior and its chemical forms in the municipal sewage treatment processes. Samples for analysis were taken from Cheongju sewage treatment plant once a month during the period from March to October in 1995. Total phosphorus inlet concentration into the sewage treatment plant is 3.95㎎/ℓ, and its fractions are TRP 57.8%, THP 22.2% and TOP 20.3%. TP concentration was increased about 50% higher than that of inlet concentrations by mixing with overflow from thickener and anaerobic digester. Suspended total phosphorus is removed about 42.8% in the primary settling tank, and phosphate fraction-DTP and STP-of inlet into the biological process is nearly same. The DTP removal is about 55% by the biological process. Total phosphorus concentration of the final effluent is 1.33㎎/ℓ, and it was found that the main forms were TRP(84.2%).

김광수 , 박청길 , 조은일 Gwang Su Kim , Chung Kil Park , Eun Il Cho

DOI: Vol.12(No.4) 383-399, 1996

The distributions of residual flows and dissolved oxygen concentration in the Yellow Sea were simulated and reproduced by an eco-hydrodynamic model which is composed of a three-dimensional hydrodynamic model and an ecosystem model. In order to estimate the environmental capacity of the Yellow Sea, the simulations for predicting the situation of unfavorable environment such as the formation of oxygen-deficient water mass in bottom layer were performed by controlling quantitatively the pollution loads of rivers flowing into the Yellow Sea. The field surveys and the seawater analyses were conducted over the Yellow Sea in summers, 1993 and 1994. The computed residual flows showed the counter-clockwise water circulation to exist in the surface and middle levels and no evident water circulation in the bottom level of the Yellow Sea. In the simulation of water quality with an ecosystem model, the more the pollution loads of 14 major rivers flowing into model region increase, the more evident appear the reductions of dissolved oxygen concentrations around the adjacent areas of estuaries receiving pollutants. In case the pollution loads of all 14 rivers become 7∼10 times as high as the present loads, the concentration of dissolved oxygen appears to be reduced to 5.0㎎ /ℓ or less in the bottom level of the water area being located eastward 60∼120㎞ away from the Changjiang estuary. Therefore, in order to keep the concentration of dissolved oxygen being 5.0㎎O₂/ℓ and above, which is the Korean criterion of the third class seawater quality, the environmental capacity of the Yellow Sea may be estimated to be 7∼10 times as high as the present pollution loads.

최홍복 , 황경엽 , 신응배 Hong Bok Choi , Kyung Yub Hwang , Eung Bai Shin

DOI: Vol.12(No.4) 401-407, 1996

The effect of sludge pretreatment on the anaerobic digestion of waste-activated sludge(WAS) was studied. In this sludge pretreatment process, bacteria in the WAS were ruptured by mechanical jet and smash under pressurized conditions. The protein concentrations in the WAS varied significantly before and after pretreatment. Protein concentration increased according to jet times and pressure. Efficiencies of volatile solids(VS) removal were 40∼45% when the pretreated WAS once under pressure of 30 bar was fed into an anaerobic digester with 4-day hydraulic retention time(input organic loading, 2. 95 ㎏ VS/㎥.d). When intact WAS was fed into the digester, WAS was not digested efficiently even with a longer hydraulic retention time(10 days). Therefore, it is recognized that higher digestion efficiencies and stabilization of the WAS were obtained through a mechanical pretreatment of WAS.

박우균 , 정광용 , 신응배 Woo Kyun Park , Kwang Yong Jung , Eung Bai Shin

DOI: Vol.12(No.4) 409-416, 1996

In most cases, wastewater treatment processes have been developed for the treatment of organic matters and suspended solids. However, the removal of nitrogen and phosphorus from wastewater have attracted little attention. This study seeks a possibility of cost reduction and of simple to operation through a modification of existing processes which have already been well developed. The study was conducted to evaluate removal efficiencies of organic matter, nitrogen and phosphorus which are coexistent in wastewater. The laboratory scale experiment was done in using various concentrations of synthetic wastewater. BOD removal efficiency between modified anaerobic-oxic process and activated sludge process was similar 94.7%, 91.4%, respectively. Nitrogen and Phosphorus removal efficiency were 81.67%, 87.91%, respectively in modified anaerobic-oxic process, but nitrogen and phosphorus removal efficiency in activated sludge process were only 32.88%, 65.17%, respectively. The removal efficiency of organic matter in anaerobic-oxic process with was observed to be 94% regardless of influent concentration of organic matter with of wastewater, and over 80% removal being occurred in anaerobic tank. Nitrogen removal efficiency in nitrogen level of 25, 50 and 75㎎/l of inflow were 43.14, 81.67 and 41.54%, respectively. Higher nitrogen removal efficiency was observed with a higher influent concentration of nitrogen. In case of simultaneous result was not observed. The results demonstrated that the modified anaerobic-oxic process may better be applied to a rural treatment plant for a simultaneous removal of organic matter, nitrogen and phosphorous.

Dong Hyun Kim , Tomokazu Iyoda , Kazuhito Hashimoto , Akira Fujishima

DOI: Vol.12(No.4) 417-423, 1996

Disinfection of Escherichia coli(E. coli) (∼2×10³ cells/mL) in reservoir water (100mL) was demonstrated by photocatalysis using UV-illuminated titanium dioxide(TiO₂) powder and thin film sup ported on a Pyrex tube. In the experiments employing T₁O₂, powder, when UV light was employed, all of the E. coli cells were killed photocatalytically in less than 15 min.. Meanwhile, the total disinfection of E. coli was achieved in less than 3 hours for the film.

홍정선 , 서정범 , 윤조희 , 류덕희 , 김용석 , 류재근 , 서윤수 Jeong Seon Hong , Jeong Beom Seo , Cho Hee Yoon , Deok Hee Rhew , Yong Seok Kim , Jae Keun Ryu , Yoon Soo Suh

DOI: Vol.12(No.4) 425-433, 1996

Sewage which nitrogen and phosphorus are much contained relatively in comparison with others was treated by the anaerobic/anoxic/oxic process of pilot-scale. The sewage characteristics and treatability were studied and the results obtained at a given experimental condition can be summarized as follows. Pollutant concentrations of sewage were shown in the ranges of TBOD 180∼470㎎/L (average 281㎎/L), TCOD 72∼157㎎/L(average 94㎎/L), SS 119∼570㎎/L(average 274㎎/L), TN 19∼107㎎/L(average 51㎎/L) and TP 2.2∼14.6㎎/L(average 5.3㎎/L). Influent concentration of pollutants was highest at 7 AM. In steady state, average removal efficiencies by this process were shown to be 92.5% in TBOD, 83.7% in TCOD, 93.9% in SS, 55.7% in TN and 75.3% in TP, respectively. TBOD removal in anaerobic basin was about 75% of total removed TBOD. It was possible to operate in volumetric loading rate of 1.5kg TBOD/㎥·day. Removal efficienices in this loading rate were shown to be above 80% in TBOD and SS, above 50% in TN and above 60% in TP. Observed microbial yield was 0.21g MLSS/g TBOD. Therefore, generation of excess sludge was about 50∼60% smaller than ones of activated sludge process.

김영철 Young Chur Kim

DOI: Vol.12(No.4) 435-445, 1996

Effects of CO₂ Partial pressure(pCO₂) on the characteristics of organic matter degradation, bacterial trophic populations and metabolic activity in methanogenic phase has been investigated by using CSTR anaerobic digester fed with VFA(Volatile fatty acids) as the major organic carbon source. Three kinds of single substrates contain acetic, propionic, and butyric acid were used in this study. The pCO₂ of the methanogenic phase was controlled in the range from 0.2 to 0.8atm. The substrate removal efficiency decreased significantly when pCO₂ exceeded 0.7atm at the acetic acid reactor. The substrate removal efficiency of propionic acid and butyric acid were not much influenced by the change in pCO₂. The number of acetate consuming methanogenic bacteria(AMB) and H₂ consuming methanogenic bacteria(HMB) enumerated by the most probable number method, decreased when pCO₂ exceeded 0.7atm. pCO₂ does not have much effect on the bacterial numbers of sulfate reducing bacteria, bacteria degrading propionate and butyrate. The specific substrate utilizing activity(SUA) and specific methanogenic activity(SMA) of AMB increased as pCO₂ increased from 0.3 to 0.6atm. It was considered that the inhibition of methanogenic bacteria at pCO₂ above 0.7atm would depend on free CO₂ concentration in solution.

김용환 , 조재현 , 김무훈 , 이용우 Yong Hwan Kim , Jae Hyun Cho , Moo Hoon Kim , Yong Woo Lee

DOI: Vol.12(No.4) 447-454, 1996

The objective of this research is to evaluate the treatment efficiency of biofilm media for organic wastewater. Several types of biofilm media including submerged filter and fluidized porous media were tested to know which biofilm media is the most appropriate for removal of organics from wastewater. Each reator system adapting Saran- lock(submerged filter type) and B company product(coated with charcoal) showed no bulking phenomena even at high organic loading(9.1Kg TCOD/㎥/day), while others failed to endure high organic loading. It was thought that much attached biomass for Saran-lock and high organic sorption capacity for B company product are responsible for their high organic removal rate.

강화성 , 이광우 Hwa Seong Kang , Kwang Woo Lee

DOI: Vol.12(No.4) 455-461, 1996

In order to investigate the historical aspect of trace metal pollution, 19 surface sediment samples and 6 core samples were obtained from the coastal bays of Kwangyang, Masan and Ulsan which were known to be somewhat polluted. Eight trace metals(Cd, Cr, Co, Cu, Mn, Ni, Pb and Zn) in sediments were analysed by atomic absorption spectrophotometry and sedimentation rates were determined by the isotopic method using radioactive ^(210)Pb. The mean sedimentation rates, calculated from ^(210)Pb contents, were 0.68, 0.55 and 0.59 cm/yr for Kwangyang, Masan, and Ulsan Bay, respectively. The sediment compositions of each bays were clayey silt for Kwangyang Bay, silt and clayey silt for Masan Bay, and silt for Ulsan Bay. The concentrations of Pb, Co, Zn, Ni, Cu and Cr were relatively high in the surface sediments and gradually decreased at the 20∼30㎝ depth.

윤조희 , 김용석 Cho Hee Yoon , Yong Suk Kim

DOI: Vol.12(No.4) 463-470, 1996

This study was performed to investigate and evaluate the treatabilities and the behavior characteristics of organics and nitrogen in two-type swine wastewater treatment systems using anaerobic-anoxic-oxic (A₂/O) process. Two-type systems were distinguished by flow pattern in oxic process. One was named plug flow reactor(PFR) and another was named completely mixed flow reactor(CMFR). These systems were applied to a laboratory scale reactor in the range 0.2∼1.0 ㎏TOC/㎥/d with a temperature of 22±1℃. And a total of 32 hours hydraulic retention time(HRT) including 8/8/16 hours of anaerobic/anoxic/oxic zones was used to simulate the swine wastewater treatment plants with an average 4,000㎎/L MISS with the external/internal recycle of 100/300 percentage ratios for all experiment. The two systems behaved almost identically for TOC removal efficiency, but a few difference in the TN removal efficiency was observed. Average removal efficiencies for TOC in their two systems were 83.5% and 82.2%, and for TN 78.1% and 75.7%, respectively. High nitrogen loading rates and high ratios of nitrogen and organics were appeared not to be oxided to nitrate nitrogen(NO₃-N) and to cause nitrite nitrogen(NO₂-N) accumulation despite of operating l6 hours HRT for nitrification under oxic process.

김응호 , 유기상 , 조진규 Eoung Ho Kim , Ki Sang Yoo , Jin Kyu Cho

DOI: Vol.12(No.4) 471-476, 1996

A completely mixed batch system was used to investigate the effects of Ca^(2+), alkalinity and temperature on the phosphorus removal efficiency per specific surface area and the long-time phosphorus removal characteristics, when the converter slag powder was used for phosphorus removal. As alkalinity of wastewater increased, phosphorus removal rate and pH gradually decreased. It was because Ca^(2+), carbonate in wastewater were decreased by producing CaCO₃. Phosphorus removal rate increased in case of temperature and specific surface area increased. For a 80-hr mixing, 0.188 of Ca^(2+) was gushed out per 1g of converter slag. Among this 75.9% came out during first 48 hours and then the amount of Ca^(2+) and pH decreased, and the rate of phosphorus removal decreased significantly. In case of adding converter slag of 1W/V% passing through the 200 mesh at 20℃, a reactoin order m was about 1.055 and rate constant k was about 1.081 hr¹ in the equation of -dt/ dC=kC^m Also, when adding 0.5W/V%, m and k was about 1.42 and 1.0883( mg/L)^(0.42) hr¹, respectively.