유춘만 , 위인선 , 이종빈 C . M . Yu , I . S . Wui , J . B . Lee

DOI: Vol.11(No.2) 61-67, 1995

This study was attempted to construct the pollution map of off shore water in south-west in korea by bioassay of sea water quality using both gamete and embryo of Schapechinus brevis and also to examine the relationship between embryo development and environmental paramenter. Sea urchin(Schapechinus brevi) gametes and embryos were inhibited strongly by seawater sampled from Youngsan river Hakun and Kwangyang bay inland sea, inhibited weakly by seawater sampled from Muan, Hampeung, Wondo, KangJin inland sea. Temperature: Pluteus was not developed at temperature less than 7℃ and Temperature is proportioned to development velocity. pH : High embryos fertilization was observed the range from pH 7.5 to pH 8.5 and gametes and embryos were strongly inibited below pH 4.5 and above pH 9.5. Salinity : High embryos formation ratio was observed at salinity 28-30‰ and sand dollar gametes and embryos were strongly inhibited below 28 and above 30‰. Sensitivity to sperm exposure time and embryos formation by natural seawater was great in 60 min exposure of sperm. The more sperm exposure time, the more normal pluteus were appeared normal pluteus formation. Embryos formation and concentration of COD and NH₃`-N, SiO₂Si were regularly correlation.

강준원 , 김종배 Joon Wun Kang , Jong Bae Kim

DOI: Vol.11(No.2) 69-75, 1995

The effect of ozone application in the drinking water on the production of assimilable organic carbon (AOC) was evaluated. The typical procedure to determine AOC is suggested by van der Kooij, which is the method of bacterial growth measurement by colony forming units using the strain P17 and/or NOX. The bacterial indicator species used for this study is Acinetobncter calcoaceticus which was isolated and identified ozonating the Nakdong river water. This strain could never be isolated from the raw water, but this strain was the predominant isolate in the ozonated water. Within a short incubation time, this organism was found to replicate well on acetate and oxalate as a sole carbon source. The yield coefficient of this organism for acetate and oxalate are the same order of magnitude of the value of P17 and NOX. The advantage of AOC determination using A. calcoaceticus might be the shortening of assay time due to the more rapid growth of this organism compared with that of P17 and NOX. With the full scale experiments, A.calcoaceticus was found to increase after ozonation, but did not decrease upon chlorination. The addition of biological treatment process such as biological activated carbon (BAC) filters after post-ozonation may appear to be an ideal solution to reduce the AOC concentration.

임재명 , 이찬기 , 한동준 Jay Myoung Rim , Chan Ki Lee , Dong Joon Han

DOI: Vol.11(No.2) 77-85, 1995

A laboratory experiment was performed to investigate the mine drainage treatment using the biological sulfate reduction. An acetate-added synthetic wastewater was used because of low organic content in the acid mine drainage. The presence of heavy metals in the synthetic wastewater was an operational variable for the laboratory experiment. On the basis of series of experiment, it was found that the sulfate reduction rate and organic removal rate increased with an increment of hydraulic retention time in the laboratory reactors. It was also note that the reactor fed with wastewater containing heavy metals showed a better performance. It was reasoned that the reduction of sulfide(S^2) toxicity due to the heavy metal complexation, resulting an enhanced microbial activity in the reactor fed with wastewater containing heavy metals. Total removal rate of heavy metals in the lab reactor was highly correlated with the sulfate reduction rate, and the sulfate reduction rate was closely related with COD removal rate. In addition, an order of heavy metal removals during the sulfate reduction was found as follows : Zn＞Pb＞Co＞Ni＞Cu.

최승일 , 김정민 Suing Il Choi , Jung Min Kim

DOI: Vol.11(No.2) 87-95, 1995

The maximum contamination level of NO₃-N which is known to causes methemoglobinimea to baby at high concentration is set as 10 ㎎/ℓ. Although biological denitrification has been used to remove NO₃-N in wastewater, it may cause some trouble in drinkingh water treatment. An ion exchange process could be an alternative for drinking water treatment. The bed depth-service time equation by Thomas has been used as a design tool to predict and/or evaluate the performance of ion exchange column. To utilize the equation, the kinetic rate constant K₁ and the maximum solid phase concentration q_0 should be determined from the pilot study. However, there has not been enough understanding on the behavior of K₁ and q_0 according to the change of the flow rate and influent concentration. Thus the research has been conducted to investigate the behavior of K₁ and q_0 by the change of influent concentration, flow rate, and the presence of humic acid. A commercially available NO₃-N selective anion exchange resin has been used and the results are summarized as; 1. The influent nitrate concentration has not affected the rate constant K₁ and the maximum solid phase concentration q_0. But the flow rate has changed the rate constant K₁ significantly although its influence on the maximum solid phase concentration q_0 is almost neglegible. 2. The difference in the sodium concentration in the regeneration solution has not affected the maximum solid phase concentration q_0. 3. It seems that the humic acid reduce the rate constant K₁ and increase the maximum solid phase concentration q_0. However the effect of humic acid and other organic matters on the NO₃-N ion exchange should be investigated more thoroughly to reveal the effect clearly. This study has increased the understanding of the behavior of kinetic rate constant K₁ and maximum solid phase concentration q_0 in the Thomas` BDST equation. The result could be used in utilizing the equation for designing ion exchange column, especially for NO₃-N removal.

이재복 , 권일 , 곽복식 Jae Bok Lee , Il Kwon , Bok Sik Kwak

DOI: Vol.11(No.2) 97-107, 1995

Sludge dewatering is a common practice in many wastewater treatment plants. At the beginning of the cake filtration, particles smaller than the openings of filter medium pass through the medium. However, adhesion or trapping of solids occurs as the filtrate containing fine particles flows through the porous filter medium. The principal role of a filter medium is to separate solids from flowing liquid with a minimum consumption of energy. The particle size distribution of sludges were measured using Malvern Mastersizer, which was based on laser diffraction. The median values in particle size distribution were 20.75㎛ and 40.25㎛ respectively for the anaerobically digested sludge and the waste activated sludge used in this study. Increases of the medium resistance in according to the cake mass were found from the permeability test. The results were well explained by Tiller`s empirical equation including the medium resistance constant and the medium clogging constant. Total resistance in cake filtration was also measured with the permeability test and the average specific resistance was calculated from the slope of the regression result. The proper selection of filter medium will cause to decrease the energy consumption for the biological sludge dewatering.

김응호 , 임수빈 Eoung Ho Kim , Soo Bin Yim

DOI: Vol.11(No.2) 109-114, 1995

The characteristics of optimum seed crystals for phosphorus removal have been studied comparatively by a column reactor for the leaching test and the phosphorus removal test by crystallization. As seed materials, phosphorus rock, electron arc furnace slag, blast furnace slag and converter slag have been chosen. The converter slag shows the most leaching quantity of Ca^(2+) and OH ion among the above slags. The average phosphorus removal efficiencies of phosphorus rock, electron arc furnace slag, blast furnace slag and converter slag are 35.9%, 74.2%, 99.1%, 94.5% under 20, l7, 24 and 158 days water flowing condition, respectively. X-ray diffraction pattern shows that blast furnace slag and converter slag transform from amorphous to crystalline phase. The SEM observation reveals that the finely distributed cubical crystalline are formed on the surface of converter slag during the crystallization period. The composition ratio (=Ca/P) of crystalline analyzed by EDS mapping is found to be 1.97 which is determined to be hydroxyapatite. By comparing the 4 seed crystals in technical and economical aspects, it is concluded that the converter slag is the best seed material for phosphorus crystallization process.

박대원 , 정진영 , 정윤철 , 윤운영 Dae Won Park , Jin Young Jung , Yun Chul Chung , Woon Young Yun

DOI: Vol.11(No.2) 115-121, 1995

Experiments were conducted to investigate the effect of MLSS concentration on the performance of a sequencing batch reactor (SBR) treating industrial wastewater containing high concentration of organics and nitrogen. Three laboratory-scale reactors were designed and operated at different MLSS concentration. Total organic carbon and nitrogen concentration in the reactors were monitored over reaction time. The higher MLSS concentration in the reactor resulted in the greater COD removal rate with up to 1.24㎏ COD/㎥.day. The higher MLSS concentration resulted in the lower TOC concentration in the effluent. It was observed from monitoring ammonia in the reactor that the higher MLSS concentration in the reactor resulted in the higher rate of ammonia oxidation and the earlier production of NO₃-N. MLSS concentration was observed to be an important factor determining removal rate of organic and ammonia

강선홍 , 최상일 Seon Hong Kang , Sang Il Choi

DOI: Vol.11(No.2) 123-128, 1995

Zinc metal and zinc sulfide were recovered by oxidative dissolution using Thiobacillus ferrooxidans, which is aerobic, autotrophic, and acidophilic bacteria. Thiobacillus ferrooxidans derive energy from oxidation of ferrous iron and elemental sulfur using molecular oxygen as an electron acceptor. From the 10,000㎎/L of initial zinc concentration, 97% solubilization of zinc metal was obtained from coarse FeS₂ due to microbial action. Also, about 70% metal solubilization occurred with fine sized materials in 58days. The general trend observed for the ZnS systems was a decrease in pH with time. The pH drop is an indication that microorganisms are acclimating and producing acidic by-products. The iron oxidation state changes due to substrate containing coarse particle size FeS₂ was shown. The sharp drop of ratio of Fe(II)/Fe(Total) and sharp increase of ratio of Fe(III)/Fe(Total) was observed in 20days after inoculation. Thus, microbial activity began more rapidly for the coarse particle size substrate than for the fine FeS₂.

안규홍 , 송경근 , 박준홍 , 권지향 , 김형수 K . H . Ahn , K . G . Song , J . H . Park , J . H . Kweon , H . S . Kim

DOI: Vol.11(No.2) 129-134, 1995

Powdered activated carbon(PAC) process was combined with crossflow ultrafiltration (PAC-UF process) to investigate the effect on permeability of ultrafiltration. Study was conducted with laboratory scale PAC-UF process and UF system. Secondary sewage effluent of RBC process was fed into two systems. PAC concentration of 450㎎/ℓ and contact time of two hours were maintained and the backwashing was carried out for 90 seconds with high pressure of 2.5㎏f/㎠ during operation. The following conclusions are drawn : 1) By adding PAC as a pretreatment process, the membrane fouling caused by refractory organic matters was controled. 2) When the duration of filtration was increased from 15 minutes to an hour, the permeate flux was significantly decreased because PAC layer accumulated on membrane surface and gel layer formed by adsorption of PAC. 3) In case of a dense membrane module, circulation of crossflow was hindered by accumulated PAC between housing and membrane. Thus, packing density of membrane module was to be designed in consideration of added PAC.

신항식 , 임경호 Hang Sik Shin , Kyeong Ho Lim

DOI: Vol.11(No.2) 135-142, 1995

In this study, organic stabilization and nitrogen removal were investigated using a household-type hollow fiber membrane separation bioreactor of 1.9L volume. The process employed direct solid-liquid separation by the hollow fiber membrane module and an aeration tank. There was a distinct effect of solid content on the membrane flux. The steady water flux decreased as MLSS concentration increased from 3,500 to 13,300㎎/ℓ. The reduction of influent COD aver 95% was obtained in the system without sludge wastage. However, by-products of cell degradation could accumulate and have adverse effect in the biological reactor if sludge was not wasted. SS was completely removed from the effluent so that clean effluent could be obtained by the membrane bioreactor. Enteric bacteric such as E. coli was not detected in the effluent. By the ultrafiltration membrane bioreactor, TKN was removed up to 90% or more by simultaneous nitrification and aerobic denitrification. Endogenous denitrification rate of 0.0139g NO₃-N/g VSS.day was observed.