정재춘 Jae Chun Chung

DOI: Vol.7(No.2) 85-99, 1991

The enrichment of Beggiatoa was derived in a lab-scale continuous flow fixed-film growth system. Under a low aeration and high BOD organic loading condition, the enrichment of Beggiatoa was easily achieved on the glucose-fed slime while it took fairly long time on the acetate-fed one. An increased aeration resulted in a decrease in the Beggiatoa population for the acetate-fed slime, but not for the glucose-fed slime, except slightly at very high aeration level. Sulfate removal rate in both Beggiatoa dominated slimes was generally low, between 10-30%. The glucose-fed slime showed a much higher sulfate removal at high organic loadings. The aeration effects on Beggiatoa and sulfate removal were understandable in the context of the Beggidtod-Desulfovibrio interaction, diffusion and uptake rate of substrate. Glucose diffusion and uptake may more rapid, thus air could not penetrate as efficiently into the sulfide-emitting anaerobic layer inhabited by sulfate reducing bacteria such as Desulfovibrio. This may have resulted in less inhibitory effects on the sulfate reducing bacteria.

이성규 , 심점순 , 김용화 , 노정구 Sung Kyu Lee , Jeom , Soon Shim , Yong Hwa Kim , Jung Koo Roh

DOI: Vol.7(No.2) 100-109, 1991

To evaluate the toxic potentials of the effluents which meet the current domestic permit limits for industrial effluents to aquatic organisms and human health, the toxicity test using fish (Oryzias latipes), water flea (Daphnia magna), and algae (Selenastrum capricornutum), and Ames`test with Salmonella typhimurium were performed with treated effluents from 29 manufacturing facilities covering 9 different types of industry. Effluents were taken three times by grab sampling at the end-of-pipe at 3 month intervals. The quality of effluents in terms of BOD and COD of 28 industries satisfied the current permit limits well. Six effluents out of the ten chemical manufacturing industries and the effluents from leather manufacturing industries were acutely toxic to all aquatic organisms tested ; the metal industry effluent was toxic to aquatic invertebrate and algae ; the textile effluents were toxic to algae. When the 0.3 TUa criterion for permit based on toxicity measurements was applied at the end-of-pipe, 45% of the effluents which met the curent permit limits of BOD and COD measurements did not satisfy the criterion. Mutagenicity at TA98 strain with microsomal activation was consistently seen through the 3 sampling periods from samples of the two textile manufacturing facilities, implying the presence of possible carcinogens. It was suggested that the current regulatory permit limits, such as BOD, COD, and other elements, should not be sufficient to protect the aquatic organisms and human health. Therefore, additional assessment using ecotoxicological and genotoxicological approach is recommended.

옥치상 , 정용 Chi Sang Ok , Yong Chung

DOI: Vol.7(No.2) 110-118, 1991

For the purpose of reducing the risk by chlorination of drinking water, this study was carried out to predict the risk of drinking water by chlorination and to manifest the influence of disinfectants, chlorine and chlorine dioxide. Productions of Trihalomethanes (THMs) and nonvolatile extractable organic matter (EOM), and the Salmonella mutagenicity by the disinfection were investigated. Cl₂ and ClO₂ with their concentrations of 1㎎/ℓ, 5㎎/ℓ and 10㎎/ℓ, respectively were mixed as the ratio as l : 1, 1 : 2. And the influence by the disinfection with Cl₂, ClO₂ and mixture of Cl₂/ClO₂ in water added with humic acid(10㎎/ℓ) and raw water (3rd quality) for 2hrs and 24hrs were evaluated. The results were summarized as follows; The formation of THMs and EOM, and mutagenicity showed that in comparison with Cl₂ disinfection, 1 : 1 mixture of Cl₂/ClO₂ decreased in 45-65% THMs, 26-56% EOM and 20-40% mutagenicity ; 1 : 2 mixture of Cl₂/ClO₂ decreased in 73-85% THMs, 58-63% EOM and 30- 55% mutagenicity ; ClO₂ disinfection decreased in 95% THMs, 66-70% EOM and 40-60% mutagenicity, respectively. All of mutagencity were increased according to the increase of EOM in plate. Based on the assessed above results, it is concluded that the chlorine dioxide would be one of the alternatives of disinfectants in drinking water. However, in view of prevention of water born disease by pollution during distribution of tap water, the mixed disinfect of Cl₂/ClO₂ could be recommended.

김환기 , 양봉용 Hwan Gi Kim , Bong Yong Yang

DOI: Vol.7(No.2) 119-128, 1991

An experimental study on the oxygen transfer characteristics in a U-type deep shaft system of 32m depth as an aeration tank has been performed. According to the results of this study, total over-all oxygen transfer coefficient(K_La) in downcomer had calculated to be 45.8∼174.7/hr. Oxygen transfer ability in this deep shaft system was higher than diffused aeration, since oxygen transfer rate was 0.7∼1.8 ㎏-O₂/㎥ hr and oxygen dissolution efficiency was 17.3-6.1%, average oxygen transfer efficiency was 2.25 ㎏-O₂/Kw ·hr.

최의소 , 정정권 Eui So Choi , Chung Kwon Chung

DOI: Vol.7(No.2) 129-135, 1991

SEM(Scanning Electronic Microscope) observations were made to compare the microbial characteristics between UASB and fixed film (FF) reactors with various wastes: concentrated vs diluted, and complex vs simple volatile waste. It appeared that the sludge granulation was influenced by the wastes fed to the reactor rather than the reactor type itself. Stable granulations were not developed with the concentrated waste as well as the simple volatile waste. Microbial washout was pronounced as the volatile fraction of waste was increased. Rod and cocci shape bacteria were easily washout but filamentous bacteria seemed to entangle those bacteria not to washout easily.

김홍석

DOI: Vol.7(No.2) 136-144, 1991