김종향 J . H . Kim , 변종환 J . H . Byun

DOI: Vol.16(No.2) 159-167, 2000

Reactive dyestuffs (Red 195, Yellow 145, Blue 19) and Disperse dyestuffs (Red 60, Yellow 54. Blue 56) were photodegraded by UV irradiation with or without photocatalyst, TiO₂ powder. The photoreaction were conducted in a quartz annular reactor equipped with 39 w (x2) mercury lamp. The extent of decolorization and removal of organic compounds were 92%, 60% for Red 195 in reactive dyestuff with UV irradiation and were 98%, 99% for Red 195 in reactive dyestuff with UV irradiation and TiO₂ powder, respectively. The extent of decolorization and removal of organic compounds were 7%, 52% for Red 60 in disperse dyestuff with UV irradiation and were 96%, 94% for Red 60 in disperse dyestuff with UV irradiation and TiO₂ powder, respectively. These results were measured UV-Vis spectrophotometry and colors were calculated by platinum-cobalt standard method.

이승환Seung Hwan Lee,암피티야H . K . Ampitiya,보가디J . J . Bogardi

DOI: Vol.16(No.2) 169-177, 2000

The derivation of optimal operation policies for a multiple-reservoir system is very complex due to the dimensionality constraints. This paper presents a methodology devised to overcome that difficulty during the determination of the operational policies for a multiple-reservoir system. The algorithm starts by the decomposition of the system into single-reservoir subsystems. Subsequently, each subsystem`s operation is individually optimized using a stochastic dynamic programming (SDP) based optimization model and then simulated using a reservoir operation simulation model. The methodology has been successfully applied to derive optimal operation policies for the reservoirs in the complex Mahaweli Development Scheme in Sri Lanka.

강윤호Yun Ho Kang,이우범Woo Bum Lee

DOI: Vol.16(No.2) 179-189, 2000

The health effects of bathing in marine waters contaminated with domestic sewage have been an area of scientific controversy. In this study, an epidemiological model is incorporated into a water quality model, to predict distribution of faecal streptococci concentration. The risk of gastroenteritis via the production of risk map is then assessed along bathing beaches in Swansea, west of UK. Such quantification facilitates the assessment of health gain benefits for any specific scheme of urban wastewater treatment. The schemes are designed to effect water quality improvement; including primary, secondary and tertiary systems involving, respectively, settlement alone, biological treatment together and disinfection by UV light or micro filtration. The epidemiological model involves with the dose response relationship linking the probability (p) of gastroenteritis and exposure indexed by faecal streptococci density at chest depth. In the solute transport model, advection terms in the advective-diffusion equation are represented in the finite difference form using the third order accurate QUICKEST scheme and ULTIMATE algorithm. This study provides a basis for both health related water quality objectives and advice to the public on potential health risks from bathing at local recreational waters.

최정우Jeung Woo Choi,현길수Kil Soo Hyun,강용태Yong Tae Kang

DOI: Vol.16(No.2) 191-198, 2000

Nonbiodegradable organic carbon in the Nakdong river has been gradually increased due to the inflow of inappropriately treated domstic and industrial wastewaters. Most of the existing water treatment plants in the Nakdong river basin depend on rapid sand filtration process, which consists of prechlorination, coagulation-flocculation and sedimentation, rapid sand filtration processes. It has been inappropriate to produce good quality drinking water. Thus the objectives of this research are to optimize the operating conditions of the GAC and the BAC processes based on the results of total organic carbon (TOC), UV-254㎚ absorbance (UV_(254)), and trihalomethanes (THMs) removals. Based on the results of this research, the optimum empty bed contact time (EBCT) and packed depths of all the GAC and the BAC beds were 12 minutes and more than 320㎝, respectively. Conversion rates of dissolved organic carbon (DOC) to biodegradable DOC (BDOC) by ozonation ranged from 22 to 30%. Effect of the BAC bed on BDOC and non-biodegradable DOC (NBDOC) removals averaged 44% and 19%, respectively. The removal percentage of the GAC and the BAC processes averaged 22% and 34% for TOC and 10% and 14% for THMs, respectively. For TOC removal, the BAC bed was about 10% higher than the GAC.

임경호Kyeong Ho Lim,박영오Young Oh Park,배병욱Byung Uk Bae

DOI: Vol.16(No.2) 199-209, 2000

Rapid sand filters in water treatment plants (WTP) is one of the most important step in order to remove fine particle including pathogens such as Criptosporidium and Giardia. Filters should be assessed based on their capability to achieve a treated water quality of less than 0.1 NTU on a continuous basis to ensure the integrity of the filtration process as a viable barrier in the treatment scheme. This is less than the 1.0 NTU standard, but operation of filters to produce filtered water quality confidence that pathogens are being removed prior to the last barrier, disinfection. In this study, to optimize existing filtration unit process, rapid sand filters working in S-WTP were evaluated for various factors. The results of comprehensive performance evaluation were followings. From the filter media analysis, effective size and uniformity coefficient of media was 0.90∼1.0 ㎜ and 1.44∼1.47, respectively. Therefore, the replacement of media is needed to optimize filter performance. Media loss was caused by air binding in the filter bed and improper operation of backwashing process. The ratio of the water used for filter washing to the amount of filtered water was 2.5∼3.0% during the winter and 1∼2% in the summer. At the beginning of a filter run, filtered water turbidity was over 0.5 NTU during about 20 min. Shorter filter run lengths was attributed to an overabundance of filter clogging algae (Synedra. sp), air binding, and too much floc in the filter influent.

김창수Chang Soo Kim,최승일Suing Il Choi,이기창Gi Chang Lee

DOI: Vol.16(No.2) 210-222, 2000

As the raw water quality has been deteriorated, the use of powdered activated carbon has been prevailed. However, it is pointed out that the adsorptive capacity of powdered activated carbon is confined since coagulant is added just after the injection of powdered activated carbon. The objectives of this study are to investigate the effect of coagulation on the adsorption capacity of powered activated carbon and to investigate whether the optimum dosage of coagulant changes because of the powdered activated carbon injection. The sodium dodecyl benzene sulfonate (SDBS), fenitrothion, phenol, chloroform have been used as adsorbates and polyaluminum chloride (PAC) has been used as a coagulant. The result shows that the optimum coagulant dosage has little been changed due to the addition of powdered activated carbon. When only powdered activated carbon is added to the raw water, the residual concentrations of adsorbates have been reduced gradually for 20∼30 minutes. However, when coagulant is added just after the injection of powdered activated carbon, the residual concentrations of adsorbates are flattened within a few minutes indicating no more adsorption. The amounts of adsorbates removed by the simultaneous use of powdered activated carbon and coagulant are less than the sum of removals by each treatment. Therefore, it has been concluded that the floc formation by addition of coagulant has confined the adsorptive capacity of powdered activated carbon, though its effects are different with various adsorbates.

서정범Jeong Beom Seo,임연택Yeon Taek Rim,권오상Oh Sang Kwon,한기봉Gee Bong Han,유재근Jae Keun Ryu

DOI: Vol.16(No.2) 223-230, 2000

This study was focused on investigation of operational efficiencies in terms of BOD, SS, TN and TP for treatment facility built on-site apartment building. The sequencing batch reactor (SBR) activated sludge process of 40㎥/day capacity was applied for sewage treatment system. The results of the research showed that the sewage flow rate and BOD concentration was particulary high at about 8:00 p.m. and 10:00 a.m., respectively. The average sewage concentration of BOD. SS, TN and TP were 145.4㎎/L, 101.l㎎/L, 33.3㎎/L and 2.8㎎/L, respectively. In operational steady state, BOD removal was observed to be 94.9% on average while SS removal to be 88.2% on average. Denitrification/nitrification were accomplished during SBR processes and average removal rate of nitrogen was 71.8% in terms of total nitrogen. Nitrogen removal was not affected by the winter season. Removal efficiency of phosphorus was 76.9% in terms of total phosphorus. The average effluent concentration of BOD, SS, TN and TP were 8.3㎎/L, 11.4㎎/L, 9.0㎎/L and 0.6㎎/L, respectively. Observed microbial yield coefficient was 0.29gMLSS/gBOD. This experiment may prove that the SBR process can be employed to treat organic matter as well as nutrients in sewage that are generated from such sources as apartment building and community area.

정연규Youn Kyoo Choung,김한수Han Soo Kim

DOI: Vol.16(No.2) 231-242, 2000

Mathematical model based on the kinetic aspect of the intermittent aeration system with continuous inflow (IASWCI) was developed. This model is a dynamic model dealing with the overall relationship between biomass concentration and contaminants in a reactor. Before modeling, it is advisable to understand the general behavior of a water quality model. Sensitivity analysis is accomplished by varying the numerical value of the parameters in the process model and determining the resulting impact on the predicted response. Based on the results, the significance of various model components can be assessed. Consequently, the full scale program should be designed specifically to provide accurate estimates of sensitive parameter.

이동열Dong Yeol Lee,차기철Gi Cheol Cha,심진기Jin Kie Shim,이영무Yong Moo Lee,유익근Ik Keun Yoo,안승호Seung Ho Ann

DOI: Vol.16(No.2) 243-253, 2000

Membrane Bioreactor (MBR) process for food wastewater was studied to find the treatment chracteristics and the operating parameters at the hydraulic retention time (HRT) of 0.5 and 0.25day. Plate and frame membrane module was submerged in laboratory-scale MBR of 12L volume. Membrane suction-idle operation of l0minutes-on and 5minutes-off cycle showed the stable permeate flux and suction pressure. The BOD and COD removal efficiencies were obtained over 96% and 91%, respectively. During the operation, the increase of E260/DOC ratio (scale of non-degradable organic matter) was observed in the MBR. The resistance value of cake layer was measured 1.24 X 10^(11) (1/m) and this value showed more significant affect on flux drop than that of among other resistance layers.

안재환Jae Hwan Ahn,이현동Hyun Dong Lee

DOI: Vol.16(No.2) 255-264, 2000

More than 85% of cow farms are raising below 10 heads, while more than 58% of pig farms below 100 heads. As the small-scale livestock farms are widely scattered in Korea, the load of pollution generated from these small farms becomes over the control. This investigation was conducted to suggest the best management for the livestock wastewater. Totally 104 livestock farms, including 63 for pig and 41 for cow, and the livestock wastewater treatment facilities were surveyed for 5 provinces and 6 cities (or districts) in the regions of Seoul metropolitan, water quality protection area, seashores and the mountain side. In order to reduce the pollution load from the livestock farm and to improve the management of treatment facilities, the solid-liquid separation facilities should be employed to the new farms and the farms with increasing livestock. For the small-scale livestock farms, it is rather reasonable to have the simple storage type of facility. In the other hand, the political support should be made for the farm cooperations units to produce and store the recycled fertilizer for good-time sale.

최의소Eui So Choi,이영행Young Haeng Lee,길경익Kyung Ik Gil,윤주환Zu Whan Yun

DOI: Vol.16(No.2) 265-273, 2000

The purpose of this research was to study nitrogen removal from anaerobic digester supernatant via nitrite nitrification-denitrification. As a result, the major reasons for nitrite build-up were the inhibition of Nitrobacter by free ammonia and the short SRT which didn`t allow Nitrobacter to acclimate to the high FA levels. In an integral nitrite nitrification-denitrification process, the comparison of the shortened pathway with the traditional nitrification-denitrification pathway revealed (1) a 50% reduction of COD during denitrification (2) a lower biomass yield during anoxic growth. So the nitrite nitrification-denitrification process of anaerobic digester supernatant is very effective and economical modification for the existing wastewater treatment plants. The results of this study are very helpful in treating highly nitrogenous wastewater like leachate, piggery wastewater, nightsoil and supernatant of septage, etc.

양승태Seung Tae Yang,이화성Hwa Sung Lee

DOI: Vol.16(No.2) 275-282, 2000

Two methods for determining formaldehyde in aqueous environmental samples by the visible spectrophotometry are described. The phenylhydrazine hydrochloride method is based on the formation of phenylhydrazone of formaldehyde with phenylhydrazine hydrochloride, its oxidation with ferricyanide and color development by addition of base, and absorbance is read at a wavelength of 533nm. The phenylhydrazine hydrochloride method was compared with the chromotropic acid method in the characteristics of determination such as detection limit, linear range, precision and accuracy, and effects of the chloride ion, total hardness and COD_(Mn) of samples. The phenylhydrazine hydrochloride method with mean recovery of 106.0% and RSD of 9.8% was higher in accuracy and precision than the chromotropic acid method, and the method was suitable for the measurement of formaldehyde in aqueous environmental samples.