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Objectives:The purpose of this study is to evaluate the effects of heavy metals (Zn2+, Pb2+, Hg2+, Cd2+) toxicity in a real-time biosensor which is based on measuring the attenuation of light intensity emitted by Vibrio fischeri.Methods:The inhibition test included four heavy metals and the spiked effluent wastewater. The toxicity of the test samples was assessed by freeze-dried bacteria (Vibrio fischeri NRRL-B-11177). The pH of the samples was adjusted to 7±0.2 before conducting the toxicity tests in oder to eliminate potential pH effects. The results obtained from the real-time biosensor that can be measuring the toxicity of the samples as a function of the emitted light. within a short period time (2 min). And then EC20 and EC50 values was estimated from inhibition curves.Results and Discussion:In case of the inhibition test for dilluents of heavy metals, EC20 values were estimated as < 0.2 mg/L for Zn(II), 0.45 mg/L for Hg(II), 0.58 mg/L for Cd(II) and 1.95 mg/L for Pb(II) and EC50 values were estimated as 0.25 mg/L for Zn(II), 0.5~1.0 mg/L for Hg(II), 1.38 mg/L for Cd(II) and 3.76 mg/L for Pb(II). The sensitivity ranking of heavy metals was in order as Zn(II) > Hg(II), > Cd(II) > Pb(II). In case of the inhibition test for the spiked effluent wastewater, EC20 values were estimated as 0.38 mg/L for Hg(II), 0.58 mg/L for Zn(II), 1.45 mg/L for Pb(II) and 1.95 mg/L for Cd(II) and EC50 values were estimated as 0.53 mg/L for Hg(II), 1.13 mg/L for Zn(II), 6.44 mg/L for Pb(II) and 7.82 mg/L for Cd(II). The sensitivity ranking of the spiked effluent wastewater was in order as Hg(II) > Zn(II) > Pb(II) > Cd(II). Compared to the Emssion Limit Value (ELV) in Korea, the EC20 value of Zn(II) was found to be lower than ELV so that it was suitable for screening of Zn(II) as to meet the criteria of effluent wastewater. However, the other EC20 value of heavy metals can be used to control the unit processes and avoid accidental discharge.Conclusions:The assessment of the toxicity of four heavy metals and spiked samples with them was performed in this study, by real-time biosensor using bioluminescent bacteria. The EC20 value of the spiked sample with Zn(II) has been found to be 0.58 mg/L lower than its ELV so that it was considered as a suitable screening for determining whether or not to exceed the permissible limit value. The use of real-time biosensor is required in combination with physicochemical analyses for an integrated screening of the industrial effluent properties.

【In order to suggest the methodology for improving the equity of flow distribution in open channel with multiple outlet, CFD simulations were carried out for actual scale distribution channel being operated in domestic G_WTP(Water Treatment Plant). Also, before and after installing the longitudinal multi hole(diameter=250 mm, 116 holes) baffle suggested by this research, turbidity measurements data were collected for evaluating the effects of hydraulic modification for inlet flow equity. From the both results, total turbidity of settled water was lowered by 30 % and equity of flow distribution was improved about 60 % compared with before hydraulic structure modification.】

In this study, to investigate the influence of fluctuation in hydraulic loads on both the operation of filtration process and the quality of filtered water for a domestic water treatment plant, two different control methods were analyzed and compared with each other: (1) constant-rate filtration using a flow meter and a flow modulation valve (rate control method; RC method), (2) constant-level filtration using equal-flow splitting inlet weirs, water level sensors, and a flow modulator valve (level control method; LC method). From the results of experiments, it could be showed that a sudden flow surge may cause significant particle detachment in terms of particle count in filtered water under conditions of LC method. In addition, this method can lead to difficulty in maintaining residual chlorine at the outlet of clear well. On the other hand, the RC method, in two aspects – the process operation and the quality, is evaluated to be more appropriate than the LC method with seriously large fluctuatio...

This study was conducted to qualify the equality of the flow distribution from open channel between rapid mixing basin and flocculation basins in a domestic S_ water treatment plant, and to suggest a remedy for improving the equality. In order to evaluate the feasibility of the suggested remedy, computational fluid dynamics (CFD) technique are used, and for verifying the CFD simulation results tracer tests were carried out. From the results of CFD simulation and tracer tests, it was investigated that the modification of hydraulic structure in the distribution channel, which is to install the longitudinal orifice baffle in flow direction, could improve the equality of the flow distribution over 75%.

Down Stream K River has high COD (4-10 mg/L) and high NH3-N concentration (3.5 mg/L during winter period). Although NH3-N itself is not reported harmful at this level, it must be removed to meet drinking water standard (0.5 mg/L). We constructed a pilot plant modifying the processes of conventional drinking water facilities. Prechlorination and powdered activated carbon (PAC) dechlorination was adopted prior to a flocculation tank to remove ammonia and prevent disinfection byproducts (DBPs) formation. Also, GAC processes was included after sand filter to remove residual DOC. This pilot having a capacity of 36 ton/day was operated for one year. The GAC processes were successful to remove ammonia and many organic pollutants (DOC, MBAS, UV254 nm absorbance, etc). Influent DOC concentrations were very high as 3~6 mg/L throughout the plant operation. It was impossible to achieve 1.0 mg/L effluent DOC, indicating that bed depth (2 m) should be increased to achieve more strict DOC quality standards. When Cl2 dose was well controlled (Cl2/NH3-N ratio 10~11 on a weight basis), NH3-N removal was 98% and THMs was very low possibly due to low free residual chlorine and PAC dechlorination.

Seven major water treatment plants in Seoul Metropolitan Area, which are under Korea Water Resources Corporation (KOWACO)'s management, take water from the Paldang Reservoir in the Han River System for drinking water supply. There are taste and odour (T&O) problems in the finished water because the conventional treatment processes do not efficiently remove the T&O compounds. This study evaluated T&O removal by ozonation, granular activated carbon (GAC) treatment, powder activated carbon (PAC) and an advanced oxidation process in a pilot-scale treatment plant and bench-scale laboratory experiments. During T&O episodes, PAC alone was not adequate, but as a pretreatment together with GAC it could be a useful option. The optimal range of ozone dose was 1 to 2 mg/L at a contact time of 10 min. However, with ozone alone it was difficult to meet the T&O target of 3 TON and 15 ng/L of MIB or geosmin. The GAC adsorption capacity for DOC in the three GAC systems (F/A, GAC and O3 + GAC) at an EBCT of 14 min is mostly exhausted after 9 months. However, substantial TON removal continued for more than 2 years (>90,000 bed volumes). GAC was found to be effective for T&O control and the main removal mechanisms were adsorption capacity and biodegradation.

In the case of S water treatment plant, it was designed to be mostly operated by direct filtration mode all the year round. To evaluate the conditions of such operation mode, in this study, we operated pilot plant by direct filtration process by making flocculation treatment water flow into anthracite filter and active carbon (Calgon, Norit) filter which is an assembly of deep bed filter paper, and studied to find out the principle in which turbidity is removed in filter paper by measuring turbidity and head loss by the depth of filter, and an appropriate operation method. Also we conducted comparison evaluation according to kinds of coagulant and evaluation according to the injection of a polymer coagulant, a filter aid, before letting filter flow into flocculation treatment water. On the basis of the optimum operation of direct filtration process using deep bed filtration, it is necessary to decide and inject the optimum injection volume of filter aids taking account for the quality of raw water and to operate anthracite filter, which will also contribute to lowering the operation expenses of a filtration plant and improving the quality of treatment water.

Dissolved air flotation (DAF) is a solid–liquid separation system that uses fine bubbles rising from the bottom to remove particles in water. In this study, we investigated the effect of L/W(L; length, W; width) on the hydrodynamic behavior in a DAF system using CFD (computational fluid dynamics) and ADV (acoustic Doppler velocimetry) technique. The factual full-scale DAF system, L/W ratio of 1:1, was selected and various L/W ratio conditions (2:1, 3:1, 4:1 and 5:1) were simulated with CFD. For modelling, 2-phase (gas–liquid) flow equations for the conservation of mass, momentum and turbulence quantities were solved using a Eulerian–Eulerian approach based on the assumption that a very small particle is applied in the DAF system. Also, for verification of CFD simulation results, we measured the actual velocity at some points in the full-scale DAF system with the ADV technique. Both the simulation and the measurement results were in good accordance with each other. We concluded that the L/W ratio and outlet geometry play an important role for flow pattern and fine bubble distribution in the flotation zone. In the ratio of 1:1, the dead zone is less than those in other cases. On the other hand, in the ratio of 5:1, the fine bubbles were more evenly distributed.

The major objective of this research is to determine engineering GAC adsorber design criteria for removal of various organic contaminants found in the 3 drinking water sources in the Keum river basin. Dissolved Organic Carbon (DOC) and UV absorbance at 254 nm were chosen as parameters for overall organics level in raw and treated water. Removal of micropollutants including organophosphorus pesticides, MBAS, volatile organic chemicals (VOCs), phenol and NH3-N were also taken into consideration in bench and/or pilot studies. Treatment efficiencies for target contaminants in three different pilot plants with different raw water quality in the same Keum river basin were compared. Identification and decision of the treatment objectives were found to be important factors for determining design parameters such as GAC bed depth. Range of appropriate bed depth and reactivation frequency for different treatment levels were suggested based on pilot studies.