The aim of this research was to apply experimental design methodology in the optimization condition of electrochemical oxidation of Rhodamine B(RhB). The reactions of electrochemical oxidation were mathematically described as a function of parameters amounts of current, NaCl dosage, pH and time being modeled by the use of the central composite design, which was used for fitting quadratic response surface model. The application of response surface methodology using central composite design(CCD) technique yielded the following regression equation, which is an empirical relationship between the removal efficiency of RhB and test variable in actual variables: RhB removal (%) = 3.977 + 23.279․Current + 49.124․NaCl － 5.539․pH － 8.863 ․time － 22.710․Current․NaCl + 5.409․Current․time + 2.390․NaCl․time + 1.061․pH․time － 0.570․time2. The model predicted also agree with the experimentally observed result(R2 = 91.9%).

This study has carried out to evaluate the effect of NaCl as electrolyte of single (electrolysis and UV process) and complex (electrolysis/UV) processes for the purpose of removal and mineralization of Rhodamine B (RhB) dye in water. It also evaluated the synergetic effect on the combination of electrolysis and UV process. The experimental results showed that RhB removal of UV process was decreased with increase of NaCl, while RhB removal of electrolysis and electrolysis/UV process was increased with increase of NaCl. The decolorization rate of the RhB solution in every process was more rapid than the mineralization rate identified by COD removal. The latter took longer time for further oxidation. Absorption spectra of an aqueous solution containing RhB showed a continued diminution of the RhB concentration in the bulk solution: concomitantly, no new absorption peaks appeared. This confirmed the decolorization of RhB, i.e., the breakup of the chromophores. It was observed that RhB removal in electrolysis/UV process is similar to the sum of the UV and electrolysis. However, it was found that the COD of RhB could be degraded more efficiently by the electrolysis/UV process than the sum of the two individual process. A synergetic effect was demonstrated in electrolysis/UV process.

Fabrication and oxidants production of 3 or 4 components metal oxide electrode, which is known to be so effective to destruct non-biodegradable organics in wastewater, were studied. Five electrode materials (Ru as main component and Pt, Sn, Sb and Gd as minor components) were used for the 3 or 4 components electrode. The metal oxide electrode was prepared by coating the electrode material on the surface of the titanium mesh and then thermal oxidation at 500℃ for 1 h. The removed RhB per 2 min and unit W of 3 components electrode was in the order: Ru:Sn:Sb=9:1:1 > Ru:Pt:Gd=5:5:1 > Ru:Sn=9:1 > Ru:Sn:Gd=9:1:1 > Ru:Sb:Gd=9:1:1. Although RhB decolorization of Ru:Sn:Sb:Gd electrode was the highest among the 4 components electrode, the RhB decolorization and oxidants formation of the Ru:Sn:Sb=9:1:1 electrode was higher than that of the 3 and 4 components electrode. Electrogenerated oxidants (free Cl and ClO2) of chlorine type in 3 and 4 components electrode were higher than other oxidants such as H2O2 and O3. It was assumed that electrode with high RhB decolorization showed high oxidant generation and COD removal efficiency. OH radical which is electrogenerated by the direct electrolysis was not generated the entire 3 and 4 components electrode, therefore main mechanism of RhB degradation by metal oxide electrode based Ru was considered indirect electrolysis using electrogenerated oxidants.

Fabrication and oxidants formation of 1 and 2 component metal oxide electrode, which is known to be so effective to destruct non-biodegradable organics in wastewater, were studied. Five electrode materials (Ru, Pt, Sn, Sb and Gd) were used for the 1 and 2 component electrode. The metal oxide electrode was prepared by coating the electrode material on the surface of the titanium mesh and then thermal oxidation at 500℃ for 1 h. The removed RhB per 2 min and unit W for one component electrode decreased in the following sequences: Ru/Ti > Sb/Ti > Pt/Ti > Gd/Ti > Sn/Ti. The concentration of oxidants generated in 1 and 2 component electrodes was in the order of: ClO2 > free Cl > H2O2 > O3. OH radical was not generated from in entire one and two component electrodes. RhB degradation rate and generated oxidants of the Ru-Sn=9:1 electrode was higher than that of the two component electrode. The exact relationship between the removal of RhB and the generated oxidants concentration was not obvious. However, it was assumed that electrode with high RhB decolorization had high oxidant concentration.

The feasibility study of the application of the photoelectrocatalytic and electrolytic/UV decolorization of Rhodamine B (RhB) was investigated in the photoelectrocatalytic and electrolytic/UV process with TiO₂ photoelectrode and DSA (dimensionally stable anode) electrode. Three types of TiO₂ photoelectrode were used. Thermal oxidation electrode (Th-TiO₂) was made by oxidation of titanium metal sheet; sol-gel electrode (SG-TiO₂) and powder electrode (P-TiO₂) were made by coating and then heating a layer of titania sol-gel and slurry TiO₂ on titanium sheet. DSA electrodes were Ti and Ru/Ti electrode. The relative performance for RhB decolorization of each of the photoelectrodes and DSA electrodes is: Ru/Ti > Ti > SG-TiO₂ > Th-TiO₂. It was observed that photoelectrocatalytic decolorization of RhB is similar to the sum of the photocatalytic and electrolytic decolorization. Therefore the synergetic effect was not showed in pthotoelectrocatalytic reaction. Na₂SO₄ and NaCl showed different decolirization effect between pthotoelectrocatalytic and electrolytic/UV reaction. In the presence of the NaCl, RhB decolorization of Ru/Ti DSA electrode was higher than that of the other photoelectrode and Ti electrode. Optimum current, NaCl dosage and UV lamp power of the electrolytic/UV process (using Ru/Ti electrode) were 0.75 A, 0.5 g/L and 16 W, respectively.

This study was carried out to evaluate the effect of water quality of cooling tower on Legionella pneumophila disinfection using Ru/Ti electrode. The influences of parameters such as pH, turbidity, CaCO₃ and TOC were investigated using laboratory scale batch reactor. Oxidants such as free Cl, ClO₂, H₂O₂ and O₃ were measured. The results showed that all of the water quality parameters of cooling tower had deteriorated disinfection of Legionella pneumophila. When the turbidity, CaCO₃ and TOC was increased, oxidants which was generated during electrolysis was decreased. pH, free Cl, ClO₂ and H₂O₂ concentration were decreased with the increase of pH, whereas O₃ concentration was increased with the increase of pH. The order of effect of water quality on the disinfection performance for Legionella pneumophila was turbidity > CaCO₃ > TOC > pH. To obtain the safety standard (1000 CFU/L), the simultaneous increase current and NaCl dosage was needed.

The electro-chemical decolorization of Rhodamine B (RhB) in water has been carried out by electro Fenton-like process. The effect of distance, material and shape of electrode, NaCl concentration, current, electric power, H2O2 and pH have been studied. The results obtained that decrease of RhB concentration of Fe(+)-Fe(-) electrode system was higher than that of other electrode system. The decrease of RhB concentration was not affected electrode distance and shape. Decolorization of electro Fenton-like reaction, which was added H2O2 onto the electrolysis using electrode was higher than electrolysis. Addition of NaCl decreased the electric consumption. The lower pH is, the faster initial reaction rate and reaction termination time observed.

This study was carried out to get more operational characteristics of Anoxic(anaerobic)-Oxic-Anoxic-Oxic (AO)2 sequencing batch biofilm reactors (SBBRs) at the low TOC concentration. The operating time in anoxic (anaerobic) time to oxic time was 1：1. Experiments were conducted to find the effects of the aeration time distribution on the organic matters and nutrients removal. Three lab-scale reactors were fed with synthetic wastewater based on glucose as carbon source. During studies, the operation mode was fixed. The first aeration time to the second aeration time in SBBR-1 was 2：3, and those in SBBR-2 and SBBR-3 were 1：4 and 3：2, respectively. The organic removal efficiency didn't show large difference among three reactors of different aeration time distribution. However, from these study results, the optimum aeration time distribution in the first and the second aeration time for biological nutrient removal was shown as 3：2. The release of phosphorus was inhibited at the second non-aeration period because of the low TOC concentration and the nitrate produced by the nitrification at the first aeration period.

In order to know the effect of autoclaving on the heavy metal removal using chitosan, lead removal capacities and removal rates by various chitosans in aqueous solution were compared according to the various autoclaving time. The lead removal efficiencies and removal rates by the autoclaved chitosan were found to be on the order of 15 min(98%) 〉10 min(95%) 〉30 min(83%) 〉5 min(53%) 〉60 min(47%) 〉0 min(22%) chitosan. The molecular weight of chitosan was decreased by the increase of autoclaving time. Therefore, the heavy metal removal capacity was not well correlated to the molecular weight. Langmuir isotherm was well fitted to experimental results of equilibrium adsorption on chitosan. In order to examine the process of lead removal by the autoclaved chitosan, TEMs, SEMs and FT-IR analyses were used. The surface of autoclaved chitosan was much more porous and the lead removal was mainly occurred on the surface of chitosan. The structure of autoclaved chitosan was same as that of controlled chitosan.

This study was carried out to get more operational characteristics of the sequencing batch biofilm reactors with media volume/reactor volume ratio of 15 %, 25 % and 35 %. Experiments were conducted to find the effects of the media packing ratio on organic matters and nutrients removal. Three laboratory scale reactors were fed with synthetic wastewater. During studies, the operation mode was fixed. The organic removal efficiency didn't show large difference among three reactor of different packing media ratios. However, from the study results, the optimum packing media ratios for biological nutrient removal was shown as 25%. The denitrifying PAOs could take up and store phosphate using nitrate as electron acceptor.

In order to examine the pre-treatment effect of crab shell on Pb2+ removal by crab shell in aqueous solution, acid and alkali pre-treated crab shell were used. Electron microscopy techniques such as TEM (transmission electron microscopy) and SEM (scanning electron microscopy), and EDX (energy dispersive X-ray) and FTIR (Fourier transform infrared) spectrometry techniques were used to investigate the process of Pb2+ removal by acid and alkali pre-treated crab shell. The Pb2+ removal by acid pre-treated crab shell was much lower than that by untreated crab shell because of the decrease of CaCO3 from the crab shell. However, the Pb2+ removal by alkali pre-treated crab shell increased compared to that by untreated crab shell. The results were confirmed by TEM, SEM, EDX and FTIR.

An evaluation of the application of SBR and biofilm on small sewerage system was conducted. A newly developed small sewerage system, using SBR, was successfully applied to the nutrient treatment using municipal wastewater. The system was consisted of 6 compartments. Two systems, with SBR (A type) or without SBR (B type), were compared by several parameters (COD, SS, T-N, NH4+-N, NO3--N, NO2--N, alkalinity, pH, DO) in all experimental periods. Also, the time variation of several parameters (DO, pH, NH4+-N, NO3--N, NO2--N) was examined in a SBR applied sewerage system. T-N removal efficiency of B type was higher than that of A type by the effect of nitrification and denitrification even though the COD removal efficiencies were similar. In aeration stage, the pH was decreased from 6.4 to 6.3 within 1 h and increased to 6.65 at the end of aerobic stage, and pH was decreased to 6.2 in non-aeration stage, and these phenomena were explained. The effects of nitrification and denitrification were compared in A type and B type sewerage system, and the typical nitrificaion and denitrification were observed in B type sewerage system.

In order to examine the inhibition effect of other heavy metal ions on the removal of heavy metal ions by crab shell in aqueous solution, 10 heavy metal ions (Cr3+, Cd2+, Ni2+, Zn2+, Hg2+, Cu2+, Mn2+, Fe2+, Fe3+, Pb2+) were used as single heavy metal ions and mixed heavy metal ions, respectively. In single heavy metal ions, Pb2+, Cr3+, Cu2+ were well removed by crab shell, however, Cd2+, Ni2+, Zn2+, Mn2+ were not. The heavy metal removal increased as the increase of covalent index (Xm2r), and the relationship classified heavy metal ions as 2 heavy metal groups (Fe3+, Fe2+, Cu2+, Cr3+, Mn2+, Ni2+, Zn2+ group and Pb2+, Hg2+, Cd2+ group). In mixed heavy heavy metal ions, the removals of Fe2+, Fe3+, Pb2+, Cu2+ as 0.49 mmol/g, regardless of the existence of other heavy metal ions, were similar to the result of single heavy metal ions experiment. The removals of Mn2+, Cd2+, Ni2+ decreased as the existence of other heavy metal ions, however, the removal of Zn2+, Cr3+, Hg2+ increased.

In order to provide the basic information on the environmental pollution of Kyungsan province, the contents of Pb, Cd, Cr, Cu, Mn and Zn in soil, stream water, aquatic sediment and groundwater were investigated, and also the values of pH, COD, KMnO4-C, NH3-N, NO2-N, NO3-N and Cl- of stream water and groundwater were determined. The results were as follows. The values of COD, NH3-N, NO2-N and NO3-N of the stream waters were very low. The contents of Pb, Cd, Cr, Cu and Zn in the stream waters were respectively at range of 0.014～0.063 ㎎/ℓ, 0.004～0.007 ㎎/ℓ, 0～0.045 ㎎/ℓ, 0～0.008 ㎎/ℓ and 0.001～0.175 ㎎/ℓ, and these values were much lower than those of contaminated stream water in Korea. The contents of Cd, Cr, Cu and Zn in the soils were respectively at range of 0.12～0.71 ppm, 0.88～2.65 ppm, 2.86～22.33 ppm and 3.89～26.39 ppm, and these values were much lower than those of ordinary polluted areas in Korea. The contents of Cd, Cr, Cu, As, Zn and Mn in the aquatic sediments were respectively at range of 3.05～3.81 ppm, 14.6～70.6 ppm, 13.74～61.59 ppm, 76.8～465.5 ppm, 12.56～190.83 ppm and 333.3～1188.3 ppm. The values of pH, KMnO4-C, NH3-N and NO3-N of the groundwaters were respectively at range of 7.6～8.4, 0～3.95 ㎖, 0.05～0.15 ㎎/ℓ and 0.05～0.42 ㎎/ℓ. The contents of Pb, Cd and Cr in the groundwaters were respectively at range of 0.015～0.061 ㎎/ℓ, 0.006～0.009 ㎎/ℓ and 0.005～0.045 ㎎/ℓ.

Several effects on Pb2+ removal by crab shell from aqueous solution were investigated. As the increase of initial Pb2+ concentration and decrease of initial crab shell concentration, the time required to reach an equilibrium state and the residual Pb2+ concentration increased. In our experimental ranges, the optimum initial Pb2+ concentration and crab shell concentration were below 103 mg/l and over 0.5 mg/l, respectively. Also, in order to investigate the mechanism of Pb2+ removal by crab shell in aqueous solution, the crab shell was compared with chitosan and chitin on aspects of Pb2+ removal capacity and Pb2+ removal rate. The Pb2+ removal by crab shell was greater than that by chitin and chitosan. The role of chitin was not so great in Pb2+ removal by crab shell. The Pb2+ removal by chitosan was not exactly correlated to the molecular weight of chitosan.

Pb^2+ removal capacity and initial Pb^2+ removal rate were compared between non-biomaterials (granular activated carbon, powdered activated carbon, ion exchange resin, zeolite) and biomaterials (activated sludge, Aureobasidium pullulans, Saccharomyces cerevisiae). The Pb^2+ removal capacity of biomaterials were greater than that of non-biomaterials, generally. The Pb^2+ removal capacities of non-biomaterials and biomaterials were shown on the order of ion exchange resin > zeolite > granular activated carbon > powdered activated carbon and A. pullulans > S. cerevisiae > activated sludge, respectively. In the initial Pb^2+ removal rate, the non-biomaterials showed powdered activated carbon > granular activated carbon > zeolite > ion exchange resin and the biomaterials showed A. pullulans > activated sludge > S. cerevisiae. Comparing the Pb^2+ removal capacity and initial Pb^2+ removal rate of activated sludge with those of other non-biomaterials and biomaterials, activated sludge may have an availability on the removal of heavy metal ions by the economical and pratical aspects.

The effects of temperature, initial Pb^2+, concentration and initial sludge concentration on the initial Pb^2+ removal rate and maximal Pb^2+ removal amounts in activated sludge, respectively, were investigated. The removal of Pb^2+ in activated sludge was proved to be temperature-dependent process. The initial Pb^2+ removal rate increased from 187.5 to 261.4 ㎎ Pb^2+/g sludge dry weight·min, in response to the promoted temperature from 10℃ to 60℃, while the maximal Pb^2+ removal amount (78.5 ㎎ Pb^2+/g sludge dry weight) occurred at 30℃. As the initial Pb^2+, concentration increased from 36 to 228 ㎎ Pb^2+/L at the constant temperature of 30℃ and initial sludge concentration of 1.5 g sludge dry weight/L, the time to reach an equilibrium state was almost independent of the initial Pb^2+ concentration and the equilibrium Pb^2+ removal amount was increased from 41.9 to 73.6 ㎎ Pb^2+/g sludge dry weight. On the contrary, the equilbrium Pb^2+ removal amount was decreased from 87.7 to 65.3 ㎎ Pb^2+/g sludge dry weight as the increase of initial sludge concentration from 0.22 to 1.76 g sludge dry weight/L.

The variations of gas hold-up, overall volumetric oxygen mass transfer coefficients and liquid circulation velocity in an internal loop reactor were investigated to manifest scale-up effect. The relationship between superficial gas velocity and gas hold-up were found as Ugr = 0.045 εr in the pilot-scale and Ugr = 0.056 εr in the bench-scale reactor. The overall volumetric oxygen mass transfer coefficient, K_La was slightly increased in the pilotscale than in the bench-scale reactor. Flow regime was changed from the bubble flow to the churn-turbulent flow when the superficial gas velocity reached to 3.5 - 4 ㎝/sec in the pilot-scale.