Jin Chul Joo

Photocatalytic degradation of trichloroethylene in aqueous phase using nano-ZNO/Laponite composites

The feasibility of nano-ZnO/Laponite composites (NZLc) as a valid alternative to TiO2 to mineralize trichloroethylene (TCE) without difficulties for recovery of photocatalysts was evaluated. Based on the experimental observations, the removal of TCE using NZLc under UV irradiation was multiple reaction processes (i.e., sorption, photolysis, and photocatalysis). Sorption of TCE was thermodynamically favorable due to the hydrophobic partitioning into crosslinked poly vinyl alcohol, and the adsorption onto high-surface-area mineral surfaces of both ZnO and Laponite. The degradation efficiency of TCE can be significantly improved using NZLc under UV irradiation, indicating that ZnO-mediated heterogeneous photocatalytic degradation occurred. However, the degradation efficiency was found to vary with experimental conditions (e.g., initial concentration of TCE, loading amount of NZLc, the intensity of light and initial solution pH). Although the removal of TCE by NZLc was found to be a complex function of sorption, photolysis, and photocatalysis, the photocatalytic degradation of TCE on the surface of ZnO was critical. Consequently, developed NZLc can be applied as a valid alternative to suspended TiO2 powder, and overcome drawbacks (e.g., filtration and recovery of photocatalysts) in degradation of TCE for various water resources.

Removal of Metaldehyde Through Photocatalytic Reactions Using Nano-Sized Zinc Oxide Composites

Metaldehyde is a selective molluscicide used in the agricultural and residential sector to control slugs and snails for a wide variety of crops. In recent years, some water companies have started monitoring drinking water supply catchments for presence of this compound, with positive and concern results. Conventional techniques are yet to achieve complete efficient and feasible removal of metaldehyde. The aim of this study was to measure the efficiency of nano-sized zinc oxide/laponite composites (NZnC) in the effective removal of metaldehyde (influent concentration of 500xa0μgu2009dm−3) through the interaction of photocatalysis. Reaction time, pH of sample solution and NZnC mass were tested against each other using a rotatable central composite design method of experimentation. Statistical tests showed that linear effects of time, quadratic/linear effects of NZnC mass and the interaction of pH and NZnC mass proved to be the most significant variables for degrading metaldehyde. Optimal values of each variable for the highest removal efficiency were achieved, being pH equal to 10.4 and NZnC mass added equal to 28xa0g. The rate of reaction was then predicted by non-linear regression of four models. The best fit was provided by the modified first-order with residual kinetic model, with the apparent degradation coefficient k equal to 0.0363xa0min−1 and the lowest remaining metaldehyde concentration observed among all runs was 278.7xa0μgu2009dm−3. NZnC has shown to be a prominent nanotechnology for metaldehyde removal.

Degradation of Humic Acid by Photocatalytic Reaction Using Nano-sized ZnO/Laponite Composite (NZLC)

Humic acids (HA) are known as the precursors of carcinogenic compounds formed by the disinfection of drinking water. While conventional treatments were found to be inefficient HA removal processes in drinking water, advanced oxidation processes have been proven to have a significant effect in the treatment of HA. The degradation of HA was investigated using nano-sized zinc oxide (ZnO)/laponite composite (NZLC). The reactions occurred in a UVC reactor by considering following variables: pH, initial HA concentration, catalyst loading, addition of hydrogen peroxide (H2O2), and catalyst reuse. Water samples containing HA were analysed by ultraviolet/visible spectrophotometer and high-performance size-exclusion chromatography. Initial HA concentrations were tested by the Langmuir–Hinshelwood model with k and Kads values, determined to be 0.126xa0mg/L.min and 0.0257xa0L/mg, respectively. The change in pH affected the HA degradation efficiency by the photocatalytic activity where it was higher under acidic conditions rather than alkaline ones. Optimal catalyst loading was proved to be a constrained factor in influencing the photocatalytic efficiency: the increase of catalyst concentration enhanced the HA decomposition efficiency up to an optimum value of 20xa0g/L, where there was no further degradation with excess loading. The addition of H2O2 was investigated through homogenous and heterogeneous photocatalysis, and, heterogeneous photocatalysis showed higher removal efficiency due to the combined effect of both catalysts and H2O2. Finally, NZLC was effective for reuse and exhibited an excellent stability after six times of usage.

Field application of waterworks automated meter reading systems and analysis of household water consumption

AbstractAfter the construction of waterworks automated meter reading (AMR) systems with a 15-mm diameter smart water meter developed in this study, both the feasibility of field application of waterworks AMR and the patterns of household water consumption were evaluated. Average reception rate was 94.1% due to the communication blackout, and one-to-one communication with RF UHF and Internet (i.e. TCP/IP) was found to be more stable in AMR systems than multiple-to-one communication with RF UHF, DCU, and Wibro. Household water consumption clearly showed seasonal periodicity due to weather factors. Based on the analysis of liters per capita day (LPCD) for 80 households, the LPCD values were found to decrease gradually as the number of residents increased due to the saving effects through common consumption (i.e. washing, cooking, cleaning, irrigation, etc.). Relative to LPCD values of 100 control households without AMR systems, the LPCD values of 80 pilot households with AMR systems were reduced by 5.3%. Con...

Sorption of nonpolar neutral organic compounds to low-surface-area metal (hydr)oxide- and humic acid- coated model aquifer sands

The roles of mineral-bound humic acid (HA) and mineral surfaces in the sorption of six nonpolar neutral organic compounds with relatively high aqueous solubility, Sw , (1,2,4-trichlorobenzene, 1,4-dichlorobenzene, chlorobenzene, m-xylene, toluene, and benzene) to low-surface-area (i.e., ≤ 1.2 m2/g) metal (hydr)oxide- and HA-coated sands with low organic carbon fractions (i.e., 0.006% ≤ foc ≤ 0.044%) were investigated using well-characterized mineral surfaces [i.e., α-FeO(OH)- or Al2O3- coated sands], terrestrial HA, and solutions with relatively constant pH and ionic strength. Sorption isotherms of all six compounds to low-surface-area metal (hydr)oxide-and HA-coated sands were practically linear (i.e., 0.898 ≤ n ≤ 1.06), and resulted from a combination of sorption to both mineral-bound HA and mineral surfaces, with the dominance of either contribution depending on the properties of the sorbents (e.g., foc ) and organic compounds (e.g., Sw and Kow ). Compared to HA-associated high-surface-area, pure metal (hydr)oxides or clay minerals illustrating that loading levels of HA significantly impacted sorption affinity (i.e., Koc ) and linearity (i.e., n) for particularly hydrophobic compounds (i.e., phenanthrene, anthracene and pyrene) due to the changes in fractionation, and structural and chemical properties of mineral-bound HA, the subsequent changes of sorption affinity and linearity appeared to be insignificant for the sorption of organic compounds with relatively high Sw to low-surface-area metal (hydr)oxide- and HA-coated sands with low foc values. Thus, the predictive models for the sorption of organic compounds with relatively high Sw to low-surface-area metal (hydr)oxide- and HA-coated sands may not be remarkably improved by incorporating the complex changes of sorption affinity and linearity caused by the changes in fractionation, and structural and chemical properties of mineral-bound HA, although the mineral surfaces apparently caused physical and chemical changes of HA, and vice versa during adsorption onto mineral surfaces.

Analysis of Water Quality Improvement of Ceratophyllum demersum under Laboratory Condition - by Nutrients Removal Efficiency

To evaluate the ability of the submerged plant, Ceratophyllum demersum’s (C. demersum) to remove nutrients and to inhibit growth of cyanobacteria, a total of 6 mesocosms were conducted in a batch reactor for 9 days. From the 84 hr of the experiment, C. demersum was stabilized and showed daily cycle trends according to changes in pH and DO levels. The concentration of nutrients, NH3, NO3 and PO4 continuously decreased until 9 days of the experiment, with the rapid decrease in nutrient concentration for the first 24 hours. High correlation coefficient (r≥ 0.96, p < 0.001) between the amount of C. demersum’s biomass per unit area and the nutrients removal level were derived, and greater C. demersum’s biomass per unit area showed higher removal efficiency of nutrients. However, there were differences in the C. demersum’s activity level between batch reactors with higher and similar density of the C. demersum, but nonetheless water purification effect appears to have a significant influence due to attached algae and microorganisms. The growth rate of harmful cyanobacteria, Microcystis aeruginosa (M. aeruginosa) with C. demersum’s density of 2,500 g fw/m (100% of cover degree) was 0.31 /day, compared to the growth rate of 0.47 /day for the control group (0% of cover degree). In terms of number of cells, the control group had 1.7 times higher number of cells than the experimental group, proving that C. demersum has the ability to inhibit the growth of harmful cyanobacteria.

Synergistic Removal of Humic Acid in Water by Coupling Adsorption and Photocatalytic Degradation Using TiO2/Coconut Shell Powder Composite

The feasibility of applying nanoscale TiO2/coconut shell powder TCNSP composite to remove HA in aqueous solution was evaluated, and the optimization of the photocatalytic systems using newly developed TCNSP composite was performed. The developed TCNSP composite has high specific surface area i.e., 454u2009m2/g and great porosity i.e., 66.9% with pore size of less than 5u2009μm. High removal efficiencies ≥95% of HA were observed due to the significant synergistic effects by coupling adsorption and photocatalytic reaction of TCNSP composite. As the initial concentration of HA increased, the degradation rate Kapp decreased due to HA sorption saturation to the surface of TCNSP composite and the photon interception by HA molecules in aqueous solution. Since the increased loading amount of TCNSP composite enhanced the number of active sites, Kapp values increased until the optimum loading amount of TCNSP composite. As pH values increased, HA removal efficiency decreased due to increasing electrostatic repulsion between HA and TCNSP composite. Based on the response surface methodology, higher HA removal efficiencies were obtained with acidic condition, longer reaction time, and appropriated loading amount of TCNSP. Further pilot-scale study is in progress using TCNSP composite combined with UVC to remove HA from large amounts of surface water i.e., 200u2009m3/d.

An Experimental Approach to Secure Freshwater Fish Shelter according to the Water Level Fluctuations in a Shallow Pond

Physical disturbance, which induces a lack of flow rate, frequently occurs in freshwater ecosystem. Due to this, it is required to provide a new fish shelter to resolve. We installed a pilot scale test-bed to scrutinize the relationship between water level and the influence of fish shelter. The proposed ADP (artificial deep pool) is a fish shelter which composed of concrete materials. From the monitoring results in test-bed, it was observed that the population of fish was the highest at the 0.5 m in depth from the water level of experimental pond. But it was more appropriate for shallow water level (<0.3 m) to conserve the total number of fish by increasing the number per unit area despite of lower inner temperature and DO than outer environment. Therefore, inner of ADP was more efficient lentic system for fish to live due to higher WCS, OS, SS, and TS. In addition, there was a relative abundance of WCS fish species such as Acheilognathus koreensis (A. koreensis), Carassius carassius (C. carassius). Considered these results, it is suggested that ADP is appropriate to use for fish shelter and habitat for the fishes in lentic ecosystem.

Evaluation on Removal Efficiency of Methylene Blue Using Nano-ZnO/Laponite/PVA Photocatalyzed Adsorption Ball

In order to overcome drawbacks (i.e., filtration and recovery) of conventional powder type photocatalysts, nano-ZnO/Laponite/PVA (ZLP) photocatalyzed adsorption balls were developed by using in situ mixing of nanoscale ZnO as a photocatalyst, and Laponite as both adsorbent and supporting media in deionized water, followed by the poly vinyl alcohol polymerization with boric acid. The optimum mixing ratio of nano-ZnO:Laponite:PVA:deionized water was found to be 3:1:1:16 (by weight), and the mesh and film produced by PVA polymerization with boric acid might inhibit both swelling of Laponite and detachment of nanoscale ZnO from ZLP balls. Drying ZLP balls with microwave (600 watt) was found to produce ZLP balls with stable structure in water, and various sizes (55~500 ) of pore were found to be distributed based on SEM and TEM results. In the initial period of reaction (i. e., 40 min), adsorption through ionic interaction between methylene blue and Laponite was the main removal mechanism. After the saturation of methylene blue to available adsorption sites for Laponite, the photocatalytic degradation of methylene blue occurred. The effective removal of methylene blue was attributed to adsorption and photocatalytic degradation. Based on the results from this study, synthesized ZLP photocatalyzed adsorption balls were expected to remove recalcitrant organic compounds effectively through both adsorption and photocatalytic degradation, and the risks of environmental receptors caused by detachment of nanoscale photocatalysts can be reduced.

Field Application of Waterworks Automatic Meter Reading and Analysis of Household Water Use

After the construction of waterworks automatic meter reading with 15 mm diameter digital water mater with magnetoresistance sensor developed in this study at 96 households of apartment complexes located in Incheon-City B-Gu S-Dong, the feasibility of field application of waterworks automatic meter reading was evaluated. The field application of waterworks automatic meter reading was performed from July to December in 2011, and average reception rate was as low as 84.6% due to the instable wibro networks, the existence of communication blackout and temporary malfunction of router. After the extraction of 10 households with one to five residents out of 96 households by using stratified random sampling method and analysis of domestic water use, it was found that domestic water use was significant at August and showed a decreasing trend at September, followed by increase in domestic water use at November and decrease in domestic water use at December. This phenomenon should be attributed to weather factors (temperature, humidity, etc.), which significantly affected domestic water use. Similar trend in domestic water use in terms of weather factors was obtained in case of Liter per capita day of water use after the extraction of 30 households out of 96 households by using stratified random sampling method. After analysis of Liter per capita day for 96 households, single residents increases resulted in reduction of domestic water usage by about 14% of Liter per capita day. These results might be due to the fact that domestic water usage such as laundry, beverages, catering, cleaning, etc. should be required for even the household with one resident, whereas domestic water usage for those common utilization can be significantly saved for the household with more than one resident.