The precipitation reaction between the orthophosphate and Fe2+ ions was studied to describe the optimum condition for the removal of orthophosphate from the aqueous solution. The effects of pH, Fe:P molar ratio, and alkalinity were evaluated for the initial orthophosphate concentrations in the range from 1.55 to 31.00 mg/L - PO4(3-) -P. The optimum pH was found to be 8.0 in all orthophosphate concentration ranges. When the stoichiometric moles of Fe2+ were added, the removal efficiencies were significantly less than the theoretical values. It is likely that the precipitation of Fe(OH)2(s) is partially formed. For the initial orthophosphate concentration of 3.10 mg/L PO4(3-) -P or greater, the removal efficiencies with the Fe:P molar ratio of 3.0:1.0 approached to the theoretical values, yielding greater than 98.5%. If the molar ratio of Fe:P was great enough, the precipitation reaction was completed within 1 h. As the alkalinity increases, the experimental removal efficiencies were significantly greater than the theoretical values. This is because the formation of vivianite is favoured over FeCO3(s). Finally, it was demonstrated that the orthophosphate (1.40-6.80 mg/L PO4(3-) -P) in the secondary effluents from wastewater treatment plants was effectively removed by dosing sufficient amount of Fe2+ ions.

Abstract-A composite adsorbent was synthesized by immobilizing ferric oxide or three different iron oxides into alginate beads (HFOAB) for the removal of arsenate [As(V)] and heavy metals from aqueous phase. Sorption studies were conducted on single and binary sorbate systems, and the effects of contact time, initial adsorbate concentration, and pH on adsorption performance of HFOAB were monitored. The sorption process for As(V) and Cu(II) reached an equilibrium state within 240 h and 24 h. The maximum sorption capacity of As(V) was 13.8 mg g -1 after 168 h. The effect of arsenic species on Cu(II) sorption was insignificant. The adsorption of As(III), As(V), and Cu(II) followed pseudo second order kinetics. Kinetic studies showed that adsorption process reached equilibrium within 8 h at an initial concentration of 10 mg/L. Pb(II) and Cd(II) showed a greater sorption capacity on NCBs, which might be due to sorption sites provided by the immobilized GNC. The sorption affinity of divalent metal ions on NCB was in the following order: Pb=Cu=Cd >Zn=Ni> Co>Mn. The study demonstrates that the synthesized sorbent could be useful for the simultaneous removal of both anionic and cationic contaminants from wastewater.Index Terms-Adsorption, alginate beads, hydrous ferric oxide, nano carbon, arsenic, heavy metals.

 Mobile water treatment package system comprises an alternative for stable emergency water supply in response to various situations. This study is aimed at developing technologies to ensure mobility by simplifying process configuration and realizing modularization of various process technologies. Based on the various combinations of unit processes, they were presented according to each treatment process, indicating the possibility of achieving the water quality objectives. Water treatment unit processes were established by setting water quality objectives. Four kinds of water treatment process combinations were proposed based on the classification of water treatment unit process into pre-treatment or primary treatment (filtration using PCF, MF, RO), and posttreatment (filtration process using AC and disinfection process using UV). Each process combination was made to ensure the processing capacity of 30 m 3 /day. In addition, a mobile water treatment package system was manufactured using two 20ft containers compliant with IOS standards for increased mobility. In this study, the removal efficiency and power consumption of each process combination was assessed by installing a mobile water treatment package system. Based on the operation results of the mobile water treatment package system, reviews are being made on advancing the module to maximize performance of the mobile water treatment package system.

The effect of the physical parameters in the reactor (aeration depth, bubble size, and surface area) and the alkalinity of the solution on the ammonia stripping by bubbling were evaluated. When an airflow of 30 L/min was bubbled below the solution surface in the range 6-53 cm, the ammonia removal rate were observed to be the same regardless of the bubbling depths. At pH 10.0 and a temperature of 30℃, the average rate constant and the standard deviation were 0.178 h -1 and 0.004. No appreciable changes in the ammonia removal rate were also observed with varying the bubble size and the air-contacting surface area. Alkalinity of the solution was found to affect the ammonia removal rate indirectly. This is expected because the pH of the solution would vary with dissolution of gaseous CO2 by air bubbling. The real wastewaters from landfill site and domestic wastewater treatment plant were tested. In the case of domestic wastewater (pH = 7.1, alkalinity = 75 mg/L), the ammonia removal rate was poor even with the control of pH to 9.3. The raw landfill leachate (pH = 8.0, alkalinity = 6,525 mg/L), however, showed the appreciable removal rate with increasing pH during aeration. When the initial pH of the leachate was adjusted 9.4, the removal rate was significantly increased without changing the pH during aeration.

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