Keum-Yong Kim

Long term operation of pilot-scale biological nutrient removal process in treating municipal wastewater.

The performance of a pilot-scale biological nutrient removal process has been evaluated for 336 days, receiving the real municipal wastewater with a flowrate of 6.8m(3)/d. The process incorporated an intermittent aeration reactor for enhancing the effluent quality, and a nitrification reactor packed with the porous polyurethane foam media for supporting the attached-growth of microorganism responsible for nitrification. The observation shows that the process enabled a relatively stable and high performance in both organics and nutrient removals. When the SRT was maintained at 12 days, COD, nitrogen, and phosphorus removals averaged as high as 89% at a loading rate of 0.42-3.95 kg COD/m(3)d (corresponding to average influent concentration of 304 mg COD/L), 76% at the loading rate of 0.03-0.27 kg N/m(3)d (with 37.1mg TN/L on average), and 95% at the loading rate of 0.01-0.07 kg TP/m(3)d (with 5.4 mg TP/L on average), respectively.

Application of Adsorption Characteristic of Ferrous Iron Waste to Phosphate Removal from Municipal Wastewater

This study proposed the method of phosphate recovery from municipal wastewater by using ferrous iron waste, generated from the mechanical process in the steel industry. In the analysis of XRD, ferrous iron waste was composed of (magnetite), practically with and . It had inverse spinel structure. In order to identify the adsorption characteristic of phosphate on ferrous iron waste, isotherm adsorption test was designed. Experimental results were well analyzed by Freundlich and Langmuir isotherm theories. Empirical constants of all isotherms applied increased with alkalinity in the samples, ranging from 1.2 to 235 . In the regeneration test, empirical constants of Langmuir isotherm, i.e., (maximum adsorption capacity) and b (energy of adsorption) decreased as the frequency of regeneration was increased. Experiment was further performed to evaluate the performance of the treatment scheme of chemical precipitation by ferrous iron waste followed by biological aerated filter (BAF). The overall removal efficiency in the system increased up to 80% and 90% for total phosphate (TP) and soluble phosphate (SP), respectively, and the corresponding effluent concentrations were detected below 2 mg/L and 1 mg/L for TP and SP, respectively. However, short-circuit problem was still unsolved operational consideration in this system. The practical concept applied in this study will give potential benefits in achieving environmentally sound wastewater treatment as well as environmentally compatible waste disposal in terms of closed substance cycle waste management.

Treatment of N, P of Auto-Thermal Thermophilic Aerobic Digestion Filtrate with Struvite Crystallization

Recently, auto-thermal thermophilic aerobic digestion (ATAD) has a great attention for destruction of wasted sludge biomass in wastewater treatment plant. Reduction of sludge concentration has been successfully achieved with pilot scale ATAD and ceramic filtration process in field condition. However, high concentration of COD, total nitrogen (TN) and total phosphorus (TP) was observed in filtrate, which should be treated before recirculation of filtrate to biological wastewater treatment plant. This study was focused on removal of nitrogen and phosphorus contained in the filtrate of ATAD, using struvite crystallization method. The effect of operational and environmental parameters (such as, N, P and Mg ion concentration and molar ratio, pH, reaction time, agitation strength, seed dosage, and reaction temperature) on the treatment of TN and TP with struvite crystallization were evaluated. Magnesium (as MgCl26H2O) and phosphorus (as K2HPO4) ions were, if necessary, added to increase nitrogen removal efficiency by the crystal formation. Average concentration of NH4-N and PO4-P of the filtrate were 1716.5 mg/L and 325.5 mg/L, respectively. Relationship between removal efficiencies of nitrogen and phosphorus and molar ratios of Mg and PO4-P to NH4-N was examined. Crystal formation and nitrogen removal efficiencies were significantly increased as increasing molar ratios of magnesium and phosphorus to nitrogen. As molar ratio of Mg : PO4-P : NH4-N were maintained to 2 : 1 : 1 and 2 : 2 : 1, removal efficiencies of nitrogen and phosphorus were 71.6% and 99.9%, and 93.8% and 98.6%, respectively. However, the effect of reaction time, mixing intensity, seed dose and temperature on the struvite crystallization reaction was not significant, comparing to those of molar ratios. Settled sludge volume after struvite crystallization was observed to be reduced with increase of seed dose and to be increased at high temperature.

Effect of Calcium Sources for the Treatment of Wastewater Containing High Fluoride

As production of LCD increases, it has become necessary to find an economically efficient way of treating LCD wastewater with high concentration of fluoride. This study focuses on the calcium sources : CaCl2, Ca(OH)2 and CaCO3 for the treatment of the LCD wastewater including high concentration of fluoride. Of course considering removal efficiency and economical aspect, study is continued. Then this study have objective giving aid to field. Consequently, each calcium sources removal efficiency was measured in various pH, calcium dosage, reaction time, and mixing intensity. The optimum operational conditions for CaCl2 were found to be pH of 7, calcium dosage of 0.4[Ca] / [F] (mol / mol), 1 hr of operation and 200 rpm of mixing intensity. For Ca(OH)2, they were pH of 7, calcium dosage of 30 mL/L, 1 hr of operation, and 200 rpm of mixing intensity. While CaCO3 had operational conditions of pH of 4, calcium dosage of 30 mL/L, 1 hr operation and 200 rpm of mixing intensity. But it is recommended to use calcium sources according to various field conditions.

Nitrogen Removal Characteristics in DynaFlow Biofilter System Using Sewage Wastewater of Low C/N Ratio

In this study, a 3-stage biological aerated filter (BAF) system was proposed to enhance nitrogen removal in the treatment of low carbon to nitrogen ratio (C/N ratio) municipal wastewater. Laboratory experiments were conducted to evaluate the effects of dynamic-flow at the HRT of 6 h. Results of the long-term operation of 3-stage BAF systems showed that the dynamic-flow enabled the total nitrogen removal (T-N) removal efficiency of the system to be about 7 % higher than that of non-dynamic-flow system in treating domestic wastewater due to the more efficient use of organic substrates. The overall NH4-N removal performance was stable during the operational period due to the unique system configuration where independent nitrification occurred. It was concluded that the 3-stage BAF system proposed in this study provided excellent performance in the removal of nitrogen by employing dynamicflow and three columns functioning as sorption, denitrification and nitrification, respectively.

Phosphorus Removal Characteristic of the Aluminum (III)-loess Composite

In this work, the adsorption characteristic of the composites by adding loess with aluminum (“Al-loess”) and Loess with lanthanum (“La-loess”) which have been developed to effectively remove phosphorus, the substance which causes the eutrophic lake has been evaluated. According to the result of the work, as the amount of aluminum or lanthanum put in 1g of loess increases, the combined amount also increases accordingly. When the loess with no aluminum or lanthanum attached was used, the rate of removing phosphorus was different in comparison with the case of using the composites of 0.5, 1 and 2 mg of aluminum and 0.5, 1 and 3 mg of lanthanum in each gram of loess. It was observed the amount required to remove 1 mg PO4-P/L of phosphorus completely is approximately 2 to 10 times less for the composite of Al-loess than loess alone. Also, in case of the composite of La-loess, the amount was decreased by about 1.5 to 10 times. In order to observe the rate of adsorption phosphorus with Al-loess and La-loess, the composites were used for the observation up to three times by water washing. As a result, the water washing of the composite did not affect phosphorus removal. According to the effect of pH, there is a high rate of removing phosphorus in the pH range of 5~8. It seems that the developed composite will effectively remove phosphorus when it is spread in the natural water system. Also, since Al-loess and La-loess composites are rapidly precipitated within 30 minutes, it is stabilized quickly at the bottom of the eutrophic lake and becomes responsible for the removal of phosphorus in water and eluted from the water and the sedimentary layer.