• Journal of Environmental Health Sciences
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• v.32 no.5 s.92
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• pp.469-477
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• 2006

When denitrification was connected with a single stream process by using biofilter and sulfur-limestone, it was found that such connection enabled highly efficient nitrification without special unit operation of microorganisms or injection of external carbon sources which is being shown in general biological treatment processes. It was observed that in the trickling filter bed, decomposition of organic substances and highly efficient nitrification by both the forced pressure feed trickling and the air fan were simultaneously done. In the denitrification tank where sulfur-limestone was mixed at a certain ratio, limestone was used by autotrophic microorganisms as a source of supply for alkalinity, and nitrate $NO_{3}^{-}$-N was denitrified into nitrogen gas. And in the sulfur-limestone autotrophic denitrification, $NO_{3}^{-}-N\;or\;NO_{2}^{-}-N$ was denitrified as a sulfur compound in reduction state was oxidized into a final output of $SO_{4}^{-2}$. The mean concentration of the discharge water was 8.6 mg/l for T-N and 0.8 mg/l for T-P, respectively, and their mean treatment efficiency was 79.2% and 80.8%, respectively. Implementing highly efficient denitrification without injection of an external organic carbon source or internal return, it is concluded that the proposed process is suitable for a sewerage in a small village with the merits of low power consumption and easy maintenance.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.6
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• pp.720-727
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• 2005

This study was performed to advance nitrogen removal efficiency by employing an single biofilter packed with granular sulfur, which consists of nitrification occurring at upper part and denitrification at lower part of the reactor. Continuos nitrification/denitrification was carried out with different alkalinity sources, which were $NaHCO_3$ and $CaCO_3$(limestone). In the downflow nitrification/denitrification biofilter packed with granular sulfur, first, terms for nitrogen removal was decided. As results, nitrification and denitrification rate with NaHCO3 at 0.85 kg $NH_4^+-N/m^3{\cdot}d$ were accomplished $0.80kg\;N/m_3{\cdot}d$, $0.43kg\;N/m^3{\cdot}d$, respectively. In the sulfur/limestone packed downflow nitrification/denitrification biofilter, sulfur and limestone were mixed packed, preliminary test showed sulfur/limestone mixing ratio was 3:1 and that was ideal. In the result, nitrification and denitrification rate at $0.7kg\;NH_4^+-N/m^3{\cdot}d$ were accomplished$0.65kg\;N/m^3{\cdot}d$, $0.34kg\;N/m^3{\cdot}d$, respectively. In general, employing granular sulfur can be implemented for only denitrification, but this system can accomplish nitrification as well as denitrification in a single reactor even though low carbon concentration was present in influent limiting to nutrient removal process. This biofilter system of limestone and granular sulfur packed together can successfully apply for nutrient removal effectively.

• Journal of Environmental Science International
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• v.11 no.10
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• pp.1089-1096
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• 2002

The objectives of this study were to investigate the desulfurization kinetics of paper sludge and limestone in a fluidized bed reactor according to bed temperature and air velocity. The experimental results were presented as follows ; First, the bed temperature had a great influence on the desulfurization efficiency of limestone and paper sludge. In paper sludge, the optimum condition in desulfurization temperature was at 80$0^{\circ}C$ and in limestone, that was at 850 $^{\circ}C$ or 900 $^{\circ}C$ Second, as air velocity increased, the desulfurization efficiency(or the absorbed amount of sulfur dioxide) by limestone and paper sludge decreased. And the absorbed amount of sulfur dioxide by paper sludge was larger than that of by limestone. Third, as the velocity increased and the optimum desulfurization temperature became, ks and the removal efficiency increased. So, ks, kd highly depended on the air velocity and bed temperature.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.2
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• pp.75-86
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• 2007

This process which has a connection of biofilter and sulfur-limestone has been developed to treat organic substances including BOD, COD and SS etc. and to treat sulfur-limestone is for denitrification.. The whole process consists of chemical reaction tank, sedimentation tank, trickling filter, denitrification tank The trickling filter is equipped with a reactor filled with absorptive filter, and the sulfur denitrification tank is filled with sulfur-limestone mixed media. After setting up practical facilities whose capacity is 60 tons a day, we have observed the removal efficiencies of pollutants through 60 experiments during Summer and Winter seasons. The average concentration of polluted water was BOD for 3.6 mg/L, $COD_{Mn}$ for 11.3 mg/L, SS for 2.8 mg/L, T-N for 8.6 mg/L, and T-P for 0.8 mg/L, and the rate of treatment efficiencies 96.5%, 84.7%, 96.5%, 79.2%, and 80.8%, respectively was found through the experiments. The average treatment efficiency for BOD and $COD_{Mn}$ was 85.0% and 55.7%, respectively and the average removal efficiency for NH4+-N was 84.9% in the trickling filter. The removal efficiency in the denitrification tank is as follows; The removal rate of $NO_3^--N$ was as high as 93.2% within the compass of pH 6.3 to 7.3 through $16.8{\sim}37.0mg/L$ flown into $NO_3^--N$ and $0.1{\sim}8.3mg/L$ outflown. It had observed that this process has implemented highly efficient and advanced treatment without external carbon sources and internal recycle during its process. In conclusion, this process is suitable for a sewerage in a small village due to the merits of low power consumption and easy maintenance.

• Journal of Korean Society of Water and Wastewater
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• v.14 no.3
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• pp.271-280
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• 2000

This study was conducted to determine the applicable loading rate and to evaluate the possibility of using limestones as an alkalinity source for the removal of ${NO_3}^{-}-N$ remaining after denitrification/nitrification process with the down-flow sulfur packed bed reactor(SPBR). The pretreated sewage was fed to SPBR. Three SPBRs were filled with elemental sulfur particles and limestones and the volumetric ratios of sulfur to limestone were 0%, 12.5% and 25% for R-0%, R-12.5% and R-25%, respectively. The applicable loading rate was evaluated increasing flow rate with influent ${NO_3}^{-}-N$ concentration of 20 mg/L. For R-0% with external alkalinity supply, denitrification efficiency was greater than 96% up to loading rate of $354.8g\;{NO_3}^{-}-N/m^3{\cdot}day$, and corresponding EBCT was 1.4hr. For R-12.5% and R-25%, where alkalinity was supplied by the limestone filled in the reactor, denitrification efficiency was greater than 94% up to loading rate of $283.8g\;{NO_3}^{-}-N/m^3{\cdot}day$, and corresponding EBCT was 1.7hr. The slightly better performance of R-12.5 compared to R-25 suggests that the volumetric sulfur to limestone ratio of 12.5% was enough for the supply of alkalinity required for sulfur-utilizing denitrification. DO was appeared not showing inhibitory effect on sulfur-utilizing denitrification. The clogging of SPBR caused by the produced gas can effectively be eliminated by regular introduction of treated water in up-flow mode.

• Journal of Environmental Science International
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• v.4 no.1
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• pp.41-52
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• 1995

The effects of reaction temperature, SO2 and CO2 concentration in an air gas stream, particle sizes of limestone on the reactivity and capacity of SO2 removal have been determined in a thermogravimetric analyser(TGA). The apparent reaction order of sulfation reaction of pre-calcined lime(CaO) with respect to SO2 is found to be close to unity. The apparent activation energies are found to be 17,000 kcal/kmol for sulfation of pre-calcined lime and 19,500 kcal/kmol for direct sulfation of limestone(CaCO3). The initial sulfation reaction rate of pre-calcined lime increases with increasing temperature, whereas the sulfur capture capacity exhibits a maximum value at 90$0^{\circ}C$. In direct sulfation of limestone, sulfation reactivity and sulfur capature capacity of sorbent increase with increasing temperature and decreasing CO2 concentration in a gas bulk stream. The main pare of pre-calcined lime is shifted to the larger pore sizes and pore volume decreases with increasing sulfation time and temperature. The surface area of lime decreases with increasing calcination temperature under an air atmosphere, whereas is yearly constant under a CO2(5, 10%) atmosphere in a gas stream.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.46-52
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• 2007

As flue gas desulfurization (FGD) wastewater contains high concentrations of nitrate and is very low in organic carbon, the feasibility of nitrate removal by autotrophic denitrification using Thiobacillus denitrificans was studied. This autotrophic bacteria oxidizes elemental sulfur to sulfate while reducing nitrate to elemental nitrogen gas, thereby eliminating the need for addition of organic compounds such as methanol. Owing to the unusually high concentrations of dissolved salts $(Ca^{2+},\;Mg^{2+},\;Na^+,\;K^+,\;B^+,\;SO_4^{2-},\;Cl^-,\;F^-,)$ in the FGD wastewater, extensive laboratory-scale and pilot-scale tests were carried out in sulfur-limestone reactors (1) to determine the effect of salinity on autotrophic denitrification, (2) to evaluate the use of limestone for pH control and as source of inorganic carbon for microbial growth, and, (3) to find the optimum environmental and operational conditions for autotrophic denitrification of FGD wastewater. The experimental results demonstrated that (1) autotrophic denitrification is not inhibited up to 1.8 mol total dissolved salt content; (2) inorganic carbon and inorganic phosphorus must be present in sufficiently high concentrations; (3) limestone can supply effective buffering capacity and inorganic carbon; (4) the high calcium concentration may interfere with pH control, phosphorus solubility and limestone dissolution, hence requiring pretreatment of the FGD wastewater; and, 5) under optimum conditions, complete autotrophic denitrification of FGD wastewater was obtained in a sulfur-limestone packed bed reactor with a sulfur:limestone volume ratio of 2:1 for volumetric loading rates up to 400g $NO_{3^-}N/m^3.d$. The interesting interactions between autotrophic denitrification, pH, alkalinity, and the unusually high calcium and boron content of the FGD wastewater are highlighted. The engineering significance of the results is discussed.

• Journal of Surface Science and Engineering
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• v.26 no.5
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• pp.255-262
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• 1993

Major parameters determining the extent of Ca utilization were investigated for their calcination/sulfation behavior of limestone in the AFBC(Atmospheric Fluidized Bed Combustion) environments. Three different particle sizes of Fredonia limestone were investigated in the lab-scale tubular reactor. The results of the calcination codnversion of limestone imply that thesd decomposition rate of CaCO3 into CaO is dependent on the amount of heat which limestone absorbed. Hg porosimeter measurement of calcined limestone illustrated that surface area and pore volume are increased with decreasing particle size. Raw Fredonia limestone and sequentially as well as simultaneously calcined/sulfated limestones were also examined using SEM. The SEM Studied showed that the surface of the calcined limestone particles is more diffusive nature than that of the parent calcite. However, the sulfur distribution pattern of simultaneously-treated particles and that of the se-quentially-treated one shows no difference.

• Journal of Environmental Science International
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• v.7 no.6
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• pp.783-791
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• 1998

The objectives of this study were to investigate the characteristics of desulfurization under different experimental conditions and the effects of desulfurization bed fluidized bed combuster installed with the screen. The experimental results were as follows ; First, as the height of fluidized bed combustor becomes higher, the concentrations of $SO_2$ mainly increased and sulfur retion of paper sludge was higher than that of natural limestone. Second, the desulfurzation by natural limestone occurred at in-bed and the desulfurization by paper sludge occurred in the whole of fluidized bed combuster. In addition, we identified calcium sulfate by the analysis of SEM and XRD. Third, screen at splash region increased sulfur retention 2~5%, air velocity and anthracite fraction had a little effect on the sulfur retention.

• Clean Technology
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• v.3 no.1
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• pp.106-113
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• 1997

The objectives of this study were to investigate the characteristics of limestone calcination and sulfation in a fluidized bed reactor with bed temperature and air velocity. The experimental results were presented as follows ; First, the bed temperature had a great influence on the calcination and the sulphur retention of limestone and paper sludge. In paper sludge, the optimum conditions in calcination and desulfurization temperature was at $800^{\circ}C$ and in natural limestone, that was at $850^{\circ}C$ or $900^{\circ}C$. Second, as air velocity increased, the specific surface area of particles decreased. But the difference of surface area according to air velocity was not too large. The specific surface area of paper sludge was larger than that of natural limestone. Third, as air velocity increased, the absorbed amount of sulfur dioxide decreased. And the absorbed amount of sulfur dioxide by paper sludge was larger than that of by natural limestone. Therefore, we knew that paper sludge was excellent absorbent and bed temperature had a great important variable on the calcination and sulphur retention in a fluidized bed.