• KSBB Journal
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• v.23 no.1
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• pp.70-76
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• 2008

Surface of hydrophobic media was modified to become hydrophilic by ion beam irradiation. Fixed bed biofilm reactors packed with or without surface modification were used to remove organics, nitrogen, and phosphorus from sewage. This system composed of anoxic/oxic cycles to increase the nutrient removal. A cylindrical polyethylene was used as a packing media in this study. With 12 hours of hydraulic retention time (HRT), the reactors with and without surface modification showed 95% and 92% $COD_{cr}$ removal, respectively. Both reactors showed over 95% $COD_{cr}$ removals for a longer HRT of 16 hours. Nitrogen removal ranged 54.8% to 70.2% for the surface modified system and 57.5% to 76.5% for the non-modified system under same condition. Finally, phosphorus removal ranged 59.4% to 69.8% for the surface modified system and 51.3% to 63.4% for the non-modified system under same condition. From this study organics and phosphorus were better removed in using surface modified media and vice versa for nitrogen removal.

• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.206-215
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• 2007

The objective of this study was to establish the optimal system operating strategies for nitrogen and phosphorus removal through model simulation system built for advanced wastewater treatment targeting on simultaneous temporal/special phase isolation BNR process. The simulation system was built with unit process modules using object modules in GPS-X code. The system was well verified by field experiment data. Simulation study was carried out to investigate performance response to design and operation parameters, i.e. hydraulic retention time (HRT), solids retention time (SRT), and cycle time. The process operated at HRTs of 10~15 hours, longer SRTs, and cycle time of 2 hours showed optimal removal of nitrogen. The HRTs of 10~15 hours, SRTs of 20~25 days, and longer cycle time was optimal for phosphorus removal. Both simulation and field studies showed that optimal operating strategies satisfying both the best nitrogen and phosphorus removals include HRTs ranged 10~15 hours, SRTs ranged 20~25 days, and cycle times of 4~8 hours. The simulation system with modularization of generalized components in BNR processes was, therefore, believed to be a powerful tool for establishing optimal strategies of advanced wastewater treatment.

• Journal of Korean Society of Water and Wastewater
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• v.11 no.1
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• pp.33-41
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• 1997

An attempt was made to enhance anaerobic treatment efficiency by adopting the anaerobic sequencing batch reactor(ASBR) process at a thermophilic temperature. Operational characteristics of the ASBR process were studied using laboratory scale reactors and concentrated organic wastewater composed of soluble starch and essential nutrients. Effects of fill to react ratio (F/R) were examined in the Phase I experiment, where the equivalent hydraulic retention time(HRT) was maintained at 5 days with the influent COD of 10g/L. A continuous stirred tank reactor(CSTR) was operated in parallel as a reference. Treatment efficiency was higher for the ASBRs because of continuous accumulation of volatile suspended solids(VSS) compared to the CSTR. However, the rate of gas production and organic removal per unit VSS in the ASBRs was much lower than the CSTR. This was caused by reduced methane fermentation due to accumulation of volatile acids(VA), especially for the case of low F/R, during the fill period. When the F/R was high, maximum VA was low and the VA decreased in short period. Consequently, more stable operation was possible with higher F/R. Effects of hydraulic loading rate on the efficiency was studied in the Phase II experiment, where the organic loading rate was elevated to 3333mg/L-d with the F/R of 0.12. Reduction of organic removal along with rapid increase of VA was observed and the stability of reaction was seriously impaired, when the influent COD was doubled. However, operation of the ASBR was quite stable, when the hydraulic loading rate was doubled and a cycle time was adjusted to 12 hour. It is essential to avoid rapid accumulation of VA during the fill period in order to maintain operational stability of the ASBR.

• Membrane and Water Treatment
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• v.11 no.4
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• pp.283-294
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• 2020

This work aims at studying the feasibility of continuous removal of mixed heavy metal ions from simulated zinc plating wastewaters by coupling a microbial fuel cell and a microbial electrolysis cell in batch and continuous modes. The discharging voltage of MFC increased initially from 0.4621 ± 0.0005 V to 0.4864 ± 0.0006 V as the initial concentration of Cr⁶⁺ increased from 10 ppm to 60 ppm. Almost complete removal of Cr⁶⁺ and low removal of Cu²⁺ occurred in MFC of the MFC-MEC-coupled system after 8 hours under the batch mode; removal efficiencies (REs) of Cr⁶⁺ and Cu²⁺ were 99.76% and 30.49%. After the same reaction time, REs of nickel and zinc ions were 55.15% and 76.21% in its MEC. Cu²⁺, Ni²⁺, and Zn²⁺ removal efficiencies of 54.98%, 30.63%, 55.04%, and 75.35% were achieved in the effluent within optimum HRT of 2 hours under the continuous mode. The incomplete removal of Cu²⁺, Ni²⁺ and Zn²⁺ ions in the effluent was due to the fact that the Cr⁶⁺ was almost completely consumed at the end of MFC reaction. After HRT of 12 hours, at the different sampling locations, Cr⁶⁺ and Cu²⁺ removal efficiencies in the cathodic chamber of MFC were 89.95% and 34.69%, respectively. 94.58%, 33.95%, 56.57%, and 75.76% were achieved for Cr⁶⁺, Cu²⁺, Ni²⁺ and Zn²⁺ in the cathodic chamber of MEC. It can be concluded that those metal ions can be removed completely by repeatedly passing high concentration of Cr⁶⁺ through the cathode chamber of MFC of the MFC-MEC-coupled system.

• Journal of Biosystems Engineering
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• v.37 no.5
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• pp.302-313
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• 2012

Purpose: The biogas productivity potential of fish waste (FW) was evaluated. Methods: Batch trials were carried out in 1.3 L glass digesters kept in a temperature controlled chambers at $36.5^{\circ}C$. The first order kinetic model and the modified Gompertz model were evaluated for biogas production. The Chen and Hashimoto model was used to determine the critical hydraulic retention time (HRT $_{Critical}$) for FW under mesophilic conditions. The feasibility of co-digestion of FW with animal manure was studied. Results: The biogas and methane potential of FW was found to be 757 and 554 mL/g VS, respectively. The methane content in the biogas produced from FW was found to be 73% and VS removal was found to be 77%. There was smaller difference between measured and predicted biogas production when using the modified Gompertz model (16.5%) than using first order kinetic model (31%). The time period for 80%-90% of biogas production ($T_{80-90}$) from FW was calculated to be 50.3-53.5 days. Similarly, the HRT $_{Critical}$ for FW was calculated to be 13 days under mesophilic conditions. The methane production from swine manure (SM) and cow manure (CM) digesters could be enhanced by 13%-115% and 17%-152% by mixing 10%-90% of FW with SM and CM, respectively. Conclusions: The FW was found to be highly potential substrate for anaerobic digestion for biogas production. The modified Gompertz model could be more appropriate in describing anaerobic digestion process of FW. It could be promising for co-digestion of FW with animal manure.

• Geomechanics and Engineering
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• v.1 no.4
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• pp.291-306
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• 2009

One-dimensional soil-column studies were carried out to understand the interaction of three industrial effluents namely amino acid ('highly acidic'), surfactant ('highly organic') and pharmaceutical ('organic and toxic') on the physicochemical behavior, index properties and shear strength of bentonite due to artificial contamination extending to nearly 300 days. Changes in inorganic and organic pollutants present in the effluents due to the interaction of the above effluents and soil were assessed to understand the physico-chemical behaviour. Batch and continuous modes of operation, 8 hrs and 16 hrs Hydraulic Retention Time [HRT] and 25%, 50% concentrations of effluents, were the parameters considered. Amino acid, surfactant and pharmaceutical effluents have shown a high variation in pH (7 to 8) after artificial contamination on bentonite that is their original characteristics of the above effluents have been completely reversed. Further, it is found that the shear strength of bentonite has reduced by about 20%, and with respect to liquid limit and plastic limit shows an increasing trend with time within the period of contamination.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.4
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• pp.31-44
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• 1985

The application of anaerobic attached microbial films in the expanded bed process has recently been examined at high temperatures ($55^{\circ}C$) and with particulate matter. Extrapolation of the kinetics suggested that waste activated sludge (WAS) could be efficiently digested at hydraulic retention times as short as six hours in the expanded bed process. This would represent a 99 percent digester reactor volume reduction and would introduce interesting solids management alternatives if such a high rate process were developed. This paper presents a summary of a 1.5 year study of the feasibility of such a process. Three continuously fed $55^{\circ}C$ laboratory reactor systems were used to define the kinetics and the site of reactions-control completely mixed reactors were compared to the expanded beds (AAFEB) with and without a hydrolysis unit preceding the attached film unit. Well defined laboratory-generated WAS was compared to actual WAS from a domestic sewage treatment facility. Sixty percent of the biodegradable organics were converted in an AAFEB at a 15-hour hydraulic retention time without hydrolysis, whereas greater than 95 perccent of the biodegradable organics were stabilized in a two-stage system consisting of a 3-day HRT hydrolysis reactor followed by a 15-hour HRT AAFEB. The limitations of this high rate process and its potential application are discussed.

• Korean Journal of Environmental Agriculture
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• v.20 no.3
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• pp.143-149
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• 2001

A contact oxidation canal system with sedimentation basin was installed to study the efficiency of water quality purification. The primary sedimentation basin with 60 min of HRT (Hydraulic Retention Time) included in the system was aimed to sediment pollutants in the water and the deposit being released by the drainage culvert located at the bottom of the system. The oxidation canal aerated by nozzle was to contact the pollutants and oxygen in the surface of plastic filter to purify the water. Discharge, HRT, length of the oxidation canal were $200\;m^3/day$, 90 min, 20 m, respectively. The treatment efficiency of total nitrogen was lower compared with other water quality items such as SS, BOD, TP because the anoxic condition for denitrification was not ensured after the oxidation canal. However, $25%{\sim}89.6%$ of SS, $75.0%{\sim}91.5%$ of BOD, $44.3%{\sim}95.3%$ of TP were removed in this system. Overall, the results indicates that this system appears to have a potential capability for water quality improvement of the reservoirs or the canals in the agricultural watershed.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.9
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• pp.935-939
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• 2006

The biological nutrient removal from domestic wastewater with low C/N ratio is difficult. Therefore, this study was performed to examine effect of operational parameters such as air supply, hydraulic retention time, pH on the nitrogen removal by ammonia stripping and to increase influent C/N ratio without required carbon source. The ammonia stripping system used for the bench-scale experiment in laboratory had a dimension of 15 cm diameter and 150 cm height. The ammonia stripping reactors were classified into two types, type AS I and type AS II, according to there using or not media. Results of the research showed that the T-N removal efficiency of AS I using plastic media is slightly higher than AS II without media. In experimental condition of air supply 30 L/min and pH 12.5, T-N removal efficiencies increased as HRT of ammonia stripping reactor became longer from 8 hr to 36 hr. In experimental condition of HRT 36 hr, it was also found that the T-N removal efficiencies improved through increase of air supply. On the other hand, C/N ratio of wastewater was increased from average 3.9 to 5.4 by ammonia stripping.

• Journal of the Korean GEO-environmental Society
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• v.8 no.6
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• pp.21-28
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• 2007

The objective of this study was to investigate the effect of hydraulic retention time (HRT) on removal efficiencies of organic matter, nitrogen and phosphorus in MBR-RO process for treating synthetic sewage. In MBR process, turbidity was less than average 2 NTU and average removal efficiency showed more than 99% during the operation period(MBR 105 day). As a result of HRT variation, average removal efficiencies of $COD_{Cr}$ on HRT 6, 12, 18 and 24hour were about 72.4, 84, 88.6 and 92.5%, respectively. The $NH_4{^+}-N$ removal efficiency was about 60.2 85.5, 91.3 and 92.2%, respectively. T-N and T-P removal efficiencies increased from 53.7 and 56.8 to 82.5 and 86.4%, respectively as the HRT increased from 6 hour to 24 hour. In RO process, average removal efficiencies of color and $COD_{Cr}$ in RO permeate were about 99.9% and 96.8%, respectively. Also, removal efficiencies of T-N, $NH_4{^+}-N$, $NO_3{^-}-N$ and T-P were all above average 90%.