• Journal of Korean Society of Environmental Engineers
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• v.36 no.7
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• pp.483-491
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• 2014

In this study, we developed an M-COS (molit coagulant-dosing optimization system), which enables to apply the optimum coagulant dose determined in real time, in order to satisfy the total phosphorus (TP) regulation (0.5 mg/L), and then tested its field applicability. Field tests were conducted at three different periods in 2014 in a pilot plant where the M-COS was installed. Coagulant reduction rate by the M-COS was 10.4%, 15.3%, and 9.0% for each period (average 11.6%), when comparing with a control where coagulants were applied at a constant rate. Total cost for the M-COS or control was estimated by summing up the coagulant cost and sludge treatment cost, and then the resulting cost increase was predicted. Cost reduction rate by the M-COS was 13.8%, 20.0%, and 11.4% for each period (average 15.0%). This study indicates that the M-COS can be an alternative to a conventional system for TP treatment, with a better cost efficiency.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.8
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• pp.839-846
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• 2008

The flocculation characteristics of polyacrylamide base flocculants were estimated to reduce the moisture content of the dehydrated cakes. The dewaterability for sewage sludge was found to have a marked effect depending on the flocculant type, agitating speed and time, kind of dissolution water, etc. The optimal agitating speed and time were 700 rpm and 3 sec, respectively, in this experimental condition. and the dewaterability was proportion to the agitating speed upto 700rpm. When recycle water as the dissolution water was used, the solution viscosity of all kind of flocculants was decreased. However, the change of its viscosity are not proportioned to the dewaterabilities for each flocculant. Flocculation system of combinations of the first and sencond flocculation using single flocculant was investigated. Effects of the ratio of first and second dosage for dual flocculation on the dewaterability were also investigated. The optimum conditions of dual flocculation system are 75% and 50% as first dosages for low and high viscous flocculant for total dosage of common flocculation, respectively. Based on the results, an overall mechanism of dual flocculation system is proposed and it is envisaged that optimization of flocculation processes in this way can result in considerable savings in cost.

• Journal of Environmental Science International
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• v.24 no.11
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• pp.1485-1491
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• 2015

There are two treatment processes that are currently applied to ships are the biological treatment process using the activated sludge and the electrochemical treatment. However, neither of them are able to remove both nitrogen and phosphorus due to their limited ability to remove organic matters, which are main causes of the red tide. This study was conducted to identify the characteristics of nitrogen removal factors from manure wastewater by replacing the final settling tank in SBR (Sequencing Batch Reactor) process and applying immersion type hollow fiber membrane. SBR process is known to have an advantage of the least land requirement in special environment such as in ship and the immersion type hollow fiber membrane is more stable in water quality change. As the result, the average in the cases of DO (Dissolved Oxygen) is 2.9(0. 6~3.9) mg/L which was determined to be the denitrifying microorganism activity in anaerobic conditions. The average in the cases of ORP (Oxidation Reduction Potential) is 98.4~237.3 mV which was determined to be the termination of nitrification since the inflection point was formed on the ORP curve due to decrease in the stirring treatment after the aeration, same as in the cases of DO. Little or no variation in the pH was determined to have positive effect on the nitrification. T-N (Total Nitrigen) removal efficiencies of the finally treated water were 71.4%, 72.3% and 66.5% in relatively average figures, thus was not a distinct prominence. In being applied in ships in the future, the operating conditions and structure improvements are deemed necessary since the MEPC (Marine Environment Protection Committee). 227(64) ship sewage nitrogen is less than the standard of 20 Qi/Qe mg/L or the removal rate of 70%.

• Journal of Dairy Science and Biotechnology
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• v.27 no.1
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• pp.13-18
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• 2009

We confirmed methane production and reduction of pollution during anaerobic digestion of milk waste and analyzed the economic potential of using milk waste as a renewable energy source. The milk waste sludge was obtained from the Pasteur milk factory and processed by anaerobic digestion to produce methane. The methane production from two completely mixed tank reactors with an effective capacity of 6 ${\ell}$, 15 days of hydraulic retention time (HRT), and a mid-temperature of $35^{\circ}C$ averaged 4.11 ${\ell}$/day. The total chemical oxygen demand (TCOD) during production decreased from an initial 31,416 mg/${\ell}$ to 13,500 mg/${\ell}$, showing a maximum TCOD removal efficiency of 60%. When HRT was reduced to 12 days, methane production increased by 44% under a high-temperature condition of $55^{\circ}C$. An economic analysis based on these results was applied to a Korean milk factory of typical size and demonstrated that the installation of an anaerobic digester could provide sufficient economic profit.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.378-384
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• 2019

In the food wastewater treatment facilities, the water quality improvement effect and the greenhouse gas emission amount followed by the change in electricity usage through a change of the aeration tank ventilation system were evaluated. also, the amount of greenhouse gas emission followed by the change in electricity usage through the change of the sludge dewatering, storage, transporting method was also evaluated. The total GHG emission from food wastewater treatment facility improvement were divided into direct emissions from the treatment processes and indirect ones from electricity usage. The water quality improvement effect of wastewater treatment plant was found to be 63.3% for BOD removal rate, 42.0% for COD removal rate, 71.0% for SS removal rate and 39.6% for T-N removal rate. and according to the results of calculating output by applying both direct emissions of greenhouse gas (Scope 1) and the indirect emission (Scope 2) of greenhouse gas followed by changes in power consumption. It was estimated that there was a total of 276.0tCO2eq./yr(7.5%) greenhouse gas reduction effect from 3,668.8tCO2eq./yr before improvement to 3,392.8tCO2eq./yr after improvement. In this result is not due to the effects of water quality improvement of emission source, but because the reduction in electricity use has reduced the amount of greenhouse gas emissions.

• Journal of the Korean Society of Mineral and Energy Resources Engineers
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• v.55 no.6
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• pp.527-537
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• 2018

Column tests of a sulfate reducing bacteria (SRB) bioreactor were conducted to determine the design factors for sulfate-rich mine drainage. Various substrates were applied to the bioreactor, including cow manure and its mixture with a mushroom compost, with rice straw and limestone as subsidiary materials. This procedure provided a removal efficiency of up to 82% of the total sulfur with the mixture of cow manure (70%), mushroom compost (10%) and rice straw (20%), and higher efficiencies were observed after 2 days of retention time. In the downflow condition of the flow direction, oxygen supply and re-oxidation of the sulfates occurred, causing a decrease in sulfate removal efficiency. The addition of an inorganic sludge containing heavy metals, which was intended for production of metal-sulfides in the bioreactor, had a negative effect on the long-term operation owing to arsenic release and toxicity to the SRB. The results thus show that a bioreactor using a mixed substrate with cow manure and operating in the downflow direction could reduce sulfates and total dissolved sulfur content; this process confirms the applicability of the SRB bioreactor to sulfate-rich saline drainage.

• Journal of the Korea Organic Resources Recycling Association
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• v.17 no.2
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• pp.93-100
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• 2009

This research was performed to figure out the optimal mixing ratio of food- to livestock wastewater for the best degradation of organic matter in the anaerobic digestion. The presence of various microorganisms, such as Escherichia coli and Staphylococcus aureus, was also investigated in both wastewater in this process. Enteric bacteria were only found in livestock wastewater, whereas pathogenic bacteria like S. aureus were detected in both wastewater. The optimal mixing ratio of food- to livestock wastewater for the best mineralization was found to fifty to fifty, with reduction ratios of $BOD_5$, CODcr SS as 23.2%, 24.7%, 19.7%, respectively. Hygiene of the digested sludge was also analyzed by counting the number of total colonies and various pathogens. Enterobacteriaceae including E. coli were barely detected in 10 days after reaction. Meanwhile, S. aureus was gradually reduced during reaction, even showing 1,000~5,000 CFU/mL in final days.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.172-172
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• 2011

Anaerobic digestion(AD) has successfully been used for many applications that have conclusively demonstrated its ability to recycle biogenic wastes. AD has been successfully applied in industrial waste water treatment, stabilsation of sewage sludge, landfill management and recycling of biowaste and agricultural wastes as manure, energy crops. During AD, i.e. organic materials are decomposed by anaerobic forming bacteria and fina1ly converted to excellent fertilizer and biogas which is primarily composed of methane(CH4) and carbon dioxide(CO2) with smaller amounts of hydrogen sulfide(H2S) and ammonia(NH3), trace gases such as hydrogen(H2), nitrogen(N2), carbon monoxide(CO), oxygen(O2) and contain dust particles and siloxanes. The production and utilisation of biogas has several environmental advantages such as i)a renewable energy source, ii)reduction the release of methane to the atomsphere, iii)use as a substitute for fossil fuels. In utilisation of biogas, most of biogas produced from small scale plant e.g. farm-scale AD plant are used to provide as energy source for cooking and lighting, in most of the industrialised countries for energy recovery, environmental and safety reasons are used in combined heat and power(CHP) engines or as a supplement to natural. In particular, biogas to use as vehicle fuel or for grid injection there different biogas treatment steps are necessary, it is important to have a high energy content in biogas with biogas purification and upgrading. The energy content of biogas is in direct proportion to the methane content and by removing trace gases and carbon dioxide in the purification and upgrading process the energy content of biogas in increased. The process of purification and upgrading biogas generates new possibilities for its use since it can then replace natural gas, which is used extensively in many countries, However, those technologies add to the costs of biogas production. It is important to have an optimized purification and upgrading process in terms of low energy consumption and high efficiency giving high methane content in the upgraded gas. A number of technologies for purification and upgrading of biogas have been developed to use as a vehicle fuel or grid injection during the passed twenty years, and several technologies exist today and they are continually being improved. The biomethane which is produced from the purification and the upgrading process of biogas has gained increased attention due to rising oil and natural gas prices and increasing targets for renewable fuel quotes in many countries. New plants are continually being built and the number of biomethane plants was around 100 in 2009.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.8
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• pp.922-929
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• 2007

The complete oxidation of ammonia to nitrate is a distinctive two-step process divided into the oxidation of ammonia to nitrite(nitritation) by Nitrosomonas and the oxidation of nitrite to nitrate(nitratation) by Nitrobacter. The nitrogen removal via nitrite accumulation offers several advantages such as saving costs for aeration, saving carbon source and finally reduction of sludge discharge. In this work a suspended bioreactor coupled with membrane filtration(MBR) was used to find the process conditions of nitrite build-up. The MBR enables to reach sufficient nitrifying bacteria in the bioreactor, although the autotrophic bacteria can be easily washed out due to their lower growth rate. The dissolved oxygen concentration $c'_{O2}$ and ammonia concentration $c_{NH3}$ in the reactor were varied and investigated as parameters for nitrite accumulation. As a result the higher ammonia concentration in the reactor is very effective for starting nitrite build-up and the effect was strengthened in combination with lower dissolved oxygen concentration. With lower $c'_{O2}<0.3$ $mgL^{-1}$ $O_2$ and high $c_{NH3}=6.3\sim14.9$ $mgL^{-1}$ $NH_3N$ the 74% of the nitrite accumulation was achieved. Specially, it was found that the nitrite accumulation could occur not only in biofilm reactor as many references showed but also in the membrane bioreactor carried out in this study.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.9
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• pp.948-954
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• 2008

Membrane bioreactor(MBR) processes have been widely applied to wastewater treatment for last decades due to its excellent capability of solid-liquid separation. However, membrane fouling was considered as a limiting factor in wide application of the MBR process. Excess aeration into membrane surface is a common way to control membrane fouling in most MBR. However, the excessively supplied air is easily dissipated in the reactor, which results in consuming energy and thus, it should be modified for effective control of membrane fouling. In this study, cylindrical tube was introduced to MBR in order to use the supplied air effectively. Membrane fibers were immersed into the cylindrical tube. This makes the supplied air non-dissipated in the reactor so that membrane fouling could be controlled economically. Two different air supplying method was employed and compared each other; nozzle and porous diffuser which were located just beneath the membrane module. Transmembrane pressure(TMP) was monitored as a function of airflow rate, flux, and ratio of the tube area and cross-sectioned area of membrane fibers(A$_m$/A$_t$). Flow rate of air and liquid was regulated to obtain slug flow in the cylindrical tube. With the same flow of air supply, nozzle was more effective for controlling membrane fouling than porous diffuser. Accumulation of sludge was observed in the tube with the nozzle, if the air was not suppled sufficiently. Reduction of membrane fouling was dependent upon the ratio, A$_m$/A$_t$. For diffuser, membrane fouling was minimized when A$_m$/A$_t$ was 0.27, but 0.55 for nozzle.