• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.371-378
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• 1996

A prototype of expert system which can support the operation for the municipal waste water treatment plant located at Kyoung-Ki Do, Kwang-ju Kun was developed and tested. This system provides (i) tracking the cause of the problem, (ii) analysis, and (iii) solution Knowledge-base consists of about 100 production-rules for the biological wastewater process, such as bio-reactor and final clarifier. Rules were obtained from the analysis of the problems such as sludge bulking. The system provides stable process control and management and effectively helps inexperienced operators with advanced and standard technologies. Future works will focus to develop a statistical process control model and associate with expert system. The control model can process the operation data statistically; analyze the relationship between affecting factors and control variables; and provide optimum operation parameters.

• Microbiology and Biotechnology Letters
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• v.9 no.4
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• pp.219-223
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• 1981

Experiments on methane gas digestion were conducted to prevent livestock pollution and develop substitute energy. When about 30(w/w)% of sludge was added to cow feces, pig feces, and poultry feces and digested at 37$^{\circ}C$ for 20 days, methane gas produced per Kg of organic matter for cow feces, pig feces, poultry feces was 131, 248 and 235 l, respectively. pH decreased slightly at first but increased gradually afterwards during digestion period. When 20, 30, and 40(w/w)% of sludge were added to the mixture of cow feces (300g) and water (200g), the volumes of gas produced were 6.1, 14.5 and 13.4 l, respectively. Volume of methane gas produced from the mixture of cow feces and saw dust was much more than that from the mixture of cow feces and rice polishings. The contents of N, K, P for digestion residues were sufficient to be utilized as a fertilizer. When methane gas digestion was carried out with cow feces in a submersible pump digester the volume of methane gas produced per Kg of organic matter was 188 l. The price of total methane gas produced at this digestion was similar to that of the electric power consumed.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.91-96
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• 2011

The design, construction and management of underground facilities as infrastructure of nation should be properly carried out. One of reasons for underground facilitie's failure is a non-proper construction of backfill materials. This is common for circular underground pipes. A non-proper compaction is the cause of settlement and decrease of performance of underground facilities. The use of controlled low strength materials is an alternative to reduce the couple of failure problems. The flowability, self-cementation, and non-compaction are the major advantages to use the controlled low strength materials. In this research, couple of recycled materials, such as in-situ soil, water-treatment sludge, and crumb rubbers, were adopted. The basic properties of each materials were determined according to KS or ASTM. Also, couple of laboratory tests were carried out to get the design parameters for geotechnical and roadway area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.4
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• pp.113-125
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• 1984

Water supply has been mainly dependent on the construction of the dams in Korea. It is difficult, however, to continue to construct dams for many reasons, such as the decrease of construction sites, the increase of construction costs, the compensation of residents in flooded areas, and the environmental effects. Water demands have increased and are expected to continue increasing due to the concentration of people in the cities, the rise of the living standard, and rapid industrial growth. It is acutely important to find countermeasures such as development of ground water, desalination, and recycling of waste water to cope with increasing water demands. Recycling waste water includes all means of supplying non-potable water for their respective usages with proper water quality which is not the same quality as potable water. The usages of the recycled water include toilet flushing, air conditioning, car washing, yard watering, road cleaning, park sprinkling, and fire fighting, etc. Raw water for recycling is obtained from drainage water from buildings, toilets, and cooling towers, treated waste water, polluted rivers, ground water, reinfall, etc. The water quantity must be considered as well as its quality in selecting raw water for the recycling. The types of recycling may be classified roughly into closed recycle systems and open recycle systems, which can be further subdivided into individual recycle systems, regional recycle systems and large scale recycle system. The treatment methods of wastewater combine biochemical and physiochemical methods. The former includes activated sludge treatment, bio-disc treatment, and contact aeration treatment, and the latter contains sedimentation, sand filtration, activated carbon adsorption, ozone treatment, chlorination, and membrane filter. The recycling patterns in other countries were investigated and the effects of the recycling were divided into direct and indirect effects. The problems of water reuse in recycle patterns were also studied. The problems include technological, sanitary, and operational problems as well as cost and legislative ones. The duties of installation and administrative organization, structural standards for reuse of water, maintenance and financial disposal were also studied.

• Journal of Korean Society on Water Environment
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• v.29 no.4
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• pp.559-567
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• 2013

In recent years, NF (nanofiltration) membrane has been receiving great attention for hardness removal and has begun to replace traditional lime soda ash softening process, particularly in Florida, USA, mainly due to less sludge production and easy operation. This study aimed to provide detailed surface characteristics of various commercial NF membranes by performing sophisticated surface analysis, which would help more fundamentally understand the performance of NF membranes. More specifically, a total of 7 NF membranes from top NF/RO manufacturers in the world were examined for basic performance tests, surface analysis, and fouling potential assessment. The results demonstrated that NF membranes are classified into two groups in terms of surface zeta potential; they are highly negatively charged ones, and neutral and/or less negatively charged ones. Their hydrophobicities, measured by contact angle, varied from hydrophilic to slightly hydrophobic ones. The AFM measurements showed various surface roughness, ranging from 23 nm (smooth) to 162 nm (rough) of average peak height. Lab-scale fouling experiments were performed using feedwater obtained from conventional water treatment plants in the province of Korea, and their results attempted to correlate to surface characteristics of NF membranes. However, unlike typical RO membranes, no clear correlation was found in this study, indicating that fouling mechanisms of NF membrane may be different from those of typical RO membranes, and both cake deposition and pore blocking mechanisms should be considered simultaneously.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.916-921
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• 2009

This study was aimed to both enhance the fluoride removal and to reduce the phosphorus removal in treating semiconductor wastewater using $Ca(OH)_2$ at low pH so as to facilitate struvite crystallization reaction. The struvite crystallization could be introduced after fluoride removal by retaining the phosphorus source. As the results, the method applied in this study achieved high fluoride removal efficiency (about 91%) with retardation of phosphorus removal at pH 4, compared to conventional methods where the removal of fluoride and phosphorus were done at pH 11. Therefore, the fluoride removal at low pH would contribute to the enhancement of nitrogen and phosphorus removals in a consecutive struvite crystallization reactor. Treatment of semiconductor wastewater at low pH using $Ca(OH)_2$ also had lower (about 20%) water content of precipitated sludge compared to conventional method. As the molar ratio of Ca to F increased the removal efficiencies of fluoride and phosphorus increased. Although the amount of seed dosage didn't affect the removal of fluoride and phosphorus, its increase reduced the water content of precipitated matter. Finally, considering consecutive struvite reaction, the optimum condition for the removal of fluoride and phosphorus was as follow: pH: 4, the molar ratio of Ca:F: 1:1.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.69-79
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• 2017

Protected area of water for supply source is located mostly of rural area in Korea. Normally, sewage treatment system is poor to manage in rural, because low population and density. Rural area need sewage treatment system to supervise supply source of water. In this study, analysis on operation result of 4 RCSTP and MWTP is located at the rural area. Higher concentration of pollutant were inflows to MWTP than RCSTP, and effluent quality standard is satisfaction. However, RCSTP effluent pollutant concentrations was researched higher than MWTP. The organic matter(BOD, COD) were about 5% of a high treatment efficiency to a median. The nutrient(T-N, T-P) were detected Up to high 30%. Also, we analyzed to effect reactor operational parameters on the pollutant treatment efficiency like mixed liquer suspended solid(MLSS), dissolved oxygen(DO) and sludge retention time(SRT). As a result, pollutant treatment efficiency showed fluctuation in accordance with operating condition. Thus, it is necessary to manage the reactor operation condition for management of rural area sewage treatment.

• Economic and Environmental Geology
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• v.53 no.6
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• pp.667-675
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• 2020

An Alum-sludge based adsorbent (ASBA) was synthesized by the hydrothermal treatment of alum sludge obtained from settling basin in water treatment plant. ASBA was applied to remove fluoride and arsenic in artificially-contaminated aqueous solutions and mine drainage. The mineralogical crystal structure, composition, and specific surface area of ASBA were identified. The result revealed that ASBA has irregular pores and a specific surface area of 87.25 ㎡ g-1 on its surface, which is advantageous for quick and facile adsorption. The main mineral components of the adsorbent were found to be quartz(SiO2), montmorillonite((Al,Mg)2Si4O10(OH)2·4H2O) and albite(NaAlSi3O8). The effects of pH, reaction time, initial concentration, and temperature on removal of fluoride and arsenic were examined. The results of the experiments showed that, the adsorbed amount of fluoride and arsenic gradually decreased with increasing pH. Based on the results of kinetic and isotherm experiments, the maximum adsorption capacity of fluoride and arsenic were 7.6 and 5.6 mg g-1, respectively. Developed models of fluoride and arsenic were suitable for the Langmuir and Freundlich models. Moreover, As for fluoride and arsenic, the increase rate of adsorption concentration decreased after 8 and 12 hr, respectively, after the start of the reaction. Also, the thermodynamic data showed that the amount of fluoride and arsenic adsorbed onto ASBA increased with increasing temperature from 25℃ to 35℃, indicating that the adsorption was endothermic and non-spontaneous reaction. As a result of regeneration experiments, ASBA can be regenerated by 1N of NaOH. In the actual mine drainage experiment, it was found that it has relatively high removal rates of 77% and 69%. The experimental results show ASBA is effective as an adsorbent for removal fluoride and arsenic from mine drainage, which has a small flow rate and acid/neutral pH environment.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.3
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• pp.331-339
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• 2007

The purpose of this study was to investigate the biodegradability and performance of organic removal and methane production rate when treating piggery wastewater using a pilot scale two-phase anaerobic system operated up to a volumetric rate of $10m^3/day$. The pilot scale two-phase anaerobic process is consisted of a continuous-flow stirred-tank reactor (CFSTR) for the acidification phase and an Upflow Anaerobic Sludge Blanket reactor (UASB) for the methanogenesis. The acidogenic reactor played key roles in reducing the periodically applied shock-loading and in the acidification of the influent organics. The acidogenic CFSTR was operated at organic loading rates (OLR) between 1.8 and $14.4kgCOD/m^3{\cdot}day$, and the UASB reactor was operated between 0.5 and $5.6kgCOD/m^3{\cdot}day$. A stable maximum biogas production rate was $81m^3/day$ and the methane conversion rate of the organic matter varied from 0.30 to $0.42L\;CH_4/g\;COD_{removed}$(0.40) at hydraulic retention time (HRT) above 3.5days. The methane contents ranged from 73 to 82% during the experimental period. It is known that most of the removed organic matter was converted to methane gas, and the produced biogas might be high quality for its subsequent use.

• Journal of Korean Society on Water Environment
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• v.24 no.3
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• pp.273-279
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• 2008

Space separation method that use independent reactor for nitrification and other reactor for denitrification has been commonly used for biological nitrogen removal process like $A^2O$ process. However, this method needs large space and complicate pipelines and time separation method such as SBR process have a difficulty in continuous treatment. Thus biological nitrogen removal process which is capable of continuous treatment, easy opeation and space saving is urgently required. In this research, submerged moving media was used for a biofilm process and suspended sludge was used for biological nitrogen removal at the same time. In particular DO environment by controlling air flow rate was investigated for simultaneous nitrification/denitrification. Total nitrogen removal in aeration rate more than $67L/min{\cdot}m^3$ showed 51~53% and rose to 65%, 70% and 78% in $50L/min{\cdot}m^3$, $58L/min{\cdot}m^3$ and $25L/min{\cdot}m^3$ respectively. Total phosphorus removal was very low about 10~20% more than $67L/min{\cdot}m^3$ aeration rates. But total phosphorus removal roses when reduces aeration rate by $58L/min{\cdot}m^3$ low and it showed total phosphorus removal of 72% in aeration rate $25L/min{\cdot}m^3$.