• Journal of Korean Society of Water and Wastewater
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• v.27 no.6
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• pp.779-785
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• 2013

This study investigated the applicability of a two step microfiltration(MF) and reverse osmosis(RO) membrane system for reuse of tunnel wastewater. In this two step process, the MF system first treated only micropollutants in tunnel wastewater such as suspended solids(SS) and heavy metals, achieving less than 0.2 NTU turbidity, less than 1.1 mg/L chemical oxygen demand($COD_{Mn}$) and less than 0.8 mg/L total manganese(Mn). The RO system then removed over 95 % of the remaining pollutnats and particles, resulting in less than 0.02 NTU turbidity, less than 0.5 mg/L chemical oxygen demand($COD_{Mn}$), less than 0.04 mg/L total nitrogen(T-N) and less than 0.01 mg/L total phosphorus(T-P). In particular, addition of an RO system could lead to markedly reduced high salt concentrations in tunnel wastewater, approaching almost zero. Thus, reclaimed water using the combined membrane system could satisfy current South Korean regulations concerning wastewater reuse(turbidity ${\leq}2.0$ NTU; T-N ${\leq}10mg/L$; T-P ${\leq}0.5mg/L$; Salinity ${\leq}250mg{\cdot}Cl/L$).

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.2
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• pp.77-87
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• 2006

The reuse of wastewater for agricultural irrigation may cause human health risk as a result of exposure to pathogens. This study conducted the quantitative microbial risk assessment in paddy field irrigated with treated wastewater. Six treatments were used to irrigate the paddy field from Year 2003 to Year 2005: biofilter-effluent, UV-disinfected water (6, 16, 40, 68 $mW s cm^{-2}$), pond-treated water, wetland-treated water, conventional irrigation water and tap water. Total coliforms, fecal coliforms and E. coli were monitored during rice growing period. Beta - Poisson model was employed to calculate the microbial risk of pathogens ingestion that may occur to farmers and neighbor children. Uncertainty of risk was estimated using Monte Carlo simulation. In this study, the microbial risk was higher during initial cultivation (end of May$\sim$June), and it decreased with time. Biofilter effluent (secondary effluent) irrigation showed higher risk values than others (>$10^{-4}$) and irrigation with UV-disinfected water has the lowest risk range ($10^{-6}{\sim}10^{-5}$). The risk value estimated in 2005 was lower than risk value in 2003 and 2004, it is likely due to clean tap water irrigation in initial transplanting stage. It is suggested that irrigation with UV-disinfected water and pond-treated water would reduce the microbial risk associated with wastewater irrigation in paddy field. In addition, the first irrigation water quality significantly affected the subsequent microbial risk.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.5
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• pp.151-159
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• 2003

Absorbent Biofilter Systems (ABS), composed of an anaerobic septic tank, a pump chamber and an absorbent biofilter tank, have been found to economically provide rural on-site wastewater treatment. This study was conducted to assess the potential of ABS effluent as an alternative water resource for agricultural and environmental use, with respect to the removal of pathogenic microorganism and their fertilization effect. A pilot scale ABS was used to compare its removal efficiency of pathogens from effluent water. Overall, more than 95 percent of Salmonella and E. coli were removed. This result demonstrates that a significant reduction in the pathogenic microorganism of effluents can occur in ABS, which implies the feasibility for the use of ABS effluent in agriculture and environment, with the provision of a further simple disinfection step, in order to satisfy the WHO guidelines for the microbiological quality in agriculture. In addition, because of the abundant nutritional content of ABS effluent, the substitution effect of fertilizer (N, P and K) in paddy irrigation, i.e. 2/3 for nitrogen, l/3 for phosphorus and 1/5 for potassium would be expected. Based on the experimental data, the ABS effluent could be used as a new alternative water resource for paddy irrigation, as well as for environmental purposes, such as supplying water to ecological parks in rural villages.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.7
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• pp.14-24
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• 2002

The effect of reclaimed water irrigation on paddy rice culture was evaluated by pilot study at the experimental field of Konkuk University in Seoul, Korea. The sewage was treated by constructed wetland system, and its effluent was used as irrigation water for four treatments and one control plots with three replications. Irrigation of reclaimed water onto paddy rice cultures did not adversely affect the growth and yield of rice. Instead, experimental rice plots of reclaimed water irrigation displayed about 10 to 50% more yield on average than controls. This implies that reclaimed water irrigation might be beneficial rather than harmful to rice culture as long as the sewage is treated adequately and used properly. The amount of irrigation water had little effect on experimental rice cultures, but its strength was important. The strength of treated sewage was not a limiting factor in this study, and no lodging was observed even with a relatively high nitrogen concentration (up to 160mg/L). In general the paddy soil was not affected by reclaimed water irrigation. However, there was an indication that continuous irrigation with high strength of reclaimed water might cause salt accumulation in the soil. Supplemental use of reclaimed water with existing sources of irrigation water is recommended rather than irrigation with a single source of reclaimed water. Overall, the results demonstrated that reclaimed water could be reused as a supplemental source of irrigation water for paddy rice culture without causing adverse effects as long as it is properly managed. For full-scale application, further investigation should be done on environmental risks, tolerable water quality, and fraction of supplemental irrigation.

• Environmental Engineering Research
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• v.19 no.4
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• pp.387-393
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• 2014

The purpose of this study is to evaluate integrated anaerobic hydrogen fermentation and membrane bioreactor (MBR) for on-site domestic wastewater treatment and resource recovery. A synthetic wastewater (COD 17,000 mg/L) was used as artificial brown water which will be discharged from urine diversion toilet and fed into a continuous stirred tank reactor (CSTR) type anaerobic reactor with inclined plate. The effluent of anaerobic reactor mixed with real household grey water (COD 700 mg/L) was further treated by MBR for reuse. An optimum condition maintained in anaerobic reactor was HRT of 8 hrs, pH 5.5, SRT of 5 days and temperature of $37^{\circ}C$. COD removal of 98% was achieved from the overall system. Total gas production rate and hydrogen content was 4.6 L/day and 52.4% respectively. COD mass balance described the COD distribution in the system via reactor byproducts and effluent COD concentration. The results of this study asserts that, anaerobic hydrogen fermentation combined with MBR is a potent system in stabilizing waste strength and clean hydrogen recovery which could be implemented for onsite domestic wastewater treatment and reuse.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.661-666
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• 2005

Wastewater reuse are exposed public health risk by pathogens. Therefore, this study was examined for microbial risk assessment after irrigation as treated wastewater in paddy rice plots. Five treatments were used: biofilter effluent, UV disinfected water, pond treatment, wetland treatment and conventional irrigation water. Risk assessment was calculated based on the beta-Poisson model by concentration of E. coli from 2003 to 2005. Monte-Carlo simulation (n=10,000) was used to estimate the risk characterization of uncertainty. The risk range was from $10^{-5}$ to $10^{-8}$ except biofilter effluent was $10^{-4}$ in June. The USEPA(1992) has recommended that risk of < $10^{-4}$ is acceptable level of safety for potable waters. In 2005, risk value was lower than 2003, 2004 because of the first irrigation for plowing water is lower E. coli concentration used tap water. It is shown that the first irrigation water quality was important for wastewater irrigation in paddy. UV disinfection and natural treatment used pond and wetland were thought to be an effective for wastewater reuse.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.3
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• pp.305-314
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• 2014

A pilot plant (Q=5 $m^3/d$) study was implemented for small and medium sized personal wastewater treatment plant effluent to evaluate MBR and A/O processes utilizing self-sufficient energy composed of wind and solar energy. The removal efficiencies of BOD, SS, turbidity and color were sufficient for legal water quality standards for gray water. However, those of nitrogen and phosphorus could not meet legal regulations which suggested that further removal of those contaminants were needed for reuse of the treated water. Self-sufficient energy rate was 100 % for the pilot plant due to excessive design capacity. In this research, wind and solar energy system was applied considering geological characteristics, which significantly improved energy self-sufficiency. Substantial improvement on energy self-sufficiency can be obtained by optimized investment and operation at a full scale wastewater treatment plant.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.10
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• pp.678-683
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• 2012

One of alternatives to solve the global water shortages is the reuse of wastewater. The aim of this study was to evaluate whether it can be reused for industrial water from wastewater in "A" City with ultrafiltration (UF) and reverse osmosis (RO) process. The results obtained in this study were that the inorganics such as Na, Mg, Cl, Ca, Mn, $PO_4$, $SO_4$, etc. were removed with high treatment efficiency (more than 97%), respectively. However, the removal of $NH_4$-N, TN, $NO_3$-N, BOD was found to be 35.71%, 85.21%, 87.05% and 56%, respectively. The removal efficiency of nutrients was relatively low compared to other metal ions. Despite low nutrients removal, the treated wastewater is recommended to reuse, because the nutrient contents in influent from the secondary wastewater treatment plant were small amount. In addition, all other metrics in the wastewater were found to be lower amount than wastewater reuse criteria. Therefore, the wastewater treated by UF-RO could be sufficient to reuse for industrial waster.

• Membrane and Water Treatment
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• v.11 no.5
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• pp.323-331
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• 2020

With the increasing demand on reverse osmosis (RO) membranes for water purification worldwide, the number of disposed membrane elements is expected to increase accordingly. Thus, recycling and reuse of end-of-life RO membranes should be a global environmental action. In this work, we aim to reuse the spent RO membrane for nanofiltration (NF) and ultrafiltration (UF) process by subjecting the spent membrane to solvent and oxidizing solution treatment, respectively. Our results showed that solvent-treated RO membrane could perform as good as commercial NF membrane by achieving similar separation efficiencies, but with reduced water permeability due to membrane surface fouling. By degrading the polyamide layer of RO membrane, the transformed membrane could achieve high water permeability (85.6 L/㎡.h.bar) and excellent rejection against macromolecules (at least 87.4%), suggesting its reuse potential as UF membrane. More importantly, our findings showed that in-situ transformation on the spent RO membrane using solvent and oxidizing solution could be safely conducted as the properties of the entire spiral wound element did not show significant changes upon prolonged exposure of these two solutions. Our findings are important to open up new possibilities for the discarded RO membranes for reuse in NF and UF process, prolonging the lifespan of spent membranes and promoting the sustainability of the membrane process.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.3
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• pp.91-104
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• 2013

The objectives of this study were to monitor and assess the environmental impacts of indirect wastewater reuse on water quality and soil in paddy fields. Yongin monitoring site (YI) irrigated from agricultural reservoir and Osan monitoring site (OS) irrigated with treated wastewater diluted with stream water were selected as control and treatment, respectively. Monitoring results for irrigation water quality showed a significant statistical difference in salinity, exchangeable cation and nutrients. Pond water quality showed a similar tendency with irrigation water except for the decreased difference in nutrients due to the fertilization impact. Soil chemical properties mainly influenced by fertilization activity such as T-N, T-P, and $P_2O_5$ were changed similarly in soil profiles of both monitoring sites, while the properties, EC, Ca, Mg, and Na, mainly effected by irrigation water quality showed a considerable change with time and soil depth in treatment plots. Heavy metal contents in paddy soil of both control and treatment did not exceed the soil contamination warning standards. This study could contribute to suggest the irrigation water quality standards and proper agricultural practices including fertilization for indirect wastewater reuse, although long-term monitoring is needed to get more scientific results.