• 한국물환경학회지
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• 제31권4호
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• pp.387-391
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• 2015

This study was performed to evaluate the effect of pH (8-12) and molar ratio of magnesium and phosphate ($[Mg^{2+}]/[PO_4{^{3-}}]$) (0.6-1.4) on struvite crystallization of anaerobic digester supernatant using seawater as magnesium source. pH range of 9-10 is favorable for ammonium and phosphate recoveries. The recovery efficiency of ammonium was highest at $[Mg^{2+}]/[PO_4{^{3-}}]$ of 1.0 and pH 10. On the other hand, high phosphate recovery efficiency (> 99%) was achieved at ($[Mg^{2+}]/[PO_4{^{3-}}]$) of 1.4 and pH 10. The results demonstrated that seawater can be considered as low-cost magnesium source to recover phosphorus from anaerobic digester supernatant.

• 한국물환경학회지
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• 제34권1호
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• pp.96-108
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• 2018

Large efforts have recently been made on research and development of sustainable and energy-efficient short-cut nitrogen removal processes owing to strong attention to the energy neutral/positive wastewater treatment system. Anaerobic ammonium oxidizing bacteria (anammox bacteria) have been highlighted since 1990's due to their unique advantages including 60% less energy consumption, nearly 100% reduction for carbon source requirement, and 80% less sludge production. Side-stream short-cut nitrogen removal using anammox bacteria and partial nitritation anammox (PN/A) has been well established, whereas substantial challenges remain to be addressed mainly due to undesired main-stream conditions for anammox bacteria. These include low temperature, low concentrations of ammonia, nitrite, free ammonia, free nitrous acid or a combination of those. In addition, an anammox side-stream nitrogen management is insufficient to reduce overall energy consumption for energy-neutral or energy positive water resource recovery facility (WRRF) and at the same time to comply with nitrogen discharge regulation. This implies the development of the successful main-stream anammox based technology will accelerate a conversion of current wastewater treatment plants to sustainable water and energy recovery facility. This study discusses the status of the research, key mechanisms & interactions of the protagonists in the main-stream PN/A, and control parameters and major challenges in process development.

• 멤브레인
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• 제32권3호
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• pp.191-197
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• 2022

기체투과막 기술을 이용하여 가축분뇨 폐기물 등으로부터 암모니아성 질소를 효과적으로 회수할 수 있다. 이는 폐기물 내 암모니아 기체가 폐기물에 함침된 기체투과막의 미세공극을 투과하여 막반대편에 도달하게 된다. 투과된 암모니아 기체분자는 막 반대편에 존재하는 용액 내 황산 등 산에 의해 포획 및 회수된다. 막 유입부 내 암모니아성 질소 제거 효과를 높이기 위해서는 우선 유입 폐기물 내 pH를 높게 유지해야 하는데 pH 상승에 필요한 염기성 약품 투입비용이 문제가 될 수 있다. 기존 연구에서는 보다 저렴한 소석회 투입하거나 폭기 혹은 질산화억제를 통해 높은 pH를 효과적으로 유지시키는 방안이 거론되고 있다. 한편 암모니아성 질소 회수에 쓰이는 기체투과막의 재질은 적절한 내열성이나 내화학성 이외에도 소수성을 띈다는 특징이 있으며 이를 통해 막기공을 통해 암모니아 기체를 선택적으로 투과시킬 수 있다. 향후 연구에서는 다양한 성상을 가진 현장 폐기물을 이용하여 실증 Test를 수행하고 이를 기반으로 최적 설계/운전 조건 규명 및 경제성 제고 방안을 수립하여야 한다.

• 한국환경농학회지
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• 제41권3호
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• pp.167-176
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• 2022

BACKGROUND: Nitrogen (N) is an important element for turfgrass (Zoysia matrella) growth; however, standard N application rate for turfgrass is not established yet. This study was conducted to evaluate the effect of N application rates on the growth and quality of turfgrass for establishment of standard N application rate. METHODS AND RESULTS: Treatments were as follows; control (0 N g/m²/month), 1N (1 N g/m²/month), 2N(2 N g/m²/month), 3N (3 N g/m²/month), 4N (4 N g/m²/month), and 5N (5 N g/m²/month). N application improved visual turfgrass quality. Compared with the control, clipping yield of all N treatments increased by 90~194%. The grass shoot weight of 3N, 4N, and 5N treatments increased by 52%, 43%, and 111%, respectively, and the stolon weight of 4N and 5N treatments increased by 412% and 201%, respectively, compared to the control. The N uptake amount and N recovery rate were estimated to be 4.10~6.28 g/m² and 14~58%, respectively. CONCLUSION(S): These results indicate that considering visual quality, clipping yield, N uptake amount, and N recovery, the application rate of 2~3 N g/m²/month was suggested to be suitable for Z. matrella production.

• 한국작물학회지
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• 제50권1호
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• pp.16-21
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• 2005

This study was conducted to establish the elaborate nitrogen fertilization method to enhance N use efficiency in direct-seeded rice on flooded paddy. The nitrogen uptake by rice plants was insignificant until 25 days after seeding, and increased gradually thereafter. During this early growth stage, rice plants absorbed only the $4\%$ of basal applied N, while the $45\%$ of N fertilizer remained in the paddy soil. The absorption of basal N by rice plants was almost completed at 46 days after application. Nitrogen top-dressed at 5-leaf stage was well matched to crop nutrient demand, so it could be absorbed so actively in 8days after application. As a result, we could cut down the amount of N fertilizer to $36\%$ of the basal N level without significant difference in yield. Plant recoveries of fertilizer $^{15}N$ applied with different application timings were $7.8\%$ for basal, $9.4\%$ for 5-leaf stage, $17.1\%$ for tillering stage, and $23.4\%$ for panicle initiation stage, respectively. When urea was applied with nitrogen fertilization practice based on basal incorporation (BN), plant recovery of $^{15}N$ at harvest was $31.0\%$, which was originated from $13.7\%$ for grain, and $21.3\%$ of the fertilizer $^{15}N$ remained in the soil, and the rest could be uncounted. Plant recovery of fertilizer $^{15}N$ applied with nitrogen fertilization practice based on topdressing at 5-leaf stage (TN), where N rate was reduced by $18\%$ compared with BN, was $35.1\%$ (grain $15.6\%$), and $19.9\%$ of the fertilizer $^{15}N$ remained in the soil, and the rest could be uncounted. TN showed a higher $^{15}N$ recovery than BN because it was to apply N fertilizer at a time to well meet the demand of rice plant direct-seeded on flooded paddy. We concluded that TN would be the nitrogen fertilization method to enhance N use efficiency in direct-seeded rice on flooded paddy.

• Journal of Biosystems Engineering
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• 제31권1호
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• pp.46-51
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• 2006

This study was carried out to recover phosphorus in animal wastewater using a magnesium source. $MgCl_2$, as a magnesium source, was shown a SP (soluble phosphorus) recovery rate of 98% in both the aeration and the NaOH tests to adjust pH around 8.5. In case of MgO, the recovery rate of SP were 88% with the aeration and 58% with the NaOH. In case of ammonia nitrogen recovery, $MgCl_2$ was shown the recovery rate of 17% with aeration and 18% with NaOH. MgO was shown the ammonia recovery rate of 18% with aeration and 11% with NaOH. At low temperature of $6-8^{\circ}C$ with the animal wastewater from piglet stall, the recovery rate of SP was shown 95% with NaOH and 92% with aeration using $MgCl_2$. The recovery rate of ammonia nitrogen was shown 9% with NaOH and 12% with aeration, respectively. It was observed that the pH can be raised by aeration. The reaction was completed within 5 minutes and the struvite cristal structure was formed and could be observed with an electronic microscope.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2005년도 추계학술발표회 요지
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• pp.192-193
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• 2005

• Membrane and Water Treatment
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• 제13권3호
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• pp.147-166
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• 2022

Liquid-liquid membrane contactor (LLMC), a device that exchanges dissolved gas molecules between the two sides of a hydrophobic membrane through membrane pores, can be employed to extract ammoniacal nitrogen from a feed solution, which is transported across the membrane and accumulated in a stripping solution. This LLMC process offers the promise of improving the sustainability of the global nitrogen cycle by cost-effectively recovering ammonia from wastewater. Despite recent technological advances in LLMC processes, a comprehensive review of their feasibility for ammonia recovery is rarely found in the literature. Our paper aims to close this knowledge gap, and in addition to analyze the challenges and provide potential solutions for improvement. We begin with discussions on the operational principles of the LLMC process for ammonia recovery and membrane types and membrane configurations commonly used in the process. We then assess the performance of the process by reviewing publications that demonstrate its practical application. Challenges involved in the implementation of the LLMC process, such as membrane fouling, membrane wetting, and chemical requirements, are presented, along with discussions on potential strategies to address each. These strategies, including membrane modification, hybrid process design, and process optimization based on cost-benefit analysis, guide the reader to identify key areas of future research and development.

• 멤브레인
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• 제22권4호
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• pp.251-257
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• 2012

n-Pentane의 분리 및 회수를 위해 분리막의 제조가 용이하고 유기용매에 대한 내용매성이 있는 polyetherimide (PEI)를 지지체로 poly (dimethyl siloxane) (PDMS)를 코팅하여 중공사 복합막을 제조하였다. 제조된 기체 분리막의 특성을 알아보기 위하여 n-Pentane과 질소를 이용하여 공급농도와 stage cut의 변화에 따른 n-pentane과 질소의 투과도, permeate, retentate의 농도, 농축도, 회수율을 측정하였다. n-pentane과 질소의 투과도는 각각 2485.3, 9.9 GPU를 나타내었고, stage cut이 감소하고 공급농도가 증가할수록 투과측의 n-pentane 농도는 증가하는 경향을 나타내었다. 반면 회수효율의 경우에는 stage cut이 증가할수록 공급농도가 감소할수록 증가하는 경향을 나타내었다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 1999년도 제1회 학술대회논문집(KIASC 1st conference 99)
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• pp.169-172
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• 1999

The exergy method is used for analysis and evaluation of the cryogenic nitrogen production process which is operated by expansion turbene and liquid nitrogen. The exergy loss and thermodynamic effeciency are calculated for the each process. Also the operating efficiency and the exergy distribution are examined for each unit of proces. The optimal conditions to minimize the exergy loss of nitrogen column are found that nitrogen recovery ratio is maximum and operating pressure is 5.0 kg/cm2g. The exergy method can be used to design a plant and to evaluate its process.