• Journal of the Korean Society for Marine Environment & Energy
• /
• v.15 no.1
• /
• pp.9-18
• /
• 2012

Annual power consumption of our country is positioned in the upper percentile in the world, and because the proportion of fossil power generation is high, which ranks the 10th $CO_2$ emission country. In this regard, government has established and is implementing the National Energy Basic Plan to realize to get out of fossilization in energy supply while focusing on securing the technology for renewable energy as well as its commercialization in order to reduce greenhouse gas. Resource recovery technology for deep seawater thermal energy which is one of renewable energies is newly getting attention domestically as well as in overseas for securing resources and environmental improvement as a core technology for multilateral use of marine resources for low carbon and green growth. Economic feasibility analysis was conducted for the research and development as follows on the use of ocean thermal energy conversion and seawater air conditioning. First, in the case of power generation using deep seawater and warm discharge water from ocean thermal energy conversion plant of 1MW level, it is judged that the economic feasibility is insufficient but the feasibility will be significantly improved if we consider not only power generation but also drinking water and certified emission reduction by developing the power plant to the size for commercialization. Second, the economic feasibility for the use of deep seawater as air conditioning for the power plant of 1,000RT level turned out to be very good. Especially, when we consider certified emission reduction, it will be possible to secure sufficient economic feasibility. When we use it in connection with ocean thermal energy conversion, water conversion and agricultural and fishery use, it is judged that economic ripple effect will be significant and therefore it will be necessary to conduct research and development for early commercialization, distribution and diffusion of deep seawater energy.

• Journal of Life Science
• /
• v.25 no.5
• /
• pp.496-506
• /
• 2015

This study explored adequate water temperature ranges for maintaining stable water quality in a biofloc- based zero-water exchange culture system. Five experimental tanks with the following temperatures were set up: 10℃, 15℃, 20℃, 25℃, and 30℃. First, a biofloc-based culture system was developed in the experimental tanks; then, the tanks were stocked with goldfish and went without a water exchange for 60 days. Conditions for developing a biofloc-based culture system and stable water quality in low concentrations of inorganic nitrogen compounds at 10℃, 15℃, 20℃, 25℃, and 30℃ were maintained after 17, 26, 43, 68, and 78 days, respectively. Beginning from when the goldfish were stocked in the biofloc-based culture tanks, concentrations of $NH_4{^+}-N$ remained constant and at low levels at 10℃ and 15℃, but they showed a gradual increase at 20℃, 25℃, and 30℃. Concentrations of $NO_2{^-}-N$ and $NO_3{^-}-N$ at 10℃ and 15℃ did not remain at low levels and immediately increased. While $NO_2{^-}-N$ concentrations at above 20℃ remained constant and stable at relatively low levels, $NO_3{^-}-N$ concentrations showed a gradual increase. Conditions of 15℃ and below could not maintain low and stable concentrations of $NO_2{^-}-N$. In the pH range of 4.0 to 6.0, $NH_4{^+}-N$ concentration decreased as the pH rose. However, there was no correlation between pH and $NH_4{^+}-N$ concentration in the pH range of 6.0 to 8.0. These results indicate that pH levels should be kept at pH 6.0 and above to maintain a low and stable concentration of $NH_4{^+}-N$ at above 20℃.

• Journal of Wetlands Research
• /
• v.25 no.1
• /
• pp.35-47
• /
• 2023

Korean facility horticulture and hydroponic cultivation methods increase, requiring the management of waste water generated. In this study, the amount of fertilizer contained in the discharged waste liquid was determined. By evaluating this as a price, it was suggested to reduce water treatment costs and recycle fertilizer components. It was evaluated based on the results of major water quality analysis of waste liquid by crop, such as tomatoes, paprika, cucumbers, and strawberries, and in the case of P component, it was analyzed by converting it to the amount of phosphoric acid (P₂O₅). The amount of nitrogen (N) can be calculated by discharging 1,145.90kg·ha^-1 of tomatoes, 920.43kg·ha^-1 of paprika, 804.16kg·ha^-1 of cucumbers, 405.83kg·ha^-1 of strawberries, and the fertilizer content of P₂O₅ is 830.65kg·ha^-1 of paprika, 622.32kg·ha^-1 of tomatoes, 477.67kg·ha^-1 of cucumbers. In addition, trace elements such as potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), and manganese (Mn) were also analyzed to be emitted. The price per kg of each item calculated by averaging the price of fertilizer sold on the market can be evaluated as KRW, N 860.7, P 2,378.2, K 2,121.7, Ca 981.2, Mg 1,036.3, Fe 126,076.9, Mn 62,322.1, Zn 15,825.0, Cu 31,362.0, B 4,238.0, Mo 149,041.7. The annual fertilizer loss amount for each crop was calculated by comprehensively considering the price per kg calculated based on the market price of fertilizer, the concentration of waste by crop analyzed earlier, and the average annual emission of hydroponic cultivation. As a result of the analysis, the average of the four hydroponic crops was 5,475,361.1 won in fertilizer ingredients, with tomatoes valued at 6,995,622.3 won, paprika valued at 7,384,923.8 won, cucumbers valued at 5,091,607.9 won, and strawberries valued at 2,429,290.6 won. It was expected that if hydroponic drainage is managed through self-treatment or threshing before discharge rather than by leaking it into a river and treating it as a pollutant, it can be a valuable reusable fertilizer ingredient along with reducing water treatment costs.