• Journal of Microbiology and Biotechnology
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• v.34 no.2
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• pp.407-414
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• 2024

Phosphorus is an essential but non-renewable nutrient resource critical for agriculture. Luxury phosphorus uptake allows microalgae to synthesize polyphosphate and accumulate phosphorus, but, depending on the strain of algae, polyphosphate may be degraded within 4 hours of accumulation. We studied the recovery of phosphorus from wastewater through luxury uptake by an engineered strain of Synechocystis sp. with inhibited polyphosphate degradation and the effect of this engineered Synechocystis biomass on lettuce growth. First, a strain (∆phoU) lacking the phoU gene, which encodes a negative regulator of environmental phosphate concentrations, was generated to inhibit polyphosphate degradation in cells. Polyphosphate concentrations in the phoU knock-out strain were maintained for 24 h and then decreased slowly. In contrast, polyphosphate concentrations in the wild-type strain increased up to 4 h and then decreased rapidly. In addition, polyphosphate concentration in the phoU knockout strain cultured in semi-permeable membrane bioreactors with artificial wastewater medium was 2.5 times higher than that in the wild type and decreased to only 16% after 48 h. The biomass of lettuce treated with the phoU knockout strain (0.157 mg P/m²) was 38% higher than that of the lettuce treated with the control group. These results indicate that treating lettuce with this microalgal biomass can be beneficial to crop growth. These results suggest that the use of polyphosphate-accumulating microalgae as biofertilizers may alleviate the effects of a diminishing phosphorous supply. These findings can be used as a basis for additional genetic engineering to increase intracellular polyphosphate levels.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.22-27
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• 2006

Thermal treatment and ozone oxidation methods were examined to reuse waste activated sludge (WAS) produced from a livestock wastewater treatment plant. Analysis of WAS property was made to study usefulness of the recycled waste as fertilizer. From the results of quantitative analysis, WAS particles were found to be composed of 44.25 wt% carbon, 8.43 wt% nitrogen, and 1.35 wt% phosphorus. It was confirmed that the inactivation of pathogenic microorganism was required from the quantitative analysis of microbes. From the results of TSS, COD, SCOD, and pathogenic microorganism measurement, the optimal operating conditions of thermal treatment and ozone oxidation were determined to be 70, 10 min and $0.6L\;O_3/L\;solution{\cdot}min$, 60 min, respectively. The optimized thermal treatment and ozone oxidation represented the efficient pathogen inactivation and particle dissolution, respectively. However, the two methods examined were not themselves sufficient but they need to combine with another treatment for the effective reuse of wastes.

• Korean Journal of Ecology and Environment
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• v.33 no.2 s.90
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• pp.145-151
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• 2000

A porous silicate material named as CellCaSi was tested for the removal of microalgae in the water sample from a eutrophic pond. The effects of the CellCaSi on water qualities were investigated on the basis of both the particle size (under 1, 2,and 4 mm) and the added amount (0, 1, 5, and 10 g/l) of the CellCaSi. The removal efficiency of chlorophyll-a was highest at 79% by the addition of 10 g/l of the CellCaSi (under 1 mm) at day 3 after treatment. That is, the removal efficiency of chlorophyll-a by the CellCaSi increased with smaller particle size and more added amount. The dominant species, Chlorella ellipsoidea, was not changed by the addition of the CellCaSi, but the species number and standing crop of the algae diminished. Total nitrogen concentration was not changed much by the addition of the CellCaSi, whereas total phosphorus concentration was reduced. pH and turbidity were not changed by the addition of the CellCaSi, whereas conductivity showed a high correlation with the amount of added CellCaSi ($Y\;=\;29.2 {\cdot}X+306$, $r^2\;=0.984$). Therefore, it seems to be necessary to limit the amount of the CellCaSi under 6.6 g/1 in consideration of a registered maximum conductivity of $500\;{\mu}mhos/cm$ for raw and potable waters.

• Journal of fish pathology
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• v.33 no.1
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• pp.97-101
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• 2020

Although aquaculture production rates grown over the years, aquatic animal diseases occur every year which causes substantial economic losses. When an aquatic animal is infected with an aquatic animal pathogen it is either incinerated or buried according to the aquatic life disease control act. Although these methods prevent the spread of disease, it is not environment friendly. Here, we developed an aquatic animal rendering equipment for disposal of fish waste which is environment-friendly and efficient. Also, fertilizer components of fish waste were evaluated value for recycling. The mobile rendering equipment was designed for field operation and/or high temperature and pressure system, oil and water separator, and shredding drying apparatus. During the experiment (July-2016 to November-2016), a total of 53,824 kg fish waste was collected, and 29,216 kg compost of rendering by-product was made. Also, compost made from viral (Viral hemorrhagic septicemia virus) infected fish did not reflect any detectable pathogen. The concentration of nitrogen, phosphorus, and organic matter in the fish waste compost were 2.17%, 26.98%, and 92.44%, respectively. The results suggest that fish waste used in this study was decomposed efficiently as per the official standard for fertilizer product. This equipment can be useful for efficient inactivation of the aquatic animal pathogenic agents and recycling of the fish waste in an environment-friendly manner.

• Journal of Korean Society on Water Environment
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• v.25 no.3
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• pp.386-393
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• 2009

This study was carried out to assess water quality and to introduce the management measures for water quality improvement with the collected data from 87 agricultural reservoirs in Han river watershed. According to the water quality criteria (WQC) for lake based on the COD, TP, TN and chl.a concentration, 18, 16, 4 and 19 of 87 reservoirs exceed class IV, respectively. Based on the trophic state index (TSI) with chl.a concentration, 51 of selected reservoirs appeared to be eutrophic. Phosphorus was limiting nutrient on algal growth in 58 reservoirs. TP, chl.a and COD concentration in 23 of 49 agricultural reservoirs with chl.a concentration ${\geq}25{\mu}g/L$ and eutrophic exceed class IV by WQC. Also, the mean depth in 21 of 23 reservoirs was below 5m. Our results suggest that advanced wastewater treatment and crop land control in watershed of reservoirs with TP concentration ${\geq}0.1mg/L$ would be a effective tool to improve water quality. Dredging would to be effective measure in reservoirs with mean depth < 5 m and relatively old age. In reservoirs with chl.a concentration ${\geq}50{\mu}g/L$, application of technique such dissolved air flotation (DAF) and P inactivation be effective to improve water quality by removing particulate matters in water column. The management measure to control inflow such as sedimentation basin, Pre-dam and diversion would to be application in reservoirs with shallow depth, while large watershed and surface area.