• Membrane and Water Treatment
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• v.14 no.2
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• pp.77-83
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• 2023

As a result of algal bloom, algal organic matters (AOMs) are rapidly increased in surface water. AOMs can act as precursors for the formation of harmful disinfection by-products (DBPs), which are serious problems in water treatment and human health. The main aim of this study is to characterize the formation of DBPs from AOMs produced by three different algae such as Oscillatoria sp., Anabaena sp., and Microcystis aeruginosa under different algal growth phases. In an effort to examine formation of DBPs during chlorination, chloroform (TCM), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) were determined under various CT (product of disinfectant concentration and contact time, mg·min/L) values. Generally, the amounts of DBPs tended to increase with increasing CT values at the most growth phases. However, there was a significant difference between the amounts of DBPs produced by the three algal species at different growth phases. This result is likely due to the chemical composition variability of AOM from different algae at different growth phases. In addition, the effect of pre-ozonation on coagulation for the removal of AOMs from three algal species was investigated. The pre-ozonation had a positive effect on the coagulation/flocculation of AOMs.

• Journal of Korean Society on Water Environment
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• v.31 no.2
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• pp.110-119
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• 2015

The construction of the eight large weirs in the Nakdong River, the second largest river in Korea, caused big changes in the physical environment of the water system. Algal communities and their correlations with environmental factors, mainly nutrients were studied at five weir areas in the Nakdong River from 2010 to 2013. Water quality, hydrodynamics and algal composition were investigated. Results showed that flow velocities were reduced compared with that before weir construction near the areas where are located in the mid and upstreams of the Nakdong River. A seasonal algal community succession was observed and it was mainly correlated with temperature and phosphorus. Diatoms were dominated from winter to spring months and massive diatomic blooms of Stephanodiscus sp. occurred early in March during survey period. Cyanobacterial blooms of Microcystis sp. occurred from July to September 2013 and was preceded by the lower total phosphorus concentration of $0.05mg\;L^{-1}$. The correlations between total phosphorus concentrations and algal abundances were not significant during the survey periods. However, significant correlation with cyanobacteria was found in the period of weir construction after only at the GG survey site and blooms periods of 7 times in the survey sites, and its correlation coefficients were 0.53 (p<0.001) and 0.42 (p<0.01) respectively. When algal bloom was observed, partially low nutrient concentration was observed in the Nakdong River. In conclusion, partially low nutrient concentration which may result from algal bloom was observed, and we presume it caused the reduction of algal abundunces.

• Korean Journal of Ecology and Environment
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• v.40 no.1
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• pp.121-129
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• 2007

This study was conducted to evaluate the causes and effects of cyanobacterial development and succession in a shallow eutrophic reservoir from March 2003 to February 2004. Phytoplankton succession, sedimentation rate, and sediment composition were analyzed. Algal bioassay also was conducted with the consideration of light, water temperature and nutrients. Cyanobacteria dominated throughout the year, except for spring season (March${\sim}$April) in which diatoms and flagellates dominated. Total cell density increased in July and November when P loading through inflows was high. Oscillatoria spp. and Aphanizomenon sp. were dominant in May and June, respectively, but replaced with Microcystis spp. in July. Thereafter, Microcystis spp. sustained until December, and again shifted to Oscillatoria spp. and Aphanizomenon sp. The dominance of Oscillatoria spp. in May was accompanied with high TN/TP ratio and the increase of water temperature and light intensity. While the dominance of Microcystis spp. was related with relatively low TN/TP ratio, ranging from 46 to 13 (average: 27). The sedimentation rate was highest in March (0.6 m $day^{-1}$) when diatoms dominated. During the period of cyanobacterial dominance, relatively high sedimentation rate was observed in May (0.4 m $day^{-1}$) and October (0.36m $day^{-1}$). C/N ratio of the sediment ranged $6{\sim}8$. Inorganic P concentration in the pore water was low when DO concentration was < 2 mg $O_2$ $L^{-1}$ in the hypolimnion, reflecting the P release from the sediment. Cyanobacterial growth rate depended on phosphorus concentration and water temperature, and high P concentration compensated for the low temperature in the growth rate. Our results suggest that the potential of cyanobacterial development and substantiality in eutrophic reservoirs be high throughout the year, as being supplied with enough P, and emphasize the consideration of sediment man. agement for the water quality improvement and algal bloom control.

• Korean Journal of Ecology and Environment
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• v.39 no.2 s.116
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• pp.271-283
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• 2006

A systematic water quality survey was conducted in August, 2005 for a drinking water supply reservoir (the Jeolgol reseuoir located in an island), which is at an early stage of impoundment, to investigate the causes of water color deterioration of the reservoir and the clogging of filter beds of a water treatment plant. The reservoir shape was simple and its average depth was 5.5 m, increasing from upreservoir toward the downreservoir end near the dam. Dissolved oxygen (DO) and chloropllyll-a (chi-a) showed a large variation while water temperature had a smaller range. Transparency ranged from 0.6 to 0.9 m (average 0.7 m). The average value of turbidity was 9.3 NTU, ranging from 8.0 ${\sim}$ 12.1 NTU. The transparency and the turbidity appear to be affected by a combination of biological and non-biological factors. The poor transparency was explained by an increase of inorganic colloids and algal bloom in the reservoir. The blockage of the filter bed was attributed to the oversupply of phytoplanktons from the reservoir. The range and the average concentration of chi-a within the reservoir were 31.6 ${\sim}$ 258.9 ${\mu}g\;L^{-1}$, 123.6 ${\mu}g\;L^{-1}$ for the upper layer, and 17.0 ${\sim}$ 37.4 ${\mu}g\;L^{-1}$, 26.5 ${\mu}g\;L^{-1}$ for the bottom layer, respectively. A predominant species contributing the algal bloom was Dinophyceae, Peridinium bipes f. occultatum. The distribution of Peridinium spp. was correlated with chi-a concentrations. The standing crop of phytoplankton was highest in the upreservoir with $8.5\;{\times}\;103\;cells\;mL^{-1}$ and it decreased toward the downresevoir. Synedra of Bacillariophyceae and Microcystis aeruginosa of Cyanophyceae appeared to contribute to the algal bloom, although they are not dominated. It is mostly likely that sloped farmlands located in the watershed of the reservoir caused water quality problems because they may contain a significant amount of the nutrients originated from fertilizers. In addition, the aerators installed in the reservoir and a shortage of the inflowing water may be related to the poor water quality. A long-term monitoring and an integrated management plan for the water quality of the watersheds and the reservoir may be required to improve the water quality of the reservoir.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.11 no.4
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• pp.158-164
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• 2006

Yongdam Lake is the fifth largest artificial lake in Korea newly formed by the first impounding the Yongdam Multi-purpose Dam on December, 2002. Yongdam Lake, with her total water storage of 820 million M/T, is located at the roof-top region of the streams flowing into the just-constructed new Saemankeum Lake. Seasonal succession of phytoplakton in Yongdam Lake might affect cyanobacterial blooms in Saemankeum Lake by inoculating seasonal dominants. During 2002-2003 when the first impounding after the construction of Yongdam Multi-purpose Dam was still undergoing, summer cyanobacterial blooms by Anabaena, Microcystis, and Aphanizomenon were observed. Among these three, filamentous Anabaena is well known to have its species with $N_2-fixing$ ability and special cells such as heterocysts and akinetes as well as the vegetative cells. We established a clonal culture of Anabaena spiroides v. crasse (KNU-YD0310) from the live water samples collected at the bloom site of Yongdam Lake. The N- and P-nutrient requirement of the KNU-YD0310 was explored by the experimental cultivation of the laboratory strain. Ratio of heterocysts to vegetative cells increased as N-deficiency extended with its maximum at $N_2-fixing$ condition. The strain KNU-YD0310 exhibited considerable growth under N-limiting conditions while its growth was proportional to the initial phosphate-P concentration under P-deficient conditions. Under P-limiting conditions akinete density increased, which could be interpreted as an adaptation strategy to survive severe environment by transforming into resting stage. The above eco-physiological characteristics of Anabaena spiroides v. crassa might be useful as an ecological criterion in controlling cyanobacterial blooms at Shaemankeum Lake in near future.

• Korean Journal of Ecology and Environment
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• v.37 no.1 s.106
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• pp.47-56
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• 2004

To understand the effect of nutrient deficiency on the plankton community in three stations with different water qualities in Pal'tang Reservoir, Korea, phytoplanktons(> 10 ${\mu}m$) were cultured in nutrient enrichment Allen's media (AM) and nutrient-deficient Allen's media. A distinct shift in the species composition and biomass of phytoplankton (as chlorophyll- a) showed in all treatments. In particular, it was very interesting that the new development of cyanobacterium Microcystis aeruginosa occurred by the Fe-deficient AM. Except for Si, a community growth (as chlorophyll- a) was inhibited in all nutrient deficient treatments. Species diversity after nutrient deficiency was changed to below 2.0; slightly increased in N and P-deficiency, while decreased in Si and Fe, respectively. As suggested, dominance was entirely opposite to diversity. Therefore, the nutrient deficient effectively induced the succession of species and biomass, phytoplankton community, suggesting a possibility as a reliable tool to control the algal bloom in eutrophic lakes and reservoirs.

• Journal of environmental and Sanitary engineering
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• v.11 no.1
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• pp.27-37
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• 1996

The taxa of phytoplankton in the Dongbok reservoir consisted of 6 classes, 9 orders, 4 4 suborders, 21 families, 42 genus, 86 species, 4 varieties and 1 formula; totally 91 t taxa appeared. It contained 3 major groups that is Chlorophyceae 51 taxa(56.0 % the most high rate), Bacillariophyceae 23taxa(25.2%), Cyanophyceae 10taxa(10.9%). The most abundant with 47 taxa was in December, the least with 11 taxa was in March during research every month. The component ratio of biomass each main groups, Bacillariophyceae(51 %, the most h high rate), Cyanophyceae(38.9%), Chlorophyceae(9.8%). The most abundant class at the biomass component ratio were Cyanophyceae which contained 82.6-98.0 % of it in May and September, Chlorophyceae 79.0% in August, and Bacillariophyceae increased continuously, specially in winter and autumn. The seasonal dominant groups were Microcystis aemginosa belong to Cyanophyceae in spring and autumn, some species of Chlorophyceae in summer and Melosira granulata belong to Bacillariophyceae in winter and late autumn. Dominant index ranged from 0.33 to 0.95. The season of the lowest index was autumn and the highest was spring. Species diversity indices ranged from 1.09 to 3.99. The water environmental factors of the Dongbok reservoir were that the values of water temperature ranged between $2.4~28.9^{\circ}C$, pH 7.2~8.3, conductivity 77.0~105.5us/cm, and transparency 1.2~2.8m, also the concentration of dissolved oxygen(DO) ranged of 6.9-14.6mg/L, total nitrogen(T-N) 0.38-1.84mg/L, total phosphorus (T-P) 0.011~0.028mg/L, and chlorophyll-a $7.0~29.9mg/m^3$. In this research the proper temperature of water for algae growth, $15~20^{\circ}C$, was maintained in April. May, November and December 1 The number of species that induced water color were 14 species, that caused taste-and-odor problems were 3 species and that caused filter clogging were 5 species. A Among them, the bloom of Anahaena macrospora that caused odor problem occurred l in May and of Microcystis aeruRinosa and M. lνensenberRii that caused filter clogging in May and September.

• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.313-321
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• 2005

Based on the result that biological control agent (BCA) increased the dissolved microcystin-LR in a field experiment to control the cyanobacterial bloom (Kim etal., 2005), a laboratory experiment was used to evaluate the effects of dissolved microcystin-LR (MCLR) with different concentrations on abundance, dominance, diversity of phytoplankton community, concentration of chlorophyll a and microcystin concentration in replicated microcosms. The treatments in this laboratory experiment comprised different concentrations of T1 (natural MCLR concentration), T10 (ten times to natural MCLR concentration), and T100 (one hundred times to natural MCLR concentration). MCLR treatment of exclusively Stephanodiscus hantzschii-dominated community in Chonho bridge hardly changed in algal species, but abundance. In Kildong pond, Aulacoseira and Dinobryonrich community was replaced by green algae Scenedesmus-rich community especially in T100 experiment. However, in Yangsoori-Ryukgakji Pond having the highest concentration of initial MCLR, Microcystis aeruginosa was decreased in abundance. Therefore, the treatment of BCA to control M. aeruginosa severely changed the Phytoplankton community in term of algal species, abundance (chlorophyll a) and dissolved microcystin-LR via a high release of MCLR.

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.221-231
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• 2010

A simple extraction method was applied to control four selected cyanobacteria, solitary (SMA) and colonial Microcystis aeruginosa (CMA), and green algae, Scenedesmus quadricauda and Chlorella vulgaris using a domestic plant and mineral. Three kinds of concentrations (1, 5, and 10 mg $L^{-1}$) of three fresh plants Camellia sinensis, Quercus acutissima, and Castanea crenata, three minerals loess, quartz porphyry, and natural zeolite, and plant-mineral composite, totally seven materials were prepared with the simple extraction processes: drying and grinding of material, water-extraction by high temperature-sonication and filtering. Cyanobacteria SMA and CMA (over 60% of control) were effectively inhibited with the low concentration (1 mg $L^{-1}$) of plants Q. acutissima and C. crenata and natural zeolite, while green alga S. quadricauda (below 50% of control) also retarded in growth. Low concentrations (1 mg $L^{-1}$) of C. sinensis effectively increased the growth of C. vulgaris, while loess also induced the algal growth of S. quadricauda. Therefore, our results indicate that crude extract of domestic plants, Q. acutissima and C. crenata can be also useful to control the cyanobacterial bloom in eutrophic lake, whereas C. sinensis and loess may be a good growth factor or useful media for the algal mass culture.

• Journal of Korean Society on Water Environment
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• v.27 no.4
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• pp.491-498
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• 2011

We investigated the ranges of total cellular microcystins content of cyanobacterial blooms collected in Korean lakes and rivers from 2005 to 2009. The amount and composition of microcystins of Korean cyanobacteria varied depending on the sampling water bodies and dominant cyanobacterial genera. Toxic cyanobacterial cell numbers equivalent to $1{\mu}g$ MCYSTs/L using total cellular microcystin content of Korean cyanobacteria were in the range of 2,348 to 66,980,638 cells/mL. Only four samples among forty nine samples showed less cell numbers than current criterion of Harmful Algae Alert System, 5,000 cells/mL indicating current criterion do not reflect properly the microcystins content of Korean cyanobacteria. Anabaena and Aphanizomenon spp. showed three to six times higher cell numbers equivalent to $1{\mu}g$ MCYSTs/L than Microcystis spp. To propose criteria of Harmful Algae Alert System for Korean toxic cyanobacteria, we calculated about 50% selective geometrical means of cyanobacterial cell numbers equivalent to $1{\mu}g$ MCYSTs/L in order of toxic content. The proposed criteria for Microcystis, Oscillatoria, Anabaena, and Aphanizomenon spp., are 10,000, 20,000, 40,000, and 80,000 cells/mL, respectively.