• Journal of Korean Society of Environmental Engineers
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• v.32 no.12
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• pp.1087-1093
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• 2010

Autotrophic denitrification is known as an effective and economical alternative for heterotrophic denitrification using external carbon sources such as methanol. In this study, we evaluated design and operation parameters for a sulfur denitrification reactor (SDR) treating high strength nitrogen wastewater. The SDR was filled with spherical sulfur media in connected to a pilot-scale nutrient removal process (daily flow rate, $Q=18\;m^3/d$) using moving spongy media. Total nitrogen (TN) concentration of the final effluent was below the 7.0 mg TN/L because nitrate was additionally removed through autotrophic denitrificationin without adding alkalinity (initial alkalinity was $169.4{\pm}20.8\;mg$ $CaCO_3$/L). During the test period, 60~80% of nitrogen in the influent was removed even in low temperature (below $15^{\circ}C$). The alkalinity consumption for nitrate removal in SDR was $4.09{\pm}1.29$ g $CaCO_3/g$ ${NO_3}^-$-N, and the residual alkalinity of influent of SDR was higher than that of theoretical requirements for full conversion of nitrate. The consumption of sulfur was 943.8 g S/d and it was 2.4 times higher than theoretical value (400.1 g S/d) due to abrasion and loss of sulfur media in backwash, etc.

• 한국해양학회지
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• v.30 no.5
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• pp.413-425
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• 1995

Abundances and bacterivory of heterotrophic and mixotrophic nanoflagellates were investigated fourtimes between October 1993 and March 1995 in an estuarine system of the Mankyung and Dongjin rivers to understand distributions of nanoflagellates and ecological significance of bacterivory of nanoflagellates. Bacterivory of nanoflagellates were measured with fluorescently labeled bacteria (FLB). Heterotrophic and autotrophic flagellates showed a rage of 438-4,159 cells ml/SUP -1/ (mean of 2,145 cells ml/SUP -1/, n=20) and 971- 4,935 cells ml/SUP -1/ (mean of 2,2226 cells ml/SUP -1/, n-20), respectively. These two groups of nanoflagellates generally showed similar distributions of abundance. Abundances of heterotrophic nanoflagellates, known as major grazers of bacteria, and those of autotrophic nanoflagellates with chloroplasts showed statistically significant correlations with bacterial abundance (respectively, r$^2$=0.51 and r $^2$=0.47, p>0.05). Mixotrophic nanoflagellates seemed to comprise at least 4-23% of autotrophic nanoflagellate populations. Individual predation rates of heterotrophic nanoflagellates ranged from 2.2 to 14.2 bacteria flagellate/SUP -1/ h/SUP -1/ (mean of 4.9 bacteria flagellate/SUP -1/h/SUP -1/, n=16), and those of mixotrophic nanoflagellates from 1.6 to 9.7 bacteria flagellate/SUP -1/ h/SUP-1/ (mean of 3.7 bacteria flagellate /SUP -1/ h/SUP -1/, n=16). Bacterivory by mixotrophic nanoflagellates comprised from 30 to 69% of total nanoflagellates grazing on bacteria, indicating the significant role of mixotrophic nanoflagellates as grazers on bacteria in the study area. The ratios of grazing rates on bacteria to bacterial secondary production ranged widely from 0.06 to 1.23. In June, when abundances of total nanoflagellates were low, removal of bacteria by bacterivory of nanoflagellates was also a small fraction (0.08${\pm}$ 0.01, n=4) of bacterial production. In other seasons, nanoflagellates usually grazed on bacteria in significant fraction (0.06${\pm}$0.37, n=9) of bacterial production. Both heterotrophic and mixotrophic nanoflagellates appear to be major grazers on bacteria, and might transfer bacterial secondary production to higher trophic level in an estuarine system of the Mankyung and Dongjin rivers.

• KSBB Journal
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• v.24 no.4
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• pp.377-382
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• 2009

The culture condition of growing Chlorella minutissima was optimized to produce biodiesel for fed-batch cultivation. First, under heterotrophic cultivation, the optimum level of glucose was determined to be 10 g/L for 20 days. After, three cultivation conditions were operated: autotrophic, heterotrophic, and mixotrophic growth. The lipid level and the maximum cell concentration from the fed-batch heterotrophic process were 32.0 (%, v/v) and 15.0 (g-dry wt./L) in 20 L flask, respectively. In addition, since the relatively constant specific lipid production rate was observed as 0.040 (% lipid/g-dry wt./day) at the latter period of cultivation time, the fed-batch process could maintain continuous lipid production. Fed-batch process is higher than those values from the batch process. The lipids from the fed-batch process contained over 38% of $C_{18}$, known as the suitable composition for the biodiesel application. For mixotrophic and heterotrophic growth under fed-batch condition, glucose was proved to be an appropriate carbon source for a large scale outdoor cultivation. For fed-batch cultivation, the feeding rate of seawater medium containing glucose was decided to be 0.5 L/day. The mixotrophic cultivation maintained maximum cell concentration of 24 (g-dry wt./L) and the lipid level of 43 (%, w/w). The lipid composition from this process was also proved to be suitable for the biodiesel production. The fatty acids from the mixotrophic growth contains 18% of $C_{17}$ and 49% of $C_{18}$, implying It also tells that C. minutissima is a suitable resource of biodiesel. Especially, the mixotrophic cultivation with fed-batch process might be useful for the large scale cultivation for the biodiesel production.

• Korean Journal of Environmental Biology
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• v.35 no.3
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• pp.361-372
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• 2017

This study described the spatial distribution of dinoflagellate cyst assemblages in the Ulsan Coastal Waters (UCW). Surface sediment samples from 15 stations revealed the occurrence of 33 species involving the Groups Protoperidinioid (51.5%), Gonyaulacoid (30.4%), Calciodineloid (9.1%), Gymnodinioid (3.0%), Diplopsallid (3.0%) and Tuberculodinioid (3.0%). The recorded cyst abundance in the UCW recorded was low ($260{\sim}1,680cysts\;g-dry^{-1}$) compared to Korean coastal waters. The abundance of heterotrophic cysts is higher in the Ulsan harbour and northwestern parts of UCW with eutrophic areas, however autotrophic species are more prevalent in the southern parts with open sea environments. The dinoflagellate cyst assemblages in the UCW were characterized by the dominance of Gonyaulax scrippsae, Protoperidinium sp. (Brigantedinium sp.), and Gonyaulax spinifera complex. The advent of the toxic dinoflagellate, Pyrodinium bahamense var. bahamense was recorded for the first time in the East-south sea of Korea. Therefore, as a result of ongoing monitoring and management for new toxic dinoflegallates from tropical or subtropical regions, analysis of dinoflagellate cyst assemblages in the UCW has been deemed necessary.

• Korean Journal of Environmental Biology
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• v.23 no.2 s.58
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• pp.163-172
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• 2005

Field survey on the marine environmental characteristics by the distribution of dinoflagellate cysts and organic matter carried out bimonthly at 14 stations in the central parts of South Sea, Korea from April 2002 to January 2003. The range of environmental factors on surface sediments such as water content, ignition loss (IL), chemical oxygen demand (CODs), particulate organic carbon (POC), particulate organic nitrogen (PON) and phaeopigment were $38.7\~68.9\%,\;3.9\~12.5\%,\;9.60\~44.05mgO_2\;gdry^{-1},\;3.12\~13.14mgC\; gdry^{-1},\;0.49\~2.01mgN\;gdry^{-1}\;and\;1.61\~29.51{\mu}g\;gdry^{-1}\;gdry-1$, respectively. A total dinoflagellate cysts identified were 33 species, which belonged to 18 genera,31 species, and 2 unidentified species. A cysts density were $42\~2,880\; cysts\;gdry^{-1}$. The dominant species of dinoflagellate cysts were Spinrferites bulloideus and Scrippsiella trochoidea all the year and autotrophic species was more abundant than heterotrophic species. The organic matter and dinoflgellate cysts were more abundant nearshore than offshore, and the origin of organic matter was autochthonous rather than from terrestrial. The two factors derived from the loading factor of PCA. Factor 1 was 'accumulation of oragnic matter in the offshore', factor 2 was 'cysts abundance', and the central parts of Korean South Sea was separated with 3 regions by score distribution of PCA.

• Journal of Environmental Science International
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• v.17 no.11
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• pp.1243-1253
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• 2008

The seasonal variations of picoplankton including Prochlorococcus, Synechococcus and Picoeukayotes around Ulneung Island were investigated by flow cytometry in spring, summer and autumn in 2006. All groups of picoplankton showed clear seasonal patterns in population abundance. Among the group, Synechococcus showed the most prominent seasonal variation during the study period. The maximal abundance of Synechococcus occurred in summer and the lowest in autumn. The seasonal distribution of Prochlorococcus displayed the reverse tendency with that of Synechococcus. The abundance of Prochlorococcus ranged from $2.9{\times}10^3$ cells/ml in summer to $311{\times}10^3$ cells/ml in autumn. However, the seasonal distribution of Picoeukaryotes was shown to be relatively constant, and the maximal abundance was $81.5{\times}10^3$ cells/ml in summer. The highest abundance of Picoeukaryotes occurred in summer and the lowest in autumn and the seasonal distribution in abundance of Picoeukaryotes showed a similar trend with that of Synechococcus. The estimated total carbon biomass of picoplankton were ranged from $74.7\;mg\;C/m^2$ to $1,055.9\;mg\;C/m^2$. The highest total carbon biomass occurred in summer, but lowest occurred in autumn. The pattern of the contribution of three picoplankton to total autotrophic picoplankton carbon is different. The contribution of Synechococcus to total autotrophic picoplankton carbon is increased to 75%, but the contribution of Prochlorococcus dropped to 12% in summer. The contribution of Picoeukaryotes is ranged from 24% in summer to 72.5% in spring.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.8
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• pp.852-859
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• 2006

The novel microbial process such as Anammox(anaerobic ammonium oxidation) and Canon(completely autotrophic nitrogen removal over nitrite) processes is promising biotechnology to remove nitrogen from ammonium-rich wastewater like anaerobic sludge digester liquid. In this research, a new Canon-type nitrogen removal process adopting upflow granular sludge bed type configuration was investigated on its feasibility and process performance, using synthetic wastewater and sludge digester liquids. Air as an oxygen source was provided in an external aeration chamber with flow recirculation. In the first experiment using the synthetic wastewater(up to 110 mg $NH_4$-N $L^{-1}$), the ammonium removal was about 95%(92% for T-N) at effective hydraulic retention time(HRT) for 3.8 days. In the second experiment using the sludge digester liquids($438{\pm}26$ mg $NH_4$-N $L^{-1}$), the total nitrogen removal was $94{\pm}1.7%$ at HRT for 5.4 days and $76{\pm}1.5%$ at HRT for 3.8 days, respectively. Little nitrite and nitrate were observed in the effluent of both experiments. The process revealed quite a lower oxygen($0.29{\sim}0.59$ g $O_2$ $g^{-1}N$) and less alkalinity($3.1{\sim}3.4$ g $CaCO_3$ $g^{-1}N$) consumption as compared to other new technology in microbial nitrogen removal. The process also offers the economical compact reactor configuration with excellent biomass retention, resulting in lower cost for investment and maintenance.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.3
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• pp.405-415
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• 2000

Experiments for autotrophic denitrification were performed using an upf10w reac1.or packed with sulfur particles as an electron donor. The influent $NO_3{^-}$-N concentration was kept almost constant, but the hydraulic retention time(HRT) and temperature varied. Results of the research showed that the denitrification efficiency and gas generation rate decreased as the HRT and temperature were reduced. During the HRT effect experiment, alkalinities of 3.44~5.71g, with an average of 4.67 g which is close to the theoretical value of 4.57g were consumed for each gram of $NO_3{^-}$-N removed. During the temperature effect experiment, however, the values were 6.58~13.41 g with an average of 9.12 g which is almost twice the theoretical value Denitrification along the length of the reactor appeared to be a first-order reaction with a reaction rate constant of 0.1648/hr. On the other hand, the sulfate generation showed a zero-order reaction with a reaction rate constant of 241/hr. There was some discrepancy in the nitrogen mass balance between the theoretical and measured values, requiring further researches.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.302-308
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• 2005

Nitrate is one of common contaminants frequently found in the bank filtrate. Biological autotrophic denitrification into permeable reactive barrier(PRB) system to reduce nitrate concentration in bank filtrate was implanted. The objectives of research are to investigate effect of inoculation, to evaluate alternative alkalinity sources, and to determine effect of hydraulic characteristics, such as retention time, flow rate on the performance of semi-pilot PRB system. Semi-pilot scale biological PRB system was installed using elemental sulfur and limestone/oyster shell as reactive materials near Nakdong River in Kyoungnam province, Korea. Nitrate concentration in bank filtrate was reduced by indigenous microorganisms in oyster shell as welt as by inoculating microorganisms isolated from the sludge of an anaerobic digester in a wastewater treatment plant. Oyster shell as well as limestone can be used as an alkalinity source. However, oyster shell resulted in suspended solids of effluent. As the flow rate in the system increased from 66 to 132 mL/min and accordingly the residence time decreased from 15 to 7.5 hours, nitrate concentration in effluent increased and nitrate removal efficiencies decreased from 75 to 58% at the fixed thickness of 80 cm of PRB.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.4
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• pp.433-442
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• 2010

BER at different packing ratios of bio-ring media(BRM) was tested to investigate the effect of varying hydraulic retention time (HRT) and current density on the nitrate removal and current efficiency. In the preliminary batch mode experiment of BERs, current density was applied at 2.0 A/$m^2$, 4.0 A/$m^2$, 4.8 A/$m^2$, which correspond to the designation of reactor #1, #2, #3, respectively. The reactor #2 showed a highest nitrate removal rate of 162.0 mg $NO_3{^-}$-N/L/d, and the kinetics of nitrate removal rate was defined as the Zero order reaction. In the primary experiment of BERs, four BERs packed with BRM were operated in varying HRT and current, and the packing ratios of reactor #1, #2, #3 and #4 were 0%, 8%, 16%, 24%. respectively. This results of the experiments indicated that the nitrate removal rate and current efficiency were increased significantly cause of growing of autotrophic denitrification microorganisms on the surface of cathode and media by increasing of the current density and decreasing of HRT. However, The decreasing of nitrate removal rate and current efficiencies were observed in the condition of HRT of 5.25 hr and 4.8 A/$m^2$ of current density. With more increasing current density and decreasing of HRT, the hydrogen inhibition occurred at the surface of cathode. Moreover, nitrate removal rate by autotrophic denitrification microorganisms attached on the media surface was observed to be limited by no longer increasing dissolved hydrogen concentration of each reactor. In conclusion, the highest nitrate nitrogen removal and current efficiency could be achieved when the BER was operated at the conditions of 7 hr HRT, current density of 4.0 A/$m^2$, and 16% packing ratio. And it was found that the amount of nitrate removal by microorganisms attached on the surface of cathode and media (BRM) was 178.2 mg/L and 52.2 mg/L respectively. and the amount of nitrate removal per MLVSS was 0.435 g $NO_3{^-}$-N/g $MLVSS{\cdot}d$ and 0.336 $NO_3{^-}$-N/g $MLVSS{\cdot}d$.