• Journal of Korean Society of Water and Wastewater
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• v.11 no.1
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• pp.81-87
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• 1997

Coagulation is very important process in water works. The subsequent processes are directly affected by this process. Many factors such as turbidity, alkalinity, pH, hardness, total organic carbon(TOC), velocity gradient and flocculation time effect on coagulation process. Among these factors, specially TOC is being concerned target substance to be removed due to trihalomenthanes(THMs) precursor and alkalinity is being one of the major parameter for removing TOC. We have researched the consumption of coagulant with TOC alkalinity concentration of water and removal efficiency of residual TOC and turbidity with alkalinity. Furthermore we have investigated particle size distributions with velocity gradient and alkalinity. The consumption of coagulant was proportionally increased to TOC and alkalinity concentration and the removal of TOC in Nakdong river water was very difficult more than 150 mg/l in alkalinity but large morecular weight organic such as humic acid could be removed easily. Coagulation of low alkalinity water was more rapidly occured than of high alkalinity water by analyzing the particle size distributions. High alkalinity water needed higher mixing energy for a good coagulation within limited flocculation time.

• Journal of Environmental Science International
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• v.22 no.1
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• pp.1-6
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• 2013

A fixed biofilm reactor system composed of anaerobic, anoxic(1), anoxic(2), aerobic(1) and aerobic(2) reactor was packed with synthetic activated ceramic (SAC) media and adopted to reduce the inhibition effect of low temperature on nitrification activities. The changes of nitrification activity at different wastewater temperature were investigated through the evaluation of temperature coefficient, volatile attached solid (VAS), specific nitrification rate and alkalinity consumption. Operating temperature was varied from 20 to $5^{\circ}C$. In this biofilm system, the specific nitrification rates of $15^{\circ}C$, $10^{\circ}C$ and $5^{\circ}C$ were 0.972, 0.859 and 0.613 when the specific nitrification rate of $20^{\circ}C$ was assumed to 1.00. Moreover the nitrification activity was also observed at $5^{\circ}C$ which is lower temperature than the critical temperature condition for the microorganism of activated sludge system. The specific amount of volatile attached solid (VAS) on media was maintained the range of 13.6-12.5 mg VAS/g media at $20{\sim}10^{\circ}C$. As the temperature was downed to $5^{\circ}C$, VAS was rapidly decreased to 10.9 mg VAS/g media and effluent suspended solids was increased from 3.2 mg/L to 12.0 mg/L due to the detachment of microorganism from SAC media. And alkalinity consumption was lower than theoretical value with 5.23 mg as $CaCO_3$/mg ${NH_4}^+$-N removal at $20^{\circ}C$. Temperature coefficient (${\Theta}$) of nitrification rate ($20^{\circ}C{\sim}5^{\circ}C$) was 1.033. Therefore, this fixed film nitrogen removal process showed superior stability for low temperature condition than conventional suspended growth process.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.10
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• pp.1789-1797
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• 2000

The objective of this study was to assess parameters affecting nitrite accumulation, which offers advantages in terms of less aeration energy and carbon consumption for denitrification. The influence of the alkalinity to $NH_4{^+}-N$ concentration ratio, pH, FA(free ammonia) concentration and temperature on nitrite accumulation was investigated. The experiment was performed with supernatant from dewatering process of anaerobic digested sludge using a submerged biofilm reactor. The influent contains high strength of ammonium nitrogen and the alkalinity was insufficient for complete nitrification. An increased nitrite accumulation was observed with increase in alkalinity to $NH_4{^+}-N$ concentration ratio. The increase in alkalinity to $NH_4{^+}-N$ concentration ratio has been a maior reason for the high pH value and FA concentration in the reactor. It can be considered that selective inhibition of Nitrobacter can be causes of nitrite accumulation. The nitrite accumulation increased with increment of temperature at fixed alkalinity to $NH_4{^+}-N$ concentration ratio.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.7
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• pp.783-792
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• 2007

To investigate the effects of alkalinity on the nitrification capability of the nonwoven fabric filter bioreactor(NFBR), an experiment was performed for 641 days at a hydraulic retention time of approximately 11 hours by changing the influent concentration of $NH_3-N$ from 54 mg/L to 1,400 mg/L and alkalinity from 43 mg/L to 10,480 mg/L. The MLSS concentration reduced from an initial value of 2,650 mg/L down to 830 mg/L, then increased up to 8,340 mg/L. Though the volumetric loading rate varied in a range of $0.120\sim3.130$ kg $NH_3-N/m^3-day$, the F/M ratio showed a narrow range of $0.067\sim0.414$ kg $NH_3-N/kg$ MLSS-day. The average nitrification efficiency at each experimental stage resulted in the range of $35.2\sim100%$, and the maximum nitrification rate was 2.970 kg $N/m^3-day$ or 0.489 g N/g MLVSS-day. The nitrifiers' fraction of the MLVSS increased up to 100% from an initial value of 7.1% and the biofilm formed on the nonwoven fabric filter showed a very low nitrifiers' fraction of mere 2.2%. The growth yield of the MLSS and the alkalinity consumption rate were computed to be 0.117 g VSS/g N removed and 7.08 g alkalinity/g $NO_x^--N$ produced, respectively. Results of the research suggest that NFBR could be an adequate process for nitrification of wastewaters with high ammonia concentrations.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.9
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• pp.851-856
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• 2010

A sulfur utilizing nitrite denitrification process could be placed after the shortcut biological nitrogen removal (SBNR) process. In this study, removal of nitrite using sulfur oxidizing denitrifier was characterized in batch tests with granular elemental sulfur as an electron donor and nitrite as an electro acceptor. At sufficient alkalinity, initial nitrite nitrogen concentration of 100 mg/L was almost completely reduced in the batch reactor within a incubation time of 22 h. Sulfate production with nitrite was 4.8 g ${SO_4}^{2-}/g$ ${NO_2}^-$-N, while with nitrate 13.5 g ${SO_4}^{2-}/g$ ${NO_3}^-$-N. Under the conditions of low alkalinity, nitrite removal was over 95% but 15 h of a lag phase was shown. For nitrate with low alkalinity, no denitrification occurred. Sulfate production was 2.6 g ${SO_4}^{2-}/g$ ${NO_2}^-$-N and alkalinity consumption was 1.2 g $CaCO_3/g$ ${NO_2}^-$. The concentration range of organics used in this experiment did not inhibit autotrophic denitrification at both low and high alkalinity. This kind of method may solve the problems of autotrophic nitrate denitrification, i.e. high sulfate production and alkalinity deficiency, to some extent.

• Analytical Science and Technology
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• v.13 no.5
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• pp.652-658
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• 2000

Chemical degradation of aqueous humic acid by ozonation was studied with respect to the direct reactions of ozone and the indirect reactions due to its preliminary decomposition to secondary oxidant, OH radical. This was characterized by analyzing TOC, $UV_{254}$ and ozone consumption measured in different experimental conditions in which ozone reacted in the presence of various concentrations of $H_2O_2$ and $HCO_3{^-}$ concentrations ranging from 20 to 100 mg/L. and different pH (5-9). The results suggest that the TOC removal is mainly dependent on indirect reactions of OH radical whereas $UV_{254}$ reduction is mainly dependent on direct reactions of ozone with humic acid molecules. It has been also found that ozone consumption was most likely to be affected by pH and alkalinity in the solution.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.1995-2005
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• 2000

The use of heterotrophic denitrification as an alternative method for supplying alkalinity during sulfur-utilizing autotrophic denitrification was evaluated by examining the effects of external carbon source (both type and concentration) and HRT on denitrification efficiency. Concentrations of $NO_3{^-}-N$ and $COD_{Cr}$ of nitrified landfill leachate used for experiment were 700-900mg/L and 900-2500mg/L. respectively, All experiment was conducted with sulfur packed bed reactors (SPBRs) which were operated at $35^{\circ}C$. The fraction of $NO_3{^-}-N$ removed by heterotrophic denitrification ($HDNR_{fraction}$) to balance the alkalinity consumption by autotrophic denitrification varied with the type of external carbon source. When methanol and sodium acetate was added at theoretical HDNRfraction value. 100% denitrification was achieved without alkalinity addition. However, glucose and molasses require $HDNR_{fraction}$ value greater than theoretical value for complete denitrification. The EBCT and volumetric loading rate at which 100% denitrification efficiency could be achieved were 6.76 h and $2.84kg-NO_3{^-}-N/m^3{\cdot}d$, respectively, based on the fact that 100% denitrification occurred within the bottom 11.5 cm layer of the SPBR. The maximum nitrogen removal rate occurred with 89% removal efficiency at loading rate of $5.05kg-NO_3{^-}-N/m^3{\cdot}d$. However, at short EBCT, clogging of SPBR was observed with excess growth of heterotrophic denitrifiers. This problem may be eliminated by back washing or by separating of heterotrophic denitrification from sulfur-utilizing denitrification.

• Journal of environmental and Sanitary engineering
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• v.16 no.3
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• pp.96-103
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• 2001

This study was carried out to investigate the major factors for the removal of NOMs (Natural Organic Matters) by alum ferric chloride and blended coagulants that consisted of alum and ferric chloride. Investigated factors were pH, the dosage of coagulant, alkalinity, hardness and bloc strength. The particle size contained in the test water came from the Han River was also measured. DOC(Dissolved Organic Carbon) removal at pH 6 was two to three times higher than at pH 8.5. The blended coagulant showed 9 to 10 percent higher DOC removal efficiency and 2 to 4 percent higher turbidity under the same condition. Alkalinity consumption of alum, ferric chloride and blended coagulant was 81%, 90% and 86% of theoretical value, respectively. The limit concentration of alkalinity to avoid pin floe was 10 mg $CaCO_3/L$ when alum was used. Hardness had no apparent effect on coagulation. The residual turbidity and $UV_{254}$ showed a tendency of increasing with floc strength($sec^{-1}$) increase. The order of floe strength was the following; alum >blended coagulant > ferric chloride. The particle counter test showed 89 percent of the small particle size(SPS, $1~5{\;}{\mu}textrm{m}$) and 11 percent of the medium to large particle size(M.LPS, $5~125{\;}{\mu}textrm{m}$). At PH7.85, the particle removal efficiencies of SPS($1~5{\;}{\mu}textrm{m}$) and M.LPS($5~125{\;}{\mu}textrm{m}$) in the coagulation process were 81% and 95%, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.2
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• pp.180-185
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• 1999

Rotating Biological Contactor (RBC) was tested for the treatment of artificial rearing water in n simulated aquaculture system. Performance of RBC on the removal of TAN and COD was evaluated by controlling hydraulic residence time (HRT). As HRT of RBC was increased, TAN removal rate ana removal efficiency of RBC and TAN concentration of rearing water were increased, but COD removal rate was decreased. Total alkalinity consumption rate was increased by increasing HRT of RBC. Ratio between total alkalinity consumption rate and TAN removal rate was 7.73. HRT for maintaining lowest TAN and COD concentration of artificial rearing water was 14,6 minutes and at that condition TAN and COD concentration of the water was 1.28 and $5.59 g/m^3$, respectively.

• Korean Journal of Environmental Agriculture
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• v.29 no.3
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• pp.221-226
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• 2010

Swine wastewater contains high amounts of organic matter and nutrients (nitrogen and phosphorus). The biological nitrogen removal can be achieved by nitrification and denitrification processes. Nitrification-denitrification can be performed via nitrite which is called as the short-cut process. This Short-cut process saves up to 25% of oxygen and 40% of external carbon during nitrification and denitrification. In this study, the batch tests were conducted to assess the different parameters for the nitrite sulfur utilizing denitrification, such as alkalinity, temperature, initial nitrite concentration, and dissolved oxygen. The experimental results showed that the nitrite removal efficiency of the reactor was found to be over 95% under the optimum condition ($30^{\circ}C$ and sufficient alkalinity). Autotrophic nitrate denitrification was inhibited at low alkalinity condition showing only 10% removal efficiency, while nitrite denitrification was achieved over 95%. The nitrite removal rates were found similar at both $20^{\circ}C$ and $30^{\circ}C$. In addition, nitrite removal efficiencies were inhibited by increasing oxygen concentration, but sulfate concentration increased due to sulfur oxidation under an aerobic condition. Sulfate production and alkalinity consumption were decreased with nitrite compared those with nitrate.