• Journal of Korean Society of Environmental Engineers
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• v.39 no.3
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• pp.105-111
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• 2017

This study was conducted to evaluate the effects of pH control and ozonation, coagulation on trihalomethanes (THMs) formation during prechlorination of the Nakdong river water. The results showed that lower pH was reduced THMs formation during prechlorination. THMs formation of water lowered pH 9.5 to 9.0, was reduced 18.3% and lowered pH 9.0 to 8.0 was reduced 14%, lowered pH 8.0 to 7.0 was reduced 7%, lowered pH 9.5 to 8.0 was reduced 29%. A low ozone dose ($0.11{\sim}0.48mg{\cdot}O_3/DOC$) before chlorination reduced the yields of THMs (reduced 6~24% in chlorination) compared with no preozonation. Thus the low ozone dose pretreatment is relatively effective plan to reduce THMs formation during chlorination. When ozone 1.0 mg/L, Alum 40 mg/L and sulfuric acid 6 mg/L dosed, The yields of THMs formation was reduced 42% compared with only chlorination. Input of chlorine after preozonation (followed coagulation, pH control) is more effective than only decline pH at a intake station to control THMs formation in a water treatment process. When chlorine 2.5 mg/L was added before coagulation (alum 40 mg/L), THMs formation was reduced 19% by lower pH and decreased 18% by a natural organic matter (NOM) removal compared with only chlorine 2.5 mg/L addition. Because coagulation could induce simultaneously lower pH and NOM removal, THM formation concentration is more effectively lowed than decreasing pH in the Nakdong river water.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.7
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• pp.721-728
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• 2008

DBPs(Disinfection By-Products) are most formed through the reactions between chlorine and NOM(Natural Organic Matter) in water treatment. In this study, occurrence of DBPs including THMs(Trihalomethanes) is evaluated. Also, influencing factors by the seasons and raw water quality were investigated for correlation among them and the characteristics of THMs formation by prechlorination process. This study investigated the operation condition for THMs removal depending on raw water quality. Water treatment plant from intake station to gauging well flows for about 10 hours in Y Water Supply Office. It is limited to control of THMs formation because of excessive reaction time between chlorine and THMs precursors in the intake station. Therefore, as multi-points prechlorination from intake station to gauging well, THMs formation was decreased in the water treatment, and it was willing to prevent overdosage of chlorine. The concentration of THMs was 0.021 mg/L in the summer, 0.015 mg/L in the winter, respectively. Also, THMs formation showed that 0.013 mg/L in the water of gauging well after prechlorination, 0.014 mg/L in the flocculation/sedimentation/filtration, 0.016 mg/L in the water after postchlorination, respectively. THMFP(Trihalomethane Formation Potential) removed 42.7% and 50% through the flocculation/sedimentation and filtration, respectively, and it is similar TOC removal efficiency. In this study, multi-points prechlorination from intake station to gauging well decreases in contact time and concencrations of NOM and chlorine. Also, it decreases in THMs and amount of chlorine uesd. In the result of multi-points prechlorination in the summer, the concentration of THMs was 0.013mg/L in the treated water. In view of these facts, THMs formation can be decreased approximately 50%.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.3
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• pp.286-292
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• 2008

This study was conducted to analyze and determine the formation potential of chlorination DBPs from seven urinary compounds with or without Br$^-$. Three of seven components were kynurenine, indole and uracil that were relatively shown high the formation potential of chlorination DBPs concentrations. The reported results of THMs/DOC with or without Br$^-$ in kynurenine showed that THMs/DOC was detected 86.9 $\mu$g/mg when Br$^-$ was not added, and THMs/DOC was detected 100.8 $\mu$g/mg when Br$^-$ was presented. In indole, THMs/DOC was increased from 6.58 $\mu$g/mg to 31.4 $\mu$g/mg when Br$^-$ was added. Moreover, among them, the highest, second-highest and third-highest HAAs/DOC were shown in kynurenine, uracil and indole respectively. Specially, HAAs/DOC was significantly deceased in kynurenine and indole when Br$^-$ was presented. This was a totally different phenomenon for THMs/DOC. TCAA was dominated in HAAs for kynurenine and indole, and DCAA was also dominated in HAAs for uracil. The highest formation of HANs/DOC was shown in kynurenine whether or not Br$^-$ presented, and DCAN was predominant in HANs. HANs was not formed by chlorination in uracil. In addition, the formation of CH/DOC was relatively low in kynurenine and indole. The formation of CH/DOC was specially high(1,270 $\mu$g/mg) in uracil when Br$^-$ was not added. The formation of CH/DOC was 1,027 $\mu$g/mg in uracil when Br$^-$ was added. The formations of THMs and HAAs were also investigated in kynurenine, indole and uracil when Br$^-$ was presented or not. The formation of THMs/DOC was higher in kynurenine and indole when Br$^-$ was presented. The formation of HAAs/DOC was reduced in kynurenine when Br$^-$ was added. The result could be attributed to higher formation of THMs/DOC in kynurenine when Br$^-$ was added. The formation of HAAs/DOC was also reduced in indole when Br$^-$ was added. To the contrary, this result was not attributed to higher formation of THMs/DOC in indole when Br$^-$ was added.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.762-770
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• 2005

Adsorption and biodegradation performance of chlorinated by-products such as trihalomethanes(THMs) and haloacetic acids(HAA5) on granular activated carbon were evaluated in this study. The coconut-based activated carbon was found more effective than others in adsorption of THMs due to larger pore volume of less than $20{\AA}$. The wood-based activated carbon was less effective than coconut- and coal-based activated carbon in adsorption nevertheless having larger pore volume and specific surface area than others. The maximum adsorption capacity(X/M) of coconut-based carbon for THMS was 1.1-1.5 times larger than coal based carbon and 14.1-31.4 times larger than wood based activated carbons. Activated carbon usage rate(CUR) of coconut-, coal- and wood-based activated carbons for chloroform were 9.4, 11.2 and 38 g/day respectively. In the evaluation of adsorption isotherm of THM species for coconut-, coal- and wood-based activated carbons, k value of chloroform was the lowest in the THM species, It menas that chloroform is difficult to remove by activated carbon adsorption. and BDCM, CDBM, bromoform are in the succeeding order of adsorption. In the evaluation of biodegradation rate, mean biodegradation rate was chloroform 7%, BDCM 5%, CDBM 4% and bromoform 3%, respectively THMs are difficult materials to be biodegraded. In the evaluation of characteristics of adsorption and biodegradation for HAA5 species, HAA5 species appear to be removed effectively by activated carbon. Most of the HAA5 are adsorbed at the beginning of operation periods and HAA5 except TCAA were almost biodegraded from bed volume of 2,000 and more than 90 percent of biodegradation of TCAA was started from bed volume around 4,000 and after that biodegradation rate was increased with increasing bed volume.