Disinfection Byproduct Formation Potential Reduction by Ozonation-Biologically Active Carbon Filtration: A case study on Kinmen Island
Date Issued
2014
Date
2014
Author(s)
Wu, Sheng-Pei
Abstract
Tai Lake, one of the major water sources on Kinmen Island, suffers from eutrophication and seasonal algae bloom due to livestock farming and agricultural husbandry. The conventional treatment process can only remove partial dissolved organic carbon. Therefore, disinfection by-products (DBPs), such as trihalomethanes (THMs), haloacetic acids (HAAs), and halonitromethanes (HNMs), haloacetonitrile (HANs) were a major concern in finished water. Ozone, a strong oxidant, can remove hydrophobic organic compounds effectively. Combined with biologically active carbon (BAC) filtration, it can reduce dissolved organic material and reduce DBP formation in finished water. The objective of this study was to reduce dissolved organic carbon (DOC) and DBP formation by operating ozonation-BAC in multiple repeating cycles. DBP formation potential (DBPFP) and formation kinetics were used to evaluate DBP precursors removal efficiency with different disinfectants. In the continuous mode, sodium acetate solution was used as stimulant for biostimulation to evaluate if the removal efficiency of THM4, HAA9, HANs and trichloronitromethane were enhanced. After ozone-BAC, DOC removal efficiency with 1 to 3 times ozone-BAC process were 48%, 53.2% and 75.9%, respectively. THM4 and HAA9 formation potential were also reduced by multiple ozone-BAC processes. After 3 times ozone–BAC, the removal efficiency of THM4 and HAA9 formation potential was 90.7%, 86.7% with sodium hypochlorite, and 81.3%, 87.6% with monochloramine, respectively. For the haloacetics acids, ozonation could reduce the formation potential of trihaloacetic acids but enhance the dihaloacetics acids formation potential. At the same time, dihaloacetics acids and trihaloacetic acids formation potential could be reduced after BAC filtration. As for nitrogenous-DBPs, ozonation could remove most precursors of the HANs. The overlapping of formation kinetics indicated that some of HANs precursors still remained after ozonation. In addition, HANs formation potential was reduced during BAC filtration process. With the same dosage, concentration of HANs was higher with sodium hypochlorite than with mono-chloramine in the beginning of the reaction. Ozonation enhanced the formation concentration of trichloronitromethane; meanwhile, it was reduced after BAC filtration. In the continuous mode, the addition of sodium acetate could slightly improve the removal of DOC. However, the removal of precursors of trihalomethanes, haloacetic acids, haloacetonitriles and trichloronitromethane was remained the same. In summary, ozonation and BAC filtration can reduce dissolved organic carbon concentrations as well as THM4 and HAA9 formation potential successfully. In the subsequent disinfection, mono-chloramine not only produces lesser THM4 and HAA9 but also reduces the HAN formation. These results provide evidence that the ozonation-BAC-monochloramine process can reduce the DBP concentration successfully in high organic water.
Subjects
臭氧
生物活性碳
鹵乙腈
消毒副產物生成潛勢
SDGs
Type
thesis
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